561 Sentences With "subducted" | Random Sentence Generator

The remains of the subducted part of the continent, which was about 60 miles thick, are also still detectable with seismometers.

They infer that the slab could have have subducted from 66 to 46 million years ago, causing an ancient area of volcanic activity called the Challis Absaroka arc.

For example, Mauna Loa contains higher proportions of an igneous rock called pyroxenite, which comes from subducted ocean crust that typically melts at deeper levels than the model suggests.

However, over time, the Earth cooled sufficiently, aided by the onset of plate tectonics, in which the colder outer crust of the planet is subducted back into the hot mantle.

Then, as the sun grew brighter and hotter, rainfall scrubbed the carbon dioxide from the atmosphere and plate tectonics later subducted it into the Earth's mantle (the layer of hot rock above the core), locking it away.

Scientists have seismic evidence that the deep part of the mantle is a graveyard where long ago slabs of earth were subducted, or thrust underneath one another, creating separate regions with different chemical compositions that eventually made their way to the surface in a hot mantle plume, or upwelling, as the core heated the rock into magma.

Continental plates converged and folded up the ocean to form West Junggar residue sea. 5. Rifting occurred again to form Junggar Ocean (JO) (in pink) and Kelamaili Ocean (KO) (in brown), which showed separation from Bogda arc (BA), Kalameili arc (KA) and Altai Arc (AA). 6. JO subducted over KA while KO subducted over AA. 7. Junggar ocean crust subducted over the combined Kelamaili-Altai arc and showed slab rollback. 8.

The ultimate origin of the El Laco iron may be subducted metal-containing sediment.

Lopevi is on the New Hebrides Plate, where it lies above the subducted Australian Plate to the west. Because there are no earthquakes between 50 and 200 km below the Earth's surface, it is thought that the subducted plate has fractured, and does not appear between these depths.

Tectonic plates of the world The Ring of Fire is a direct result of plate tectonics: the movement and collisions of lithospheric plates. The eastern section of the ring is the result of the Nazca Plate and the Cocos Plate being subducted beneath the westward-moving South American Plate. The Cocos Plate is being subducted beneath the Caribbean Plate, in Central America. A portion of the Pacific Plate and the small Juan de Fuca Plate are being subducted beneath the North American Plate.

Possibly, as such a seamount or a seamount chain subducted it indented the trenches, forming a re- entrant.

Some fracture zones have been created by mid-ocean ridge segments that have been subducted and may not longer exist.

The LIP-arc collision occurred north of its present location, but oblique plate convergence has migrated the subducted plateau southward.

Subducting plates are colder than the mantle into which they are moving. This creates a fast anomaly that is visible in tomographic images. Both the Farallon plate that subducted beneath the west coast of North America and the northern portion of the Indian plate that has subducted beneath Asia have been imaged with tomography.

Even subducted sediment may rise as diapirs from the subducting plate and accumulate to form UHP terrains.Currie, C. A., Beaumont, C., and Huismans, R. S., 2007, The fate of subducted sediments: A case for backarc intrusion and underplating: Geology, v. 35, p. 1111-1114. Studies of numerical geodynamics suggest that both subducted sediment and crystalline rocks may rise through the mantle wedge diapirically to form UHP terranes.Stöckhert, B., and Gerya, T. V., 2005, Pre-collisional high pressure metamorphism and nappe tectonics at active continental margins: a numerical simulation: Terra Nova, v. 17, p. 102-110.

When the Piemont-Liguria oceanic crust had completely subducted beneath the Adriatic plate in the Paleocene, the Briançonnais microcontinent, according to some a piece of the Iberian plate, arrived at the subduction zone. The Briançonnais microcontinent and Valais Ocean (with island arcs) subducted beneath the Adriatic plate. They stayed at around 70 km (45 mi) below the surface during the Eocene, reaching the eclogite facies and becoming intruded by migmatites. This material would later become the Penninic nappes, but a large part of the Briançonnais terrane subducted further into the mantle and was lost.

5 km depth and ca. 20–25 km depth (which is the approximate depth of subducted Pacific plate at that location).

In present day, the Pacific-Farallon Ridge no longer formally exists since the Farallon Plate has been broken up or subducted beneath the North American Plate, and the ridge has segmented, having been mostly subducted as well. The most notable remnant of the Pacific-Farallon Ridge is the 4000 km Pacific-Nazca segment of the East Pacific Rise.

Yinshan Block was subducted under Ordos Block at 1.92 Ga, forming Inner Mongolia Suture Zone with some basaltic oceanic crust in between.

The shallowing of subducted slab beneath north-central Chile and Argentina is linked to a series of changes in volcanism and tectonics.

The common view is that these eclogites were originally basic volcanic rocks within the leading edge of the continental crust of the Arabian Plate. This leading edge was then subducted by a NE-dipping subduction zone. However, some geologists have interpreted that these eclogites were subducted through a SW-dipping subduction zone. The two culminations are separated by the Semail Gap.

The Carnegie Ridge is seen to extend eastwards over 1,000 km from the Galapagos islands to the Colombia-Ecuador trench and is interpreted to continue beneath northern Ecuador for about a further 700 km. The subducted extent is disputed, with some workers arguing that there is no evidence of a subducted ridge beneath Ecuador extending more than about 60 km from the trench.

Knowledge of the now-subducted Izanagi Plate is limited to Mesozoic magnetic lineations on the Pacific Plate that preserve the record of this subduction.

However tidal tomography cannot say exactly how the excess mass is distributed. The overdensity may be due to primordial material or subducted ocean slabs.

These oceanic rocks were derived from the seafloor of the prehistoric Slide Mountain Ocean, the Intermontane Plate, which was subducted under the North American plate.

The Mezcalera Ocean is an inferred ancient ocean preserved in rocks in western Mexico. The Mezcalera oceanic plate was likely subducted and consumed into the mantle allowing the Guerrero Terrane to accreted to western Mexico in the Early Cretaceous. Speculative reconstructions suggest that Mezcalera plate experienced slab rollback in the east along the Mexican Craton and simultaneously subducted in the west beneath the Guerrero Terrane.

This, and other observations, have been interpreted as indicating that the distinct geochemical signature of ocean island basalts results from inclusion of a component of subducted slab material. This must have been recycled in the mantle, then re-melted and incorporated in the lavas erupted. In the context of the plume hypothesis, subducted slabs are postulated to have been subducted down as far as the core-mantle boundary, and transported back up to the surface in rising plumes. In the plate hypothesis, the slabs are postulated to have been recycled at shallower depths – in the upper few hundred kilometers that make up the upper mantle.

While the oceanic plate is being subducted, the continental plate is scraping off the top layers of the oceanic plate slowly bringing them to the surface.

We thus speculate that the subducted part of the WPB, dextrally offset along the LOFZ, extends beneath the Ryukyu Arc up to the latitude of Kyushu.

The Meguma terrane may have substantially subducted beneath the Avalon terrane with the point of contact marked by the Nauset fault in the middle of Cape Cod.

The Tethys Ocean closed in the Dinarides and Hellenides in the late Cretaceous. The formation of the Alps started 135 million years ago at a strike-slip fault between the Penninic and Tethys Ocean. The Northern Calcareous Alps and Gurktal Alps formed as an orogenic wedge as sedimentary rocks were torn of basement rock that was subducted back into the mantle. The crust of the Penninic Ocean subducted around 85 million years ago.

Regardless of the outcome of the continental migration, the continued subduction process causes water to be transported to the mantle. After a billion years from the present, a geophysical model gives an estimate that 27% of the current ocean mass will have been subducted. If this process were to continue unmodified into the future, the subduction and release would reach an equilibrium after 65% of the current ocean mass has been subducted.

The basement rocks of the continental crust tend to be much older than the oceanic crust. The oceanic crust can be from 0–250 million years in age, and is usually thinner (10 miles or so) and composed of basaltic rocks. Continental crust is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically subducted and replaced at subduction and oceanic rifting areas.

Research indicates that the Sierra batholith was formed from heating as the Farallon Plate subducted below the North American Plate. The episodic nature of the formation of the plutons is not yet well explained. It may involve the effects of the emplacement of various terranes along the margin of the continent. Termination of the formation process occurred as the Farallon Plate was fully subducted along the Pacific coastline west of the Sierra.

The Gulf of Tehuantepec lies above the convergent boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr (2.5 in/yr).

RTF junctions are less common, an unstable junction of this type (an RTF(a)) is thought to have existed at roughly 12Ma at the mouth of the Gulf of California where the East Pacific Rise currently meets the San Andreas Fault zone. The Guadeloupe and Fallaron microplates were previously being subducted under the North American Plate and the northern end of this boundary met the San Andreas Fault. Material for this subduction was provided by a ridge equivalent to the modern East Pacific Rise slightly displaced to the west of the trench. As the ridge itself was subducted an RTF triple junction momentarily existed but subduction of the ridge caused the subducted lithosphere to weaken and ‘tear’ from the point of the triple junction.

These sediments are progressively squeezed as they are subducted, reducing void space and forcing fluids out along the decollement and up into the overlying forearc, which may or may not have an accretionary prism. Sediments accreted to the forearc are another source of fluids. Water is also bound in hydrous minerals, especially clays and opal. Increasing pressure and temperature experienced by subducted materials converts the hydrous minerals to denser phases that contain progressively less structurally bound water.

Everything on the Pacific plate that enters the IBM trench is subducted. The next section discusses some modifications of the lithosphere just prior to its descent and the age and composition of oceanic crust and sediments on the Pacific plate adjacent to the trench. In addition to subducted sediments and crust of the Pacific plate, there is also a very substantial volume of material from the overriding IBM forearc that is lost to the subduction zone by tectonic erosion .

Schematic diagram of the formation of a continental arc. When two tectonic plates collide, relatively denser oceanic crust will be subducted under relatively lighter continental crust. Because of the subduction process, the relatively cooler oceanic crust, along with water, is subducted to the asthenosphere, where pressures and temperatures are much higher than the surface of Earth. Under such conditions, the downgoing plate releases volatiles such as H2O and CO2, which cause partial melting of the above asthenosphere.

BHT was then subducted at its eastern and western margins, which resulted in the arc magmatism that produced the Taltson Magmatic Zone 1980-1920 Ma and the 1986-1900 Ma Ksituan High.

It is a subduction zone where the Pacific Plate is being subducted under the Mariana Plate. The bottom of the trench is further below sea level than Mount Everest is above sea level.

Frontal erosion is most active in the wake of seamounts being subducted beneath the forearc. Subduction of large edifices (seamount tunneling) oversteepens the forearc, causing mass failures that carry debris towards and ultimately into the trench. This debris may be deposited in graben of the downgoing plate and subducted with it. In contrast, structures resulting from subduction erosion of the base of the forearc are difficult to recognize from seismic reflection profiles, so the possibility of basal erosion is difficult to confirm.

Rocks in the series are thought to be genetically related by fractional crystallization and to be at least partly derived from magmas of basalt composition formed in the Earth's mantle. Trends in composition can be explained by a variety of processes. Many explanations focus on water content and oxidation states of the magmas. Proposed mechanisms of formation begin with partial melting of subducted material and of mantle peridotite (olivine and pyroxene) altered by water and melts derived from subducted material.

During the early Jurassic period, the Intermontane Islands and the Pacific Northwest drew closer together as the continent moved west and the Intermontane Microplate subducted. On the continent, subduction supported a new volcanic arc that again sent intruding granite-type rocks into the ancient continental sediments. Eventually, about 180 million years ago in the middle Jurassic, the last of the microplate subducted, and the Intermontane Islands collided with the Pacific Northwest. The Intermontane Islands were too big to sink beneath the continent.

These features are only present proximal to subducted seamounts, and absent where there are no subducted seamounts. The accretionary wedge of the Manila Trench broadens going north; seeing as the southern section of the margin accumulates more trench-fill sediments than the north. The trench-fill sediments are thought to be sourced from the collisional zone of the Taiwan orogeny or by gravity controlled processes. The sequence boundary ‘t0’ represents the unconformity between the hemipelagic sediments and overlying trench-fill sediments.

During the Wopmay orogeny, subduction occurred as oceanic crust of the Slave Craton was subducted beneath an eastward moving continental plate. Likewise, during the Trans-Hudson orogeny, rifting at first separated the Superior craton from the rest of the continent. Then the Superior Craton reversed its direction and the ocean basin began to close. A subduction zone formed as the oceanic crust of the Superior Craton was subducted beneath the Hearne and Wyoming Craton with the Sask Craton in the middle.

This orogeny formed a cordillera-type volcanic arc where oceanic crust subducted below Gondwana. When a mid-oceanic ridge subducted at an oblique angle, extensional basins developed along the northern margin of Gondwana.Scenario from During the late Cambrian to Early Ordovician these extensional basins had evolved a rift running along the northern edge of Gondwana.; The rift in its turn evolved into a mid-oceanic ridge that separated small continental fragments such as Avalonia and Carolina from the main Gondwanan land mass.

These basalts, also called ocean island basalts (OIBs), are analysed in their radiogenic and stable isotope compositions. In radiogenic isotope systems the originally subducted material creates diverging trends, termed mantle components. Identified mantle components are DMM (depleted mid-ocean ridge basalt (MORB) mantle), HIMU (high U/Pb-ratio mantle), EM1 (enriched mantle 1), EM2 (enriched mantle 2) and FOZO (focus zone). This geochemical signature arises from the mixing of near- surface materials such as subducted slabs and continental sediments, in the mantle source.

Ma The Kula Plate was an oceanic tectonic plate under the northern Pacific Ocean south of the Near Islands segment of the Aleutian Islands. It has been subducted under the North American Plate at the Aleutian Trench, being replaced by the Pacific Plate. The name Kula is from a Tlingit language word meaning "all gone".p. 145 As the name suggests, the Kula Plate was entirely subducted around 48 Ma and today only a slab in the mantle under the Bering Sea remains.

Subduction zone metamorphism is characterized by a low temperature, high-ultrahigh pressure metamorphic path through the zeolite, prehnite-pumpellyite, blueschist, and eclogite facies stability zones of subducted oceanic crust.Zheng, Y.-F., Chen, R.-X., 2017.

The Pacific plate is subducted beneath the Mariana Plate, creating the Mariana trench, and (further on) the arc of the Mariana Islands, as water trapped in the plate is released and explodes upward to form island volcanoes and earthquakes . The Mariana Trench is part of the Izu- Bonin-Mariana subduction system that forms the boundary between two tectonic plates. In this system, the western edge of one plate, the Pacific Plate, is subducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west.

Continental crust differs significantly from oceanic crust. Oceanic crust is primarily composed of basaltic rocks, which have a higher density than the rocks making up the majority of continental crust. Island arcs and other volcanic rocks are also lower in density than the oceanic crust, and are therefor not easily subducted along with the oceanic crust that surrounds them. Instead, these less-dense bits of crust will collide with existing continental crust on the upper plate once the oceanic crust separating them is completely subducted.

The Panthalassic Ocean first opened around 750 million years ago at the breakup of Rodinia, but the oldest Pacific Ocean floor is only around 180 Ma old. Any older Pacific floor crust has been subducted. During the Jurassic period, four tectonic plates developed in the Pacific Basin: the Kula and the Farallon in the north, the large Pacific Plate in the centre and south and the Phoenix Plate in the far south. The Kula Plate was subducted under the eastern and south-eastern Asian landmass.

Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. Oceanic lithosphere is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at ocean trenches. Two processes, ridge- push and slab pull, are thought to be responsible for spreading at mid-ocean ridges. Ridge push refers to the gravitation sliding of the ocean plate that is raised above the hotter asthenosphere, thus creating a body force causing sliding of the plate downslope.

To the northwest of the border area between Panama and Costa Rica oceanic crust of the Cocos Plate is being subducted beneath the Caribbean Plate along the Middle America Trench. To the southeast the Nazca Plate is being subducted. The boundary between the Cocos and Nazca plates is formed by the Panama Fracture Zone, which is a right lateral transform fault that intersects with the Middle America Trench to form a triple junction. The geometry of the subduction zone differs markedly either side of this triple junction.

It is possible for oceanic crust to be subducted down into the Earth's mantle, at subduction fronts, where oceanic crust is being pushed down into the mantle by an overriding plate of oceanic or continental crust.

The Kuril Islands form part of the island arc formed above the subduction zone, where the Pacific Plate is being subducted beneath the Eurasian Plate. This convergent boundary has been the site of many large megathrust earthquakes.

For example, the picrites is proved to represent a high temperature primary magma. In addition, the basalt shows isotopic similarity with ocean island basalt (OIB) which is formed by a mantle plume triggered by subducted oceanic crust.

It is suggested that the volcanism may be caused by upwellings from the lower mantle resulting from water-rich fragments of the Farallon Plate descending from the Cascadia subduction region, sheared off at a subducted spreading rift.

This hot added material cools down by conduction and convection of heat. At the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench. This subducted material sinks through the Earth's interior. Some subducted material appears to reach the lower mantle, while in other regions, this material is impeded from sinking further, possibly due to a phase transition from spinel to silicate perovskite and magnesiowustite, an endothermic reaction.

Shallow subduction of young, buoyant slabs can result in the production of adakitic lavas via partial melting. Alternatively, metasomatised mantle wedges can produce highly oxidized conditions that results in sulfide minerals releasing ore minerals (copper, gold, molybdenum), which are then able to be transported to upper crustal levels. Mantle melting can also be induced by transitions from convergent to transform margins, as well as the steepening and trenchward retreat of the subducted slab. However, the latest belief is that dehydration that occurs at the blueschist-eclogite transition affects most subducted slabs, rather than partial melting.

In Kusky et al.'s model, ancient continental blocks formed the juvenile Western Block during 3.5-2.7 billion years ago. Prior to 2.3 billion years ago, Wutai Arc was subducted under the eastern part of the juvenile Western Block, while an exotic arc was subducted under the eastern juvenile Western Block. Between 2.3-2.0 billion year ago, the Western Block collided with the two arc on its both sides, creating Hengshan granulite belt in the southeast and Inner Mongolia-Northern Hebei Orogen with khondalite belt inside in the northwest.

Commonly, only a few eclogite enclaves or UHP minerals reveal that the entire terrain was subducted to mantle depths. Many granulite terrains and even batholithic rocks may have undergone UHP metamorphism that was subsequently obliteratedHacker, B. R., Kelemen, P. B., and Behn, M. D., 2011, Differentiation of the continental crust by relamination: Earth and Planetary Science Letters, v. 307, p. 501-516.Walsh, E. O., and Hacker, B. R., 2004, The fate of subducted continental margins: Two-stage exhumation of the high- pressure to ultrahigh-pressure Western Gneiss complex, Norway: Journal of Metamorphic Geology, v.

Continental and oceanic terranes began to be added to western South America in the Mesozoic. In north-central Ecuador, the Peltetec- Portovelo fault marks the suture between the pre-existing South American craton and the Amotape-Chaucha terrane, which partially subducted beneath a preexisting Mesozoic continental arc system. The Triassic mafic and granitoid rocks of the El Oro metamorphic complex and the component eclogite, blueschist and amphibolite are known as the Raspas metamorphic complex. This section of the terrane was previously subducted but brought to the surface with tectonic activity.

This region is characterized by low free-air gravity anomaly, bathymetric depression, and a change of convex to concave trench axis geometry (which is a feature unique to this location). The gravity anomaly shows that the subducted crust has a density of 2.92 g/cm^3, whereas the surrounding South China Sea crust has a lower density of 2.88g/cm^3.; Seamounts subducted under the Manila Trench have shown to produce some notable deformation features. Well-developed back-thrust faults, microfractures and gravitational collapse are found in the accretionary wedge of the Manila Trench.

From the Late Neoproterozoic o the Middle Cambrian the Timanide Orogen was associated to a subduction zone that existed to the northeast of it. Most studies interpret subduction as going inward (subducted plate moving southwest) albeit one suggest the opposite (subducted plate moving to the northeast). In the Cambrian the Timanide Orogen is believed to have developed in a continental collision context as Baltica and Arctida collided between 528 and 510 million years ago. Some researchers do however dissent from this view suggesting there was never such a collision.

Volcanism in the area ceased in the Late Miocene (11-5 Ma). Plate reconstructions time the collision of the Nazca Ridge with the subduction zone at 11.2 Ma at 11 degree S, which implies that the northern extent of the Peruvian flat slab may require some other subducted feature like an oceanic plateau. A putative subducted plateau, the Inca Plateau, has been argued for. The Pampean or Chilean flat slab segment is located between 27 degrees S and 33 degrees S, extending ~550 km along the strike of the subduction zone.

Oceanic crust can be subducted, while continental crust cannot. Eventually, the subduction of the underthrusting oceanic crust can bring the volcano chain close to a continent, and collide with it. When the overriding plate collides with the continent, instead of being subducted, it is accreted to the edge of the continent and becomes a part of that continent. Thin strips or fragments of the underthrusting plate may also remain attached to the edge of the continent causing those fragments of oceanic crust to be wedged and tilted between the converging plates.

The tectonic environment of this region is dominated by the motions of the Arabian Plate, the Indian Plate, and the Eurasian Plate. This earthquake occurred as a result of normal faulting within the lithosphere of the subducted Arabian Plate.

Hotspots are supplied by a magma source in the Earth's mantle called a mantle plume. Although originally attributed to a melting of subducted oceanic crust, recent evidence belies this connection. The mechanism for plume formation remains a research topic.

The Nankai Trough is a convergent boundary where the Philippine Sea Plate is being subducted beneath the Eurasian Plate. Large earthquakes have been recorded along this zone since the 7th century, with a recurrence time of 100 to 200 years.

In the history of Earth many tectonic plates have come into existence and have over the intervening years either accreted onto other plates to form larger plates, rifted into smaller plates, or have been crushed by or subducted under other plates.

The Lesser Antilles subduction zone is a convergent plate boundary on the seafloor along the eastern margin of the Lesser Antilles Volcanic Arc. In this subduction zone, oceanic crust of the South American Plate is being subducted under the Caribbean Plate.

This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics. Volcanoes result primarily from the melting of subducted crust material or of rising mantle at mid-ocean ridges and mantle plumes.

The about-to-be subducted plate is highly faulted, allowing seawater to penetrate into the plate interior, where hydration of mantle peridotite may generate serpentinite. Serpentinite thus generated may carry water deep into the mantle as a result of subduction.

To understand the subduction of the Farallon Plate, the creation of the Farallon Trench, and the present location of the subducted plate, detailed seismic tomography was used to render images of the existing submerged remnants. The plate can now be seen at depths of around 200 km below the central continental United States. Since the North American coast shows an extremely complicated geologic structure, intensive work has been required to understand the complexity of this system. In 2013 a new explanation emerged from recent research, proposing two additional now fully subducted plates, accounting for some of the complexity of this coast line.

That spreading ridges could be subducted was recognized early in the development of plate tectonic theory, but there was little consideration of the ensuing effects. In the 1980s came realization that the magma welling up from the asthenosphere through the subducted ridge would not reach seawater, and thus not be quenched to form rock and close the gap. Continued spreading would lead to a widening gap or "window" in the subducting plate through which there could be increased flow of magma.. The implications of this for Siletzia were first shown by and (following the pioneering work by ).; .

In the introversion model, the younger, interior, Atlantic Ocean becomes preferentially subducted and the current migration of North and South America is reversed. In the extroversion model, the older, exterior, Pacific Ocean remains preferentially subducted and North and South America migrate toward eastern Asia. As the understanding of geodynamics improves, these models will be subject to revision. In 2008, for example, a computer simulation was used to predict that a reorganization of the mantle convection will occur over the next 100 million years, creating a new supercontinent composed of Africa, Eurasia, Australia, Antarctica and South America to form around Antarctica.

The evolution of the Panthalassa–Tethys boundary is poorly known because little oceanic crust is preserved—both the Izanagi and the conjugate Pacific Ocean floor is subducted and the ocean ridge that separated them probably subducted 60–55 . Today the region is dominated by the collision of the Australian Plate with a complex network of plate boundaries in south-east Asia, including the Sundaland block. Spreading along the Pacific-Phoenix ridge ended 83 Ma at the Osbourn Trough at the Tonga-Kermadec Trench. During the Permian atolls developed near the Equator on the mid-Panthalassic seamounts.

At Taiwan the oceanic crust has all been subducted and the arc is colliding with continental crust of the Eurasian Plate. To the north of Taiwan the Philippine Sea Plate is in contrast subducting beneath the Eurasian Plate, forming the Ryukyu Arc.

As a convergent plate boundary, the trench forms part of the boundary between two tectonic plates. Here, the Pacific Plate is being subducted under the North American Plate at a dip angle of nearly 45°. The rate of closure is per year.

Continental collision is occurring at the Zagros fold and thrust belt west of the Musandam Peninsula. This collisional plate boundary transitions into a subduction zone, towards the east. Here, oceanic crust of the Arabian Plate is subducted northwards beneath Eurasia, called the Makran subduction zone.

A discussion of North American geology can also include other continental plates including the Cocos and Juan de Fuca plates being subducted beneath western North America. A portion of the Pacific Plate underlies Baja California and part of California west of the San Andreas Fault.

Hellenic arc, a subduction zone. The arrows give the direction of plate movement. The southernmost part of the arc is moving north east, to be subducted under the Hellenic plate. The plate itself is extending southwest into the subduction zone, generating a fault-block topography.

Some subducted slabs seem to have difficulty penetrating the major discontinuity that marks the boundary between upper mantle and lower mantle at a depth of about 670 kilometers. Other subducted oceanic plates have sunk all the way to the core-mantle boundary at 2890 km depth. Generally slabs decelerate during their descent into the mantle, from typically several cm/yr (up to ~10 cm/yr in some cases) at the subduction zone and in the uppermost mantle, to ~1 cm/yr in the lower mantle. This leads to either folding or stacking of slabs at those depths, visible as thickened slabs in Seismic tomography.

The Izanagi Plate (named after the Shinto god Izanagi) was an ancient tectonic plate, which began subducting beneath the Okhotsk Plate 130–100 Ma years ago. The rapid plate motion of the Izanagi Plate caused north-west Japan and the outer zone of south-west Japan to drift northward. High-pressure metamorphic rocks were formed at the eastern margin of the drifting land mass in the Sanbagawa metamorphic belt, while low-pressure metamorphic rocks were formed at its western margin in the Abukuma metamorphic belt. At approximately 95 Ma, the Izanagi Plate was completely subducted and replaced by the western Pacific Plate, which also subducted in the north-western direction.

The Explorer Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Vancouver Island, Canada and is partially subducted under the North American Plate. Along with the Juan De Fuca Plate and Gorda Plate, the Explorer Plate is a remnant of the ancient Farallon Plate which has been subducted under the North American Plate. The Explorer Plate separated from the Juan De Fuca Plate roughly 4 million years ago. In its smoother, southern half, the average depth of the Explorer plate is roughly and rises up in its northern half to a highly variable basin between and in depth.

Ollagüe is part of the Central Volcanic Zone (CVZ), one of the volcanic arcs that exist in the Andes. The Andes have segments with volcanic activity and segments without; volcanic activity occurs only where the angle of subduction is relatively steep. There are four such segments, the Northern Volcanic Zone, the CVZ, the Southern Volcanic Zone and the Austral Volcanic Zone. The subducted part of the plate (slab) loses water as it sinks into the mantle, and this water and other components migrate into the mantle that lies between the subducted plate and the overlying crust (mantle wedge) and cause the formation of melts in the wedge.

Part of the Nazca Plate has been shoved over the South America Plate at the Taitao Peninsula resulting in the formation of the Taitao ophiolite. A number of fracture zones cross the Nazca Plate and are subducted in the trench; one of these is subducted directly under Mentolat and may explain anomalous traits of the Mentolat magmas. The Andes are a site of volcanic activity, which is usually subdivided into four separate volcanic zones: the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone. These volcanic zones are separated by gaps where no recent volcanic activity has occurred.

Daiichi- Kashima lies south of the Japan Trench on a seafloor of Valanginian age, very close to the trench. The Pacific Plate is subducting beneath Japan at a rate of and close to the Daiichi-Kashima Seamount lies the Boso Triple Junction between the Japan Trench, the Sagami Trench and the Izu-Bonin Trench. The subduction process may cause the downgoing oceanic plate to buckle and form normal faults that run parallel to the trench. Since about 100,000 years, the western half of Daiichi-Kashima is being subducted in the Japan Trench and about one third to one quarter of the seamount has been subducted already.

The northern part of the Farallon was subducted under North America while its southern section, together with the Phoenix Plate, was subducted under South America and the Antarctic. During the late Tertiary period, the Farallon plate broke up, leaving the Juan de Fuca Plate in the north, the Cocos Plate off today's Central America, and the Nazca and Phoenix Plates in the southern Pacific. Charles Darwin had proposed a theory of the slow subsidence of the ocean floor based on his studies of Pacific oceanic islands, seamounts (underwater volcanoes) and guyots (flat- topped seamounts). His observations have been verified and expanded in the development of plate tectonic theory.

The Rocky Mountains were formed by a series of events, the last of which is the Laramide Orogeny. One of the outstanding features of the Rocky Mountains is the distance of the range from a subducting plate; this has led to the theory that the Laramide Orogeny took place when the Farallon plate subducted at a low angle, causing uplift far from the margin under which the plate subducted. The lithology of the Rocky Mountains in western Canada includes a thin-skinned fold and thrust belt involving Neoproterozoic through Mississippian series of carbonates, shales, argillites and sandstones. The Colorado Plateau is a stable region dating back at least 600 million years.

While most of the large earthquakes occur at the contact zone between both tectonic plates, related to the friction during subduction, others are produced in the Pacific Plate due to its bending. The Pacific crust that descends into the trench is old, 100–140 Ma, and relatively cold and it can therefore store a lot of elastic energy. As it reaches deep into the mantle, more than , and encounters barriers, it is being contorted, which produces deep mantle earthquakes. beneath the North Fiji Basin, a detached segment of the subducted Australian Plate has collided with the subducted Pacific Plate which produces many large-scale earthquakes.

In geology, a slab window is a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone and plate divergence at the ridge and convergence at the subduction zone continue, causing the ridge to be subducted. Thorkelson, Derek J., 1996, Subduction of diverging plates and the principles of slab window formation, Tectonophysics, v. 255, p. 47-63 Formation of a slab window produces an area where the crust of the over-riding plate is lacking a rigid lithospheric mantle component and thus is exposed to hot asthenospheric mantle (for a diagram of this, see the link below).

The Carnegie Ridge is a 1,350-km-long and up to 300-km-wide feature on the ocean floor of the northern Nazca Plate that includes the Galápagos archipelago at its western end. It is being subducted under South America with the rest of the Nazca Plate.

In northeastern Afghanistan, a number of medium- intensity deep focus earthquakes of depths of up to occasionally occur. They are caused by the collision and subduction of the Indian Plate under the Eurasian Plate, the deepest earthquakes centered on the furthest subducted sections of the plate.

The trench formed as a result of the subduction zone, which formed in the late Cretaceous, that created the Kuril island arc as well as the Kamchatka volcanic arc. The Pacific Plate is being subducted beneath the Okhotsk Plate along the trench, resulting in intense volcanism.

