where are deep ocean trenches located relative to the moving plates of earth's crust
Geology of the United States


of breaks in the oceanic crust where new ocean crust is created. On one side of the spreading ridge new Pacific Plate crust is made, then moves away from the ridge. On the other side of the spreading ridge the Juan de Fuca Plate and Gorda Plate move eastward. There are some unusual features at the Cascade subduction zone. Where the Juan de Fuca Plate sinks beneath the North American Plate there is no deep trench, seismicity (earthquakes) are fewer than expected, and there is evidence of a decline in volcanic
17519745
Crust (geology)


and it is constantly creating new ocean crust. That means that old crust must be destroyed somewhere, so, opposite a spreading center, there is usually a subduction zone: a trench where an ocean plate is being shoved back into the mantle. This constant process of creating new ocean crust and destroying old ocean crust means that the oldest ocean crust on Earth today is only about 200 million years old. In contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in
15455362
Tonga Trench


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. 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
3059512
Plate tectonics


late 1950s and early 1960s. The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken into tectonic plates. The Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries (or faults)
5129457
Northern Cordilleran Volcanic Province


an area where the Earth's crust and lithosphere is being pulled apart. This differs from other portions of the Pacific Ring of Fire as it consists largely of volcanic arcs formed by subducting oceanic crust at oceanic trenches along continental margins circling the Pacific Ocean. The continental crust at the Northern Cordilleran Volcanic Province is being stretched at a rate of about per year. This incipient rifting formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench, which extends along the southern
7725044
Island arc


heat is lost, the reduction in pressure may cause pressure release or decompression partial melting. On the subducting side of the island arc is a deep and narrow oceanic trench, which is the trace at the Earth's surface of the boundary between the down-going and overriding plates. This trench is created by the downward gravitational pull of the relatively dense subducting plate on the leading edge of the plate. Multiple earthquakes occur along this subduction boundary with the seismic hypocenters located at increasing depth under the island arc: these quakes define
728743
Subduction


. At a depth of greater than 60 kilometers, the basalt of the oceanic crust is converted to a metamorphic rock called eclogite. At that point, the density of the oceanic crust increases and provides additional negative buoyancy (downwards force). It is at subduction zones that Earth's lithosphere, oceanic crust and continental crust, sedimentary layers and some trapped water are recycled into the deep mantle. Earth is so far the only planet where subduction is known to occur. Subduction is the driving force behind plate tectonics, and without
15455935
Earth


, two plates slide past one another laterally. Along these plate boundaries, earthquakes, volcanic activity, mountain-building, and oceanic trench formation can occur. The tectonic plates ride on top of the asthenosphere, the solid but less-viscous part of the upper mantle that can flow and move along with the plates. As the tectonic plates migrate, oceanic crust is subducted under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges
9155332
Ryukyu Trench


The , also called Nansei-Shotō Trench, is a 1398 km (868 mi) long oceanic trench located along the southeastern edge of Japan's Ryukyu Islands in the Philippine Sea in the Pacific Ocean, between northeastern Taiwan and southern Japan. The trench has a maximum depth of 7460 m (24,476 ft). The trench is the result of oceanic crust of the Philippine Plate obliquely subducting beneath the continental crust of the Eurasian Plate at a rate of approximately 52 mm/yr. In conjunction with the adjacent Nankai Trough to
16604144
Mid-ocean ridge


of rocks much younger than the Earth itself. Most oceanic crust in the ocean basins is less than 200 million years old. As the oceanic crust and lithosphere moves away from the ridge axis, the peridotite in the underlying mantle lithosphere cools and becomes more rigid. The crust and the relatively rigid peridotite below it make up the oceanic lithosphere, which sits above the less rigid and viscous asthenosphere. Oceanic lithosphere is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at ocean trenches. Two processes,
1762581
Hikurangi Trench


the Indo-Australian Plate. By contrast, the Kermadec and Tonga trenches represent the parts of the subduction zone where oceanic crust of the Pacific Plate is subducting beneath oceanic crust of the Indo-Australian Plate. Although shallower than the trenches north of it, the Hikurangi Trench reaches depths of 3,000 metres as close as 80 kilometres from shore. Its maximum depth is about . At the southern end of the trench, off the coast of the Marlborough region, the seabed rises sharply, and because of the prevailing winds and tides
11116229
Mariana Trench


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. 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 more dense; hence its great height difference relative to the higher-riding (and younger) Mariana Plate. The deepest area at the plate boundary is
19317953
British Mid-Ocean Ridge Initiative