Eclogites typically result from high to ultrahigh pressure metamorphism of mafic rocks at low thermal gradients of < as they were subducted to the lower crust to upper mantle depths in a subduction zone. They are generally formed from precursor mineral assemblages typical of blueschist-facies metamorphism.

Deep-focus earthquakes occur at a depth where the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.

See also . Mantle plumes and slab windows both feature voluminous magmatism; the main difference is that slab windows would form only where the spreading ridge is subducted. This implies formation at the continental margin, and then rifting, in the manner of the second class of models.

The interpretation is that the belt was formed as oceanic crust subducted below the Armorica land mass in a similar way to the Andes. Sediments deposited on the continental margin were pushed up onto the continent, at the same time as intrusions of calc-alkaline magmas occurred.

The accretionary wedges are formed from the accumulation of marine sediment scraped off from the oceanic crust before it is subducted. The sedimentary basin is formed from the accumulation of erosive material from the volcanoes, which lying flatly between the volcanoes and the topographic high of the accretionary wedge.

Costa Rica is located on the Caribbean Plate. It borders the Cocos Plate in the Pacific Ocean which is being subducted beneath it. This forms the volcanoes in Costa Rica, also known as the Central America Volcanic Arc. The Caribbean Plate began its eastward migration during the Late Cretaceous.

The Pacific Ocean was born 750 million years ago at the breakup of Rodinia, although it is generally called the Panthalassic Ocean until the breakup of Pangea, about 200 million years ago. The oldest Pacific Ocean floor is only around 180 Ma old, with older crust subducted by now.

The earthquake was an intermediate-depth event, with a hypocentral depth of 115.6 km. The focal mechanism shows that this was a normal fault event, within the subducted Nazca Plate. Finite-fault modelling of the earthquake suggests that the fault plane responsible dips to the west at about 15°.

The tracer code has a wide range of applications in the mantle convection. It can be used in tracing the trajectory of passive particles, in delineating the top boundary of subducted slabs to define the low viscosity wedges, or in tracking the evolution of the chemical composition field.

The northern Melanesian arc collided with the subducted south-eastern segment of the Ontong Java Plateau 10–8 Ma. This collision reversed the direction of subduction in the Vitiaz Trench and thus initiated the clockwise rotation of the Vanuatu arc and the opening of the NFB 8–3 Ma.

From the Cretaceous period until about 29 million years ago (29 Ma), the oceanic Farallon Plate subducted eastward beneath the west coast of the North American Plate.Atwater, T. A., Implications of plate tectonics for the Cenozoic evolution of western North America, Geol. Soc. Am. Bll., 81, 3513-3536, 1970.

Cross Section of Molucca Sea Collision Zone modified by Zhang et al. While the scientific community has not come to a consensus as to when the Molucca Sea Plate became fully subducted, the dominant theory is that the Molucca Sea Plate has been completely subducted beneath the overriding Halmahera and Sangihe Plates. When actively subducting, the crustal collision of the Molucca Sea Plate was formed by surface intersection of “oppositely dipping Benioff zones” (also known as divergent double subduction) which results in the Sangihe and Halmahera volcanic arcs. The force exerted by the thick overlying collision complex of the Halmahera and Sangihe Plates effectively depressed the crust of the Molucca Sea Plate.

About 125 million years from now, the Atlantic Ocean is predicted to stop widening and begin to shrink because some of the Mid-Atlantic Ridge will have been subducted. In this scenario, a mid- ocean ridge between South America and Africa will probably be subducted first; the Atlantic Ocean is predicted to have narrowed as a result of subduction beneath the Americas. The Indian Ocean is also predicted to be smaller due to northward subduction of oceanic crust into the Central Indian trench. Antarctica is expected to split into two and shift northwards, colliding with Madagascar and Australia, enclosing a remnant of the Indian Ocean (called the Indo-Atlantic Ocean), and creating the supercontinent Terra Orientalis.

Along the northern portion, the northwestward-moving Pacific Plate is being subducted beneath the Aleutian Islands arc. Farther west, the Pacific Plate is being subducted along the Kamchatka Peninsula arcs to the south past Japan. The southern portion is more complex, with a number of smaller tectonic plates in collision with the Pacific Plate from the Mariana Islands, the Philippines, Bougainville, Tonga, and New Zealand; this portion excludes Australia, since it lies in the center of its tectonic plate. Indonesia lies between the Ring of Fire along the northeastern islands adjacent to and including New Guinea and the Alpide belt along the south and west from Sumatra, Java, Bali, Flores, and Timor.

Beginnings of the San Andreas Fault Much of the west coast of North America was part of a large convergent plate boundary between the Farallon Plate and North American Plate from 165 to 55 million years ago. Here, the Farallon Plate subducted under the North American Plate creating volcanoes about 100 miles east of this boundary which can still be seen as the Sierra Nevada which it has its southern border about 30 miles east of Grapevine, California in the Tejon Pass. The Farallon Plate was subjected to high temperatures and pressures as it subducted under the North American Plate. This led to the formation of molten plutons which rose because they were less dense than the surrounding magma.

The cessation of volcanism in the Pemberton Belt might have been caused by steepening of the subducted Juan de Fuca slab after the Explorer Plate formed about 6.0 million years ago. This change in tectonics created the modern Canadian Cascade Arc, as well as the Cascade Range and Olympic Mountains.

A deep-focus earthquake in seismology (also called a plutonic earthquake) is an earthquake with a hypocenter depth exceeding 300 km. They occur almost exclusively at convergent boundaries in association with subducted oceanic lithosphere. They occur along a dipping tabular zone beneath the subduction zone known as the Wadati–Benioff zone.

The final phase of the process came in the Miocene and Pliocene, during the Mesogean orogeny, when the combined Mesogean-African plate subducted beneath what is now Greece, the Aegean and parts of western Turkey. In the process, the Crete and southern Peloponessus core complexes were exhumed to the surface.

Oceanic trenches are narrow topographic lows that mark convergent boundaries or subduction zones. Oceanic trenches average wide and can be several thousand kilometers long. Oceanic trenches form as a result of bending of the subducting slab. Depth of oceanic trenches seems to be controlled by age of the oceanic lithosphere being subducted.

The western portion of the plate is occupied by Central America. The Cocos Plate in the Pacific Ocean is subducted beneath the Caribbean Plate, just off the western coast of Central America. This subduction forms the volcanoes of Guatemala, El Salvador, Nicaragua, and Costa Rica, also known as the Central America Volcanic Arc.

The Valais Ocean is a subducted oceanic basin which was situated between the continent Europe and the microcontinent Iberia or so called Briançonnais microcontinent. Remnants of the Valais ocean are found in the western Alps and in tectonic windows of the eastern Alps and are mapped as the so-called "north Penninic" nappes.

The Hikurangi Plateau first subducted beneath New Zealand around 100 Ma during the Gondwana collision and it is currently subducting a second time as part of the convergence between the Pacific and Australian plates. These subducted parts are reaching into the mantle beneath the North Island and northern South Island. The extent of the Hikurangi Plateau slab suggests that it has played a significant role in the geology of New Zealand during the past 100 Ma. The Southern Alps in central South Island are being uplifted along the plate boundary there, a fault zone which parallels the western edge of the slab of the Hikurangi Plateau. The Australian and Pacific plates converge obliquely in the Tonga-Kermadec- Hikurangi subduction zone.

The plate interface above the subducted part of the ridge has a shallower dip than the area to both north and south, the boundaries interpreted to consist of two large tears in the downgoing Nazca Plate. The northern part of Ecuador overlies the subducted part of the Carnegie Ridge and is an area where the Nazca Plate is interpreted to be strongly coupled to the South American Plate, causing an unusually large degree of intraplate deformation. The main active fault zones of Ecuador are SSW-NNE trending dextral strike-slip faults running parallel to the main subdivisions of the Andes, two major SW-NE dextral strike-slip zones, the Pallatanga and Chingual faults, and north-south trending reverse faults such as the Quito fault.

Most of the oceanic plates that formed the ocean floor of Panthalassa have been subducted and traditional plate tectonic reconstructions based on magnetic anomalies can therefore only be used for remains from the Cretaceous and later. The former margins of the ocean, however, contain allochthonous terranes with preserved Triassic–Jurassic intra-Panthalassic volcanic arcs, including Kolyma–Omolon (northeast Asia), Anadyr–Koryak (east Asia), Oku–Niikappu (Japan), and Wrangellia and Stikinia (western North America). Furthermore, seismic tomography is being used to identify subducted slabs in the mantle, from which the location of former Panthalassic subduction zones can be derived. A series of such subduction zones, called Telkhinia, defines two separate oceans or systems of oceanic plates—the Pontus and Thalassa oceans.

The Finlayson Lake district preserves the Slide Mountain Terrane which has chert, greenstone, phyllite, conglomerate and metavolcanic rocks in the Fortin Creek Group overlain by chert, limestone, argillite and quartzite as well as gabbro and ultramafic rocks. Eclogite from 270 million years provides evidence that the Slide Mountain Terrane subducted beneath the Yukon-Tanana Terrane.

Numerous thrust faults developed due to compressional strain, placing older rocks on top of younger units. In the northwest, the Luning-Fencemaker thrust fault developed in the Jurassic and thrust the Jungo terrane to the east, forming the undulating Nevadaplano. As the Farallon Plate subducted, the Sevier Orogeny generated large mountain ranges in the east.

The Insular Mountain range covers some 133,879 km2 (51,691 sq mi). It experiences frequent seismic activity, with the Pacific Plate and the Juan de Fuca Plate being subducted into the Earth's mantle. Large earthquakes have led to collapsing mountains, landslides and fissures. During the last glacial period, ice enclosed nearly all of these mountains.

Chile lies above the destructive plate boundary, where the Nazca Plate is being subducted beneath the South American Plate. In the Tarapacá region the plates converge at a rate of 78 mm per year. This boundary is associated with many large earthquakes, both along the plate interface and within the downgoing slab (Nazca Plate).

Volcanic activity in the belt is usually linked to the dehydration of the subducting slabs, which causes water and other subducted components to be added to the overlying mantle. In the case of the CVZ, this addition generates magmas that are further modified by the thick crust in the area, forming andesites, dacites and rhyolites.

A collision zone occurs when tectonic plates meeting at a convergent boundary both bearing continental lithosphere. As continental lithosphere is usually not subducted due to its relative low density, the result is a complex area of orogeny involving folding and thrust faulting as the blocks of continental crust pile up above the subduction zone.

The Juan de Fuca Plate system has its origins with Panthalassa's oceanic basin and crust. This oceanic crust has primarily been subducted under the North American Plate, and the Eurasian Plate. Panthalassa's oceanic plate remnants are understood to be the Juan de Fuca, Gorda, Cocos and the Nazca plates, all four of which were part of the Farallon Plate.

Moreover, it has been proposed that the marine transgression is related to extensional tectonic setting, such that the Late Albian has detached from India and has started to drift from the Gondwana supercontinent, Also, the Neotethys has subducted northwards beneath Asia. This event is accompanied with the Late Cretaceous global eustatic sea-level high stand as well.

A small portion of the continental crust may be subducted until the slab breaks, allowing the oceanic lithosphere to continue subducting, hot asthenosphere to rise and fill the void, and rebound of the continental lithosphere. Evidence of this continental rebound include ultrahigh pressure metamorphic rocks which form at depths of that are exposed at the surface.

DOI: 10.1038/NGEO656. If continental material is subducted within a confined channel, the material tends to undergo circulation driven by tractions along the base of the channel and the relative buoyancy of rocks inside the channel;Zheng, Y.F., Zhao, Z.F., Chen, Y.X., 2013. Continental subduction channel processes: Plate interface interaction during continental collision. Chinese Science Bulletin 58, 4371-4377.

There are many faults in the Aegean Sea and the adjacent coastal areas of Anatolia, caused by the African Plate being subducted beneath the Aegean Sea Plate. These faults result in frequent earthquakes. Ephesus, which sustained considerable damage in the 262 AD earthquake, was also struck by earthquakes in AD 17, sometime before AD 30, c. AD 42, c.

Volcanic bomb erupted from Pauliberg volcano Volcanoes were active until 15 million years ago, as a result of volatiles subducted with the Penninic Ocean crust melting rock, found in Bad Gleichenberg and Weitendorf, villages both in Styria. Basalts erupted at Mount Pauliberg, approximately 11 million years ago and small basalt flows erupted into the early Quaternary.

The tectonic setting of the intrusive belt is unusual because it is associated in space and time within the zone of compressional mountain building that defined the Taconic Orogeny. At that time, the western half of the Iapetus Ocean lying along the east coast of North America was closing, being subducted beneath the Taconic (or Bronson Hill) Island Arc.

Back-arc Rifting System in Middle Mesozoic In Middle-Jurassic, Hainan Island was in place at the back-arc rifting system. Until Early Cretaceous, the Paleo-pacific oceanic plate was then subducted under the South China Block in the northwest. As a result, the intrusive activities took place frequently as well. The granitoids produced in Jurassic, ca.

At the early Paleozoic (around 545-440 million years ago), the Erlangping island arc subducted beneath the North China Block (obduction), so that those arc-related ophiolite with melange was moved to the surface of the earth. Within an ophiolite sequence, ultramafic rock, pillow basalt. sill basalt and a small amount of chert can be found.

As magma forms, the initial melt is composed of the more silicic phases that have a lower melting point. This leads to partial melting and further segregation of the lithosphere. In addition the silicic continental crust is relatively buoyant and is not normally subducted back into the mantle. So over time the continental masses grow larger and larger.

They substantiated, based on geochemistry, that the lavas were derived by subduction (calc-alkaline). Radiometric dates also showed that the volcanism falls into two groups that range from 20 million years to recent. They also showed that the youngest volcanism consists primarily of adakites (partial melts from the subducted slab) whereas the older volcanism is normal calc-alkaline lavas.

Southwestern Mexico lies above the convergent boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr. The dip of the subducting slab is about 15° as defined by focal mechanisms and earthquake hypocenters. Seismicity in this area is characterised by regular megathrust earthquakes along the plate interface.

Erimo Seamount (also known as Sisoev Seamount) is a seamount off Hokkaido, Japan. Located close to the intersection between the Kuril-Kamchatka and Japan Trenches, it is in the process of being subducted. The Cretaceous seamount formed 100-120 million years ago and is covered by a limestone cap. Tiltmeters have been installed on its top.

The Celebes Sea is underlain by an oceanic plate with a mid oceanic spreading in the center part. This plate is subducted to the south and north. A number of seismic surveys and research drillings were done in this area to gather geological information. The geology of Sulawesi Sea has been described in the Geology of Indonesia Wikibook.

The Moa Plate was an ancient oceanic plate that formed in the Early Cretaceous south of the Pacific–Phoenix Ridge. The Moa Plate was obliquely subducted beneath the Gondwana margin, and material accreted from it is now part of the Eastern Province of New Zealand. The plate was named in 2001 by Rupert Sutherland and Chris Hollis.

Russian researchers concluded that hydrocarbon mixes would be created within the mantle. Experiments under high temperatures and pressures produced many hydrocarbons—including n-alkanes through C10H22—from iron oxide, calcium carbonate, and water. Because such materials are in the mantle and in subducted crust, there is no requirement that all hydrocarbons be produced from primordial deposits.

Tectonic evolution of the San Andreas Fault. The San Andreas began to form in the mid Cenozoic about 30 Mya (million years ago).Atwater, T., 1970, Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of Western North America At this time, a spreading center between the Pacific Plate and the Farallon Plate (which is now mostly subducted, with remnants including the Juan de Fuca Plate, Rivera Plate, Cocos Plate, and the Nazca Plate) was beginning to reach the subduction zone off the western coast of North America. As the relative motion between the Pacific and North American Plates was different from the relative motion between the Farallon and North American Plates, the spreading ridge began to be "subducted", creating a new relative motion and a new style of deformation along the plate boundaries.

Drumheller Channels, part of the Channeled Scablands formed by the Missoula Floods When the rifting of Pangaea, due to the process of plate tectonics, pushed North America away from Europe and Africa and into the Panthalassic Ocean (ancestor to the modern Pacific Ocean), the Pacific Northwest was not part of the continent. As the North American continent moved westward, the Farallon Plate subducted under its western margin. As the plate subducted, it carried along island arcs which were accreted to the North American continent, resulting in the creation of the Pacific Northwest between 150 and 90 million years ago. The general outline of the Columbia Basin was not complete until between 60 and 40 million years ago, but it lay under a large inland sea later subject to uplift.

The Boring Lava Field represents the youngest episode of volcanism within the Cascade forearc, and while there is no evidence that they were associated with a slab window (a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone and plate divergence at the ridge and convergence at the subduction zone continue, causing the ridge to be subducted), they likely interacted with the regional mantle wedge. The Boring Lava Field shows a similar composition to the High Cascades that run through Oregon and southern Washington state, with Pliocene to Pleistocene basalt lava flows and breccias. It was active during the late Tertiary into the early Quaternary. Within the field, lava shows a diverse composition overall, varying from low-K, tholeiitic to high-K, calc-alkaline eruptive products.

This hypothesis then assumes that a crustal spreading zone is also underpinned by a corresponding asthenospheric mantle spreading zone or upwelling of warmer material. The gap is created because instead of the old subducted plate continuing to sink, it quickly melts, allowing the asthenospheric upwelling zone to act directly on the underside of the overriding plate, heating it and causing it to spread apart. The fast melt is because the portion of the subducted plate nearest the spreading zone is thin and still warm from its recent creation. The slab gap hypothesis goes on to state that the upwelling can form very deep cracks, which in turn lets very fluid basalt lava quickly spread over the land surface forming shield volcanoes and vast volcanic plains called "flood basalts".

The understanding of the Farallon Plate is rapidly evolving as details from seismic tomography provide improved details of the submerged remnants.. Since the North American west coast shows a convoluted structure, significant work has been required to resolve the complexity. In 2013 a new and more nuanced explanation emerged, proposing two additional now-subducted plates which would account for some of the complexity..

He concluded that the cause of the earthquake was a megathrust reaction in the Aleutian Trench, a result of the Alaskan continental crust overlapping the Pacific oceanic crust. This meant that the Pacific crust was being forced downward, or subducted, beneath the Alaskan crust. The concept of subduction would play a role in the development of the plate tectonics theory.

On the border of the Pacific Plate and the Okhotsk and Philippine Sea Plates is one of the most active deep focus earthquake regions in the world, creating many large earthquakes including the 8.3 2013 Okhotsk Sea earthquake. As with many places, earthquakes this region are caused by internal stresses on the subducted Pacific Plate as it is pushed deeper into the mantle.

One possible model includes Armorica as part of the Hun superterrane, while other show it moving separately. The Rheic Ocean closed during the Devonian and early Carboniferous, as the oceanic crust was subducted. The Variscan orogeny marks the final closure of the Rheic Ocean as the various continental fragments, including Armorica, collided with Laurussia towards the end of the Carboniferous.

Near the peninsula lies the Chile Triple Junction where the tectonic plates of Antarctica, South America and Nazca meets. Taitao ophiolite and other geological features are associated to the triple junction. As the Chile Rise has subducted beneath the South American Plate at Taitao Peninsula it has caused an sequence of three ridge–continent collisions starting about 5 million years ago.

Sumatra lies above the convergent plate boundary, where the Australia Plate is being subducted beneath the Sunda Plate along the Sunda megathrust. The convergence on this part of the boundary is highly oblique and the strike-slip component of the plate motion is accommodated along the right-lateral Great Sumatran Fault. Movement on the Sunda megathrust has caused many great earthquakes.

The Juan Fernández hotspot is marked 16 on map. The Juan Fernández hotspot is a volcanic hotspot located in the southeastern Pacific Ocean. The hotspot created the Juan Fernández Ridge which includes the Juan Fernández Archipelago and a long seamount chain that is being subducted in the Peru–Chile Trench at the site of Papudo giving origin to the Norte Chico Volcanic Gap.

There has been little geomorphic affect to the Peru-Chile trench due to the ridge subduction beyond a shallowing from above the ridge location. However, this is a tectonic erosion margin. There is no accretionary wedge forming in the trench, and what sediment is found there is from continental sources, based on fossil assemblage. The calcareous ooze blanketing Nazca Ridge is completely subducted.

Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.

Carbon can leave the geosphere in several ways. Carbon dioxide is released during the metamorphism of carbonate rocks when they are subducted into the earth's mantle. This carbon dioxide can be released into the atmosphere and ocean through volcanoes and hotspots. It can also be removed by humans through the direct extraction of kerogens in the form of fossil fuels.

Makran subduction zone, Persian GulfArabian Sea The Makran Trench is the physiographic expression of a subduction zone along the northeastern margin of the Gulf of Oman adjacent to the southwestern coast of Balochistan of Pakistan and the southeastern coast of Iran. In this region the oceanic crust of the Arabian Plate is being subducted beneath the continental crust of the Eurasian Plate.

In the context of the Plate hypothesis, the high ratios are explained by preservation of old material in the shallow mantle. Ancient, high 3He/4He ratios would be particularly easily preserved in materials lacking U or Th, so 4He was not added over time. Olivine and dunite, both found in subducted crust, are materials of this sort. Other elements, e.g.

The transition between the two volcanic phases was characterized by a decrease in volcanic activity. The Juan Fernandez Ridge was subducted in the region between 11–8 million years ago according to Kraemer et al. 1999. This may have generated a flat subduction profile and thus allowed volcanic arc-like volcanism to occur in the region behind the actual volcanic arc.

Fragments of Piemont- Ligurian oceanic crust were preserved as ophiolites in the Penninic nappes of the Alps and the Tuscan nappes of the Apennines. These nappes were subducted, sometimes to great depths in the mantle, before being obducted again. Due to the high pressures at these depths, much of the material had been metamorphosed in the blueschist or eclogite facies.

Roughly 30 Mya the Farallon Plate subducted beneath the North American Plate, segmenting the Pacific Farallon Ridge. This subduction created new microplates and new ridges, including the Juan de Fuca Plate and Juan de Fuca Ridge. As the Juan de Fuca Plate continued to subduct underneath the North American Plate it also segmented, creating the Gorda Plate and Gorda Ridge.

Evidence of the existence of the Farallon Trench and past subduction of the Farallon Plate is evident in specific geologic units observed along paleo-coastlines of the west coast of the United States and California continental region. Late Cretaceous–Paleogene magma can be seen overlying subhorizontally subducted sediments from the Farallon Plate as far inland as Utah and Arizona. The earliest record of subhorizontal subduction of the Farallon slab is the extinguishing of magmatism in the Sierra Nevada batholith of California roughly 85 Ma. As the Farallon Plate subducted below the California continental margin an accretionary wedge was formed in the trench, which yielded unique rock types as a result of regional metamorphism. The formation of Franciscan Melange and blueschist units along paleo-coastlines resulted from this subduction and are direct evidence of the Farallon Plate's past existence.

When Ganderia was finally accreted to Laurentia during the Late Ordovician and Silurian large scale magmatism accompanied its subduction. Its accretion to Laurentia during the Late Ordovician closed large parts of the Iapetus Ocean and the accretion of its trailing edge resulted in the Salinic orogeny (the closure of the Tetagouche–Exploits back-arc basin). Avalonia was subsequently subducted beneath Ganderia during the Silurian and Devonian.

Isluga is part of the Andean Volcanic Belt, the volcanic zone on the western side of South America where the Nazca plate is subducted beneath the South American plate. Isluga is part of the segment named the Central Volcanic Zone. In the Tarapaca region other volcanoes have been active in the Holocene, such as Guallatiri, Parinacota and Taapaca. There are several volcanic units in the Isluga area.

The subducting slab undergoes backward sinking due to the negative buoyancy forces causing a retrogradation of the trench hinge along the surface. Upwelling of the mantle around the slab can create favorable conditions for the formation of a back-arc basin. Seismic tomography provides evidence for slab rollback. Results demonstrate high temperature anomalies within the mantle suggesting subducted material is present in the mantle.

Within the context of plate tectonics the city lies at a convergent margin where Nazca Plate in the Pacific is subducted beneath the South American Plate. Topographically Valdivia lies in a depression amidst the Chilean Coast Range. The basement rocks that crops out in the hills around the city are of metamorphic type. The city itself is chiefly built upon terraces made up of hardened volcanic sand.

The high topography is around two major culminations: Jabal Akhdar and Saih Hatat, which are large scale anticlines. The Saih Hatat culmination contains eclogite in the northeast at As Sifah. These rocks were subducted to about 80 km (50 mi) depth into the mantle, and then exhumed back to the surface. This exhumation event created possibly the largest megasheath fold on Earth, the Wadi Mayh megasheath fold.

The state of Guerrero lies adjacent to part of the Middle America Trench where the Cocos Plate is being subducted beneath the North American Plate. The convergence between these plates at this location is about 65 mm per year. There have been many large and destructive earthquakes in the past, such as the M 7.6 1911 Guerrero earthquake. The Guerrero seismic gap is a ca.

Subduction-related magmatism took place near the Ryoke belt. No marked tectonics occurred in the Abunkuma belt after the change of the subducted plate. The discovery of an extinct Jurassic–Cretaceous spreading system in the north-west Pacific led to the introduction of the extinct Kula Plate in 1972. The Izanagi Plate was subsequently introduced in 1982 to explain the geometry of this spreading system.

The undersea earthquake struck on a Sunday afternoon and lasted about 45 seconds. The shock affected the Peruvian regions of Ancash and La Libertad. The epicenter was located off the coast of Casma and Chimbote in the Pacific Ocean, where the Nazca Plate is being subducted beneath the South American Plate. It had a moment magnitude of 7.9 and a maximum Mercalli intensity of VIII (Severe).

The back-arc deformation may be either extensional or compressional. The overriding plate will shorten when its motion is directed towards the trench, resulting in a compression of the back- arc region. This type of deformation is associated with a shallow dipping subducted slab. Inversely, an overriding plate moving away from the trench will result in extension, and a back-arc basin will form.

"Understanding plate motions", USGS. Retrieved 26 June 2013.Britannica On the eastern side of the rise the eastward moving Cocos and Nazca plates meet the westward moving South American Plate and the North American Plate and are being subducted under them. The belt of volcanos along the Andes and the arc of volcanoes through Central America and Mexico are the direct results of this collision.

Large values of the BLT are typically found in the equatorial regions and can be as high as 50 m. Above the barrier layer, the well mixed layer may be due to local precipitation exceeding evaporation (e.g. in the western Pacific), monsoon related river runoff (e.g. in the northern Indian Ocean), or advection of salty water subducted in the subtropics (found in all subtropical ocean gyres).

Plate convergence continued through the Mesozoic, with the addition of the Black Rock-Jackson terrane in the Jurassic and Cretaceous now present in northwest Nevada. The terrane rocks are volcanic or sedimentary and originated offshore in the Paleozoic and Triassic. By the end of the Mesozoic, dry land conditions prevailed across Nevada. The Farallon Plate transported the terranes and subducted under North America in the Cretaceous.

Because IOCMs are far removed from continents they are not affected by the large volume of alluvial and glacial sediments. The consequent thin sedimentary cover makes it much easier to study arc infrastructure and determine the mass and composition of subducted sediments. Active hydrothermal systems found on the submarine parts of IOCMs give us a chance to study how many of earth's important ore deposits formed.

Ziegler (1990), pp. 37-38 During the Sudetic (main) phase of the Hercynian orogeny (330-320 million years ago, Late-Visean and Namurian/Serpukhovian) compressional tectonics had the upper hand again. In the Namurian age full-scale continental collision between Laurussia and Gondwana resulted in the destruction of the last oceanic crust of the basin. Its sedimentary fill was, however, not (totally) subducted but instead thrust northward.

The geology of Hong Kong is dominated by igneous rocks. They are rocks related to volcanic eruptions. During the middle Jurassic to the early Cretaceous period, Hong Kong was right at the convergent plate boundary where the Paleo-Pacific oceanic plate subducted beneath the Eurasian continental plate. The oceanic plate carried sea water into the hot lower crust, which lowered the melting point of the crust.

Large values of the BLT are typically found in the equatorial regions and can be as high as 50 m. Above the barrier layer, the well mixed layer may be due to local precipitation exceeding evaporation (e.g. in the western Pacific), monsoon related river runoff (e.g. in the northern Indian Ocean), or advection of salty water subducted in the subtropics (found in all subtropical ocean gyres).

Central Chile lies on the destructive plate boundary where the Nazca Plate is being subducted beneath the South American Plate. The rate of convergence at this boundary in central Chile is about 74 mm per year. The boundary has a long history of destructive earthquakes and damaging tsunamis. Events occur on the plate interface and within both the subducting slab and the over-riding plate.

Imbabura is a volcano in the southern Ring of Fire. As the Nazca Plate is subducted beneath the South American Plate, the former melts with exposure to the hotter asthenosphere. This melted rock, which is less dense than the crust above it, rises to the surface. The result is an arc of volcanoes, which includes Imbabura, 100–300 km away from the subduction zone.

The primary tectonic driving force behind this explosive volcanic activity is slab rollback. During the Laramide orogeny, the subducting Farallon Plate subducted at a very shallow angle. When this stopped, the mantle wedge was opened up, and the result was the flare-up. The specifics of this opening, including possible windows or buckling of the plate, can explain specific volcanic trends within the flare-up.

Today the Japanese archipelago is considered a mature island arc and is the result of several generations of subducting plates. Approximately 15,000 km of oceanic floor has passed under the Japanese area in the last 450 million years, with most being fully subducted. Japan is situated in a volcanic zone on the Pacific Ring of Fire. Frequent low intensity earth tremors and occasional volcanic activity are felt throughout the islands.

As data accumulated, a common view developed that one large oceanic plate, the Farallon plate, acted as a conveyor belt, conveying terranes to North America's west coast, where they accreted. As the continent overran the subducting Farallon plate, the denser plate became subducted into the mantle below the continent. When the plates converged, the dense oceanic plate sank into the mantle to form a slab below the lighter continent..

Soapstone Soapstone (also known as steatite or soaprock) is a talc-schist, which is a type of metamorphic rock. It is composed largely of the magnesium rich mineral talc. It is produced by dynamothermal metamorphism and metasomatism, which occur in the zones where tectonic plates are subducted, changing rocks by heat and pressure, with influx of fluids, but without melting. It has been a medium for carving for thousands of years.

Geophysical studies in the early 21st century posit that large pieces of the lithosphere have been subducted into the mantle as deep as 2900 km to near the core-mantle boundary, while others "float" in the upper mantle, while some stick down into the mantle as far as 400 km but remain "attached" to the continental plate above, similar to the extent of the "tectosphere" proposed by Jordan in 1988.

Beneath the inner trench wall, the two plates slide past each other along the subduction decollement, the seafloor intersection of which defines the trench location. The overriding plate typically contains a volcanic arc and forearc region. The volcanic arc is caused by physical and chemical interactions between the subducted plate at depth and asthenospheric mantle associated with the overriding plate. The forearc lies between the trench and the volcanic arc.

The Helvetic nappes consist of Mesozoic sedimentary rocks deposited on the former southern continental margin of the European plate. A narrow ocean, the Valais Ocean, existed south of Central Europe in the Mesozoic. This later developed into a convergent plate boundary where the European plate subducted beneath the Apulian plate. The sedimentary facies of the rocks from this age thus becomes deeper marine when the rocks were deposited further south.

As the oceanic crust carrying the terrane subducted under the North American plate, the terrane accreted onto the North American Plate and the limestone was subjected to heat and pressure that metamorphosed it to marble. Further tectonic movements eventually lifted the marble to about above sea level. The marble block containing the cave is at least long, wide, and about high. The cave's creation took place long after the marble formed.

Their motion can cause dynamic uplift and subsidence of the Earth's surface, forming shallow seaways and potentially rearranging drainage patterns. Geologists have imaged slabs down to the seismic discontinuities between the upper and lower mantle and to the core–mantle boundary. About 100 slabs have been described at depth, and where and when they subducted. Slab subduction is the mechanism by which lithospheric material is mixed back into the Earth's mantle.

On the closing phase of the classic Wilson cycle, two continental or smaller terranes meet at a convergent zone. As the two masses of continental crust meet, neither can be subducted as they are both low density silicic rock. As the two masses meet, tremendous compressional forces distort and modify the rocks involved. The result is regional metamorphism within the interior of the ensuing orogeny or mountain building event.

However, the previously subducted parts will remain in place, coupled with the North American Plate. A similar process to this is taking place in the Rivera triple junction where small ephemeral plates were also formed. The Explorer ridge is in the process of becoming extinct however, and high seismicity in the Explorer plate indicates that it is being severed by the establishment of this new simpler plate boundary configuration.

Continental collisions began to form the supercontinent Pangea leading to subduction along the western margin of Laurentia. As plates subducted, they spurred intense volcanic and tectonic activity, and volcanic island arcs and carbonate platforms accreted against the western shore. Dozens of terranes accumulated over 250 million year and many rock units were thrust on top of others as thrust sheets along thrust faults. Large granite bodies formed from magma.

Slab pull is therefore most widely thought to be the greatest force acting on the plates. In this current understanding, plate motion is mostly driven by the weight of cold, dense plates sinking into the mantle at trenches. Recent models indicate that trench suction plays an important role as well. However, the fact that the North American Plate is nowhere being subducted, although it is in motion, presents a problem.

It is part of a subduction zone, also known as the Lesser Antilles subduction zone, where the oceanic crust of the South American Plate is being subducted under the Caribbean Plate. This subduction process formed a number of volcanic islands, from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. The Lesser Antilles Volcanic Arc includes nineteen 'active' volcanoes.General Information.

Many of Indonesia's islands, including Sumatra, are situated within a zone of high seismic activity known as the Ring of Fire. Along the Sunda megathrust, the Indo-Australian Plate is being subducted beneath the Eurasian plate. The subduction creates regular earthquakes, many of them of megathrust type. Specifically the Sumatran segment is currently experiencing a period of increased activity that began with the catastrophic 2004 Indian Ocean earthquake.

Puerto Rico lies at the highly oblique convergent boundary between the Caribbean Plate and the North American Plate. A separate Puerto Rico–Virgin Islands microplate has been identified based on GPS observations. To the north the North American Plate is being subducted beneath this microplate along the Puerto Rico Trench. To the south of Puerto Rico the microplate is being thrust southwards over the Caribbean Plate along the Muertos Thrust system.

The most stable terrain is on the western side: Liguria, Tuscany, Umbria and Lazio. The Apennines are slumping away to the northeast into the Po Valley and the Adriatic foredeep; that is, the zone where the Adriatic floor is being subducted under Italy. Slides with large translational or rotational surface movements are most common; e.g., a whole slope slumps into its valley, placing the population there at risk.

During the Palaeozoic era at least a few thousand kilometres of ocean floor were subducted, taking of the order of a hundred million years. Sediments were deposited in the ocean floor in the form of fans formed by turbidity currents off the side of a continental slope. The flow was in the northerly direction, indicating that the continental slope was to the south. These deposits occurred during the Ordovician period.

Regional metamorphism at extreme conditions: Implications for orogeny at convergent plate margins. Journal of Asian Earth Sciences 145, 46-73. Zeolite and prehnite-pumpellyite facies assemblages may or may not be present, thus the onset of metamorphism may only be marked by blueschist facies conditions. Subducting slabs are composed of basaltic crust topped with pelagic sediments; however, the pelagic sediments may be accreted onto the forearc-hanging wall and not subducted.

The Lesser Antilles are an island arc formed above the destructive plate boundary where the North American Plate is being subducted beneath the Caribbean Plate at a rate of about 2 cm per year. Historical earthquakes in this region include large megathrust earthquakes on the plate interface, such as those in 1839 and 1843, and smaller intraplate earthquakes within the arc itself, associated with oblique convergence on the plate boundary.

Northern Chilean mineral resources are a major economic resources, and the country is the leading producer of copper, lithium and molybdenum. Most of these mineral deposits were created from magmatic hydrothermal activity. The water required to form those deposits derived from the subducted slab of the oceanic crust beneath the Andes. The Chilean Easter Island and Juan Fernández Archipelago are volcanic hotspot islands in the eastward-moving Nazca plate.

The former crust of Greater Adria now forms parts of the Alps, the Apennines, the Balkans, Anatolia, and the Caucasus. Including the Iberian Microcontinent, it also forms Iberia, the Pyrenees, and Occitania. Excluding Iberia, the only part remaining relatively intact is a strip running from Turin and Istria to the Heel of Italy, under the Adriatic. Most of the subducted remains are some under Europe, deep in the earth.

Around five hundred million years ago, an arcuate chain of volcanic islands collided with proto-North America. The North American plate was subducted under the chain of islands. The islands overrode the edge of North America, creating the Highlands and Kittatinny Valley which is of the Ordovician Martinsburg Shale. Quartz and the sedimentary conglomerate was transported to an inland sea, which was over part of the Martinsburg shale.

The Tonga Trench is the northern half of the Tonga-Kermadec subduction system which extends between New Zealand and Tonga. The Tonga Trench is an oceanic trench located in the south-west Pacific Ocean. It is the deepest trench of the Southern Hemisphere and the second deepest on Earth. The fastest plate tectonic velocity on Earth occurs here, as the Pacific Plate is being subducted westward in the trench.

The region between the Tonga trench and the Lau back-arc basin, the Tonga-Kermadec Ridge, moves independently from the Australian and Pacific plates and is subdivided into several small plates, the Tonga, Kermadec, and Niuafo'ou plates. The Tonga Plate is facing the Tonga Trench. The Tonga Trench-Arc system is an extension-dominated, non- accretionary convergent margin. The Pacific Plate is being subducted westward in the trench.

Coastal regions of Peru and Chile lie above the convergent boundary, where the Nazca Plate is being subducted beneath the South American Plate along the line of the Peru–Chile Trench. The rate of convergence across this boundary is measured at about per year. This boundary has been the site of many great megathrust earthquakes, in addition to events caused by faulting within both the subducting and over-riding plates.

The precipitation and burial of calcium carbonate in the ocean removes particulate inorganic carbon from the ocean and ultimately forms limestone. On time scales greater than 500,000 years Earth's climate is moderated by the flux of carbon in and out of the lithosphere. Rocks formed in the ocean seafloor are recycled through plate tectonics back to the surface and weathered or subducted into the mantle, the carbon outgassed by volcanoes.

Subduction zones are important for several reasons: # Subduction Zone Physics: Sinking of the oceanic lithosphere (sediments, crust, mantle), by contrast of density between the cold and old lithosphere and the hot asthenospheric mantle wedge, is the strongest force (but not the only one) needed to drive plate motion and is the dominant mode of mantle convection. # Subduction Zone Chemistry: The subducted sediments and crust dehydrate and release water-rich (aqueous) fluids into the overlying mantle, causing mantle melting and fractionation of elements between surface and deep mantle reservoirs, producing island arcs and continental crust. Hot fluids in subduction zones also alter the mineral compositions of the subducting sediments and potentially the habitability of the sediments for microorganisms. # Subduction zones drag down subducted oceanic sediments, oceanic crust, and mantle lithosphere that interact with the hot asthenospheric mantle from the over-riding plate to produce calc- alkaline series melts, ore deposits, and continental crust.

The Pacific plate subducts in the IBM trench, so understanding what is subducted beneath IBM requires understanding the history of the western Pacific. The IBM arc system subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south. It is not possible to directly know the composition of subducted materials presently being processed by the IBM Subduction Factory – what is now 130 km deep in the subduction zone entered the trench 4 – 10 million years ago. However, the composition of the western Pacific seafloor-oceanic crust – sediments, crust, and mantle lithosphere – varies sufficiently systematically that, to a first approximation, we can understand what is now being processed by studying what lies on the seafloor east of the IBM trench. The Pacific plate seafloor east of the IBM arc system can be subdivided into a northern portion that is bathymetrically ‘smooth’ and a southern portion that is bathymetrically rugged, separated by the Ogasawara Plateau.

Both Sangihe and Halmahera are exposed to the surface while the Molucca Sea plate is completely subsumed below these two microplates. The southern boundary of the Molucca Sea Plate is also the boundary of the Philippine Sea Plate and the Australian Plate, and is moving northwards. Since the Sangihe Plate and the Halmahera Plate are in continuity with the Molucca Sea Plate, this implies all three slabs are moving northward in mantle with the Australian Plate. A broad high-velocity zone beneath the Bird's Head Plate at 400–600 km depth is interpreted by R Hall and W Spakman as indicating a remnant slab subducted below the Halmahera Plate, and another broad high-velocity zone beneath the Celebes Sea at 700–1000 km depth is interpreted as a remnant slab below the Sangihe Plate, both remnants having originated from a slab subducted beneath the Philippine-Halmahera Arc 45 Ma to 25 Ma ago.

The Pacific Plate is being subducted under the Australian Plate, compressing the Wellington Region, and causing the North Island Fault System, and a series of SSW-NNE trending basins and ranges, including the Tararua and Rimutaka Ranges, and the Wairarapa- Masterton Basin. Successively newer rocks have been accreted to the east coast. The Wellington Region is prone to major earthquakes, the biggest in historical times being the magnitude 8.2 Wairarapa earthquake on 23 January 1855.

The Kula-Farallon Ridge was an ancient mid-ocean ridge that existed between the Kula and Farallon plates in the Pacific Ocean during the Jurassic period. There was a small piece of this ridge off the Pacific Northwest 43 million years ago. The rest of the ridge has since been subducted beneath Alaska. In its early stages of development, the Kula-Farallon Ridge sheared pieces of oceanic rock off the coast of California.

These quakes define inclined zones of seismicity known as Wadati–Benioff zones which trace the descending lithosphere. Seismic tomography has helped detect subducted lithosphere, slabs, deep in the mantle where there are no earthquakes. About one hundred slabs have been described in terms of depth and their timing and location of subduction. The great seismic discontinuities in the mantle, at depth and , are disrupted by the descent of cold slabs in deep subduction zones.

This supports the conjecture that the variations were due to an increasing "crustal" component in subducted sediments as the continental blocks in the north were approached (China and Taiwan). The sediment thicknesses increased toward the north along the trench. The geochemistry and tectonic setting of the southern Luzon arc has been studied in detail. The geochemistry suggested that continental crust (probably from sediments) played an important role in the Macolod corridor and the Mindoro segments.

Hotspot volcanoes are considered to have a fundamentally different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries. When one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the over-riding plate, and this water mixes with the rock, thus changing its composition causing some rock to melt and rise.

If that subducted eclogite is subsequently carried upward with peridotite, as in a mantle plume, it may melt by decompression melting (see discussion in igneous rock) at lower temperature than the accompanying peridotite. Eclogite-derived melts may be common in the mantle, and contribute to volcanic regions where unusually large volumes of magma are erupted. The eclogite melt may then react with enclosing peridotite to produce pyroxenite, which in turn melts to produce basalt.

When the last of the Mid-Atlantic Ridge is subducted beneath the Americas, the Atlantic Ocean is predicted to close rapidly. At 200 million years in the future, the Atlantic is predicted to have closed. North America is predicted to have already collided with Africa, but be in a more southerly position than where it drifted. South America is predicted to be wrapped around the southern tip of Africa, completely enclosing the Indo-Atlantic Ocean.

Creation (accretion) occurs as mantle is added to the growing edges of a plate. This hot added material cools down by conduction and convection of heat. At the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction at an ocean trench. This subducted material sinks to some depth in the Earth's interior where it is prohibited from sinking further.

It separated the London-Brabant Massif to the north from the Normannian and Mid-German Highs to the south.As in Ziegler (1990), pp. 31-32 and enclosure 11 In the Middle Devonian (from 390 million years ago) a subduction zone existed south of Laurussia, where oceanic lithosphere of the Rheic Ocean subducted beneath the Mid-German/Normannian highs. Volcanism above the subduction zone created a cordillera-type mountain chain, the Ligerian cordillera.

Sulfur has been found encased in ejecta, which are often covered in volcanic glass from the interaction between seawater and lava. Volcanic rocks are porphyritic and contain many vesicles. The magma erupted at NW Rota-1 is among the most water rich of the entire Mariana Arc. The formation of NW Rota-1 magmas appears to involve the melting of subducted, water-bearing sediments and the interaction of the resulting melts with the mantle wedge.

Smaller rings corresponds to larger features and vice versa. The tectonic settings of volcanoes on Earth and Mars are very different. Most active volcanoes on Earth occur in long, linear chains along plate boundaries, either in zones where the lithosphere is spreading apart (divergent boundaries) or being subducted back into the mantle (convergent boundaries). Because Mars currently lacks plate tectonics, volcanoes there do not show the same global pattern as on Earth.

On the eastern side the eastward moving Explorer Plate is being subducted under the North American Plate. The belt of volcanoes along the Pacific Ranges are the direct results of this collision. The western side of the Explorer Ridge is associated with the northwest trending Pacific Plate which has formed the Queen Charlotte Fault, an active transform fault along the coast of British Columbia and southeast Alaska. The Explorer Ridge is also seismically active.

By the end of the Triassic, the Peninsular Terrane had also joined the Wrangellia composite terrane. A subduction zone existed on the west side of Wrangellia. Seafloor rocks too light to be subducted were compressed against the west edge of Wrangellia; these rocks are now known as the Chugach Terrane. A complex fault system, known as the Border Ranges Fault, is the modern expression of the suture zone between Wrangellia and Chugach Terranes.

The Rio Grande rift's tectonic evolution is fairly complex. The fundamental change in the western margin of the North American plate from one of subduction to a transform boundary occurred during Cenozoic time. The Farallon plate continued to be subducted beneath western North America for at least 100 million years during Late Mesozoic and early Cenozoic time. Compressional and transpressional deformation incurred by the Laramide Orogeny lasted until about 40 Ma in New Mexico.

Ancient recycled mantle lithosphere in the Hawaiian plume: Osmium/Hafnium isotopic evidence from peridotite mantle xenoliths. Earth and Planetary Science Letters. This is thought to evidence of subducted ancient high Re/Os basaltic crust that is being recycled back into the mantle. This combination of radiogenic (187Os that was created by decay of 187Re) and nonradiogenic melts helps to support the theory of at least two Os-isotopic reservoirs in the mantle.

Only on Easter Island is the Sala y Gómez Ridge dry land. The volcanic Juan Fernández Islands were created by a hotspot in the Earth's mantle penetrating the Nazca Plate. The islands were carried eastward as the plate subducted the South American continent. Radiometric dating indicates that Santa Clara is the oldest of the islands (at 5.8 million years), followed by Robinson Crusoe (3.8–4.2 million years) and Alexander Selkirk (1.0–2.4 million years).

The Western Gneiss Region in northern Norway is composed of 1650–950 Ma-old gneisses overlain by continental and oceanic allochtons that were transferred from Laurentia to Baltica during the Scandian orogeny. The allochtons were accreted to Baltica during the closure of the Iapetus Ocean c. 430–410 Ma; Baltica's basement and the allochtons were then subducted to UHP depth c. 425–400 Ma; and they were finally exhumed to their present location c.

The processing of oceanic crust, lithosphere, and sediment through a subduction zone decouples the water-soluble trace elements (e.g., K, Rb, Th) from the immobile trace elements (e.g., Ti, Nb, Ta), concentrating the immobile elements in the oceanic slab (the water-soluble elements are added to the crust in island arc volcanoes). Seismic tomography shows that subducted oceanic slabs sink as far as the bottom of the mantle transition zone at 650 km depth.

The 2012 Guatemala earthquake occurred on November 7 at . The shock had a moment magnitude of 7.4 and a maximum Mercalli Intensity of VII (Very strong). The epicenter was located in the Pacific Ocean, south of Champerico in the department of Retalhuleu. The region is one of many earthquakes, where the Cocos Plate is being subducted along the Middle America Trench beneath the North American and the Caribbean Plates, near their triple junction.

An explanation has recently been proposed to explain this high elevation. As the Farallon plate was subducted into the mantle beneath the region, water trapped in hydrous minerals in the descending slab was forced up into the lower crust above. Within the crust this water caused the hydration of dense garnet and other phases into lower density amphibole and mica minerals. The resulting increase in crustal volume raised the elevation about one mile.

The Caribbean plate has been migrating eastward from the Pacific region and eventually collided with the South American plate in the middle Paleocene. This collision transformed the passive margin of northern South America into an active margin. The Caribbean plate had subducted significant amounts of oceanic Proto-Caribbean crust by this time and was now subducting beneath the South American crust. This boundary interaction was greatly affecting the region of northwestern South America.

The Bündner schists were deposited in the two small oceanic basins (the Valais Ocean and the Piemont-Liguria Ocean) that were located south of the European continent in the Mesozoic era. They formed a kilometers thick monotonous layer of dark clays, marbles and sandy limestones. These sediments were subducted to great depths during the Alpine orogeny. The resulting metamorphism and deformation turned them into calcareous phyllites and schists, strongly foliated rocks rich in micas.

Kokfelt et al. completed an isotopic examination of the mantle plume under Iceland and found that erupted mantle lavas incorporated lower crustal components, confirming crustal recycling at the local level. Some carbonatite units, which are associated with immiscible volatile-rich magmas and the mantle indicator mineral diamond, have shown isotopic signals for organic carbon, which could only have been introduced by subducted organic material. The work done on carbonatites by Walter et al.

Nicaragua lies above the convergent boundary where the Cocos Plate is being subducted beneath the Caribbean Plate. The convergence rate across this boundary is about 73 mm per year. There have been many large earthquakes in this part of the plate boundary, including events in 1982, 2001, 2012 and 2014. The 2001 and 2014 events were a result of normal faulting within the subducting Cocos Plate, with the others representing faulting along the plate interface.

Using recent ocean bottom seismograph studies, it has been determined that most of the seismicity occurs near the trough axis (Obana et al., 2006). Along the western area of the Nankai Trough, seismicity appears to be related to irregularities in crustal structure such as fractures generated from the subducted seafloor, including backarc basin crust of the Shikoku Basin, as well as due to serpentization of uppermost mantle beneath the overriding plate (Obana et al., 2006).

The 1946 Nankaido earthquake was unusual in its seismological perspective, with a rupture zone estimated from long-period geodetic data that was more than twice as large as that derived from shorter period seismic data. In the center of this earthquake rupture zone, scientists used densely deployed ocean bottom seismographs to detect a subducted seamount thick by wide at a depth of . Scientists propose that this seamount might work as a barrier inhibiting brittle seismogenic rupture.

Post-Pliocene migration was eventually driven through the narrow corridor (250 km) represented by the present Ionian Sea and thus separated the Adriatic and Sicilian sectors. Changes in lithospheric composition may have also contributed to differences in subduction geometry. For instance, during the first episode of subduction, thinned continental lithosphere underlying the Apenninic margin subducted beneath the Eurasian plate. However, in the second episode of subduction, it was instead Ionian oceanic lithosphere that was involved in subduction.

The andes mountains are one of the tallest.Map of the volcanic arcs in the Andes, and subducted structures affecting volcanism The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones which are separated by volcanic gaps.

The spreading South China Sea is blue. An outline of Indochina and South China is visible in the northwest of the diagram. The subduction model proposes that the proto-South China Sea formed a subduction zone to its east, which subsequently, by the process of slab pull, subducted the proto-South China Sea beneath northwest Borneo. When the Dangerous Grounds collided with the Mesozoic granites of the Schwaner Mountains in Borneo, it brought an end to the subduction.

During the Carboniferous–Permian Siberia, Kazakhstan, and Baltica collided in the Uralian orogeny to form Laurasia. The Palaezoic-Mesozoic transition was marked by the reorganisation of Earth's tectonic plates which resulted in the assembly of Pangaea, and eventually its break-up. Caused by the detachment of subducted mantle slabs, this reorganisation resulted in rising mantle plumes that produced large igneous provinces when they reached the crust. This tectonic activity also resulted in the Permian–Triassic extinction event.

Rupture velocities for tsunami earthquakes are typically about 1.0 km per second, compared to the more normal 2.5-3.5 km per second for other megathrust earthquakes. These slow rupture speeds lead to greater directivity, with the potential to cause higher run-ups on short coastal sections. Tsunami earthquakes mainly occur at subduction zones where there is a large accretionary wedge or where sediments are being subducted, as this weaker material leads to the slower rupture velocities.

Finally, supercontinent Columbia collided in the northern margin of the North China Craton at 1.8 billion years ago. Fig. 5. Tectonic evolution of the Western Block proposed by Kusky et al. (1) Wutai Arc in the east and an Exotic arc in the west subducted beneath the juvenile Western Block before 2.3 Ga. (2) Inner Mongolia-North Hebei Orogen formed as the exotic arc collided with the juvenile Western Block. (3) Supercontinent Columbia collided with the Western Block.

This steadiness can be attributed to many different causes. In the case of ridge-to-ridge transforms, the constancy is caused by the continuous growth by both ridges outward, canceling any change in length. The opposite occurs when a ridge linked to a subducting plate, where all the lithosphere (new seafloor) being created by the ridge is subducted, or swallowed up, by the subduction zone. Finally, when two upper subduction plates are linked there is no change in length.

When the subducting slab broke off (known as slab breakoff, slab pull) and fell away, the subducted crust began moving up. This led to the uplift of the thickened continental crust which led, in the Miocene, to extension. In the case of the Alps, the extension could only take place in a west–east direction because the Adriatic plate was still converging from the south. An enormous thrustzone evolved that would later become the Periadriatic Seam.

El Salvador lies above the convergent boundary where oceanic crust of the Cocos Plate is being subducted beneath the Caribbean Plate at rate of about 72 mm per year along the Middle America Trench. This boundary is associated with earthquakes resulting from movement on the plate interface itself, such as the 7.7 1992 Nicaragua earthquake, and from faulting within both the overriding Caribbean Plate and the subducting Cocos Plate, such as the 1982 El Salvador earthquake.

Tremor is commonly associated with the underground movement of magmatic or hydrothermal fluids. As a plate is subducted into the mantle, it loses water from its porespace and due to phase changes of hydrous minerals (such as amphibole). It has been proposed that this liberation of water generates a supercritical fluid at the plate interface, lubricating plate motion. This supercritical fluid may open fractures in the surrounding rock, and that tremor is the seismological signal of this process.

The highest ridge is the easternmost and the Ain flows southwards in the lowest valley, which lies towards the western side of the Jura. The westernmost ridge is again rather higher as the plain of the Saône valley is subducted below the Jurassic rocks (Dercourt). The whole has been glaciated but there is relatively little till remaining in the Jura. The lower Ain flows on the plain where there is much Pleistocene material, much of it glacial till.

The plate tectonics rock cycle is an evolutionary process. Magma generation, both in the spreading ridge environment and within the wedge above a subduction zone, favors the eruption of the more silicic and volatile rich fraction of the crustal or upper mantle material. This lower density material tends to stay within the crust and not be subducted back into the mantle. The magmatic aspects of plate tectonics tends to gradual segregation within or between the mantle and crust.

Key: N2 = Tertiary sedimentary rocks; αN2 = Tertiary volcanic rocks; αQ1 = Komitake volcano; α-δQ1 = Ashitaka volcano; βQ2 = Older Fuji volcano; αβQ2 = Younger Fuji volcano. Mount Fuji is located at a triple junction trench where the Amurian Plate, Okhotsk Plate, and Philippine Sea Plate meet. These three plates form the western part of Japan, the eastern part of Japan, and the Izu Peninsula respectively. The Pacific Plate is being subducted beneath these plates, resulting in volcanic activity.

South of the Cimmerian continent a new ocean, the Tethys Ocean, was created. By the Late Triassic, all that was left of the Paleo-Tethys Ocean was a narrow seaway. In the Early Jurassic epoch, as part of the Alpine Orogeny, the oceanic crust of the Paleo-Tethys subducted under the Cimmerian plate, closing the ocean from west to east. A last remnant of Paleo-Tethys Ocean might be an oceanic crust under the Black Sea.

Photomicrograph of a thin section of eclogite from Turkey. Green omphacite (+ late chlorite) + pink garnet + blue glaucophane + colorless phengite. Eclogite is a rare and important rock because it is formed only by conditions typically found in the mantle or the lowermost part of thickened crust. Eclogites are helpful in elucidating patterns and processes of plate tectonics because many represent the crustal rocks that were subducted to depths in excess of 35 km and then returned to the surface.

In slab pull the weight of a tectonic plate being subducted (pulled) below an overlying plate at a subduction zone drags the rest of the plate along behind it. The slab pull mechanism is considered to be contributing more than the ridge push. A process previously proposed to contribute to plate motion and the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor" due to deep convection (see image).Holmes, A., 1928.

Gillen, Con (2003) Geology and landscapes of Scotland, Harpenden. Terra Publishing. p. 95 The tectonic processes involved in the formation of the accretionary wedge, where sediment is scraped off the seafloor as a tectonic plate is subducted, has led to the formation of multiple, major, east-west faults that are now exploited by rivers and define valleys across the Southern Uplands. Levels of deformation associated with these faults is highly variable, but is pervasive in the finer-grained sediments.

At first, the Pacific plate was subducted under the Australian plate. The Alpine Fault that traverses the South Island is currently a transform fault while the convergent plate boundary from the North Island northwards is called the Kermadec-Tonga Subduction Zone. The volcanism associated with this subduction zone is the origin of the Kermadec and Tongan island archipelagos. Out of approximately of land, over are within New Zealand; the Hawaiian archipelago comprises about half the remainder.

The two peaks of metamorphic activity in the Karakum-Tajik microcontinent is associated with the time when the oceanic crust of the Turkestan Ocean subducted beneath the edge of the microcontinent. Collision with the Kazakh microcontinent produced a second pulse of metamorphism. Metamorphic rocks are present at the base of volcanic rocks, along with recrystallized limestone. Basalt lava flows, tuff, limestone and sandstone from the early and middle Carboniferous overlie these rocks, with a thickness of three kilometers.

The centre of Vancouver Island contains high mountains, such as Golden Hinde. Vancouver Island is mostly made up of volcanic and sedimentary rock which was formed offshore on the now disappeared Kula oceanic plate. Around 55 million years ago, a microplate of the Kula Plate subducted below the North American continental margin with great strain. A volcanic arc on the surface of the Kula Plate was thus accreted and fused onto the western edge of North America.

Tropical areas, Journal of Geophysical Research: Oceans, 112 (C10), 2007. For the western Pacific, the mechanism for barrier layer formation is different. Along the equator, the eastern edge of the warm pool (typically 28 °C isotherm - see SST plot in the western Pacific) is a demarcation region between warm fresh water to the west and cold, salty, upwelled water in the central Pacific. A barrier layer is formed in the isothermal layer when salty water is subducted (i.e.

This rift drives the island arc toward the subduction zone and the rest of the plate away from the subduction zone. This process is also known as trench rollback (also, hinge rollback). This is the backward motion of the subduction zone relative to the motion of the plate which is being subducted. As the subduction zone and its associated trench pull backward, the overriding plate is stretched, thinning the crust which is manifest in the back-arc basin.

The usual theory as to the origin of the Caribbean Plate was confronted by a contrasting theory in 2002. The mainstream theory holds that it is the Caribbean large igneous province (CLIP) which formed in the Pacific Ocean tens of millions of years ago. As the Atlantic Ocean widened, North America and South America were pushed westward, separated for a time by oceanic crust. The Pacific Ocean floor subducted under this oceanic crust between the continents.

The Juan de Fuca Plate is being subducted under the North American Plate, generating gradual, diverse volcanism. The Cascade Range was produced by convergence of the North American Plate with the subducting Juan de Fuca Plate. Active volcanism has taken place for approximately 36 million years; the nearby Challis Range features complexes as old as 55 mya. Most geologists believe that activity in the Cascades has been relatively intermittent, producing up to 3,000 volcanic calderas at a time.

Samples taken from Solimana are andesite and dacite, but more recently basaltic andesite was erupted as well. The rocks contain hornblende, hypersthene, and plagioclase, with additional olivine in the phreatomagmatic deposits. The geochemistry of volcanoes of the Central Volcanic Zone typically displays strong evidence of crustal contamination, which is attributed to the thick crust that has developed in this region. A granulitic basement may be a plausible origin of this contamination, with additional contribution of subducted sediments.

Located along the Cascadia accretionary marginPhilip, B., Denny, A., Solomon, E., & Kelley, D. (2016). Time‐series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon. Geochemistry, Geophysics, Geosystems,17(3), 1182-1196., sediment build-up in this region is driven by two subduction-related processes: #Scraping of sediments off of the subducting Juan de Fuca plate onto the overlying North American plate, and #Underplating of subducted sediments onto the overlying plate.

Foden, 1979, p. 49 Olivine is most present in the rocks with less than 53 percent SiO2, while it is absent in the more silica-rich volcanics, characterised by the presence of biotite phenocrysts.Foden, 1979, p. 50 The mafic series also contain titanium magnetite and the trachybasalts are dominated by anorthosite-rich plagioclase.Foden, 1979, p. 51 Rubidium, strontium and phosphorus pentoxide are especially rich in the lavas from Tambora, more than the comparable ones from Mount Rinjani.Foden, 1979, p. 56 The lavas of Tambora are slightly enriched in zircon compared to those of Rinjani.Foden, 1979, p.60 The magma involved in the 1815 eruption originated in the mantle and was further modified by melts derived from subducted sediments, fluids derived from the subducted crust and crystallization processes in magma chambers. 87Sr86Sr ratios of Mount Tambora are similar to those of Mount Rinjani, but lower than those measured at Sangeang Api. Potassium levels of Tambora volcanics exceed 3 weight percent, placing them in the shoshonite range for alkaline series.

USGS image The Juan de Fuca Plate is a tectonic plate generated from the Juan de Fuca Ridge that is subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone. It is named after the explorer of the same name. One of the smallest of Earth's tectonic plates, the Juan de Fuca Plate is a remnant part of the once-vast Farallon Plate, which is now largely subducted underneath the North American Plate.

Oaxaca lies above the convergent boundary where the Cocos Plate is being subducted beneath the North American Plate. The rate of convergence in this part of the boundary is 60 mm per year. This boundary is associated with many damaging earthquakes; along the plate interface, within the descending Cocos slab and within the overriding North American Plate. The most recent event in the same region as the 2020 earthquakes was the 2018 Oaxaca earthquake, which struck 225 km to the northwest.