The British Mid-Ocean Ridge Initiative (the BRIDGE Programme) was a multidisciplinary scientific investigation of the creation of the Earth’s crust in the deep oceans. It was funded by the UK’s Natural Environment Research Council (NERC) from 1993 to 1999. Mid-Ocean ridges are active volcanic mountain ranges snaking through the depths of the Earth’s oceans. They occur where the edges of the Earth’s tectonic plates are separating, allowing mantle rock to rise to the seafloor and harden, creating new crust. The addition of
1873040
Plate tectonics


continental margins where oceanic trenches—very deep, narrow canyons—are formed, e.g. along the rim of the Pacific Ocean basin. The important step Hess made was that convection currents would be the driving force in this process, arriving at the same conclusions as Holmes had decades before with the only difference that the thinning of the ocean crust was performed using Heezen's mechanism of spreading along the ridges. Hess therefore concluded that the Atlantic Ocean was expanding while the Pacific Ocean was shrinking. As old oceanic crust is "consumed"
5129521
Volcano


oceanic crust. Most divergent plate boundaries are at the bottom of the oceans; therefore, most volcanic activity on the Earth is submarine, forming new seafloor. Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed; for example, Iceland. Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or
14164431
Volcanic arc


temperature-pressure conditions for flux-melting volcanism due to chlorite destabilization will always occur at the same depth, the distance from the trench to the arc volcanoes is determined only by the dip angle of the subducting slab. On the subducting side of the arc is a deep and narrow oceanic trench, which is the trace at the Earth's surface of the boundary between the down-going and overriding plates. This trench is created by the gravitational pull of the relatively dense subducting plate pulling the leading edge of the plate downward
6469680
Continental arc


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 HO and CO, which cause partial melting of the above asthenosphere. This process can create relatively buoyant magma, which subsequently forms a series of volcanoes at the surface along the subduction zone. There are some
2708375
Oceanic trench


volcanic arc. Oceanic trenches typically extend below the level of the surrounding oceanic floor. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km/yr. There are approximately of convergent plate margins, mostly around the Pacific Ocean—the reason for the reference “Pacific-type” margin—but they are also in the eastern Indian Ocean, with relatively short convergent margin segments in the Atlantic
15455269
Challenger Deep


The Challenger Deep is the deepest known point in the Earth's seabed hydrosphere (the oceans), with a depth of by direct measurement from submersibles and slightly more by sonar bathymetry. It is located in the Pacific Ocean, at the southern end of the Mariana Trench near the Mariana Islands group. The Challenger Deep is a relatively small slot-shaped depression in the bottom of a considerably larger crescent-shaped oceanic trench, which itself is an unusually deep feature in the ocean floor. The Challenger Deep's bottom is about
7936587
Geology of the Death Valley area


under the adjacent ocean. An area of great compression called a subduction zone was formed in the early-to-mid Mesozoic, which replaced the quiet, sea-covered continental margin with erupting volcanoes and uplifting mountains. A chain of volcanoes pushed through the continental crust parallel to the deep trench, fed by magma rising from the subducting oceanic plate as it entered the Earth's hot interior. Thousands of feet (hundreds of meters) of lavas erupted, pushing the ocean over to the west. Compressive forces built up along
10878629
Mariana Trench


The Mariana Trench or Marianas Trench is located in the western Pacific Ocean about east of the Mariana Islands, and has the deepest natural trench in the world. It is a crescent-shaped trough in the Earth's crust averaging about long and wide. The maximum known depth is (± ) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep. However, some unrepeated measurements place the deepest portion at . By comparison: if Mount Everest were placed into the trench at this
19317949
Basement (geology)


. Much of the basement rock may have originally been oceanic crust, but it was highly metamorphosed and converted into continental crust via a series of events. A typical pattern is as follows. 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. When a plate of oceanic crust is subducted beneath an overriding plate of oceanic crust, as the underthrusting crust melts, it can
12134447
Geography of Mexico


, however, is being carried northeast by the underlying motion of the Cocos Plate. Ocean floor material is relatively dense; when it strikes the lighter granite of the Mexican landmass, the ocean floor is forced under the landmass, creating the deep Middle America Trench that lies off Mexico's southern coast. The westward moving land atop the North American plate is slowed and crumpled where it meets the Cocos plate, creating the mountain ranges of southern Mexico. The subduction of the Cocos plate accounts for the frequency of earthquakes near Mexico's
11841780
Geology of Costa Rica