During the Jurassic and Cretaceous time periods there was extensive volcanism and intrusions caused by the subduction of an oceanic plate. The western Pacific plate was subducted beneath SE China and SE Asia. The initiation of this subduction caused ophiolites to be emplaced and the development of the Pacific arc, a magmatic belt across SE Asia. Ophiolites are large blocks of oceanic crust that have been thrust onto continental crust due to compression that forms subduction type collisional plate boundaries.

Relative depth may be controlled by the age of the lithosphere at the trench, the convergence rate, and the dip of the subducted slab at intermediate depths. Finally, narrow slabs can sink and roll back more rapidly than broad plates, because it is easier for underlying asthenosphere to flow around the edges of the sinking plate. Such slabs may have steep dips at relatively shallow depths and so may be associated with unusually deep trenches, such as the Challenger Deep.

The absolute motion of the Nazca Plate has been calibrated at 3.7 cm/yr east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca Plate, which exhibits unusual flat slab subduction, is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed, and continues to form, the volcanic Andes Mountain Range. Deformation of the Nazca Plate even affects the geography of Bolivia, far to the east (Tinker et al.).

The ancient ocean closed as the continents of southern Yinshan Block and northern Ordos Block collided. The high pressure and temperature of continent-continent collision formed Khondalite Belt in-between the two sub-blocks and led to metamorphism in other parts of the Western Block. Fig. 4. A tectonic evolution diagram from 2.45 Ga to 1.95 Ga, proposed by Zhao et al. (1) At around 2.45 Ga, the oceanic crust of Ordos Block was subducted beneath Yinshan Block, making igneous rocks.

Calcium carbonate contributors, including plankton (such as coccoliths and planktic foraminifera), coralline algae, sponges, brachiopods, echinoderms, bryozoa and mollusks, are typically found in shallow water environments where sunlight and filterable food are more abundant. Cold-water carbonates do exist at higher latitudes but have a very slow growth rate. The calcification processes are changed by ocean acidification. Where the oceanic crust is subducted under a continental plate sediments will be carried down to warmer zones in the asthenosphere and lithosphere.

The BMC land area is the grave yards of both the Iapetus and Rheic ocean basins which were subducted under the thicker continental crust and down into the mantle. The region is mainly known for VHMS and SEDEX environments while it also hosts epithermal, mesothermal and a number of other mineral deposit forming environments. VHMS and SEDEX environments are the primary mineral hosting dynamics producing base and precious metals. Gold and silver are generally low grade associated with zinc and lead rich areas.

This is due to the plates moving parallel with each other and no new lithosphere is being created to change that length. Spreading centers constant Upper to down NEW Decreasing length faults: In rare cases, transform faults can shrink in length. These occur when two descending subduction plates are linked by a transform fault. In time as the plates are subducted, the transform fault will decrease in length until the transform fault disappears completely, leaving only two subduction zones facing in opposite directions.

Bathymetric profile of Explorer Ridge region A Bathymetric Profile of the Explorer Plate Region. The eastern boundary of the Explorer Plate is being subducted under the North American Plate. The southern boundary is a collection of transform faults, the Sovanco Fracture Zone, separating the Explorer Plate from the Pacific Plate. To the southeast is another transform boundary, the Nootka Fault, which separates the Explorer Plate from the Juan de Fuca Plate and forms a triple junction with the North American Plate.

Vesuvius was formed as a result of the collision of two tectonic plates, the African and the Eurasian. The former was subducted beneath the latter, deeper into the earth. As the water-saturated sediments of the oceanic African plate were pushed to hotter depths inside the planet, the water boiled off and lowered the melting point of the upper mantle enough to partially melt the rocks. Because magma is less dense than the solid rock around it, it was pushed upward.

The western part of Washington State lies above the Cascadia subduction zone, where the Juan de Fuca Plate is being subducted beneath the North American Plate. The seismicity of this region consists of rare great megathrust earthquakes, like the 1700 Cascadia earthquake and more common earthquakes originating from within the subducting slab. These events relate to normal faulting, associated with the bending of the slab, possibly related to a phase change below about 40 km from basalt/gabbro to eclogite.

The Hikurangi Plateau is an oceanic plateau on the Pacific Plate that attached to the Chatham Ridge after partially subducted under it, and is now subducting under the North Island. It likely formed in one of the world's largest volcanic outpourings, the greater Ontong Java event. Ophiolites, volcanic deposits from the ocean floor, have been incorporated into the continental basement of New Zealand in the Dun Mountain Ophiolite Belt, found at both ends of the South Island, and in Northland.

On the other hand, some of the world's largest tectonic plates such as the North American Plate and South American plate are in motion, yet only are being subducted in restricted locations such as the Lesser Antilles Arc and Scotia Arc, pointing to action by the ridge push body force on these plates. Computer modeling of the plates and mantle motions suggest that plate motion and mantle convection are not connected, and the main plate driving force is slab pull.

Thrusts and duplexes are also found in accretionary wedges in the ocean trench margin of subduction zones, where oceanic sediments are scraped off the subducted plate and accumulate. Here, the accretionary wedge must thicken by up to 200% and this is achieved by stacking thrust fault upon thrust fault in a melange of disrupted rock, often with chaotic folding. Here, ramp flat geometries are not usually observed because the compressional force is at a steep angle to the sedimentary layering.

During the Late Cretaceous and early Cenozoic, the Indian plate drifted northward a vast distance resulting in the closure of the Neo-Tethys Ocean. Approximately 40-50 million years ago remnants of the ocean vanished as India collided with the Eurasian plate. As the continental plates are relatively low density they cannot be subducted. This results in the Eurasian plate being thrusted up leading to the rise of the Tibetan Plateau, bounded to the south by the collisional Himalayan mountain range.

Debris from a larger subducted seamount probably dammed the trench from 2 Ma to 0.5 Ma and similar events probably redirected sediments in similar ways before that. Two oceanic plates meet at the Kermadec Trench which is located far from any larger landmass. Because of this, the Pacific Plate as well as the trench itself is only covered by of sediments. The trench is almost perfectly straight and its simple geometry is the result of the uniformity of the subducting sea-floor.

The Nazca Plate is being subducted under the South American Plate, generating volcanism and extensive seismicity. Much of South American seismic activity and volcanism originates from subduction of the oceanic Nazca Plate under the continental South American Plate and subduction of the Pacific's lithosphere under the South American continent. This seismicity extends for along the continent's western edge and probably stems from a region of northeast-trending faulting near the Ecuadorian Trench. The region of faulting may actually function as its own microplate.

Zealandia ended up at a pivot point between the Pacific and Australian Plates, with spreading in the south, and convergence in the north, where the Pacific Plate was subducted beneath the Australian Plate. A precursor to the Kermadec Arc was created. The convergent part of the plate boundary propagated through Zealandia from the north, eventually forming a proto-Alpine Fault in Miocene times (23 Ma). The various ridges and basins north of New Zealand relate to previous positions of the plate boundary.

The oldest rocks in Italy may include oceanic crust subducted during the Caledonian orogeny and 440 million year old Ordovician granites. Only detrital zircons in the Alps dates to the Precambrian. These granites are located offshore of Venice, found in the Agip Assunta well and deformed, transforming into orthogneiss during the Hercynian orogeny. Overall, Italian Paleozoic rocks commonly show evidence of the Hercynian orogeny in the Alps, Sardinia, the Apuan Alps of Tuscany, and the Peloritani mountains of Sicily and Calabria.

The states of Guerrero and Oaxaca lie above the convergent boundary where the Cocos Plate is being subducted below the North American Plate at a rate of 6.4 cm/yr (2.5 in/yr). The dip of the subducting slab is about 15° as defined by focal mechanisms and hypocenters of previous earthquakes. Seismicity in this area is characterized by regular megathrust earthquakes along the plate interface. In addition, there have been a series of historic normal fault events within the subducting slab.

The geothermal structure in a subduction zone determines the melting rate of subduction slab and asthenosphere. The change in isotherm structure may have significant impact on the intensity of magmatism. Some factors may contribute to the change in geothermal structure: a) the change in convergence velocity of two plates in subduction zone; b) the dipping angle of subduction slab; c) the amounts of subducted low temperature materials (water and oceanic sediments); d) the mantle/asthenosphere upwelling event (slab window/slab breakoff).

There are two competing interpretations for this. In the context of mantle plumes, the near-surface material is postulated to have been transported down to the core-mantle boundary by subducting slabs, and to have been transported back up to the surface by plumes. In the context of the Plate hypothesis, subducted material is mostly re-circulated in the shallow mantle and tapped from there by volcanoes. Stable isotopes like Fe are used to track processes that the uprising material experiences during melting.

In the Paleocene and the Eocene, the North Mesotethys Ocean closed, forming the Shachrud-Nishapoor thrusted-folded arc and the Eastern Iran transverse folded system. This led to the incorporation of Turkmenistan, Iran and Afghanistan into the larger Eurasian Plate. As Gondwana moved northward and interacted with Eurasia in the Paleogene, subduction began south of the current Zagros Mountains in northern Iraq and Iran. As the North Mesotethys Ocean basin was subducted, it kicked off calc-alkaline volcanism in Iran in the Eocene.

The subducted Pacific Plate is also being deformed in the collision as both slabs settle on the 660 km discontinuity. This slab collision probably occurred 5–4 Ma when the Lau Basin started to open. Oceanic trenches are important sites for the formation of what will become continental crust and for recycling of material back into the mantle. Along the Tonga Trench mantle-derived melts are transferred to the island arc systems, and abyssal oceanic sediments and fragments of oceanic crust are collected.

This earthquake was the first tsunami earthquake to be recorded using modern broadband instruments. The initial surface wave magnitude, which uses only waves of a period of 20 seconds, was estimated at 7.0–7.2. The part of the Middle America Trench off Nicaragua contains relatively little sediment, allowing the slip to propagate up-dip all the way to the trench bottom, which tends to generate large tsunamis. The trench sediment here has been subducted and this soft material lies along the plate interface.

During the Lower Ordovician parts of Gondwanas northern rim started to break off and a sliver carrying Armorica and its eastern continuation - also called the Hun Superterrane – slowly started drifting northward. This opened up the Paleotethys in the wake. As a consequence the Rheic Ocean and the Rhenohercynian Ocean to the north were more and more constricted and eventually became subducted below Armorica or the Hun Superterrane. This subduction event corresponds in the Massiv Central to the deformational phase D2.

Mount Yasur is a volcano on Tanna Island, Vanuatu, high above sea level, on the coast near Sulphur Bay, northeast of the taller Mount Tukosmera, which was active in the Pleistocene. It has a largely unvegetated pyroclastic cone with a nearly circular summit crater 400 m in diameter. It is a stratovolcano, caused by the eastward-moving Indo-Australian Plate being subducted under the westward-moving Pacific Plate. It has been erupting nearly continuously for several hundred years, although it can usually be approached safely.

In the Early Mesozoic, as the South China Craton subducted beneath the North China Craton, the accumulation of continental material facilitates orogenic belt forming at the collision area. Examples include the Qinling-Tongbai-Dabie belt, Longmenshan thrust belt and Indochina belt. The Xuefengshan-Jiuling belt lying in the middle of the South China Craton also formed due to the compressive force. Huangling massif was quite stable because its location in the middle of South China Craton was shielded from the uplift orogenic events at the rim.

He realized that this inclined array of earthquake sources indicate the position of the portion of the plate that has already been subducted. Thus, that pattern of earthquakes is known as a Wadati–Benioff zone. From the early 1930s, Benioff also worked on creating electric musical instruments; in particular a piano, violin and cello. He continued developing these instruments for the rest of his life, working for over two decades with pianist Rosalyn Tureck and also, towards the end of his life with the Baldwin Piano Company.

However, at the time of its formation Haddington Island may have been coincident with the subducted plate boundary. Also, the timing of volcanism corresponds to shifts of plate motion and changes in the locus of volcanism along the Pemberton and Garibaldi volcanic fronts. This brief interval of plate motion adjustment approximately 3.5 million years ago may have triggered the generation of basaltic magma along the descending plate edge. Although commonly referred to as andesite, by chemical composition the Haddington Island volcanic rocks are in fact dacite.

The southern part of the Philippines lies above the complex collisional zone between the Philippine Sea Plate and the Sunda Plate. The convergence between these two plates of between 6-11 cm per year is accommodated by a series of smaller plates. One of these, the Molucca Sea Plate, is currently being subducted beneath both the Philippine Sea Plate and the Sangihe Microplate, causing it to have an inverted U-shape seismic zone. The earthquakes were caused by the continuing distortion of the Molucca Sea Plate.

Metamorphic belts are a consequence of thermal perturbations, due to low temperature with respect to pressure ratios (dT/dP) in oceanic trenches and high temperature with respect to pressure ratios (dT/dP) in arcs. Paired metamorphic belts are the product of subducted colder crustal rocks, which are taken to depth, metamorphosed and then exhumed. However, if the rock unit is not exhumed relatively quickly after subduction ceases, the rock unit will re-equilibrate to the standard geothermal gradient and the geological record will be lost.

Some terranes, such as the Western Wabigoon Terrane, are formed from the setting of an oceanic arc. An oceanic arc is a chain of volcanoes which formed above and parallel to the subduction zones. Due to tectonic activities in the Earth, the relevant continental and oceanic crusts collided before 2.70 Ga. The denser oceanic crust subducted underneath the continental crust and melted into the mantle, which generated more magma. The huge amount of magma then rose up, penetrated through the crust above and erupted.

The divergent movement of the European and African plates was relatively short-lived. When the Atlantic Ocean formed between Africa and South America (about 100 Ma) Africa began moving northeast. As a result of this process, the soft layers of ocean sediment in the Alpine Tethys Oceans were compressed and folded as they were slowly thrust upwards. Caught in the middle of the merging continents, the area of the Tethys Sea between Africa and Eurasia began to shrink as oceanic crust subducted beneath the Adriatic plate.

Farallon Slab under North America In geology, a slab is the portion of a tectonic plate that is being subducted. Slabs constitute an important part of the global plate tectonic system. They drive plate tectonics – both by pulling along the lithosphere to which they are attached in a processes known as slab pull and by inciting currents in the mantle (slab suction). They cause volcanism due to flux melting of the mantle wedge, and they affect the flow and thermal evolution of the Earth's mantle.

The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench under the North American Plate well north of San Francisco. In California, the plate is sliding northwestward along a transform boundary, the San Andreas Fault, toward the subduction zone. At the same time, the North American Plate is moving southwestward, but relatively southeast along the fault.

According to one of those models, a large chunk of the subducted plate of a former ocean has survived in the uppermost mantle for several hundred million years, and its oceanic crust now causes excessive melt generation and the observed volcanism. This model, however, is not backed by dynamical calculations, nor is it exclusively required by the data, and it also leaves unanswered questions concerning the dynamical and chemical stability of such a body over that long period or the thermal effect of such massive melting.

Thus, the investigation's findings indicate that pieces of basaltic oceanic lithosphere act as the principle transport mechanism for carbon to Earth's deep interior. These subducted carbonates can interact with lower mantle silicates, eventually forming super-deep diamonds like the one found. Diagram of carbon tetrahedrally bonded to oxygen However, carbonates descending to the lower mantle encounter other fates in addition to forming diamonds. In 2011, carbonates were subjected to an environment similar to that of 1800 km deep into the Earth, well within the lower mantle.

In the Mesozoic, North America separated from the supercontinent Pangea which had formed in the late Paleozoic. Oceanic plates in the Pacific Ocean subducted in trenches offshore, carrying volatiles such as water and carbon dioxide with them, leading to rock melting and volcanic activity. Intense volcanism built up Alaska's mountains until a slowing of eruptions in the late Cretaceous around 80 million years ago. During the Middle Triassic three large terranes—Wrangellia, Alexander and Stikine—remained offshore as separate island arcs not yet joined to the continent.

The trench is a result of a convergent boundary, where the eastern edge of the oceanic Nazca Plate is being subducted beneath the continental South American Plate. Two seamount ridges within the Nazca Plate enter the subduction zone along this trench: the Nazca Ridge and the Juan Fernández Ridge. From the Chile Triple Junction to Juan Fernández Ridge the trench is filled with of sediments, creating a flat bottom topography. Sediments are mainly turbidites interspersed with oceanic deposits of clay, volcanic ash, and siliceous ooze.

At the south end of IBM, there is almost no convergence between the Caroline Plate and the Philippine Sea Plate. The IBM arc is not experiencing trench ‘roll-back’, that is, the migration of the oceanic trench towards the ocean. The trench is moving towards Eurasia, although a strongly extensional regime is maintained in the IBM arc system because of rapid PH-EU convergence. The nearly vertical orientation of the subducted plate beneath southern IBM exerts a strong “sea-anchor” force that strongly resists its lateral motion.

Outline of aseismic ridges and plate boundaries off northwestern South America, suggested continuation of Carnegie Ridge beneath Ecuador from Gutcher et al. 1999, other models suggest that this area is much smaller The Carnegie Ridge is an aseismic ridge on the Nazca Plate that is being subducted beneath the South American Plate. The ridge is thought to be a result of the passage of the Nazca Plate over the Galapagos hotspot. It is named for the research vessel Carnegie, which discovered it in 1929.

The tilting of the summit platform was the first evidence of the existence of subduction processes. In about 500,000 years the top of the seamount will end up at the bottom of the trench. Capricorn Seamount is not the first seamount there to be subducted into the Tonga Trench, and previous subduction events may have deformed the trench. An earthquake () occurred in 1919 at the trench next to Capricorn Seamount and caused a tsunami; it might also have induced a submarine landslide on the seamount.

See ; ; . However, Siletzia was too big to be subducted, and it accreted to the continent. Accretion is sometimes called "docking," but is more akin to a collision: various peripheral structures are first folded or crushed, then the main structures are deformed when they come into contact, and various parts get pushed over other parts, all this playing out over several million years. To the extent that the accretion of Siletzia to North America can be given a definite date most studies give it as about 50 Ma.; .

There has not been a major subduction zone earthquake here since the magnitude nine Cascadia earthquake; according to Japanese records, it occurred 26 January 1700. Lesser Puget Sound earthquakes with shallow epicenters, caused by the fracturing of stressed oceanic rocks as they are subducted, still cause great damage. The Seattle Fault cuts across Puget Sound, crossing the southern tip of Bainbridge Island and under Elliott Bay. To the south, the existence of a second fault, the Tacoma Fault, has buckled the intervening strata in the Seattle Uplift.

In the Cretaceous, ophiolite obducted as the Penjwin-Shlair Complex, the Qulqula Radiolarites and the Khwakurk Series volcanics as the foreland basin witnessed 270 meters of sediment deposition. The Katarash volcanic rocks are indicative of uplift and mantle convection back-arc spreading. The Red Beds Series piled up near the subduction zone, where the Neo-Tethys Ocean crust was being subducted and consumed beneath the Anatolian and Iranian Plates. The Naopurdan Group, Gimo- Qandil Group and Walash Volcanics formed in forearc and back-arc environments.

The subducting oceanic crust is thought to split from the continental margin to aid subduction. In the event that the rate of trench retreat is greater than that of the island arc complex's progression, trench rollback will take place, and by consequence, extension of the overriding plate will occur to allow the island arc complex to match the trench retreat's speed. The extension, a back-arc basin, generates oceanic crust: ophiolites. Finally, when the oceanic lithosphere is entirely subducted, the island arc complex's extensional regime becomes compressional.

In the late Jurassic, fragments of continental crust from the small content Cimmeria collided with Eurasia. Earlier, in the mid-Jurassic remnant oceanic crust formed ophiolites along the coast of Cimmeria. The oceanic crust of the Neotethys ocean subducted between the newly compounded Cimmerian-Eurasia continent, but obducted some more ophiolites onto the edge of the Cimmerian crust. Tectonic activity resumed in the early Cenozoic when the small Apulia plate collided with the Cimmerian- Eurasian rocks causing intense imbrication and the deposition of the Pindos flysch.

The metamorphic conditions the slab passes through in this process creates and destroys water bearing (hydrous) mineral phases, releasing water into the mantle. This water lowers the melting point of mantle rock, initiating melting. Understanding the timing and conditions in which these dehydration reactions occur, is key to interpreting mantle melting, volcanic arc magmatism, and the formation of continental crust. Pressure-temperature pathway for subducted crust A metamorphic facies is characterized by a stable mineral assemblage specific to a pressure-temperature range and specific starting material.

It is thought that this reservoir came from subducted ocean crust that has been entrained by the mantle plume. It has enriched Sr and Pb ratios and is enriched with trace elements. FLO is associated principally with the island of Floreana and shows up on the mixing of lavas within the Galapagos along the southern side archipelago and is diluted to the east and north of there. WD – (Wolf Darwin) is unique in the Pacific and resembles material from an Indian Ocean Ridge system.

The Yakutat plate is transported northwards along the active Fairweather Fault, which probably started more than 35 million years ago. Due to its thickness, the Yakutat plate is buoyant, resulting in surface uplift of the overriding North American plate, which formed the Talkeetna Mountains and the Alaska Range in Southcentral Alaska, located above the subducted part of the Yakutat plate. Yakutat Icefield – an expanse of ice in southeast Alaska – in 2018. The St. Elias Mountains formed at the plate boundary between the Yakutat and North American plates.

Understanding predictions of mantle dynamics helps geoscientists predict where subducted crust will end up. Crustal recycling is a tectonic process by which surface material from the lithosphere is recycled into the mantle by subduction erosion or delamination. The subducting slabs carry volatile compounds and water into the mantle, as well as crustal material with an isotopic signature different from that of primitive mantle. Identification of this crustal signature in mantle-derived rocks (such as mid-ocean ridge basalts or kimberlites) is proof of crustal recycling.

Geological Survey India News. 1978. Soon after the rifting phase ended, the compressional phase took place where the eastern Bundelkhand craton subducted under the western Marwar craton. As collision continued, the subduction zone steepened, leading to the development of an island arc between the two cratons. After collision had proceeded for a certain period of time, the uplift of the Aravalli Supergroup was induced at around 1800 Ma. In the last stage of convergence, the thrust fault further steepened and the colliding blocks eventually become sutured.

The Laramide orogeny episode near the end of the Cretaceous and early Tertiary period caused larger gravels to be deposited from the newly formed Rocky Mountains when the Kula and Farallon Plates subducted below the North American plate. In the Cypress Hills area and southern Saskatchewan, lignite deposits developed from the marshes of these Tertiary rivers. The sea waters have retreated from the areas known as Saskatchewan. The Ravenscrag formation, Cypress Hills, and Wood Mountain Formations were notable gravel deposits from the Tertiary period.

The New Hebrides central chain stretches from Ureparapara island, Banks Islands, in the north to Hunter island in the south. The New Hebrides trench retreats progressively which causes the southern end the subduction zone to bend eastward. The Australian plate subducts under Vanuatu at the New Hebrides trench which results in a complex of rifts and transforms in the NFB. The New Hebrides island chain itself is being deformed as buoyant features such as d'Entrecasteaux Ridge and West Torres Plateau are being subducted in this process.

Deep seafloor deposition is the largest long-term sink of the marine silica cycle (6.3 ± 3.6 Tmol Si year−1), and is roughly balanced by the sources of silica to the ocean. The silica deposited in the deep ocean is primarily in the form of siliceous ooze, which is eventually subducted under the crust and metamorphosed in the upper mantle. Under the mantle, silicate minerals are formed in oozes and eventually uplifted to the surface. At the surface, silica can enter the cycle again through weathering.

The northwestern side of Honshu lies on the southeastern margin of the Sea of Japan, an area of oceanic crust created by back-arc spreading associated with the convergent boundary where the Pacific Plate is subducted beneath the Okhotsk Plate. The spreading was active from the late Oligocene to middle Miocene. The extensional tectonics associated with the spreading formed a series of N-S trending extensional faults and associated sedimentary basins. Currently the area is being deformed by contractional tectonics, causing inversion of these earlier basins, forming anticlinal structures.

Tonalities were formed in Neoproterozoic, by partial melting of Yangtze Craton during subduction beneath the North China Craton. As the oceanic Yangtze Craton subducted under the continental North China Craton, magmatic activities result in the formation of hydrated mafic basaltic magma. On the other hand, trondhjemites were formed in Archean, with the source from partial melting of Archean amphibolites and granulites under the continental Yangtze Craton in a high-pressure condition. They are composed of felsic minerals such as plagioclase, quartz, and Na-K-rich feldspar and minor mafic minerals biotite and hornblende.

Today, the Atlantic basin is actively spreading at the Mid-Atlantic Ridge. Only a small portion of the oceanic crust produced in the Atlantic is subducted. However, the plates making up the Pacific Ocean are experiencing subduction along many of their boundaries which causes the volcanic activity in what has been termed the Ring of Fire of the Pacific Ocean. The Pacific is also home to one of the world's most active spreading centers (the East Pacific Rise) with spreading rates of up to 145 +/- 4 mm/yr between the Pacific and Nazca plates.

Stable subduction zones involve the oceanic lithosphere of one plate sliding beneath the continental or oceanic lithosphere of another plate due to the higher density of the oceanic lithosphere. This means that the subducted lithosphere is always oceanic while the overriding lithosphere may or may not be oceanic. Subduction zones are sites that usually have a high rate of volcanism and earthquakes. Furthermore, subduction zones develop belts of deformation and metamorphism in the subducting crust, whose exhumation is part of orogeny and also leads to mountain building in addition to collisional thickening.

The Cocos Plate was created by sea floor spreading along the East Pacific Rise and the Cocos Ridge, specifically in a complicated area geologists call the Cocos-Nazca spreading system. From the rise the plate is pushed eastward and pushed or dragged (perhaps both) under the less dense Caribbean Plate, in the process called subduction. The subducted leading edge heats up and adds its water to the mantle above it. In the mantle layer called the asthenosphere, mantle rock melts to make magma, trapping superheated water under great pressure.

Ecuador and Colombia lie above a convergent boundary where the Nazca Plate is being subducted beneath the South American Plate. The convergence rate is 55 mm per year and the subduction is significantly oblique to the boundary. This part of the plate boundary has been the location of a series of large historical earthquakes, including the =8.8 1906 Ecuador–Colombia earthquake, which ruptured 5-600 km of the plate interface. Since 1906 there have been three major earthquakes that together have re-ruptured this same segment, in 1942, 1958 and 1979.

Unlike the Zhao's and Kusky's models, the tectonic evolution of the Western Block suggested by Santosh primarily focused on the amalgamation of the Western Block, with fewer discussion on the early tectonic development before collisional events. Santosh considered the Ordos Block as a continental arc composed by TTGs and charnockites. Supported by zircon dating and tomographic data, Santosh proposed that the Yinshan Block and Ordos Block collided at around 1.92 billion years ago, with Yinshan Block subducted under Ordos Block. An accretionary wedge was formed when the two sub-blocks collided.

The specific processes by which UHP terrains were exhumed to Earth's surface appear to have been different in different locations. If continental lithosphere is subducted because of its attachment to downgoing oceanic lithosphere, the downward slab pull force may exceed the strength of the slab at some time and location, and necking of the slab initiates.van Hunen, J., and Allen, M. B., 2011, Continental collision and slab break-off: A comparison of 3-D numerical models with observations: Earth and Planetary Science Letters, v. 302, p. 27-37.

Sialic sediments were metamorphosed, melted and intruded into the rocks above as granites. By the early Carboniferous the oceanic plates were completed subducted and the eastern margin of Baltica, then on the eastern edge of Laurussia began to collide with the western edge of Angara. In the south the western edge of Kazakhstania may have been pushed under Baltica. This collision in known generally as the Variscan orogeny, and specifically as to the Urals as the Uralian orogeny The collision lasted nearly 90 million years from the Carboniferous to the early Triassic.

Magnitude of 2018 Oaxaca earthquake Map of 2018 Oaxaca earthquake Oaxaca lies on the destructive plate boundary where the Cocos Plate is being subducted beneath the North American Plate. In the region of this earthquake, the Cocos Plate moves approximately northeastward at a rate of 60 mm/yr. The earthquake occurred as a result of thrust faulting at a shallow depth. The depth and focal mechanism solutions of the event are consistent with its occurrence on the subduction zone interface between these plates, approximately 90 km northeast of the Middle America Trench.

The earliest proposed mechanism for the generation of deep- focus earthquakes is an implosion due to a phase transition of material to a higher density, lower volume phase. The olivine-spinel phase transition is thought to occur at a depth of 410 km in the interior of the earth. This hypothesis proposes that metastable olivine in oceanic lithosphere subducted to depths greater than 410 km undergoes a sudden phase transition to spinel structure. The increase in density due to the reaction would cause an implosion giving rise to the earthquake.

Dehydration reactions of mineral phases with high weight percent water would increase the pore pressure in a subducted oceanic lithosphere slab. This effect reduces the effective normal stress in the slab and allow slip to occur on pre-existing fault planes at significantly greater depths that would normally be possible. Several workers suggest that this mechanism does not play a significant role in seismic activity beyond 350 km depth due to the fact that most dehydration reactions will have reached completion by a pressure corresponding to 150 to 300 km depth (5-10 GPa).

Transformational faulting, also known as anticrack faulting, is the result of the phase transition of a mineral to a higher density phase occurring in response to shear stress in a fine-grained shear zone. The transformation occurs along the plane of maximal shear stress. Rapid shearing can then occur along these planes of weakness, giving rise to an earthquake in a mechanism similar to a shallow-focus earthquake. Metastable olivine subducted past the olivine-wadsleyite transition at 320--410 km depth (depending on temperature) is a potential candidate for such instabilities.

One theory for the formation of the basin is that it is dynamic topography due to a sinking slab of oceanic crust. This slab was subducted during latest Cretaceous and Early Cenozoic periods to the north of the Australian continent underneath New Guinea. The slab broke off and was gradually overridden by the Australian plate moving north. The sinking slab has a trace in the P-wave velocity in the mantle which is higher from 800 to 1200 km deep below the Murray basin, and also the Lake Eyre Basin.

In nature, the inverted "U" shape of the oceanic plate in divergent double subduction should not be always perfectly symmetrical like the idealized model. An asymmetrical form is preferred like the real example in Molucca Sea where the length of the subducted slab is longer on its western side beneath the Sangihe Arc while a shorter slab on its eastern side beneath the Halmahera Arc. 3D numerical modelling had been done to simulate divergent double subduction, to evaluate different factors that can affect the evolution and geometry of the system discerned below.

Part of the landward margin of the trench close to Daiichi-Kashima is uplifted, perhaps as a consequence of the subduction of the seamount, and there is periodic earthquake activity in front of Daiichi-Kashima seamount with magnitude 7 earthquakes about every 20 years. The seamount might also influence the segmentation of the trench and its earthquakes, considering that the rupture of the 2011 Tohoku earthquake spanned the trench length between Erimo Seamount and Daiichi-Kashima. The other seamounts in the area will likely be subducted after Daiichi-Kashima has been.

A tectonostratigraphic terrane is not necessarily an independent microplate in origin, since it may not contain the full thickness of the lithosphere. It is a piece of crust which has been transported laterally, usually as part of a larger plate, and is relatively buoyant due to thickness or low density. When the plate of which it was a part subducted under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. Therefore, the terrane transferred from one plate to the other.

The deficit of water on Venus due to the runaway greenhouse effect is thought to explain why Venus does not exhibit surface features consistent with plate tectonics, meaning it would be a stagnant lid planet. Carbon dioxide, the dominant greenhouse gas in the current Venusian atmosphere, owes its larger concentration to the weakness of carbon recycling as compared to Earth, where the carbon dioxide emitted from volcanoes is efficiently subducted into the Earth by plate tectonics on geologic time scales through the carbonate- silicate cycle, which requires precipitation to function.

The volcanic arc that built up during the period overthrust onto the southern margin of North America. During the Oligocene, the offshore Pacific Plate fragmented into the Cocos Plate and Nazca Plate, divided by the east- west Colon spreading ridge. The tectonics of Costa Rica are more complicated because the Cocos Plate subdivided into two blocks separated by the Costa Rica Fracture Zone (running northeast onto land), with the northern block being subducted. Submarine canyons have been used to infer the path of the Panama Fracture Zone running along the coast creating wrench faults.

The Raukumara Region of New Zealand corresponds to the East Cape of the North Island, and associated mountain ranges. To the east of the North Island is the Hikurangi Trough, a collision zone between the Pacific Plate and the Australian Plate. The Pacific Plate is being subducted under the Australian Plate, compressing the east of the North Island, and causing the North Island Fault System, and a series of SSW-NNE trending basins and ranges, including the Raukumara Range. Successively newer rocks have been accreted to the east coast.

Aguilera has erupted dacites with intermediate contents of potassium, defining a calc-alkaline suite with adakitic characteristics. Phenocrysts include amphibole, biotite, clinopyroxene, hornblende and plagioclase; plagioclase and also orthoclase and pyroxene often occur as xenoliths. Melts of subducted sediment and from the subducting slab give rise to the magmas of Aguilera and other volcanoes of the northern Austral Volcanic Zone, but they are subsequently modified by interactions with the mantle wedge and in the case of Aguilera, Lautaro and Viedma further interaction takes place with the Paleozoic crust.

High resolution tomographic data revealed evidence for an eastward under thrusting of the Indian continental lithosphere into the asthenospheric mantle underneath the TVF. This indicates that prior to continent collision, the Tengchong block along with the Burma block overlaid the subducted Neo-Tethyan oceanic lithosphere. There are a total of 68 volcanoes all of which are pyroclastic cones and around 25 of these still bear recognizable craters and cones. In addition to the volcanoes, there are 58 hot springs in the TVF all derived from the Quaternary Era.

Oceanic and continental crusts are, at the present day, produced and maintained through plate tectonic processes. However, the same mechanisms are unlikely to have produced the crustal dichotomy of the early lithosphere. This is thought to be true on the basis that sections of the thin, low density continental lithosphere thought to have originally covered the planet could not have been subducted under each other. Consequently, a proposed relative timing for crustal dichotomy has been put forward stating that the dichotomy began before the commencement of global plate tectonics.

Position of the continents after the Caledonian orogeny (Devonian to Permian times). Differences in fossil faunas on both sides of the red line (the Iapetus Suture) are evidence for the existence of an ocean between the two sides in the time before the continents were joined in the supercontinent Pangaea. Figure based on and Southwest of the Iapetus, a volcanic island arc evolved from the early Cambrian (540 million years ago) onward. This volcanic arc was formed above a subduction zone where the oceanic lithosphere of the Iapetus Ocean subducted southward under other oceanic lithosphere.

The Coast Range Arc was home to some of the world's most dangerous and explosive volcanoes. Cataclysmic eruptions at the British Columbia–Yukon border created a huge nested caldera called the Bennett Lake Volcanic Complex about 50 million years ago during the early Eocene period. These eruptions were from vents along arcuate fracture systems associated with the caldera, which discharged about of pyroclastic material. This volcanic event occurred shortly before nearly all the Kula Plate had been subducted beneath the North American Plate about 40 million years ago.

The processes could possibly vary depending on the active or passive type of margin encountered, such as Tethyan or Cordilleran margins. In Tethyan passive margins gravity sliding over accretionary terranes via low angle thrust faults was proposed. On the Cordilleran margin, lithospheric fragments are incorporated into accretionary terranes. In the Troodos, gravity surveys have implied that the ophiolite is underlain by continental crust whose relative buoyancy uplifted the ocean crust, which in some circumstances could eventually lead to sliding onto the accretionary wedge (or now Eratostines seamount subducted for Troodos).

The Explorer Plate broke away from the Juan de Fuca about 4 million years ago and shows no evidence that it is still being subducted. The Gorda platelet split away between 18 and 5 million years ago and continues to sink beneath North America. The Cascade Range made its first appearance 36 million years ago, but the major peaks that rise up from today's volcanic centers were born within the last 1.6 million years (during the Pleistocene). More than 3000 vents erupted during the most recent volcanic episode that began 5 million years ago.

The stratigraphy east of the Mariana segment differs from that being subducted beneath the Izu-Bonin segment in having a much greater abundance of Early Cretaceous intra-plate volcanics and flood basalts. About 470m of oceanic crust was penetrated at ODP site 801C during Legs 129 and 185. These are typical mid-ocean ridge basalt that were affected by low-temperature hydrothermal alteration. This crust is overlain by a 3 m thick, bright yellow hydrothermal deposit and about 60 m of alkali olivine basalt, 157.4±0.5 Ma old .

Recent seismic imaging from Natural Resources Canada employees supported lithoprobe studies in the region of Mount Cayley that created a large reflector interpreted to be a pool of molten rock roughly below the surface. It is estimated to be long and wide with a thickness of less than . The reflector is understood to be a sill complex associated with the formation of Mount Cayley. However, the available data does not rule out the probability of it being a body of molten rock created by dehydrating of the subducted Juan de Fuca Plate.

South of the Chile Triple Junction, the Antarctic Plate subducts beneath the South America Plate at a rate of . This subduction process is responsible for volcanic activity in the Austral Volcanic Zone; south of the southernmost volcano of this zone, Fueguino, the subduction gives way to strike-slip faulting. This subduction process is not accompanied by much earthquake activity. Not all volcanism at these latitudes was triggered by subduction; during the Miocene the Chile Rise was subducted here and this caused a temporary pause of the subduction process and the formation of a slab window.

This Image shows where the Yakutat microplate is subducting beneath the North American Plate. Red indicates the region where the microplate has already been subducted, while the yellow indicates where it is still present at the surface. Alaskan tectonism is mainly dominated by the subduction of the Pacific Plate beneath the North American Plate. The subduction boundary is marked by a 4,000 km long trench known as the Aleutian Trench, where seismic activity is common and the volcanic arc produced is part of the Pacific Ring of Fire.

The Nyingchi complex is thus the exposed lower crust of the magmatic arc. Derital zircons from the associated metasedimentary rocks have U–Pb ages from Ma. Metamorphic zircons from the metaplutonic and metasedimentary rocks date to Ma. The Nyingchi complex was heated to a peak of , causing granulite-facies metamorphism and partial melting. The cause may have been rollback of the flat-subducted Neo-Tethyan oceanic slab during the Early Paleogene, causing a contractional orogeny and intrusion of large volumes of mantle-derived magmas. The Linzizong Formation is distributed widely along the Gangdese Belt.

El Salvador lies above the convergent boundary where oceanic crust of the Cocos Plate is being subducted beneath the Caribbean Plate at rate of about 72 mm per year along the Middle America Trench. This boundary is associated with earthquakes resulting from movement on the plate interface itself, such as the 7.7 1992 Nicaragua earthquake, and from faulting within both the overriding Caribbean Plate associated with the active volcanic belt, such as the destructive 1936 San Salvador earthquake, and the subducting Cocos Plate, such as the 1982 El Salvador earthquake.

Peru lies above the destructive boundary where the Nazca Plate is being subducted beneath the South American Plate. The two plates are converging towards each other at a rate of about 78mm or 3 inches per year. Southwestern Peru has a history of very large earthquakes. The June 23 shock originated just southeast of the source of a magnitude 7.7 earthquake that occurred in 1996, and it appears to have involved rupture of part of the plate boundary segment that produced an earthquake of magnitude approximately 9.0 in 1868.

The atmosphere of Venus is in a "super-greenhouse" state One billion years from now, about 27% of the modern ocean will have been subducted into the mantle. If this process were allowed to continue uninterrupted, it would reach an equilibrium state where 65% of the current surface reservoir would remain at the surface. Once the solar luminosity is 10% higher than its current value, the average global surface temperature will rise to . The atmosphere will become a "moist greenhouse" leading to a runaway evaporation of the oceans.

The Wrangell and St. Elias mountain ranges that spawn the Bering Glacier were created by the collision of the Pacific and North American tectonic plates [the Pacific Plate is sliding underneath (being subducted by) the North American Plate]. The weight of the vast amount of ice in the Bering Glacier is enough to depress the Earth's crust, stabilizing the boundary between the two plates. As the glaciers lose mass, the pressure of the ice is diminished. This reduced compression allows the rocks along faults to move more freely, resulting in more earthquakes.

Both the location and origin of kimberlitic magmas are subjects of contention. Their extreme enrichment and geochemistry have led to a large amount of speculation about their origin, with models placing their source within the sub-continental lithospheric mantle (SCLM) or even as deep as the transition zone. The mechanism of enrichment has also been the topic of interest with models including partial melting, assimilation of subducted sediment or derivation from a primary magma source. Historically, kimberlites have been classified into two distinct varieties, termed "basaltic" and "micaceous" based primarily on petrographic observations.

The earthquake's focus lies close to the major fault plane where the Indo-Australian Plate is being subducted beneath the Eurasian Plate. However, the focal mechanisms determined for this event shows reverse faulting at a high angle to the trend of the subduction zone and it has been suggested that the cause was deformation within the descending slab. Another earthquake in the same subduction zone occurred only 5 days later in the ocean south of Yogyakarta. This newer quake (magnitude 6.2) is considered to be related to the West Java earthquake.

With the formation of the supercontinent Pangea in the mid- to late-Paleozoic, the vast Panthalassa ocean dominated 70 percent of the Earth's surface. The Tethys, Mongol-Okhotsk and various small domains of early Pacific ocean crust constituted other small oceans. Paleomagnetic data collected between 1987 and 2010 suggest that the Mongol-Okhotsk oceanic crust subducted under the terranes of Mongolia in the Late Jurassic or Early Cretaceous. During the early Mesozoic, the Solonker Ocean, also known as the Intra-Asian Ocean closed bringing together two large continental blocks: Amuria and the North China Block.

The onset of continental collision is determined by any point along the plate boundary where the oceanic lithosphere is completely subducted and two continental plates first come into contact. In the case of the India–Asia collision, it would be defined by the first point of disappearance of the Neo-Tethys oceanic crust, where the India and Asia continent come into contact with each other. Such process is defined by a point since the shape of continental margins is irregular. The complete consumption of the oceanic crust could occur non-synchronously along the collision front.

The active tectonics of Ecuador is dominated by the effects of the subduction of the Nazca Plate beneath the South American Plate. The high degree of coupling across the plate boundary where the Carnegie Ridge is being subducted beneath northern Ecuador causes unusually intense intraplate deformation. Known faults within the area of the earthquake epicenters are the SSW-NNE trending San Isidro, El Ángel, Río Ambi and Otavalo Faults, all considered to be dextral strike-slip faults, sometimes with reverse movement. All these faults are interpreted to have moved in the last 1.6 million years.

Capitanio et al. attributes the rise of Altiplano and the bending of the Bolivian Orocline to the varying ages of the subducted Nazca Plate with the older parts of the plate subducting at the centre of the orocline. As Andrés Tassara puts it the rigidity of the Bolivian Orocline crust is derivative of the thermal conditions. The crust of the western region (forearc) of the orocline has been cold and rigid, resisting and damming up the westward flow of warmer and weaker ductile crustal material from beneath the Altiplano.

The Cotabato Trench is an oceanic trench in the Pacific Ocean, off the southwestern coast of Mindanao in the Philippines. Along this trench the oceanic crust of the Sunda Plate beneath the Celebes Sea is being subducted beneath the Philippines Mobile Belt. It forms part of a linked set of trenches along the western side of the Philippines formed over east-dipping subduction zones, including the Manila Trench and the Negros Trench. At its northern end the rate of convergence across this boundary is about 100 mm per year.

The steeply dipping, ESE-striking rocks of the Thiviers-Payzac Unit upthrust obliquely over the Upper Gneiss Unit with a right-lateral shearing component. The Upper Gneiss Unit strikes southwest- northeast and in turn overrides The Lower Gneiss Unit to the northwest, also showing a SW-NE strike. Enclosed within the micaschists are basic and ultrabasic rocks of the Roche Noire Massif (near the hamlet La Valade), mainly metagabbros and peridotites. These are some of the very few remnants of oceanic crust left behind from a now subducted ocean.

The deepwater formation at the northern end of the Atlantic Ocean allows SST anomalies to be subducted into the deep ocean efficiently because the rate of overturning is altered by changes in salinity. The decreasing summer-time ice melting and precipitation due to the volcano cooling enhance the salinity near the Greenland Sea, and further reduces static stability, which means more surface water sinks into the deep ocean. The studies of Stenchikov et al. (2009) and Iwi (2012) suggest that both Krakatau and Pinatubo may have strengthened the overturning circulation.

South America approached Laurentia as the intervening oceanic crust was subducted. The collision of South American and Laurentian continental crust compressed and uplifted the region to form the Ouachita Mountains. During the Pennsylvanian and Permian, river systems draining westward from the Ouachita Mountains deposited sediments in north-central Texas and Oklahoma, which are now exposed at the surface. The Ouachita Mountains were extensively eroded between the Permian and the Jurassic, and much of the Ouachita system was subsequently buried beneath Mesozoic and Cenozoic sediments to the southeast and southwest.

Palaeotemperature graphs compressed together The oxygen content in the atmosphere over the last billion years Paleoclimatologists employ a wide variety of techniques to deduce ancient climates. The techniques used depend on which variable has to be reconstructed (temperature, precipitation or something else) and on how long ago the climate of interest occurred. For instance, the deep marine record, the source of most isotopic data, exists only on oceanic plates, which are eventually subducted: the oldest remaining material is old. Older sediments are also more prone to corruption by diagenesis.

300px The Chile Rise or Chile Ridge is an oceanic ridge, a tectonic divergent plate boundary between the Nazca and Antarctic plates. Its eastern end is the Chile Triple Junction where the Chile Rise is being subducted below the South American Plate in the Peru–Chile Trench. It runs westward to a triple point south of the Juan Fernández Microplate where it intersects the East Pacific Rise. The Chile Rise subducts near Taitao Peninsula where Taitao ophiolite and other geolical features are associated to the interactions at the triple junction.

The reason for this was discovered upon analyzing data from the USARRAY project. It was found that the asthenosphere had invaded the overlying lithosphere, as a result of an area of mantle upwelling stemming from either the disintegration of the descending Farallon Plate, or the survival of the subducted spreading center connected to the East Pacific Rise and Gorda Ridge beneath western North America, or possibly both. The asthenosphere erodes the lower levels of the Plateau. At the same time, as it cools, it expands and lifts the upper layers of the Plateau.

When a plate of oceanic crust is subducted beneath an overriding plate of oceanic crust, as the underthrusting crust melts, it can cause upwelling of magma that can cause volcanism along the subduction front on the overriding plate. This produces an oceanic chain of volcanoes, like Japan. This volcanism causes metamorphism of rocks, intrusions of magma that produce rocks such as granite, and thickens the crust by depositing additional layers of rock from volcanoes. This tends to make the crust lighter and thicker, as a result making it immune to subduction.

The unit shows traces of high-grade metamorphism in the form of eclogite and blueschist relicts. Most of it, especially the external and intermediate zones, is in the greenschist facies though. This greenschist metamorphic grade is seen as a late (Meso-Alpine) overprint, most researchers think the whole Sesia zone or at least part of it has been in eclogite or blueschist conditions during Paleogene subduction. Because clear evidence for high pressure metamorphism is restricted to the internal zone, it is not clear whether the other two zones have also subducted to great depth.

The fault zone that separates the two is the Periadriatic Seam that runs through the Alps. Studies indicate that in addition to deforming, the Eurasian continental crust has actually subducted to some extent below the Adriatic/Apulian Plate, an unusual circumstance in plate tectonics. Oceanic crust of the African Plate is also subducting under the Adriatic/Apulian Plate off the western and southern coasts of the Italian Peninsula, creating a berm of assorted debris which rises from the seafloor and continues onshore. This subduction is also responsible for the volcanics of southern Italy.

The geology of the suture includes Jurassic marine shale and conglomeratic strata, melange and ophiolites and volcanic rocks from multiple pulses of magmatism. Each of these lithologies can be tied to specific terranes, either island arcs or microcontinents, that were gathered in front of the Indian subcontinent as it drifted northward during the Mesozoic. During the Jurassic-Cretaceous collision of the Lhasa and Qiangtang terranes, the ancient Tethys ocean closed, creating the Bangong suture zone. Oceanic lithosphere (the Meso-Tethys) was consumed during this collision and subducted under the Qiangtang terrane.

"Cordilleran" style of arc terrane accretion onto a continental land mass. Continued subduction transports the arc terrane to the margin of the continent where it is too buoyant to be subducted so it gets accreted to the continent. The Nevadan Orogeny began with the formation of a continental volcanic arc due to east dipping subduction of the Farallon Plate beneath the North American Plate. Continued subduction of oceanic crust transported multiple oceanic arc terranes to the western margin of North America where they were accreted onto the edge of the continent.

The Aleutian subduction zone is a ~2500 mile-long convergence boundary between the North American Plate and the Pacific Plate, that extends from the Alaska Range to the Kamchatka Peninsula. Here, the Pacific Plate is being subducted underneath the North American plate and the rate of subduction changes from west to east from 7.5 cm/yr to 5.1 cm/yr. The Aleutian subduction zone includes two prominent features _,_ the Aleutian arc and the Aleutian trench. The island arc was created via volcanic eruptions from dehydration of the subducting slab at ~100 km depth.

The North American Cordillera is a well-studied plate margin that provides a good example of the effects a slab window can have on an over-riding continental plate. Beginning in the Cenozoic, the fragmentation of the Farallon Plate as it subducted caused slab windows to open that then generated anomalous features in the North American Plate. These effects include distinct fore-arc volcanism and extension in the plate which may be a contributing factor to the formation of the Basin and Range Province.Thorkelson, Derek J., Taylor, Richard P., 1989, Cordilleran slab windows: Geology, v.

Location map of Borneo in Maritime Southeast Asia, the Red River Fault is included in the map. Borneo was formed through Mesozoic accretion of microcontinental fragments, ophiolite terranes and island arc crust onto a Paleozoic continental core. At the beginning of the Cenozoic Borneo formed a promontory of Sundaland which partly separated from Asian mainland by the proto-South China Sea. The oceanic part of the proto-South China Sea was subducted during the Paleogene period and a large accretionary complex formed along the northwestern of the island of Borneo.

Magmatism associated with subduction occurred not near the plate edges (as in the volcanic arc of the Andes, for example), but far to the east, called the Coast Range Arc. Geologists call such a lack of volcanic activity near a subduction zone a magmatic gap. This particular gap may have occurred because the subducted slab was in contact with relatively cool continental lithosphere, not hotter asthenosphere. One result of shallow angle of subduction and the drag that it caused was a broad belt of mountains, some of which were the progenitors of the Rocky Mountains.

The Shetland Plate is a tectonic microplate located off the tip of the Antarctic Peninsula and contains the South Shetland Islands. The plate is bordered on three sides by the Antarctic Plate and the fourth side is bordered by the Scotia Plate. The northwestern border is defined by the South Shetland Trench separating the Shetland Plate to the south from the Antarctic Plate to the north. This trench is the remnant of a subduction zone where the defunct Phoenix Plate, now part of the Antarctic Plate, subducted under the Antarctic Peninsula and the Shetland Islands.

However, at the time of its formation the volcanic belt may have been coincident with the subducted plate boundary. Also, the timing of volcanism corresponds to shifts of plate motion and changes in the locus of volcanism along the Pemberton and Garibaldi volcanic belts. This brief interval of plate motion adjustment at about 3.5 million years ago may have triggered the generation of basaltic magma along the descending plate edge. Because the Alert Bay Volcanic Belt has not been active for at least 3.5 million years, volcanism in the Alert Bay Volcanic Belt is probably extinct.

Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches Oceanic trenches are topographic depressions of the seafloor, relatively narrow in width, but very long. These oceanographic features are the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab.

Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography. The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction. At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan. As the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time.

There are, nevertheless, traces in seamounts on Hikurangi of a second Late Cretaceous magmatic event contemporaneous with volcanism on New Zealand and associated with the final break-up of Gondwana. The Hikurangi Plateau has been partly subducted under the Chatham Rise, probably during the Cretaceous, and probably resulting in a slab more than long. The western margin of the plateau is actively subducting under the North Island of New Zealand to a depth of . With these missing portions of the plateau added to it, the Hikurangi Plateau originally must have covered , an area similar to that of the Manihiki Plateau to the north.

Slow rupture velocities are linked to propagation through relatively weak material, such as poorly consolidated sedimentary rocks. Most tsunami earthquakes have been linked to rupture within the uppermost part of a subduction zone, where an accretionary wedge is developed in the hanging wall of the megathrust. Tsunami earthquakes have also been linked to the presence of a thin layer of subducted sedimentary rock along the uppermost part of the plate interface, as is thought to be present in areas of significant topography at the top of the oceanic crust, and where propagation was in an up-dip direction, possibly reaching the seafloor.

Behn, M. D., Kelemen, P. B., Hirth, G., Hacker, B. R., and Massonne, H. J., 2011, Diapirs as the source of the sediment signature in arc lavas: Nature Geoscience, v. DOI: 10.1038/NGEO1214. Diapiric rise of a much larger subducted continental body has been invoked to explain the exhumation of the Papua New Guinea UHP terrain.Little, T. A., Hacker, B. R., Gordon, S. M., Baldwin, S. L., Fitzgerald, P. G., Ellis, S., and Korchinski, M., 2011, Diapiric Exhumation of Earth’s youngest (UHP) eclogites in the gneiss domes of the D'Entrecasteaux Islands, Papua New Guinea: Tectonophysics, v.

The central band is a mix of volcanic and sedimentary rocks of mid-to-late Ordovician age comprising the lavas and tuffs of the Borrowdale Volcanic Group, erupted as the former Iapetus Ocean was subducted beneath what is now the Scottish border during the Caledonian orogeny. The northern central peaks, such as Great Rigg, were produced by considerable lava flows. These lava eruptions were followed by a series of pyroclastic eruptions which produced a series of calderas, one of which includes present-day Scafell Pike. These pyroclastic rocks give rise to the craggy landscapes typical of the central fells.

Granitic and metasedimentary rocks are the primary constituent of the San Gabriel Mountains. Metasedimentary rocks were attached to the north american craton in the Precambrian eon, and granitic rocks formed throughout the Mesozoic as oceanic plates subducted underneath the north American west coast. Like nearly all of the other mountains in the Transverse Ranges, the San Gabriels are a series of fault blocks that were uplifted in the Cenozoic.USGS Tectonic uplift rates and erosion rates systematically increase as topography steepens eastward in the San Gabriel Mountains, where the San Andreas and San Jacinto faults meetDiBiase, R.A., Rossi, M.W. and Neely, A.B., 2018.

The Main Uralian Fault formed in the Riphean (early Neoproterozoic) in the breakup of the supercontinent Rodinia as a rift valley between the Baltica and the Angara Plate (Siberian craton). As these two plates pulled apart eventually a mid-ocean ridge formed. The ridge was of basic (basalt) and ultramafic material. Some 500 million years later, in the Silurian, a subduction zone formed on the western margin of the Angara Plate, which at the time was on the western edge of Gondwana, and the oceanic plate was subducted underneath the Angara Plate, accreting some of the basalts and ultramafics onto the Angara Plate.

Shallow-focus earthquakes are the result of the sudden release of strain energy built up over time in rock by brittle fracture and frictional slip over planar surfaces. However, the physical mechanism of deep focus earthquakes is poorly understood. Subducted lithosphere subject to the pressure and temperature regime at depths greater than 300 km should not exhibit brittle behavior, but should rather respond to stress by plastic deformation. Several physical mechanisms have been proposed for the nucleation and propagation of deep-focus earthquakes; however, the exact process remains an outstanding problem in the field of deep earth seismology.

After subduction of oceanic crust of the European plate collision nearly completely stopped in the Western and Central Alps (See map Figure 2)., These parts are still uplifted up to 2.5 mm/year in some areas. It is thought it is mainly due to rebound after weight loss from melting ice caps after the last Ice Age, intensive erosion during glactation and some processes in the Earth mantle. Adriatic plate, pushed by the African plate, still rotates counterclockwise around the axis near Ivrea in northwestern Italy and is subducted in Eastern Alps and causes tectonic uplift (thrust) there.

Plate tectonics of the Intermontane Islands arc 195 million years ago The Slide Mountain Ocean was an ancient ocean that existed between the Intermontane Islands and North America beginning around 245 million years ago in the Triassic period. It is named after the Slide Mountain Terrane, which is composed of rocks from the ancient oceanic floor. There was a subduction zone on the Slide Mountain Ocean's floor called the Intermontane Trench where the Intermontane Plate was being subducted under North America. The floor of the Slide Mountain Ocean was pushed up onto the ancient margin of North America.

Although Meiji is the oldest extant seamount in the Hawaii-Emperor chain, the question of whether there were older seamounts in the chain which have already been subducted into the trench remains open, and is the subject of ongoing scientific research. The Deep Sea Drilling Project (DSDP) Leg 19, Hole 192A, recovered of pillow lava from near the summit of Meiji. The lavas were initially classified as alkali basalts on the basis of their mineralogy, but subsequent microprobe analyses of glass and pyroxene suggested that they are tholeiitic in origin. At least five flows were found.

Map of the Bering Sea, with the Aleutian Basin clearly discernable here in the southwest portion of the sea. The Aleutian Basin is an oceanic basin under the southwestern Bering Sea. While the northeastern half of the Bering Sea overlies the North American Plate in relatively shallow water, the Aleutian Basin consists of oceanic plate--the remnant of the Kula Plate that was mostly subducted under the North American Plate.New Views of the U.S. Continental Margins (University of New Hampshire) Subduction of the Kula Plate ceased after the creation of the Aleutian Trench to its south.

The small Juan de Fuca Plate and two platelets, the Explorer Plate and Gorda Plate are the meager remnants of the much larger Farallon oceanic plate. The Explorer Plate broke away from the Juan de Fuca about 4 million years ago and shows no evidence that it is still being subducted. The Gorda platelet split away between 18 and 5 million years ago and continues to sink beneath North America. The Cascade Volcanic Arc made its first appearance 36 million years ago, but the major peaks that rise up from today's volcanic centers were born within the last 1.6 million years.

Particularly within the Quaternary, the Cocos Plate which split off the Pacific Plate in the Oligocene has subducted beneath the Caribbean and North American plates, producing a chain of volcanoes along the Pacific Coast of Guatemala. The North American and Caribbean plates are moving with strike-slip displacement along the Motagua-Polochic Fault Zone. Some have looked to the Paleozoic organic shales and the Todos Santos sandstone, with its evaporite "cap" as a potential reservoir for oil and gas. The Sierra de Santa Cruz Massif has an ophiolite zone with serpentized harzburgite around a two kilometer thick gabbro pluton with quartz diorite.

The Izu-Ogasawara Trench lies south of Japan The , also known as Izu-Bonin Trench, is an oceanic trench in the western Pacific Ocean, consisting of the Izu Trench (at the north) and the Bonin Trench (at the south, west of the Ogasawara Plateau). It stretches from Japan to the northernmost section of Mariana Trench.Deep current structure above the Izu-Ogasawara Trench The Izu- Ogasawara Trench is an extension of the Japan Trench. Here, the Pacific Plate is being subducted beneath the Philippine Sea Plate, creating the Izu Islands and Bonin Islands on the Izu-Bonin-Mariana Arc system.

For example, an igneous rock such as basalt may break down and dissolve when exposed to the atmosphere, or melt as it is subducted under a continent. Due to the driving forces of the rock cycle, plate tectonics and the water cycle, rocks do not remain in equilibrium and change as they encounter new environments. The rock cycle explains how the three rock types are related to each other, and how processes change from one type to another over time. This cyclical aspect makes rock change a geologic cycle and, on planets containing life, a biogeochemical cycle.

The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench under the North American Plate well north of San Francisco. In California, the plate borders the North American Plate along a transform boundary, the San Andreas Fault. The westward component of the North American Plate's motion and the irregularity of the San Andreas Fault results in some compressive force along the San Andreas and its associated faults, thus helping lift the Coast Ranges.

At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan. As the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced gradually to its present position in front of Taitao Peninsula at 46°15’. Taitao Peninsula lies near the triple junction and various geological features, such as the Taitao ophiolite, are related to the dynamics of the triple junction.

The Chile Triple Junction (or Chile Margin Triple Junction) is a geologic triple junction located on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula on the southern coast of Chile. Here three tectonic plates meet: the South American Plate, the Nazca Plate, and the Antarctic Plate. This triple junction is unusual in that it consists of a mid-oceanic ridge, the Chile Rise, being subducted under the South American Plate at the Peru–Chile Trench. The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene epoch forming the Chile Triple Junction.

The ridge is primarily composed of mid- ocean ridge basalt, which erupted on the Nazca Plate when the plate was already 5-13 Ma old. Based on isotopic ratios and rare earth element composition, it is estimated that the magma was sourced at approximately 95 km depth from a 7% partial melt. The Nazca Ridge has a conjugate feature on the Pacific Plate, the Tuamotu Plateau. Magnetic anomalies have shown that there was symmetrical spreading at the Pacific-Farallon/Nazca center, so the Tuamotu Plateau can be used as a proxy for the pre-subducted Nazca Ridge geometry.

The Nazca Plate began subducting into the Peru-Chile trench 11.2 Ma at 11°S. Due to the oblique orientation of the ridge to the Nazca-South American plate collision zone, the ridge has migrated south along the active margin to its current location at 15°S. Based on Tuamotu Plateau mirror relationship, it is estimated that of the Nazca Ridge has already subducted. The speed of migration has slowed over time, with the ridge migrating at per year until 10.8 Ma, then slowing to per year from 10.8-4.9 Ma. The current ridge migration rate is per year.

The Miocene-aged Cordillera Blanca Batholith intrudes the Coastal Batholith over 50 kilometer thick crust, with S-type peraluminous granites produced by deformation and uplift. The majority of rocks in the batholith are high-sodium, high-silica I-type granites, with characteristics that have been interpreted as subducted oceanic crust melts. However, it does not have positioning consistent with subduction and geologists have interpreted it as underplating leading to partial melting, the formation of trondhjemitic magmas rich in clinopyroxene, garnet and amphibole. Intense volcanism, deformation and plutonism was common in the Miocene and Pliocene in central Peru.

The geology of the island Barbados includes exposures of reef-related carbonate rocks spanning 85 percent of the island's surface. This Coral Rock Formation is 70 meters thick and dates to the Pleistocene. Unlike neighboring islands in the Lesser Antilles volcanic arc, Barbados is unusual because it is not a volcanic island (the only volcanic rocks are some ash beds from eruptions on neighboring islands). Instead, the island of Barbados is the exposed part of the Barbados Ridge Accretionary Prism, left as deep ocean sediments "scraped" to the surface as the Atlantic oceanic crust subducted beneath the Caribbean Plate.

From the Paleocene into the Oligocene, the conglomerate, coal seams and sandstone of the Amphitheatre Formation deposited atop the Alexander and Wrangellia terranes in a basin that developed along the Denali Fault. Placer gold accumulated within the conglomerate and then eroded out and became new placer material within the Kluane Ranges. During the Miocene, andesite, basalt and volcaniclastic rocks erupted as the Pacific Plate subducted beneath Alaska and the Yukon. The Ruby Range suite pluton formed the core of the Coast Plutonic Complex with tonalite and granodiorite between 64 and 56 million years ago, with significant copper-molybdenum porphyry and epithermal mineralization.

Tropical areas, Journal of Geophysical Research-Oceans, 112 (C10), 2007. For the western Pacific, the mechanism for BLT formation is different. Along the equator, the eastern edge of the warm pool (typically 28 °C isotherm - see SST plot in the western Pacific) is a demarcation region between warm fresh water to the west and cold, salty, upwelled water in the central Pacific. A barrier layer is formed in the isothermal layer when salty water is subducted from the east into the warm pool due to local convergence and warm fresh water overrides denser water to the east.

Unlike molecular H2O that is found on the surface, water in the interior exists primarily in hydrated minerals or as trace amounts of hydrogen bonded to oxygen atoms in anhydrous minerals. Hydrated silicates on the surface transport water into the mantle at convergent plate boundaries, where oceanic crust is subducted underneath continental crust. While it is difficult to estimate the total water content of the mantle due to limited samples, approximately three times the mass of the Earth's oceans could be stored there. Similarly, the Earth's core could contain four to five oceans' worth of hydrogen.

The width of the Cascadia subduction zone varies along its length, depending on the angle of the subducted oceanic plate, which heats up as it is pushed deeper beneath the continent. As the edge of the plate sinks and becomes hotter and more molten, the subducting rock eventually loses the ability to store mechanical stress; earthquakes may result. On the Hyndman and Wang diagram (not shown, click on reference link below) the "locked" zone is storing up energy for an earthquake, and the "transition" zone, although somewhat plastic, could probably rupture. USGS (dead link) See fig.

The IBM trench is where the Pacific Plate lithosphere begins to sink. The IBM trench is devoid of any significant sediment fill; the ~400 m or so thickness of sediments is completely subducted with the downgoing plate. The IBM outer trench swell rises to about 300 m above the surrounding seafloor just before the trench. The lithosphere that is about to descend into a trench starts to bend just outboard of the trench; the seafloor is elevated into a broad swell that is a few hundred meters high and referred to as the "outer trench bulge" or “outer trench rise”.

Cenozoic sediments are unimportant except for volcanic ash and Asian loess deposited adjacent to Japan and carbonate sediment s associated with the relatively shallow Caroline Ridge and Caroline plate. Strong seafloor currents are probably responsible for this erosion or non-deposition. The compositions of sediments being subducted beneath the northern and southern parts of the IBM arc are significantly different, because of the Cretaceous off-ridge volcanic succession in the south that is missing in the north. Lavas and volcaniclastics associated with an intense episode of intraplate volcanism correspond in time closely to the Cretaceous Superchron.

These volcanoes are thought to have formed as a result of the North American Plate sliding westward over a small hotspot, called the Anahim hotspot. The hotspot is considered similar to the one feeding the Hawaiian Islands. The belt is defined by three large shield volcanoes (Rainbow, Ilgachuz and the Itcha Ranges) and 37 Quaternary basalt centers. Eruptions of basaltic to rhyolitic volcanoes and hypabyssal rocks of the Alert Bay Volcanic Belt in northern Vancouver Island are probably linked with the subducted margin flanked by the Explorer and Juan de Fuca Plates at the Cascadia subduction zone.

These horsts and grabens extend from onshore areas northward into a complex offshore terrane that includes the Ionian Sea abyssal plain to the northeast. This plain is underlain by oceanic crust that is being subducted to the north and east beneath the Hellenic arc. The Pelagian province to the west, particularly the pull-apart basins of the Sabratah Basin and extending along the South Cyrenaica Fault Zone (SCFZ) and the Cyrenaica Platform to the east, is strongly influenced by extensional dextral strike-slip faulting. To the south, the Nubian Swell is the stable continental basement for this rifted basin.

With eruptions becoming infrequent and the seamount losing its ability to maintain itself, the volcano starts to erode. After finally becoming extinct (possibly after a brief rejuvenated period), they are ground back down by the waves. Seamounts are built in a far more dynamic oceanic setting than their land counterparts, resulting in horizontal subsidence as the seamount moves with the tectonic plate towards a subduction zone. Here it is subducted under the plate margin and ultimately destroyed, but it may leave evidence of its passage by carving an indentation into the opposing wall of the subduction trench.

The passive margin switched to active margin in the early-to-mid Mesozoic when the Farallon Plate under the Pacific Ocean started to dive below the North American Plate, creating a subduction zone; volcanoes and uplifting mountains were created as a result. Erosion over many millions of years created a relatively featureless plain. Stretching of the crust under western North America started around 16 Ma and is thought to be caused by upwelling from the subducted spreading-zone of the Farallon Plate. This process continues into the present and is thought to be responsible for creating the Basin and Range province.

Water is the most important component in the volcano's fumarolic gases, comprising 96.05% to 97.95% by volume. Examinations of deuterium and oxygen-18 content of the water have determined that like the water of fumaroles in other Andean volcanic centres, Irruputuncu water is a mixture of weather-related water and water contained in andesite. The helium isotope ratios indicate the magmatic component dominates the gasses at Irruputuncu, Much of the carbon dioxide comes from subducted and crustal carbonates. The gases escape from oxidizing magma at and pass through a weakly developed hydrothermal system with temperatures of .

It lies at the northern extremity of the Pacific spreading axis. To its east is the Explorer Plate, which together with the Juan de Fuca Plate and the Gorda Plate to its south, is what remains of the once-vast Farallon Plate which has been largely subducted under the North American Plate. The Explorer Ridge consists of one major segment, the Southern Explorer Ridge, and several smaller segments. It runs northward from the Sovanco Fracture Zone to the Queen Charlotte Triple Junction, a point where it meets the Queen Charlotte Fault and the northern Cascadia subduction zone.

The mountains of southern Europe that fringe the Mediterranean Sea and run generally in an east-west direction are of the folded type generated by collision of the northward-moving African Plate with the Eurasian Plate. Where the northern edge of the African Plate is being subducted in an irregular line a second orogeny occurs that is not entirely understood. The mountains of Italy and Greece are a combination of Folded Mountains and Fault-block mountains running in a northwest–southeast direction. The Hellenic Subduction carries the leading edge of the African Plate under the Aegean Sea Plate at the Hellenic Trench.

The Indo-Australian Plate and Pacific Plate boundary is the most complex boundary of the Macquarie Triple Junction region, due to the unique collision of the two plates creating two convergent boundaries separated by a transform boundary. The Puysequr Trench, which includes the Fjord Trench, is the southern region of the boundary closest to the Macquarie Triple Junction. The Puysequr Trench formed as the Indo-Australian Plate subducted beneath the Pacific plate. The Puysequr Trench ranges approximately 800 kilometers in length, from the most southern tip of the New Zealand Islands to the Macquarie Triple Junction.

The Puysequre Trench makes contact with the Macquarie Fault Zone, which is associated with the Alpine Fault. The Alpine Fault is the right-lateral transform fault boundary separating the Puysequr Trench and the northern Kermadec Trench. The Alpine Fault runs through the majority of the southern island of New Zealand and is associated with New Zealand's frequent and intense earthquake history. The last major region of the Indo-Australian Plate and Pacific Plate Boundary is the Kermadec-Tonga subduction zone at which the Pacific Plate is subducted beneath the Indo-Australian Plate, in opposition of the Puysequr Trench.

The Molucca Sea Collision Zone is the site of an orthogonal collision between two active subduction systems. Both the Halmahera subduction system to the east, and the Sangihe subduction system to the west, have subducted oceanic lithosphere of the Molucca Sea plate, which has been completely consumed, with the Sangihe arc now over-riding the Halmahera forearc.Colin G Macpherson et ors, Geochemical evolution of magmatism in an arc-arc collision: the Halmahera and Sangihe arcs, eastern Indonesia, in Robert D Larter, ed, (2003) Intra-oceanic Subduction Systems, Geological Society of London. p208 Both volcanic arcs have been active since the Neogene.

Some academic literature refers to the arcs by location – so that main arc can be referred to as the 'southern', the 'western' Situated at the centre of three converging and colliding major tectonic plates, Indo- Australia, Eurasia, Pacific, the Banda arc comprises young oceanic crust enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian continental margin. It is a complex subduction setting (where one plate moves under another, sinking into the Earth's mantle), with possibly the largest fold on Earth, extending to a depth of about , in a subducted plate.

Arc volcanism and extension occurred as the Neo-Tethys Ocean subducted under the southern margin of Laurasia during the Mesozoic. Uplift and compressional deformation took place as the Neotethys continued to close. Seismic surveys indicate that rifting began in the Western Black Sea in the Barremian and Aptian followed by the formation of oceanic crust 20 million years later in the Santonian. Since its initiation, compressional tectonic environments led to subsidence in the basin, interspersed with extensional phases resulting in large-scale volcanism and numerous orogenies, causing the uplift of the Greater Caucasus, Pontides, Southern Crimean Peninsula and Balkanides mountain ranges.

Sangay lies above a seismogenic tectonic slab located about beneath Sabancaya, reflecting a sharp difference in the thermal character of the subducted oceanic crust, between older rock beneath southern Ecuador and Peru (dated more than 32 million years old), and younger rock under northern Ecuador and Colombia (dated less than 22 million years old). The older southern rock is more thermally stable than the northern crust, and to this is attributed the long break in volcanic activity in the Andes; Sangay occupies a position at the boundary between these two bodies, accounting for its high level of activity.

To the east, the Valais oceanic crust, together with a piece of Iberian continental crust (called the Briançonnais terrane), subducted beneath the Apulian plate, a part of the African tectonic plate that had begun to move independently. This process eventually led to the formation of the Alps. To the west, no subduction took place, but the Iberian plate moved against the European plate along a large transform fault, which led to the formation of the Pyrenees. Fragments of Valais oceanic crust have been obducted and can be found as ophiolites in the Penninic nappes of the Alps.

2013 layout of installations at Ocean Networks Canada's Cascadia Basin site on the NEPTUNE observatory. The Cascadia Basin is the heavily sediment part of the Juan de Fuca Plate that extends from the base the continental margin to the west where the sediments lap on to the Juan de Fuca Ridge flank. The Juan de Fuca Plate is one of the last remnants of the Farallon Plate, the original eastern Pacific oceanic plate, which has been almost entirely subducted beneath North America. The flat sediment surface constitutes an abyssal plain, an exceedingly vast environment that covers over 50% of the planet’s surface.

This in turn produced thicker oceanic crust and thicker regions of underlying depleted lithospheric mantle. As such, the density of the lithosphere was reduced due to both differentiation of the crust from the mantle and the ensuing relative depletion of the residual mantle in Fe and Al. These expected properties have led to suggestions that oceanic lithosphere was so light that it subducted very shallowly or not at all. Scientists who favour this hypothesis argue that felsic material formed from hydrous partial melting of thickened oceanic crust in the root zones of oceanic plateaus, and not from subduction zones as generally believed.

Japanese archipelago relief (including submerged parts) The breakup of Rodinia about 750 million years ago formed the Panthalassa ocean, with rocks that eventually became Japan sitting on its eastern margin. In the Early Silurian (450 million years ago), the subduction of the oceanic plates started, and this process continues to the present day, forming a roughly 400 km wide orogeny at the convergent boundary. Several (9 or 10) oceanic plates were completely subducted and their remains have formed paired metamorphic belts. The most recent complete subduction of a plate was that of the Izanagi Plate 95 million years ago.

In the Middle Miocene, the Pacific-Farallon Ridge was subducted beneath North America ending subduction along this part of the Pacific margin; however, the Farallon Plate continued to subduct into the mantle. The movement at this boundary divided the Pacific- Farallon Ridge and spawned the San Andreas transform fault, generating an oblique strike-slip component. Today, the Pacific Plate moves north-westward relative to North America, a configuration which has given rise to increased shearing along the continental margin. The tectonic activity responsible for the extension in the Basin and Range is a complex and controversial issue among the geoscience community.

The geometry of a slab window depends primarily on the angle the ridge intersects the subduction zone and the dip angle of the down-going plate. Other influential factors include the rates of divergence and subduction as well as heterogeneities found within specific systems. There are two end-member scenarios in terms of the geometry of a slab window: the first is when the subducted ridge is perpendicular to the trench, producing a V-shaped window, and the second is when the ridge is parallel to the trench, causing a rectangular window to form. Guillaume, Benjamin et al.

The Apsheron Sill, Absheron Sill, Apsheron Ridge or Apsheron Threshold is a major northwest–southeast trending bathymetric high that runs for about 250 km across the whole of the Caspian Sea from Baku in Azerbaijan to the Cheleken Peninsula in Turkmenistan. The sill separates the central and southern parts of the Caspian Sea. It is interpreted to be the surface expression of a northeast-dipping subduction zone along which oceanic crust of the South Caspian Basin is being subducted beneath the Central Caspian as part of the complex zone of continental collision between the Arabian Plate and the Eurasian Plate.

Most of the relative motion between the Pacific and Eurasia plates is accommodated approximately to the east-southeast of the epicenter of the earthquake, where the Pacific Plate subducts beneath the Okhotsk Plate. This shallow crustal earthquake was followed 13 hours later by a deep focus magnitude 6.8 quake roughly to the west, below the Sea of Japan. The two earthquakes were generated by different mechanisms. The first earthquake was caused by deformation within the crust of the Okhotsk Plate and the second quake was likely caused by faulting resulting from internal deformation of the subducted Pacific Plate.

The Austral Volcanic Zone was identified as such in 1976, but some volcanoes were identified and localized later. Owing to their similar composition the three northerly volcanoes Lautaro, Viedma and Aguilera are grouped as the "northern Austral Volcanic Zone". Volcanism in the Austral Volcanic Zone is not well known before the Holocene; it is likely that a lull of volcanism occurred before the Pliocene while the Chile Triple Junction was being subducted in the region. Magmas from the Austral Volcanic Zone are adakitic owing to the melting of the subducting slab and the interaction of these melts with the crust and mantle.

The volcanism might have been mostly generated by asthenospheric upwelling possibly by displacement along the transform fault. If the transform fault had a section of vertical tearing to contain potentially different dip angles between the Explorer and Juan de Fuca Plates, the subducted plate asthenosphere may possibly flow upward into the mantle wedge. Similarly, if the displacement had a section of extension, a horizontal slab window-like gap would have developed, again allowing a pathway for upwelling magma. In either case, the unsettled asthenosphere might have experienced low degrees of decompressional melting and interacted with North American lithosphere to yield within plate compositions.

For the most part, the North American Plate moves in roughly a southwest direction away from the Mid-Atlantic Ridge at a rate of about 2.3 centimeters (~1 inch) per year. At the same time, the Pacific Plate is moving to the northwest at a speed of between 7 and 11 centimeters (~3-4 inches) a year. The motion of the plate cannot be driven by subduction as no part of the North American Plate is being subducted, except for a small section comprising part of the Puerto Rico Trench; thus other mechanisms continue to be investigated. One recent study suggests that a mantle convective current is propelling the plate.

Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is, therefore, cooler and denser; hence its great height difference relative to the higher-riding (and younger) Mariana Plate. The deepest area at the plate boundary is the Mariana Trench proper. The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands. These volcanic islands are caused by flux melting of the upper mantle due to the release of water that is trapped in minerals of the subducted portion of the Pacific Plate.

Other forms of evidence include the Farallon Islands, Catalina Islands, and uplift of the Diablo Mountain Range as a result of the clogged subduction zone mentioned above. These observations can be explained by a model for the weakening and ultimate falling apart of the uppermost part of the subducted oceanic plate in the 20–30 m.y. after the end of rapid subduction. As the plate falls apart, not only is compressional stress relieved, but significant back-slip along the old subduction zone is also possible, perhaps bringing blueschist rapidly upward from 20- to 30-km depths, where it can be observed along the California coast to this day.

The white line is formed because the currents bring fresh, cool and nutritious water loaded with minerals from the depths of the ocean to the surface. When this occurs, it moves west along the surface, with a 70-metre zone of cool water and a 40-metre zone of warm water, that has been subducted under the cold water leading to a lot of turbulence quite often. When these conditions are present tiny algae called Rhizosolenia, part of the diatom family, begin to flourish. No thicker than two or three times the width of a human hair, they pile up ahead of the line as it moves west.

Most earthquakes occur within the 1000 °C isotherm, in the interior of the slab that has not yet heated up to match the temperature of the surrounding mantle into which it is being subducted. At depths below the thickness of the lithosphere, earthquakes are no longer generated by thrusting at the interface of the two plates, because the asthenosphere is weak and cannot support the stresses necessary for faulting. In this region, internal deformation of the still-cool down-going slab is the source of the earthquakes. Up to depths of 300 km, dehydration reactions and the formation of eclogite are the main causes of seismicity.

The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction. At first, the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction was located near the Strait of Magellan. As the southern part of the Nazca Plate and the Chile Rise became consumed by subduction, the more northerly regions of the Antarctic Plate began to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time. The asthenospheric window associated to the triple junction disturbed previous patterns of mantle convection beneath Patagonia inducing an uplift of c.

Individual volcanoes drift southwest from the hotspot at a rate of about per year with each successive volcanic centre spending about two million years actively attached to the plume. The oldest Anahim volcano, situated on the Central Coast of British Columbia, formed 14.5 million years ago. If any prior record in the form of seamounts existed off the British Columbia Coast, this record would presumably have been subducted under North America with the Farallon/Juan de Fuca plates and lost. Thus it is unknown if the hotspot existed in the Pacific Ocean prior to being located on the North American continent from ongoing plate motion.

About 85 Ma ago the part of the Farallon plate from approximately California to the Gulf of Alaska separated to form the Kula Plate. ; ; ; ; . The period 48-50 Ma (mid-Eocene) is especially interesting as this is when the subducted Kula--Farallon spreading ridge passed below what is now the OWL.. A slightly variant view is that this piece of the Kula plate had broken off to form the Resurrection Plate , so this was actually the Resurrection--Farallon spreading ridge. (The Burke Museum has some nice diagrams of this.) This also marks the onset of the Oregon rotation, possibly with rifting along the OWL,; .

Relative plate motions of North America showing the San Francisco Bay Area centered on the strike-slip San Andreas Fault System The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench. In California, the plate is sliding northwestward along a transform boundary, the San Andreas Fault, toward the subduction zone. At the same time, the North American Plate is moving southwestward relative to the Earth's core, but southeastward relative to the Pacific Plate, due to the latter's much faster northwestward motion.

In the process, the plate under the Rheic Ocean between Euramerica and the European Hunic terranes subducted and rifts in this plate resulted in the formation of a small Rhenhercynian Ocean which lasted until Late Carboniferous time. In the Early Devonian, the eastern part of Paleo- Tethys opened up, when the Asiatic Hunic terranes, including the North and South China microcontinents, moved northward. These events caused Proto-Tethys Ocean, a precursor of Paleo-Tethys, to shrink, until the Late Carboniferous, when the Chinese blocks collided with Siberia. In the Early Carboniferous however, a subduction zone developed south of the European Hunic terranes consuming Paleo-Tethys oceanic crust.

It has also been reported from the Sixiangkou meteorite in the Gaogang District, Jiangsu Province, Taizhou Prefecture, China; the Zagami Martian meteorite, Katsina State, Nigeria and from the Umbarger meteorite, Randall County, Texas. Akimotoite is believed to be a significant mineral in the Earth's mantle at depths of in cooler regions of the mantle such as where a subducted slab enters into the lower mantle. Akimotoite is elastically anisotropic and has been suggested as a cause of seismic anisotropy in the lower transition zone and uppermost lower mantle.Shiraishi, R., Ohtani, E., Kanagawa, K., Shimojuku, A., and Zhao, D. (2008) Crystallographic preferred orientation of akimotoite and seismic anisotropy of Tonga slab.

Monowai lies at the northern end of the Kermadec Arc north of New Zealand, in the Southwestern Pacific Ocean about halfway between Tonga and the Kermadec Islands. The Kermadec Arc is the southern part of the about long Tonga-Kermadec arc; this volcanic arc contains about 12 volcanic islands and at least 37 submarine volcanoes, which occur about every . Many of these volcanoes were only recently discovered and are poorly studied; hydrothermal activity has been observed at many. The Osbourn Trough and the Louisville seamount chain are being subducted close to Monowai and might have influenced the development of the seamount and the volcanic arc and back-arc in general.

Lamproites form from partially melted mantle at depths exceeding 150 km. The molten material is forced to the surface in volcanic pipes, bringing with it xenoliths and diamonds from the harzburgitic peridotite or eclogite mantle regions where diamond formation is stabilized. Recent research, for example on the lamproites at Gaussberg in Antarctica, and lead-lead isotope geochemistry have revealed that the source of lamproites may be transition zone melts of subducted lithosphere which has become trapped at the base of the lithospheric mantle. This observation also reconciles the depth of melting with the peculiar geochemistry, which is most easily explained by melting of already felsic material under deep mantle conditions.

F) Southern Mariana region. Slab dip is ~55°; seismicity is continuous to ~225 km, with an anomalous event at 375 km. Figure courtesy of Dr. Matt Fouch, Arizona State University More recently, provided an earthquake catalog containing improved locations (Figure 10). This data set shows that, beneath northern IBM, the dip of the WBZ steepens smoothly from ~40° to ~80° southwards, and seismicity diminishes between depths of ~150 km and ~300 km (Figures 11a c). The subducted slab beneath central IBM (near 25°N; Fig. 11c) is delineated by reduced seismic activity that nevertheless defines a more vertical orientation that persists southward (Figures 11d f).

For a typical distance that oceanic lithosphere must travel before being subducted, the thickness varies from about thick at mid-ocean ridges to greater than at subduction zones; for shorter or longer distances, the subduction zone (and therefore also the mean) thickness becomes smaller or larger, respectively. Continental lithosphere is typically about 200 km thick, though this varies considerably between basins, mountain ranges, and stable cratonic interiors of continents. The location where two plates meet is called a plate boundary. Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountains, volcanoes, mid-ocean ridges, and oceanic trenches.

Although subduction is thought to be the strongest force driving plate motions, it cannot be the only force since there are plates such as the North American Plate which are moving, yet are nowhere being subducted. The same is true for the enormous Eurasian Plate. The sources of plate motion are a matter of intensive research and discussion among scientists. One of the main points is that the kinematic pattern of the movement itself should be separated clearly from the possible geodynamic mechanism that is invoked as the driving force of the observed movement, as some patterns may be explained by more than one mechanism.

Franciscan rocks are thought to have formed prior to the creation of the San Andreas Fault when an ancient deep-sea trench existed along the California continental margin. This trench, the remnants of which are still active in the Cascadia and Cocos subduction zone, resulted from subduction of oceanic crust of the Farallon tectonic plate beneath continental crust of the North American Plate. As oceanic crust descended beneath the continent, ocean floor basalt and sediments were subducted and then tectonically underplated to the upper plate. This resulted in widespread deformation with the generation of thrust faults and folding, and caused high pressure-low temperature regional metamorphism.

Some early studies (e.g., ) dated accretion as late as 42 Ma. A recent study suggests it may have been as early as 55 Ma. This date has added significance as it is also the start of a change in direction of the Pacific plate, as seen in the bend in the Hawaiian-Emperor seamount chain, and also a change in the Pacific Northwest from compressional to extensional tectonics.; ; ; . This may also be when the last of the Resurrection plate was subducted under British Columbia.. Initiation of the north-striking right-lateral Straight Creek Fault at ~48 Ma. likely resulted from strain accumulated during the accretion of Siletzia.

The second stage of activity may be due to the approach of India, preceded by the rollback of the subducted slab and peaking at the time of the collision. North-dipping seismic reflections deep in the crust below the Gangdese batholith at a depth of may mark the downdip of the Yarlung-Zangbo suture, or may mark a more recent reverse fault. The Nyingchi complex forms the eastern segment of the Gangdese magmatic arc, and is mainly composed of plutons and their metamorphosed equivalents. I-type granitoids in this complex date to Ma, and appear to have been emplaced in the Lhasa terrane at the middle to lower crustal depths.

Olivine in a peridotite weathering to iddingsite within a mantle xenolith Serpentinized and carbonated peridotite Peridotite is the dominant rock of the Earth's mantle above a depth of about 400 km; below that depth, olivine is converted to the higher-pressure mineral wadsleyite. Oceanic plates consist of up to about 100 km of peridotite covered by a thin crust; the crust, commonly about 6 km thick, consists of basalt, gabbro, and minor sediments. The peridotite below the ocean crust, "abyssal peridotite," is found on the walls of rifts in the deep sea floor. Oceanic plates are usually subducted back into the mantle in subduction zones.

A hypothesis based on research conducted on the Bay of Islands complex in Newfoundland suggests that an irregular continental margin colliding with an island arc complex causes ophiolite generation in a back-arc basin and obduction due to compression.Cawood, P.A. and Suhr, G., (1992) The continental margin, promontories and reentrants along its length, is attached to the subducting oceanic crust, which dips away from it underneath the island arc complex. As subduction takes place, the buoyant continent and island arc complex converge, initially colliding with the promontories. However, oceanic crust is still at the surface between the promontories, not having been subducted beneath the island arc yet.

These terranes were subjected to extreme warping from continued subduction of the Kula plate, leading to the formation of the distorted Insular Mountains. Much of the central mountainous region around Strathcona Park is part of the Karmutsen Formation, which is a sequence of tholeiitic pillow basalts and breccias. Since Vancouver Island has become an accretionary wedge on the North American continent, the Kula Plate has fully subducted beneath it and the remnants of the Farallon Plate, the Juan de Fuca Plate, are now subducting below the island. This process has led to Vancouver Island being one of the most seismically active regions in Canada.

The radioactive decay of 190Pt to 186Os has a half-life of 6.5(3)×1011 years (which is longer than the age of the universe, so it is essentially stable). However, in-situ 187Os / 188Os and 186Os / 188Os of modern plume related magmas show simultaneous enrichment which implies a source that is supra-chondritic in Pt/Os and Re/Os. Since both parental isotopes have extremely long half-lives, the Os-isotope rich reservoir must be very old to allow enough time for the daughter isotopes to form. These observations are interpreted to support the theory Archean subducted crust contributed Os-isotope rich melts back into the mantle.

In this model, an expanse of oceanic crust subducted westward under the volcanic arc, causing the overlying sedimentary rocks of the Havallah sequence to be scraped off the descending plate and forced over the approaching continental slope. Snyder and Brueckner supported the Speed model with detailed lithic descriptions of the Havallah. They interpreted the lithic composition of the Havallah to be the sedimentary floor of an extensive ocean basin. Brueckner and Snyder expressed some uncertainty about the exact time of final emplacement of the allochthon, but emphasized that structures associated with the Sonoma orogeny had a long history from the middle Paleozoic to the Permian-Triassic periods.

The Slave broke off of Sclavia between 2.2 and 2.0 Ga, as noted by a host of dyke swarms at its margins. The Slave Craton drifted for approximately 200 million years before its accretion with the Rae Craton around 2.0–1.8 Ga in the Taltson–Thelon orogeny. The orogenic belt accreted smaller exotic terranes before the Slave was eventually subducted eastward under the Rae, resulting in a continental magmatic arc known as the Taltson magmatic zone. Continual eastward movement of the Slave province, along with collision of the Hottah terrane on the western margin of the Slave, lead to intense deformation of the Taltson magmatic zone.

The outer magmatic arc, of which the South Shetland Islands are a part, is a westward migration of the inner magmatic arc. Similar to the inner magmatic arc, the outer is composed of subduction-related acidic volcanism. A study on Alexander Island that focused on the conditions required for the generation of andesitic lavas postulated that the source for the andesitic lavas could be either the development of a slab-window due to the subduction of a spreading ridge or the breakup of the subducted slab beneath the fore-arc basin. The South Shetland Islands are bissected by two systems of strike-slip faults.

The Aleutian Islands are a volcanic arc lying above the convergent boundary where the Pacific Plate is being subducted beneath the North American Plate. Earthquakes in the area are caused by movement along the plate interface (such as the 1965 Rat Islands earthquake), normal faulting within the outer rise and within the subducting slab. The earthquake's epicenter lies close to a major break in the Aleutian chain, between the Andreanof Islands to the east and the Rat Islands to the west, along what is known as the Amchitka channel. In this region there is evidence for a tear in the lithosphere of the descending slab.

Basin and Range extension is therefore thought to be unrelated to the kind of extension produced by mantle upwelling which may cause narrow rift zones, such as the Afar Triple Junction. Geologic processes that elevate heat flow are varied, however some researchers suggest that heat generated at a subduction zone is transferred to the overriding plate as subduction proceeds. Fluids along fault zones then transfer heat vertically through the crust. This model has led to increasing interest in geothermal systems in the Basin and Range, and requires consideration of the continued influence of the fully subducted Farallon plate in the extension responsible for the Basin and Range Province.

Large magnitude earthquakes beneath the NFB have been attributed to a detached slab segment of the subducted Australian plate which collided with the subducting Pacific plate at a depth of 5 Ma. The earthquakes are the result of these colliding slabs settling on the 660 km discontinuity. Beneath Tonga at a depth of the number of earthquakes increases dramatically while the shape of the Pacific becomes complex. Hundreds of these earthquakes occur outside the Wadati- Benioff zone (top of slab) along an horizontal plane. The eastward subduction of the Australian plate (together with the now-fused South Fiji plate) under NFB created the New Hebrides and south Solomon Islands.

As a slab window develops, the mantle in that region becomes increasingly hot and dry. The decrease in hydration causes arc volcanism to diminish or stop entirely, as magma production in subduction zones generally results from hydration of the mantle wedge due to de-watering of the subducting slab. Slab-window magmatism may then replace this melting, and can be produced by multiple processes, including increased temperatures, mantle circulation producing interaction of supra- and sub-slab mantle, partial melting of subducted slab edges and extension in the upper plate. Mantle flowing upward through the slab window in order to compensate for the decreased lithospheric volume can also produce decompression melting.

Atwater's research paper, "Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of Western North America", established the essential framework for the plate tectonics of western North America. In her work, she explains that approximately 40 million years ago, the Farallon Plate was subducting underneath the North American Plate and the Pacific Plate. The lower half of the Farallon plate was entirely subducted under Southern California and the upper half did not sink, which eventually became known as the Juan de Fuca Plate.Since the southern section of Farallon completely disappeared, the boundary of southern California was now between the Pacific Plate and the North American Plate.

For example, sulfur at the time of Earth's formation should have (barring some accretion-related fractionation process for which there is little evidence) had a δ34S value of about 0‰, while sulfate in the modern oceans (the dominant marine sulfur species) has a δ34S of about +21‰. This implies that, over geologic time, a reservoir of correspondingly depleted (i.e. 34S-poor) sulfur was buried in the crust and possibly subducted into the deep mantle. This is because sulfate's reduction to sulfide is typically accompanied by a negative isotope effect, which (depending on the sulfate- reducing microorganism's enzymatic machinery, temperature, and other factors) can be tens of per mille.

Her work on the evolution of the continental crust has been cited over one thousand times. It explored the andesitic composition of continental crust that cannot be produced by basaltic magmatism - the building blocks of the continental crust do not match the edifice. There were several theories that explained the depletion; that the foundering of the magnesium and iron- rich lower crust occurs when tectonic plates force the deep crust to recrystallise, that exposure to air and water causes chemical weathering and that the basaltic oceanic crusts melts when it is subducted. Rudnick believes all three theories could explain the paradox of the composition of the crust.

The existence of Sangihe as a tectonic plate separate from the Molucca Sea Plate is not yet entirely agreed upon by geologists. Some see Sangihe as a western slab of the Molucca Sea Plate, just as they regard Halmahera as an eastern slab of the Molucca Sea Plate. What is apparent to date is that Sangihe was part of the Molucca Sea slab subducted during the Neogene between 45 Ma and 25 Ma.R. Hall and W. Spakman, Australian Plate Tomography and Tectonics in R. R. Hillis, R. D. Müller,Evolution and Dynamics of the Australian Plate, Geological Society of America Special Papers 2003, #372, p. 377 Seismicity shows the west- dipping Sangihe reaches a depth of about .

The Farallon Plate has almost completely subducted beneath the western portion of the North American Plate leaving that part of the North American Plate in contact with the Pacific Plate as the San Andreas Fault. The Juan de Fuca, Explorer, Gorda, Rivera, Cocos and Nazca plates are remnants of the Farallon Plate. The boundary along the Gulf of California is complex. The Gulf is underlain by the Gulf of California Rift Zone, a series of rift basins and transform fault segments between the northern end of the East Pacific Rise in the mouth of the gulf to the San Andreas Fault system in the vicinity of the Salton Trough rift/Brawley seismic zone.

Formation of the Juan de Fuca (including Explorer and Gorda) and Cocos plates (including Rivera) and of the San Andreas Fault from the Farallon plate Region of the modern Cascadia subduction zone A software model by NASA of the remnants of the Farallon Plate, deep in Earth's mantle. The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California. Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate.

Geological formations related to volcanism in the Canadian Cascade Arc, including the Alert Bay Volcanic Belt The Alert Bay Volcanic Belt is a heavily eroded Neogene volcanic belt in northern Vancouver Island, British Columbia, Canada. The belt is now north of the Nootka Fault, but may have been directly above the fault at the time it last erupted. Eruptions of basaltic to rhyolitic volcanoes and hypabyssal rocks of the Alert Bay Volcanic Belt are probably linked with the subducted margin flanked by the Explorer and Juan de Fuca plates at the Cascadia subduction zone. The Alert Bay Volcanic Belt is poorly studied, but appears to have been active in Miocene to Pliocene time.

Igneous oceanic plateaus have a ratio intermediate between continental and oceanic crust, although they are more mafic than felsic. However, when a plate carrying oceanic crust subducts under a plate carrying an igneous oceanic plateau, the volcanism which erupts on the plateau as the oceanic crust heats up on its descent into the mantle erupts material which is more felsic than the material which makes up the plateau. This represents a step toward creating crust which is increasingly continental in character, being less dense and more buoyant. If an igneous oceanic plateau is subducted underneath another one, or under existing continental crust, the eruptions produced thereby produce material that is yet more felsic, and so on through geologic time.

An example of a volcanic arc having both island and continental arc sections is found behind the Aleutian Trench subduction zone in Alaska. The arc magmatism occurs one hundred to two hundred kilometers from the trench and approximately one hundred kilometers above the subducting slab. This depth of arc magma generation is the consequence of the interaction between hydrous fluids, released from the subducting slab, and the arc mantle wedge that is hot enough to melt with the addition of water. It has also been suggested that the mixing of fluids from a subducted tectonic plate and melted sediment is already occurring at the top of the slab before any mixing with the mantle takes place.

Accretion involves the addition of material to a tectonic plate via subduction, the process by which one plate is forced under the other when two plates collide. The plate which is being forced down, the subducted plate, is pushed against the upper, over-riding plate. Sediment on the ocean floor of the subducting plate is often scraped off as the plate descends, this accumulated material is called an accretionary wedge (or accretionary prism), which is pushed against and attaches to the upper plate. In addition to accumulated ocean sediments, volcanic island arcs or seamounts present on the subducting plate may be amalgamated onto existing continental crust on the upper plate, increasing the continental landmass.

Zhao et al.'s model can be divided into two major stages: Neoarchean crustal accretion and Paleoproterozoic amalgamation of the two sub-blocks (Yinshan Block and Orods Block). Zhao and other researchers proposed that there was a major crustal accretion of the juvenile Yinshan Block at about 2.7 billion years ago, forming a thick mafic crust, although it is still uncertain whether the magmatic event occurred in a continental or an oceanic setting. During 2.55-2.50 billion years ago, the juvenile Yinshan Block was partially melted to produce enormous amounts of TTG rocks, covering the whole Yinshan Block. At about 2.45 billion years ago, Ordos Block was subducted beneath the Yinshan Block.

The Coast Mountains consists of deformed igneous and metamorphosed structurally complex pre- Tertiary rocks. These originated in diverse locations around the globe: the area is built of several different terranes of different ages with a broad range of tectonic origins. In addition, oceanic crust under the Pacific Ocean is being subducted at the southern portion of the range to form a north-south line of volcanoes called the Garibaldi Volcanic Belt, a northern extension of the Cascade Volcanoes in the northwestern United States, and contains the most explosive young volcanoes in Canada. Further north the northwesterly structural trend of the Coast Mountains lies partly in a large continental rift responsible for the creation of several volcanoes.

The current leading hypothesis for the LLSVPs is the accumulation of subducted oceanic slabs. This corresponds with the locations of known slab graveyards surrounding the Pacific LLSVP. These graveyards are thought to be the reason for the high velocity zone anomalies surrounding the Pacific LLSVP and are thought to have formed by subduction zones that were around long before the dispersion—some 750 million years ago—of the supercontinent Rodinia. Aided by the phase transformation, the temperature would partially melt the slabs, to form a dense heavy melt that pools and forms the ultra low velocity zone (ULVZ) structures at the bottom of the core-mantle boundary closer to the LLSVP than the slab graveyards.

Numerous studies have addressed the geochemical signature of the lavas present on Iceland and in the north Atlantic. The resulting picture is consistent in several important respects. For instance, it is not contested that the source of the volcanism in the mantle is chemically and petrologically heterogeneous: it contains not only peridotite, the principal mantle rock type, but also eclogite, a rock type that originates from the basalt in subducted slabs and is more easily fusible than peridotite. The origin of the latter is assumed to be metamorphosed, very old oceanic crust which sank into the mantle several hundreds of millions of years ago during the subduction of an ocean, then upwelled from deep within the mantle.

Erimo Seamount lies southeast of Cape Erimo of Hokkaido, Japan. The seamount lies close to the intersection between the Kuril–Kamchatka Trench to the northeast and the Japan Trench to the south. Erimo Seamount lies oceanward and south and east from the trenches and it forms the northern tip of the Japan Trench; there the Pacific Plate subducts at a rate of , together with the seamounts on it such as Erimo which is currently entering the trench. Other seamounts in the area are Takuyo-Daiichi to the east-northeast and Ryofu-Daini to the east-southeast, and there is evidence of another seamount northwest of Erimo and in the process of being subducted.

Volcanic activity in the region is in part influenced by the Chile Triple Junction, the point where the Chile Rise is subducted into the Peru-Chile Trench. This point forms a gap in the Andean Volcanic Belt, with Southern Volcanic Zone volcanism north of the gap generated by the fast subduction of the older and colder Nazca Plate beneath the South America Plate and Austral Volcanic Zone volcanism south of the gap formed by the slow subduction of the younger and warmer Antarctic Plate. In between these two subduction processes, a slab window opened up and allowed the rise of alkali basalt magmas. Río Murta rocks are basalts with a low content of potassium.

As eruptions progressed with time, the MgO content in the volcanic rocks decreases whereas the K2O content increases. Chemical variations in HKCA suite exist due to derived petrological variations in the rocks. This includes partial melting of an enriched primitive mantle derived magma source by subducted clay-rich sediments which formed the trachybasalts (a volcanic rock with a composition between trachyte and basalt). Then followed by mantle-derived magmas forming the basaltic trachyandesites and trachyandesites originating from the lower crust by from a process called assimilation-factional crystallization (A process by which magma crystallizes with the addition of crustal material inside the magma chamber and/or the conduit of which the magma flows through).

Warmer and younger oceanic lithosphere is believed to have started to be subducted beneath South America around this time. Such kind of subduction is held responsible not only for the intense contractional deformation that different lithologies were subject to, but also the uplift and erosion known to have occurred from the Late Cretaceous onward. Plate tectonic reorganization since the mid-Cretaceous might also have been linked to the opening of the South Atlantic Ocean. Another change related to mid-Cretaceous plate tectonic changes was the change of subduction direction of the oceanic lithosphere that went from having south-east motion to having a north-east motion at about 90 million years ago.

In a subduction zone, loss of water from the subducted slab induces partial melting of the overriding mantle and generates low-density, calc-alkaline magma that buoyantly rises to intrude and be extruded through the lithosphere of the overriding plate. This loss of water is due to the destabilization of the mineral chlorite at approximately 40–60 km depth.Grove, T. L., N. Chatterjee, S. W. Parman, and E. Médard (2006), The Influence of H2O on Mantle Wedge Melting, Earth and Planetary Science Letters, 249, 74–89.Grove, T.L., C. B. Till, N. Chatterjee, and E. Médard (submitted 2008), Transport of H2O in subduction zones and its role in the formation and location of arc volcanoes, Nature.

The Cascadia subduction zone is a convergent plate boundary that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore beginning near Cape Mendocino, Northern California, passing through Oregon and Washington, and terminating at about Vancouver Island in British Columbia. The Explorer, Juan de Fuca, and Gorda plates are some of the remnants of the vast ancient Farallon Plate which is now mostly subducted under the North American Plate.

The IBM arc system formed as a result of subduction of the western Pacific plate. The IBM arc system now subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south, including the oldest (~170 million years old, or Ma) oceanic crust. Subduction rates vary from ~2 cm (1 inch) per year in the south to 6 cm (~2.5 inches) in the north. The volcanic islands that comprise these island arcs are thought to have been formed from the release of volatiles (steam from trapped water, and other gases) being released from the subducted plate, as it reached sufficient depth for the temperature to cause release of these materials.

The magnitude 9.1 Mw Fukushima Hamadōri earthquake occurred inland on 11 April 2011 at 08:16 UTC at a focal depth of , about west of Iwaki, Fukushima, or north-northeast of Tokyo. To the east of the epicentre, the oceanic Pacific Plate is subducted beneath the continental Okhotsk Plate, on which much of Honshu's Tōhoku region is situated. Building stress near the resultant plate boundary has led to the development of shallow inland faults through crustal deformation and folding along the east coast of Tōhoku. This intraplate earthquake occurred in the vicinity of the Idosawa Fault - a shallow crustal fault in the Hamadōri region near Tabito town, Iwaki city, that had previously been inactive.

In the Late Cryogenian, around 650 Ma, the oceanic crustal basement of North Lhasa experienced HP metamorphism in the subduction zone associated with the closing of the Mozambique ocean. In the Early Paleozoic around 485 Ma it experienced MP metamorphism associated with the amalgamation of Eastern and Western Gondwana. In the Early Paleozoic the North and South Lhasa terranes and the Qiangtang terrane experienced magmatism that seems to have been the result of an Andean-type orogeny caused when the Proto-Tethys Ocean was subducted after Gondwana was finally amalgamated. In the Middle Paleozoic around 360 Ma the Lhasa and Qiangtang terranes again experienced magmatism, apparently due to the subduction of the Paleo-Tethys Ocean.

As Wellington rises, and Marlborough sinks, Cook Strait is being shifted further south.New Zealand uplift and sinking from Te Ara: The Encyclopedia of New Zealand Great stress is built up in the earth's crust due to the constant movement of the tectonic plates. This stress is released by earthquakes, which can occur on the plate boundary or on any of thousands of smaller faults throughout New Zealand. Because the Pacific Plate is subducting under the eastern side of the North Island, there are frequent deep earthquakes east of a line from the Bay of Plenty to Nelson (the approximate edge of the subducted plate), with the earthquakes being deeper to the west, and shallower to the east.

The Windermere Supergroup is a geological unit formed during the Ordovician to Silurian periods ~, and exposed in northwest England, including the Pennines and correlates along its strike, in the Isle of Man and Ireland, and down-dip in the Southern Uplands and Welsh Borderlands. It underlies much of north England's younger cover, extending south to East Anglia. It formed as a foreland basin, in a similar setting to the modern Ganges basin, fronting the continent of Avalonia as the remains of the attached Iapetus ocean subducted under Laurentia. The supergroup comprises the Dent Group of turbiditic limestones, and the overlying series of shales, grits and greywackes of the Stockdale Group, Tranearth Group, Coniston Group and Kendal Group.

Full extent of the Basin and Range. (NPS image) Starting around 16 Ma in Miocene time and continuing into the present, a large part of the North American Plate in the region has been under extension by literally being pulled apart. Debate still surrounds the cause of this crustal stretching, but an increasingly popular idea among geologists called the slab gap hypothesis states that the spreading zone of the subducted Farallon Plate is pushing the continent apart. Whatever the cause, the result has been the creation of a large and still-growing region of relatively thin crust; the region grew an average of per year initially and then slowed to per year in the last 5 million years.

The Transamazonian orogeny was a mountain building event in the Paleoproterozoic, affecting what is now the São Francisco Craton and Guyana Shield. During the orogeny from 2.14 to 1.94 billion years ago two small Archean proto-continents—including the greenstone belt-dominated Gavião Block and the calc-alkaline charnockite and enderbite-dominated Jequié Block—collided. The Contendas-Jacobina Lineament represents a suture zone where the collision occurred and the Gavião Block partially subducted under the Jequié Block. At the same time, another small continental fragment, the Serrinha Block, may have collided as well and was extensively reworked and metamorphosed, with orthogneiss and migmatite reaching amphibolite-grade on the sequence of metamorphic facies.

Warmer and younger oceanic lithosphere is believed to have started to be subducted beneath South America around this time. Such kind of subduction is held responsible not only for the intense contractional deformation that different lithologies were subject to, but also the uplift and erosion known to have occurred from the Late Cretaceous onward. Plate tectonic reorganization since the mid-Cretaceous might also have been linked to the opening of the South Atlantic Ocean. Another change related to mid-Cretaceous plate tectonic changes was the change of subduction direction of the oceanic lithosphere that went from having south-east motion to having a north-east motion at about 90 million years ago.

The Lassen volcanic area lies at the southern extremity of the Cascade Range, which extends northward some from Lassen Peak within the park through Oregon and Washington and into British Columbia. Lassen Peak and the 16 other major Cascade Volcanoes form a segment of a ring of volcanoes that circle the Pacific Ocean known collectively as the 'Pacific Ring of Fire.' The Cascade Volcanoes are fed by heat generated as the Gorda and Juan de Fuca tectonic plates are being subducted below the much larger but lighter North American Plate. Lying some offshore, the spreading center of the Gorda Plate pushes out about of new crust toward the coast of Northernmost California and southern Oregon every year.

The shield-stage lavas that built the enormous main mass of the mountain are tholeiitic basalts, like those of Mauna Kea, created through the mixing of primary magma and subducted oceanic crust. Mauna Loa's summit hosts three overlapping pit craters arranged northeast-southwest, the first and last roughly in diameter and the second an oblong feature; together these three craters make up the summit caldera Mokuʻāweoweo, so named for the Hawaiian ʻāweoweo fish (Priacanthus meeki), purportedly due to the resemblance of its eruptive fires to the coloration of the fish. Mokuʻāweoweo's caldera floor lies between beneath its rim and it is only the latest of several calderas that have formed and reformed over the volcano's life.

The eastern boundary is a subduction zone, the Lesser Antilles subduction zone, where oceanic crust of the South American Plate is being subducted under the Caribbean Plate. Subduction forms the volcanic islands of the Lesser Antilles Volcanic Arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south. This boundary contains seventeen active volcanoes, most notably Soufriere Hills on Montserrat; Mount Pelée on Martinique; La Grande Soufrière on Guadeloupe; Soufrière Saint Vincent on Saint Vincent; and the submarine volcano Kick 'em Jenny which lies about 10 km north of Grenada. Large historical earthquakes in 1839 and 1843 in this region are possibly megathrust earthquakes.

As Panthalassa subducted along its western margin during the Triassic and Early Jurassic, these seamounts and palaeo-atolls were accreted as allochthonous limestone blocks and fragments along the Asian margin. One such migrating atoll complex now form a and body of limestone in central Kyushu, south-west Japan. Fusuline foraminifera, a now extinct order of single-celled organisms, developed gigantism—the genus Eopolydiexodina, for example, reached up to in size—and structural sophistication, including symbiont relationships with photosynthesising algae, during the Late Carboniferous and Permian. The Permian–Triassic extinction event 260 , however, put an end to this development with only dwarf taxa persisting throughout the Permian until the final fusuline extinction 252 .

Understanding that the differences between Earth's layers are not just rheological, but chemical, is essential to understanding how we can track the movement of crustal material even after it has been subducted. After a rock has moved to the surface of the earth from beneath the crust, that rock can be sampled for its stable isotopic composition. It can then be compared to known crustal and mantle isotopic compositions, as well as that of chondrites, which are understood to represent original material from the formation of the solar system in a largely unaltered state. One group of researchers was able to estimate that between 5 and 10% of the upper mantle is composed of recycled crustal material.

Basalts of the Wells Gray-Clearwater volcanic field have been considered to be the easternmost expression of the Anahim Volcanic Belt. However, its relationship is unknown because the age-location trend does not reach into the Wells Gray-Clearwater area, and the Wells Gray-Clearwater volcanic field is not along trend with the Anahim Volcanic Belt. The Wells Gray volcanics were thought to have formed by crustal thinning and the existence of crustal penetrating structures. More recent studies by volcanologists associated with the Geological Survey of Canada have indicated that the subducted extension of the Nookta Fault may be the primary cause of the alkalic structure of the Wells Gray-Clearwater volcanic field.

The early Pacific arc is a curved line of volcanism and intrusions where the Palaeo-Pacific Ocean subducted beneath Borneo, Vietnam and South China. The resulting long period of magmatism is evident from intrusions and extrusions reaching as far north as South China, through Hong Kong, the South China Sea continental shelf, Vietnam and to Kalimantan in southwest Borneo. This period of magmatism continued until 79Ma, when the margin moved east. The ages of magmatism in these locations are 186 Ma to 76 Ma for the Schwaner Mountains granites of Kalimantan; at 180 Ma to 79 Ma in South China; at 165 Ma to 140 Ma in Hong Kong and at 112 Ma to 88 Ma in Dalat in Vietnam.

Haddington Island is a member in the chain of eroded volcanoes that run from Brooks Peninsula northeastward across Vancouver Island to Port McNeill, called the Alert Bay Volcanic Belt. The existence of felsite and andesite at Haddington Island suggests it might have formed 3.7 million years ago as the Juan de Fuca and Explorer Plate to its west subducted under the North American Plate at the Cascadia subduction zone. As the ocean crust of the Juan de Fuca and the Explorer Plate melts, it creates magma that penetrates the crust, causing periodic eruptions of the volcanoes. The western end of the Alert Bay Volcanic Belt is now approximately northeast of the Nootka Fault, which separates the Explorer and Juan de Fuca plates.

The tectonic history of Baja California was greatly influenced by the collision of the spreading ridge between the Pacific Plate and the Farallon Plate with North America during the Oligocene. Before that time, the crust of the Pacific Ocean had been subducting beneath North America; now two triple junctions formed at the contact site with the San Andreas Fault in between. Later in the Miocene, spreading between the two plates and the subduction west of Baja California ceased about 12.5 million years ago, with the spreading ridge being either subducted or just abandoned outside of the previous trench. 6 million years ago the East Pacific Rise penetrated inland into the Gulf of California, separating Baja California from the North America Plate.

Hill, Mary (1999), pp. 168–69. As it sank, or subducted, beneath the western margin of the North American plate portions of the sea floor and overlying continental crust heated and melted, producing large molten masses (magma). Being lighter and hotter than the ancient continental crust above it, this magma forced its way upward, cooling as it rose, pp. 195–196. to become the granite rock found throughout the Sierra Nevada and other mountains in California today.Hill, Mary (1999), pp. 149–58 As the hot magma cooled, solidified, and came in contact with water, minerals with similar melting temperatures tended to concentrate together. As the magma solidified, gold became concentrated within hydrous silica solutions and was deposited within veins of quartz.Hill, Mary (1999), pp. 174–78.

Relative velocity vectors of Pacific, Farallon, and Kula plates 55 million years ago The Pacific-Farallon Ridge was a spreading ridge during the late Cretaceous that extended 10,000 km in length and separated the Pacific Plate to the west and the Farallon Plate to the east. It ran south from the Pacific- Farallon-Kula triple junction at 51°N to the Pacific-Farallon-Antarctic triple junction at 43°S.The Solid Earth As the Farallon Plate subducted obliquely under the North American Plate, the Pacific-Farallon Ridge approached and eventually made contact with the North American Plate about 30 million years ago. On average, this ridge had an equatorial spreading rate of 13.5 cm per year until its eventual collision with the North American Plate.

This sort of mantle layering is further supported by the 'basalt barrier' mechanism, which states that subducted basaltic crust is positively buoyant between the mantle depths of 660–750 km, and negatively buoyant at other depths, and can accumulate at the bottom of the transition zone and cause mantle layering. The breakdown of mantle layering and consequent mantle overturns would lead to dramatic episodes of volcanism, formation of large amounts of crust, and tectonic activity on the planet's surface, as has been inferred to have happened on Venus around 500 Ma from the surface morphology and cratering. Catastrophic resurfacing and widespread volcanism can be caused periodically by an increase in mantle temperature due to a change in surface boundary conditions from mobile to stagnant lid.

The event registered 7.2 on the moment magnitude scale and was felt as far as northern Washington state and the interior of British Columbia. The earthquake took place in the vicinity of the Cascadia subduction zone where the Juan de Fuca Plate and the Explorer Plate are being subducted under the North American Plate at a rate of and less than per year respectively, but the event was a crustal intraplate earthquake and was produced from the complicated interaction between the plates in the area. The source of the earthquake was the Nootka transform fault, which separates the Juan de Fuca and Explorer plates and has been the origin of at least five additional moderate to large events since 1918.

The onset of subduction of the Carnegie Ridge beneath the South American Plate has been dated variously from about mid-Miocene (15 Ma) to about Pleistocene (2 Ma). Although there is agreement that the ridge is being subducted, there is little agreement on the effect that this has had on either the subducting or over-riding plates. Some models argue that the buoyancy associated with the thickened crust of the ridge has caused the downgoing Nazca Plate to tear, leaving a relatively flat section carrying the ridge, flanked by two sections with steeper dip. The presence of a flat section is not supported by a more recent study of earthquake hypocenters, which found a constant dip of about 25°-35° down to 200 km.

The tectonic setting of western North America changed drastically as the Farallon Plate under the Pacific Ocean to the west was shallowly subducted below North American Plate. Called the Laramide orogeny, the compressive forces generated from this collision erased the Cretaceous Seaway, fused the Sierran Arc to the rest of North America and created the Rocky Mountains. This mountain-building event started in the Mesozoic 80 million years ago and lasted well into the first half of the Cenozoic era 30 million years ago.Smith, Windows into the Earth (2000), page 101 Teton fault block Some 60 million years ago, these forces uplifted the low-lying coastal plain in the Teton region and created the north-south-trending thrust faults of the nearby Wyoming Overthrust Belt.

Major active fault zones of New Zealand showing variation in displacement vector of Pacific Plate relative to Australian Plate along the boundary New Zealand is currently astride the convergent boundary between the Pacific and Australian Plates. Over time, the relative motion of the plates has altered and the current configuration is geologically recent. Currently the Pacific Plate is subducted beneath the Australian Plate from around Tonga in the north, through the Tonga Trench, Kermadec Trench, and Hikurangi Trough to the east of the North Island of New Zealand, down to Cook Strait. Through most of the South Island, the plates slide past each other (Alpine Fault), with slight obduction of the Pacific Plate over the Australian Plate, forming Southern Alps.

The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the southwest of the Kermadec Plate (northeast of New Zealand) to the northwest tip of the Tonga Plate, with the Pacific Plate being subducted under both the Kermadec and Tonga Plates. The Kermadec and Tonga Plates are micro oceanic plates in the Pacific Ocean, bounded by the Australian and Pacific Plates to the west and east respectively. The Kermadec Plate begins at the northeastern part of New Zealand and stretches northward to its contact with the Tonga Plate. The Tonga Plate begins 2500 km NNE of New Zealand and stretches northward, until the plate ends bounded by the Niuafo’ou Plate to the northwest and the Pacific Plate to the northeast.

At this point most of the deposited Paleozoic and Mesozoic sediments had been eroded away, exposing the plutons of diorite, which is the primary igneous rock found on the mountain. At some point the diorite plutons experienced intrusion by gabbro dikes associated with the formation of oceanic seafloor, indicating that the area may have experienced periods of submersion as the Juan de Fuca plate subducted underneath the North American plate accreted the area. This whole process of constant uplift and erosion followed by accretion is thought to have created the unique ophiolites associated with the San Juan Islands and especially the Fidalgo Complex, of which Mount Erie is a part. During the Quaternary Period the area experienced many periods of glacial advance and retreat.

Throughout this time, the area was covered by an ancient sea and thick layers of limestone and sandstone were deposited. Permian-aged strata rich in fossil brachiopods, echinoid spines, and gastropods are the only Paleozoic rocks exposed in the Chiricahua Mountains, and reflect a shallow-marine coral reef environment. These rocks are also the oldest known rocks exposed in the Chiricahuas and were formed around 280 Ma. A 150-million- year unconformity in the Chiricahua Mountains’ geologic history occurs between the Paleozoic and earliest known Mesozoic rocks due to a period of uplift and erosion. Numerous volcanoes then formed in southeastern Arizona during the Mesozoic as oceanic crust subducted beneath the southwestern portion of the United States, resulting in continued continental growth.

If these segments are combined and reconstructed back to their original location at the surface, they equal both the NFB and the subducted part of the Australian plate since 12 Ma in area. The Tonga slab is avalanching through the 660 km layer at the southern end of the New Hebrides arc and trench. The Pacific plate has been subducting at the Tonga trench for a long time which led to an accumulation of slab material at the 660 km layer south of the Vitiaz trench while the New Hebrides island arc has been pushed southward and clockwise. It also reversed the direction of subduction and opened the NFB back-arc and pushed the Vitiaz slab into the mantle and initiated the subduction at New Hebrides trench.

An additional, though less well understood, pathway includes along faults and fractures within the Earth's crust, often referred to as tectonic degassing. When the DCO was first formed in 2009 estimates of global carbon flux from volcanic regions ranged from 65 to 540 Mt/yr, and constraints on global tectonic degassing were virtually unknown. The order of magnitude uncertainty in current volcanic/tectonic carbon outgassing makes answering fundamental questions about the global carbon budget virtually impossible. In particular, one fundamental unknown is if carbon transferred to the Earth's interior via subduction is efficiently recycled back to the Earth's mantle lithosphere, crust and surface environment through volcanic and tectonic degassing, or if significant quantities of carbon are being subducted into the deep mantle.

There are multiple processes that can lead to the development of high pressure terranes. First, upper crustal rocks have to be carried to great depths, nearing the mantle boundary. This could be accomplished by continental margin subduction, microcontinent subduction, sediment subduction, intracontinental subduction, subduction erosion, or foundering of a crustal root. After burial at depth, these continental rocks can then return to the surface through: eduction - the process where a slab of continental crust is subducted due to being attached to a denser subducting oceanic plate, and at some point, the downward slab pull force exceeds the strength of the slab, thus causing necking and detachment to occur, and the positive buoyancy of the continental slab leads to its exhumation.

Map of the volcanic zones arcs in the Andes, and subducted structures affecting volcanism Off the southernmost west coast of South America, the Antarctic Plate subducts beneath the South American Plate at a rate of . This subduction process is responsible for volcanism in the Austral Volcanic Zone. The Austral Volcanic Zone is one of four volcanic zones in the Andes, the other three are the Northern Volcanic Zone, the Central Volcanic Zone and the Southern Volcanic Zone, all of which are separated from the Austral Volcanic Zone and each other by gaps where no volcanic activity occurs. Unlike the Austral Volcanic Zone, volcanism in these other zones is controlled by the subduction of the Nazca Plate beneath the South American Plate.

The Farallon tectonic plate that formed a part of the Pacific Ocean floor (separate from the Pacific plate) inched eastward toward North America about 35 million years ago and most of the sea floor subducted beneath the continental land mass of the North America plate. Some of the sea floor, however, was scraped off and jammed against the mainland, creating the dome that was the forerunner of today's Olympics. Thrust-faulting northeast into the Vancouver Island/North Cascades corner pushes Olympic rock upward and southwestward, resulting in strata that appear to be standing on edge and that intermix with strata of different mineral composition. All this occurred under water; the Olympics began to rise above the sea only 10–20 million years ago.

Juan de Fuca tectonic plate is being subducted under the North American Plate, leading to volcanic activity in the Cascades like at Trout Creek Hill. In southern Washington state, the Cascade Range sits south of the dacitic volcanic belt running from Mount Garibaldi to Lassen Peak, which spans from British Columbia in Canada to northern California in the United States. Volcanoes in the range have been produced by subduction of the Juan de Fuca tectonic plate under the North American Plate. The Washington Cascades consist of Cenozoic era volcanic and intrusive rocks, and they can be divided into two segments based on age and rock type: the Western Cascades (formed between 50 and 5 million years ago) and the High Cascades (produced within the past 5 million years).

OJP formed quickly over a mantle plume head, most likely the then newly formed Louisville hotspot, followed by limited volcanism for at least 30 million years. The extant seamounts of the Louisville Ridge started to form 70 Ma and have a different isotopic composition, and therefore a shift in intensity and magma supply in the plume must have occurred before that. The early, short-duration eruptions of OJP coincide with the global Early Aptian oceanic anoxic event (known as OAE1a or the Selli Event, 125.0–124.6 Ma) that led to the deposition of black shales during the interval 124–122 Ma. Additionally, isotopic records of seawater in sediments have been associated with the 90 Ma OJP submarine eruptions. About 80% of the OJP is being subducted beneath the Solomon Islands.

The national park sits astride the Iapetus suture, the line along which the former Iapetus Ocean closed during the Silurian period as the former micro-continent of Avalonia to the south collided with the continent of Laurentia to the north. The suture and the great slab of subducted oceanic crust from beneath the former ocean are concealed from view by a thickness of sedimentary rocks which subsequently accumulated over the area. During the Devonian period a granite pluton was emplaced in the north (under what is now the Cheviot Hills) and volcanic activity led to the accumulation of various volcanic rocks whilst to the south (under what is now the North Pennines, a granite batholith was emplaced. During the Carboniferous period, a series of blocks and basins developed across what would eventually become northern England.

The unusual disparity between the magnitude of the earthquake and the subsequent tsunami may be due to a combination of forces: # the tsunami was caused by a slope failure triggered by the earthquake # the rupture velocity was unusually low Scientists believe the effect of subducted sediment beneath the accretionary wedge was responsible for a slow rupture velocity. The effects of a 20° dipping fault along the top of the subducting plate was found to match both the observed seismic response and tsunami, but required a displacement of 10.4 m. The displacement was reduced to a more reasonable value after the extra uplift caused by the deformation of sediments in the wedge and a shallower fault dip of 10° was considered. This revised fault model gave a magnitude of =8.0–8.1.

Oceanic crust is formed at a mid-ocean ridge, while the lithosphere is subducted back into the asthenosphere at oceanic trenches Age of oceanic crust (red is youngest, and blue is oldest) Oceanic crust, which forms the bedrock of abyssal plains, is continuously being created at mid- ocean ridges (a type of divergent boundary) by a process known as decompression melting. Plume-related decompression melting of solid mantle is responsible for creating ocean islands like the Hawaiian islands, as well as the ocean crust at mid-ocean ridges. This phenomenon is also the most common explanation for flood basalts and oceanic plateaus (two types of large igneous provinces). Decompression melting occurs when the upper mantle is partially melted into magma as it moves upwards under mid-ocean ridges.

Through subduction, oceanic crust and lithosphere returns to the convecting mantle. Areas of the crust where new crust is created are called divergent boundaries, those where it is brought back into the Earth are convergent boundaries and those where plates slide past each other, but no new lithospheric material is created or destroyed, are referred to as transform (or conservative) boundaries Earthquakes result from the movement of the lithospheric plates, and they often occur near convergent boundaries where parts of the crust are forced into the earth as part of subduction. Volcanoes result primarily from the melting of subducted crust material. Crust material that is forced into the asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface—giving birth to volcanoes.

Since the downgoing slab is partly anchored in the viscous layers of the mantle, and therefore its lateral movement is significantly slower than the surface plate, then any motion of the overriding plate will cause extensional or compressional stress in the back-arc region depending on the direction of motion. In addition, mantle convection in the upper mantle wedge caused by the downward movement of the subducted slab causes stress in the upper plate and the high heat flow that characterizes back-arcs. The pulling effect of the slab as it goes down into the mantle causes a rollback motion of the trench, which also applies stress on the back- arc region of the upper plate. However, this last process has less of an impact on deformation compared to upper plate motion.

There is minor relative motion between PH and CR; furthermore, CR does not feed the IBM Subduction Factory, so it is not discussed further. The North American plate includes northern Japan, but relative motion between it and Eurasia is sufficiently small that relative motion between PH and EU explains the motion of interest. The Euler pole for PH-PA as inferred from the NUVEL-1A model for current plate motions lies about 8°N 137.3°E, near the southern end of the Philippine Sea Plate. PA rotates around this pole CCW ~1°/Ma with respect to PH. This means that relative to the southernmost IBM, PA is moving NW and being subducted at about 20–30 mm/y, whereas relative to the northernmost IBM, PA is moving WNW and twice as fast.

This sea-floor formed at the extinct Osbourn Trough, located just north of the Louisville Seamount Chain. Abyssal hills on the subducting sea-floor are oriented perpendicular to the old spreading centre and the sea-floor is 72–80 Ma near the Louisville seamounts at the northern end and more than 100 Ma near Hikurangi Plateau at the southern end. There are no seamounts on the sea-floor near the Kermadec Trench except one sitting on the trench slope at which has been dated to 54.8±1.9 Ma. The Hikurangi Plateau formed part of the Ontong-Java-Manihiki-Hikurangi large igneous province (LIP) during the Ontong Java Event 120 . The Manihiki Plateau is currently subducting under the southern part of the Kermadec Arc but most of it has already been subducted.

Puget Sound's sills, a kind of submarine terminal moraine, separate the basins from one another, and Puget Sound from the Strait of Juan de Fuca. Three sills are particularly significant—the one at Admiralty Inlet which checks the flow of water between the Strait of Juan de Fuca and Puget Sound, the one at the entrance to Hood Canal (about below the surface), and the one at the Tacoma Narrows (about ). Other sills that present less of a barrier include the ones at Blake Island, Agate Pass, Rich Passage, and Hammersley Inlet. The depth of the basins is a result of the Sound being part of the Cascadia subduction zone, where the terranes accreted at the edge of the Juan de Fuca Plate are being subducted under the North American Plate.

Mount Imbabura (Ecuador) from south-east The central belt of Ecuador that includes the Andes Mountains, inland from the coast; with volcanoes and mountain peaks that sport year-round snow on the equator; many areas long since deforested by agriculture; a number of cut-flower growing operations; at a certain altitude zone may be found cloud forests. The northern Ecuadorian Andes are divided into three parallel cordilleras which run in what is similar to an S-shape from north to south: the western, central (Cordillerra Real) and eastern (Cordillera Occidental) cordilleras. The cordilleras were formed earlier in the Cenozoic era (the current geological era), as the Nazca Plate has subducted underneath the South American Plate and has raised the mountain range. In the south, the cordilleras are not well defined.

The existence of Halmahera as a tectonic plate separate from the Molucca Sea Plate is not yet entirely agreed upon by paleogeologists. Some see Halmahera as an eastern slab of the Molucca Sea Plate, just as they regard Sangihe as a western slab of the Molucca Sea Plate. What is apparent to date is that Halmahera was part of the Molucca Sea slab subducted during the Neogene between 45 Ma and 25 Ma.R. Hall and W. Spakman, Australian Plate Tomography and Tectonics in R. R. Hillis, R. D. Müller, Evolution and Dynamics of the Australian Plate, Geological Society of America Special Papers 2003, #372, p377 Seismicity shows the east-dipping Halmahera reaches a depth of about 200 km. Seismic tomography suggests that the Halmahera goes deeper to at least 400 km.

The Alboran domain, the seafloor beneath the Alboran Sea (known as the internal zones) together with the surrounding mountains (known as the external zones; the Gibraltar Arc and Atlas Mountains), is mostly made of continental crust and marks the western-most terminus of the terranes that were subducted between the African and Eurasian Plates when the Tethys Ocean closed. Reoccurring earthquakes at a depth of about indicates that this subduction is ongoing and that complex interactions between the lithosphere and mantle are forming the region. The internal zones are made of Late Paleozoic to Triassic rocks that were piled up during the Tertiary and has been extended since the Early Miocene. The seafloor is morphologically complex with several sub-basins, including three main sub-basins named West, East, and South Alboran Basins, ridges, and seamounts.

Schematic cross section of the Upper Rhine Graben The Rhine flows from the Alps to the North Sea Basin; the geography and geology of its present-day watershed has been developing, since the Alpine orogeny began. In southern Europe, the stage was set in the Triassic Period of the Mesozoic Era, with the opening of the Tethys Ocean, between the Eurasian and African tectonic plates, between about 240 MBP and 220 MBP (million years before present). The present Mediterranean Sea descends from this somewhat larger Tethys sea. At about 180 MBP, in the Jurassic Period, the two plates reversed direction and began to compress the Tethys floor, causing it to be subducted under Eurasia and pushing up the edge of the latter plate in the Alpine Orogeny of the Oligocene and Miocene Periods.

Schematic cross section of a subduction zone with an accretionary prism formed by off-scraping sediments from the down-going plate Accretionary prisms grow in two ways: by frontal accretion, whereby sediments are scraped off the downgoing plate, bulldozer-fashion, near the trench, and by underplating of subducted sediments (and sometimes oceanic crust) along the shallow parts of the subduction decollement. Frontal accretion over the life of a convergent margin results in younger sediments defining the outermost part of the accretionary prism and the oldest sediments defining the innermost portion. Older (inner) parts of the accretionary prism are more lithified and have steeper structures than the younger (outer) parts. Underplating is difficult to detect in modern subduction zones but may be recorded in ancient accretionary prisms such as the Franciscan Group of California in the form of tectonic mélanges and duplex structures.

The onset of Cordilleran orogenesis began in the Middle Jurassic time, as a result of the breakup of Pangea and North American plate motion toward subduction zones at the western margin. Most of the Canadian Cordillera today consists of numerous tectonostratigraphic terranes that were accreted to the stable margin of North America from the Jurassic to Early Tertiary as a result of eastward and northward drifting island arcs that collided with the continental lithosphere of North America. These terranes were accreted due to upper-crustal rocks being detached from the denser lower-crustal and proto-Pacific upper mantle lithosphere that was subducted under the North American craton. The allochthonous upper crustal terranes were juxtaposed over top of each other and over the western margin of the North American craton along a system of interconnected, northeast and southwest verging major thrust faults.

The subducted portion of the plate extends downward to more than 300 km (186 mi) depth, and laterally as far as mainland Canada. The relative buoyancy of the subducting plate and the underlying mantle may be inhibiting the Explorer Plate's ability to descend further into the mantle. There is an ongoing debate regarding the process of subduction of the Explorer Plate and how the boundary between the Explorer plate and the North American Plate are defined: # The Explorer Plate has stopped and may eventually accrete, fusing with the North American plate as the subduction has fully stopped and will eventually become a plate boundary between the North American Plate and Pacific Plate rather than continuing its subduction. # The Explorer Plate consists of two parts with half being fused to the North American Plate and the other half remaining a microplate system.

His work has "enabled three-dimensional tomographic imaging of the structure of the colliding plates""Martin Reyners, Royal Society of New Zealand, List of Fellows(Retrieved 26 May 2012) and has so shown the modus operandi of plate tectonics under New Zealand, especially in relation to the Taupo Volcanic Zone, which is "the most frequently active and productive silicic volcanic system on Earth." He has cast light on the mysterious termination of volcanic activity at Mt Ruapehu and its non-continuation with the subducted Pacific plate further south under New Zealand" He is currently examining why the New Zealand tectonic plates are jammed together in some places because, if these unjam, there could be a large earthquake He is a fellow of the Royal Society of New Zealand (FRSNZ), and has been awarded the Hochstetter Lectureship, and (twice) the New Zealand Geophysics Prize.

Any model of the origin of Siletzia must account for interactions with plate boundaries that were being subducted under North America through the Eocene. Early studies were plagued by indeterminate locations for these boundaries, particularly of the Kula-Farallon (K-F) spreading ridge: basalts at the head of the Gulf of Alaska (along the Alaska panhandle) have ages and compositions corresponding to the Siletz volcanics, suggesting that the K-F ridge was offshore of the Yukon at the same time it was offshore of Washington. This can be resolved by assuming that by about 56 Ma the eastern part of the Kula plate had broken away to form the Resurrection plate, with the new Kula-Resurrection (K-R) spreading ridge running up the Gulf of Alaska towards Kodiak Island, and the former K-F (now R-F) ridge reaching Washington.See figure 1 in .

The boundary between the South American and Antarctic plates can be divided into three parts of which the SAAR forms the eastern third: The first stretches from the Chile Triple Junction in the Chile Trench at 46°S to the western Straits of Magellan at 52°S. Since 15 Ma, the oceanic crust of the Antarctic plate is being slowly subducted () under South America along this trench which is currently extending northward. In the central part, between the Straits of Magellan and the South Sandwich Trench, the two large continental plates are separated by the Scotia Plate and a number of smaller plates east of it. During the past 40 Ma (or since the opening of the Drake Passage) the South Sandwich Trench has been migrating eastward due to the evolution of a back-arc basin, effectively consuming the SAAR.

The Carolina Slate Belt (CSB) originated in the Proterozoic or Cambrian age with a volcanic arc terrane, a chain of volcanoes that form on the edge of one continental plate when it has another continental plate subducted under it. Another subduction of the eastern edge of the ancient North American continental plate (Laurentia) caused the Taconic orogeny and created a new mountain range on the eastern coast of North America. These new mountains eroded over time to form the Piedmont but while they stood their weight was just enough to metamorphose the old volcanic arc rocks into greenschist, a rock produced by some of the lowest metamorphic pressures. The eastern edge of the North American plate continued to be battered by the Avalonia continent, causing the Acadian orogeny, and the ancient African plate (Gondwana), causing the Alleghanian orogeny.

Red line is the Sagami Trough The also Sagami Trench, Sagami Megathrust, or Sagami Subduction Zone is a long trough, which is the surface expression of the convergent plate boundary where the Philippine Sea Plate is being subducted under the Okhotsk Plate. It stretches from the Boso Triple Junction in the east, where it meets the Japan Trench, to Sagami Bay in the west, where it meets the Nankai Trough. It runs north of the Izu Islands chain and the Izu-Bonin-Mariana Arc (IBM). Megathrust earthquakes associated with the Sagami Trough, known as Kantō earthquakes, are a major threat to Tokyo and the Kantō Region because of the proximity to a population center (with over 36 million living in Tokyo's metro area, with a total of 43 million living in the Kanto Region) and the magnitude the Sagami Trough can create.

The Farallon tectonic plate that formed a part of the Pacific Ocean floor (separate from the Pacific plate) inched eastward toward North America about 35 million years ago and most of the sea floor subducted beneath the continental land mass of the North America plate. Some of the sea floor, however, was scraped off and jammed against the mainland, creating the dome that was the forerunner of today's Olympics. In this particular case, the future Olympics were being jammed into a corner created by the Vancouver Island and North Cascades microcontinents attached to the western edge of the North America plate. This is thought to be the origin of the curved shape of the Olympic Basaltic Horseshoe, an arc of basalt running east along the Strait of Juan de Fuca, south along Hood Canal, and then west to Lake Quinault.

The Kula Plate began subducting under the Pacific Northwest region of North America during the Late Cretaceous period much like the Pacific Plate does, supporting a large volcanic arc system from northern Washington to southwestern Yukon called the Coast Range Arc. There was a triple junction of three ridges between the Kula Plate to the north, the Pacific Plate to the west and the Farallon Plate to the east. The Kula Plate was subducted under the North American Plate at a relatively steep angle, so that the Canadian Rockies are primarily composed of thrusted sedimentary sheets with relatively little contribution of continental uplift, while the American Rockies are characterized by significant continental uplift in response to the shallow subduction of the Farallon Plate. About 55 million years ago, the Kula Plate began an even more northerly motion.

The extension that occurred formed a triangle-shaped rift area due to the kinematics of the rifting taking place like the blades of an opening pair of scissors. The three competing models mentioned above describe this rifting and thinning during the Late Mesozoic and vary slightly between different authors. Here, the three models are illustrated as: # The extrusion model where lateral strike slip faults are projected through the South China Sea and lateral displacement caused by the India-Asia collision forces the extension # The Subduction Model which coincides well with evidence on the formation of the Dangerous Grounds where slab pull caused extension as the Proto-South China Sea was subducted beneath NW Borneo # The continental rift basin model where distant processes of slab roll back south of Borneo near Java and Sumatra caused magmatism leading to the crustal extension northwest of Borneo and formation of A-type granites.

The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene epoch. At first it subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan. As the southern part of the Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate began to subduct beneath Patagonia so that the Chile Triple Junction lies at present in front of Taitao Peninsula at 46°15' S. The subduction of the Antarctic Plate beneath South America is held to have uplifted Patagonia as it reduced the previously vigorous down-dragging flow in the Earth's mantle caused by the subduction of the Nazca Plate beneath Patagonia. The dynamic topography caused by this uplift raised Quaternary-aged marine terraces and beaches across the Atlantic coast of Patagonia.

2002 Satellite view of Taiwan The island of Taiwan is active geologically, formed on a complex convergent boundary between the Yangtze Subplate of the Eurasian Plate to the west and north, the Okinawa Plate on the north-east, the Philippine Plate on the east and south, and the Sunda Plate to the southwest. Subduction changes direction at Taiwan. The upper part of the crust on the island is primarily made up of a series of terranes, mostly old island arcs which have been forced together by the collision of the forerunners of the Eurasian Plate and the Philippine Sea Plate, which is moving to the northeast. These have been further uplifted as a result of the detachment of a portion of the Eurasian Plate as it was subducted beneath remnants of the Philippine Sea Plate, a process which left the crust under Taiwan more buoyant.

In the southern Appalachians of Alabama, Georgia, and North Carolina, the Taconic orogeny was not associated with collision of an island arc with ancient North America (Laurentia). Geologists working in these areas have long puzzled over the "missing" arc terrane typical of Taconic-aged rocks in New England and Canada. Instead, the Iapetus margin of this part of Laurentia appears to have faced a back-arc basin during the Ordovician, suggesting that Iapetus oceanic crust was subducted beneath Laurentia - unlike the New England and Canadian segments of the margin, where Laurentia was on the subducting plate. In contrast to the Ordovician geologic history of New England, rocks in Alabama, Georgia, and North Carolina, including those of the Dahlonega gold belt (GA and NC), Talladega belt (Alabama and Georgia), and eastern Blue Ridge (AL, GA, and NC), are not typical of a volcanic arc in its strictest sense.

The rest of the material is then carried upwards due to chemical buoyancy and contributes to the high levels of basalt found at the mid-ocean ridge. The resulting motion forms small clusters of small plumes right above the core- mantle boundary that combine to form larger plumes and then contribute to superplumes. The Pacific and African LLSVP, in this scenario, are originally created by a discharge of heat from the core (4000 K) to the much colder mantle (2000 K), the recycled lithosphere is only fuel that helps drive the superplume convection. Since it would be difficult for the Earth's core to maintain this high heat by itself, it gives support for the existence of radiogenic nuclides in the core, as well as the indication that if fertile subducted lithosphere stops subducting in locations preferable for superplume consumption, it will mark the demise of that superplume.

Juan de Fuca tectonic plate is being subducted under the North American Plate, leading to volcanic activity in the Cascades like at West Crater In southern Washington state, the Cascade Range, which sits south of the dacitic Garibaldi Volcanic Belt, spans from British Columbia in Canada to Lassen Peak in northern California in the United States. Volcanoes in the range have been produced by subduction of the Juan de Fuca tectonic plate under the North American Plate. The Washington Cascades consist of Cenozoic era volcanic and intrusive rocks, and they can be divided into two segments based on age and rock type: the Western Cascades (formed between 50 and 5 million years ago) and the High Cascades (produced within the past 5 million years). Whereas the High Cascades have largely been unaffected by geological deformation processes, the Western Cascades are more folded and faulted.

Variations in water depth over this time, related both to crustal extension and to the growth and decline of a south polar ice-sheet, gave rise to changes in conditions of deposition and hence a varying rock sequence. Volcanic activity began in the Ordovician period as ocean crust was subducted to the northwest of Snowdonia and continued into the early Silurian until continental collision had ceased. The nature of the volcanism and hence the character of both extrusive and intrusive igneous rocks varied over time. Most of Snowdonia is thought to have remained as land during the succeeding few hundred million years before being submerged during the Jurassic period though, with one marginal exception, no rocks dating from the Devonian onwards remain. Cardigan Bay developed as a depositional basin during the Mesozoic and some of those sediments are recorded within Snowdonia’s boundaries, albeit concealed at depth.

Volcanoes in the Andes occur in four separate regions: the Northern Volcanic Zone between 2°N and 5°S, the Central Volcanic Zone between 16°S and 28°S, the Southern Volcanic Zone between 33°S and 46°S, and the Austral Volcanic Zone, south of the Southern Volcanic Zone. These volcanic zones are separated by areas where recent volcanism is absent; one common theory is that the subduction processes responsible for volcanism form a subducting plate that is too shallow to trigger the formation of magma. This shallow subduction appears to be triggered by the Nazca Ridge and the Juan Fernandez Ridge; the areas where they subduct beneath the Peru-Chile Trench coincide with the limits of the Central Volcanic Zone. It is possible that when these ridges are subducted, the buoyancy they carry disrupts the subduction process and reduces the supply of water, which is important for the formation of melts.

Gold-bearing magma rising after being subducted under the continental crust. Geologic evidence indicates that over a span of at least 400 million years, gold that had been widely dispersed in the Earth's crust became more concentrated by geologic actions into the gold-bearing regions of California. Only gold that is concentrated can be economically recovered. Some 400 million years ago, rocks that would be accreted onto western North America to build California lay at the bottom of a large sea. Subsea volcanoes deposited lava and minerals (including gold) onto the sea floor; sometimes enough that islands were created. p. 167. Between 400 million and 200 million years ago, geologic movement forced the sea floor and these volcanic islands and deposits eastwards, colliding with the North American plate, which was moving westwards.Hill, Mary (1999), p. 168. Beginning about 200 million years ago, tectonic pressure forced the sea floor beneath the American continental mass.

Mexico's southwestern coast is parallel to the Middle America Trench (MAT), where the oceanic Cocos plate (a remnant of the ancient Farallon plate) is being subducted under the North American plate, resulting in many major earthquakes.. Most earthquakes observed in this region are similar to earthquakes seen at other subduction zones, but in the vicinity of Ometepec they tend to occur as doublets.. This earthquake is unique in being (circa 2013) the "best documented doublet and for which near and teleseismic data are available", and has been extensively studied.. The interruption of the main rupture that results in a doublet earthquake has been attributed to "asperities", patches in the fault where harder rock resists immediate rupture. However, study of this earthquake's aftershocks shows a discontinuity in their spatial distribution.. This has been interpreted as indicating a split in the subducting plate, where the plate is subducting at slightly different down angles on either side of the split..

Location of the Paleo-Tethys Ocean circa 280 million years ago The Paleo- Tethys or Palaeo-Tethys Ocean was an ocean located along the northern margin of the paleocontinent Gondwana that started to open during the Middle Cambrian, grew throughout the Paleozoic, and finally closed during the Late Triassic; existing for about 400 million years. Paleo-Tethys was a precursor to the Tethys Ocean (also called the Neo-Tethys) which was located between Gondwana and the Hunic terranes (continental fragments that broke-off Gondwana and moved north). It opened as the Proto-Tethys Ocean subducted under these terranes and closed as the Cimmerian terranes (that also broke-off Gondwana and moved north) gave way to the Tethys Ocean. Confusingly, the Neo-Tethys is sometimes defined as the ocean south of a hypothesised mid-ocean ridge separating Greater Indian from Asia, in which case the ocean between Cimmeria and this hypothesised ridge is called the Meso-Tethys, i.e.

The Pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Ring of Fire) and moves much faster than the plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates. It is thus thought that forces associated with the downgoing plate (slab pull and slab suction) are the driving forces which determine the motion of plates, except for those plates which are not being subducted. This view however has been contradicted by a recent study which found that the actual motions of the Pacific Plate and other plates associated with the East Pacific Rise do not correlate mainly with either slab pull or slab push, but rather with a mantle convection upwelling whose horizontal spreading along the bases of the various plates drives them along via viscosity-related traction forces. The driving forces of plate motion continue to be active subjects of on-going research within geophysics and tectonophysics.

The Musicians Seamounts were active during the Late Cretaceous. Ages obtained on some seamounts range from 96 million years ago for the Northwest Cluster over 94 million years ago for Hammerstein, 91 million years ago for Mahler, 90 million years ago for Brahms, 86 million years ago for Rachmaninoff, 84 million years ago for Liszt, 83 million years ago for Khatchaturian and West Schumann, 82 million years ago for West Mendelssohn, 79 million years ago for East Mendelssohn, 75 million years ago for Bach Ridge and Haydn to 65 million years ago for Paumakua. Based on considerations derived from plate tectonics, earlier volcanism could have occurred on the Farallon Plate, which has been subducted in its entirely and its volcanoes have now vanished. No volcanism in the Musicians Seamounts post- dating about 70 million years ago was discovered at first; either volcanism ceased at that time or it continued on the Farallon Plate again.

About 50 million years ago the Siletzia terrane, being borne to the northeast by the subducting plate, refused to be subducted. It ran it into the edge of the continent and embayed the overlying crust, bending the section of the Wrangellia—Pacific Rim contact now known as the San Juan fault to its current easterly orientation. This also initiated the oblique left-lateral Devils Mountain fault, including the section now known as the Leech River fault, and its right-lateral extension, the Darrington fault, that strikes southward from the town of Darrington to converge with the right-lateral strike-slip Straight Creek Fault at the OWL (see map).If connected strike-slip faults having opposite senses of movement seems strange, consider the Crescent terrane (the part of Siletzia relevant here) as a very blunt arrowhead: the point is now near Darrington (unlabelled black square on map); the Devils Mountain and Darrington faults are the opposite sides of the arrow head.

The islands of Indonesia constitute an island arc that is one of the world's most seismically active regions, with high velocity plate movement at the Sunda Trench (up to per year), and considerable threats from earthquakes, volcanic eruptions, and tsunami throughout. Java, one of the five largest in the Indonesian archipelago, lies on the Sunda Shelf to the north of the Sunda Trench, which is a convergent plate boundary where the Indo-Australian Plate is being subducted under the Eurasian Plate. The subduction zone offshore Java is characterized by a northward dipping Benioff zone, frequent earthquakes and volcanic activity that influence the regional geography, and direct or indirect stress transfer that has affected the various onshore faults. Sedimentation is closely related to tectonics, and while the volume of offshore sediment at the trench decreases with distance from the Ganges- Brahmaputra Delta at the Bay of Bengal, the onshore accrual of sediments near the Special Region of Yogyakarta has been shaped by tectonic events.

The lavas of the Louisville Seamount Chain were generated 80-90 Ma but began to subduct under the Tonga-Kermadec Ridge at 8 Ma. The Hikurangi and Manihiki plateaux, north and south of the Tonga-Kermadec Ridge respectively, form part of the Ontong Java-Hikurangi-Manihiki large igneous province (LIP), the largest volcanic event on Earth during the past 200 million years. The Osbourn Trough, located just north of the Tonga-Kermadec and Louisville intersection, is the palaeo-spreading centre between the Hikurangi and Manihiki plateaux away from which the age of the Pacific Plate increases from 85 Ma to 144 Ma. The subduction of the Hikurangi Plateau beneath New Zealand and the southern part of the Kermadec Arc has resulted in large volumes of lava and a high density of volcanoes in the arc. The initial Hikurangi-Kermadec collision, however, occurred to the north where a missing piece of the Ontong Java-Hikurangi- Manihiki LIP has already been subducted.

Early models of plate tectonics, such as Harry Hess's seafloor spreading model, assumed that the motions of plates and the activity of mid-ocean ridges and subduction zones were primarily the result of convection currents in the mantle dragging on the crust and supplying fresh, hot magma at mid-ocean ridges. Further developments of the theory suggested that some form of ridge push helped supplement convection in order to keep the plates moving, but in the 1990s, calculations indicated that slab pull, the force that a subducted section of plate exerts on the attached crust on the surface, was an order of magnitude stronger than ridge push. As of 1996, slab pull was generally considered the dominant mechanism driving plate tectonics. Modern research, however, indicates that the effects of slab pull are mostly negated by resisting forces in the mantle, limiting it to only 2-3 times the effective strength of ridge push forces in most plates, and that mantle convection is probably much too slow for drag between the lithosphere and the asthenosphere to account for the observed motion of the plates.

At Siccar Point, during the lower Silurian Llandovery epoch around 435 million years ago, thin beds of fine-grained mudstone were laid down gradually deep in the Iapetus Ocean, alternating with thicker layers of hard greywacke formed when torrents swept unsorted sandstone down the continental slope. During the following 65 million years, the ocean closed and the layers of rock were buckled almost vertically, getting forced to the surface as the ocean floor was subducted under the northern continent. Erosion of the exposed edges of layers formed a characteristic shape of ribs of hard greywracke with narrow gaps where mudstone was worn away, and fragments of greywacke lay on the surface as a talus deposit. In the Famennian Late Devonian period around 370 million years ago this was a low-lying tropical area just south of the equator, where rainy season rivers deposited sands and silts rich in iron oxide, then during the dry seasons these were blown about by winds to form easily eroded layers and dunes.

Dabajian Mountain The island of Taiwan lies in a complex tectonic area between the Yangtze Plate to the west and north, the Okinawa Plate on the north-east, and the Philippine Mobile Belt on the east and south. The upper part of the crust on the island is primarily made up of a series of terranes, mostly old island arcs which have been forced together by the collision of the forerunners of the Eurasian Plate and the Philippine Sea Plate. These have been further uplifted as a result of the detachment of a portion of the Eurasian Plate as it was subducted beneath remnants of the Philippine Sea Plate, a process which left the crust under Taiwan more buoyant. The east and south of Taiwan are a complex system of belts formed by, and part of the zone of, active collision between the North Luzon Trough portion of the Luzon Volcanic Arc and South China, where accreted portions of the Luzon Arc and Luzon forearc form the eastern Coastal Range and parallel inland Longitudinal Valley of Taiwan respectively.

The origin of this hotspot volcanism is disputed. One theory holds that a mantle plume has caused the Yellowstone hotspot to migrate northeast, while another theory explains migrating hotspot volcanism as the result of the fragmentation and dynamics of the subducted Farallon Plate in Earth's interior. The Yellowstone Caldera is the largest volcanic system in North America, and in the world, it is only rivalled by the Lake Toba Caldera on Sumatra. It has been termed a "supervolcano" because the caldera was formed by exceptionally large explosive eruptions. The magma chamber that lies under Yellowstone is estimated to be a single connected chamber, about long, wide, and 3 to 7 miles (5 to 12 km) deep. The current caldera was created by a cataclysmic eruption that occurred 640,000 years ago, which released more than 240 cubic miles (1,000 km³) of ash, rock and pyroclastic materials./ This eruption was more than 1,000 times larger than the 1980 eruption of Mount St. Helens. It produced a caldera nearly 5/8 of a mile (1 km) deep and in area and deposited the Lava Creek Tuff, a welded tuff geologic formation.

Between 1906 and 1936 seismological data were used by R.D. Oldham, A. Mohorovičić, B. Gutenberg and I. Lehmann to show that the earth consisted of a solid crust and mantle, a fluid outer core and a solid innermost core. The development of seismology as a modern tool for imaging the Earth's deep interior occurred during the 1980s, and with it developed two camps of geologists: whole-mantle convection proponents and layered-mantle convection proponents. Layered-mantle convection proponents hold that the mantle's convective activity is layered, separated by densest-packing phase transitions of minerals like olivine, garnet and pyroxene to more dense crystal structures (spinel and then silicate perovskite and post-perovskite). Slabs that are subducted may be negatively buoyant as a result of being cold from their time on the surface and inundation with water, but this negative buoyancy is not enough to move through the 660-km phase transition. Whole- mantle (simple) convection proponents hold that the mantle’s observed density differences (which are inferred to be products of mineral phase transitions) do not restrict convective motion, which moves through the upper and lower mantle as a single convective cell.