The geology of Costa Rica is part of the Panama Microplate, which is slowly moving north relative to the stable Caribbean Plate. In the late Cretaceous, an oceanic trench or backarc system formed in connection with a subduction zone, situated where the Isthmus of Panama is now located. Into the early Paleogene, deep sea, open ocean sediments and basalt lava accumulated in the backarc. Volcanic activity was intense in the Cretaceous, Paleocene and Eocene. The volcanic arc that built up during the period overthrust onto the southern margin of North
13213779
Earth


upwelling associated with mid-ocean ridges. The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans because the crust there is much thinner than that of the continents. Earth's mechanically rigid outer layer, the lithosphere, is divided into tectonic plates. These plates are rigid segments that move relative to each other at one of three boundaries types: At convergent boundaries, two plates come together; at divergent boundaries, two plates are pulled apart; and at transform boundaries
9155331
Plate tectonics


in the trenches (like Holmes and others, he thought this was done by thickening of the continental lithosphere, not, as now understood, by underthrusting at a larger scale of the oceanic crust itself into the mantle), new magma rises and erupts along the spreading ridges to form new crust. In effect, the ocean basins are perpetually being "recycled," with the creation of new crust and the destruction of old oceanic lithosphere occurring simultaneously. Thus, the new mobilistic concepts neatly explained why the Earth does not get
5129522
List of submarine topographical features


" oceanic basins (those that are associated with a moving plate tectonic boundary) also typically include an oceanic trench and a subduction zone. Abyssal plains cover more than 33% of the ocean floor (about 23% of Earth's surface), but they are poorly preserved in the sedimentary record because they tend to be consumed by the subduction process. The abyssal plain is formed when the lower oceanic crust is melted and forced upwards by the asthenosphere layer of the upper mantle. As this basaltic material reaches the surface at mid
19827292
2004 Indian Ocean earthquake and tsunami


the great Eurasian Plate) at the Sunda Trench. At this point the India Plate subducts beneath the Burma Plate, which carries the Nicobar Islands, the Andaman Islands, and northern Sumatra. The India Plate sinks deeper and deeper beneath the Burma Plate until the increasing temperature and pressure drive volatiles out of the subducting plate. These volatiles rise into the overlying plate, causing partial melting and the formation of magma. The rising magma intrudes into the crust above and exits the Earth's crust through volcanoes in the form of a volcanic
13932658
Jacques Piccard


Jacques Piccard (28 July 19221 November 2008) was a Swiss oceanographer and engineer, known for having developed underwater submarines for studying ocean currents. In the Challenger Deep, he and Lt. Don Walsh of the United States Navy were the first people to explore the deepest part of the world's ocean, and the deepest location on the surface of Earth's crust, the Mariana Trench, located in the western North Pacific Ocean. Jacques Piccard was born in Brussels, Belgium, to Auguste Piccard, who was himself an adventurer
7440103
Samuel Warren Carey


. He backed the moving of continents proposed by Alfred Wegener and decided on the expanding Earth idea as the mechanism for this and was the main proponent of this hypothesis. Carey's expanding earth bears many resemblances to the current model, including supercontinents dividing and going adrift, zones of new crust being generated in deep oceanic ridges, and other phenomena of a still active crust. His hypothesis gave the mechanism for this as an expanding earth; whereas the new hypothesis of plate tectonics accounted for it with subduction. However, in principle
8376895
Deep sea community


a few meters it may be back down to 2–4 °C. Salinity is constant throughout the depths of the deep sea. There are two notable exceptions to this rule: The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline, at a depth of 1000 fathoms (1800 m) or more. The deepest part of the deep sea is Mariana Trench located in the western North Pacific. It is also the deepest point of the earth's crust. It has a maximum
4981210
Continental collision


the underlying asthenospheric mantle and normal subduction is disrupted. The volcanic arc on the upper plate is slowly extinguished. Resisting subduction, the crust buckles up and under, raising mountains where a trench used to be. The position of the trench becomes a zone that marks the suture between the two continental terranes. Suture zones are often marked by fragments of the pre-existing oceanic crust and mantle rocks, known as ophiolites. The continental crust on the downgoing plate is deeply subducted as part of the downgoing plate during collision, defined
4663947
Obduction


of obducted oceanic lithosphere are the ophiolites. Ophiolites are an assemblage of oceanic lithosphere rocks that have been emplaced onto a continent. This assemblage consists of deep-marine sedimentary rock (chert, limestone, clastic sediments), volcanic rocks (pillow lavas, glass, ash, sheeted dykes and gabbros) and peridotite (mantle rock). This process is operative beneath and behind the inner walls of oceanic trenches (subduction zone) where slices of oceanic crust and mantle are ripped from the upper part of the descending plate and wedged
15456036
Oceanic trench


plate and the outermost forearc. The forearc consists of igneous and metamorphic crust, and this crust may act as buttress to a growing accretionary wedge (formed from sediments scraped off the top of the downgoing plate). If the flux of sediments is high, material transfers from the subducting plate to the overriding plate. In this case an accretionary prism grows and the location of the trench migrates progressively away from the volcanic arc over the life of the convergent margin. Convergent margins with growing accretionary prisms are called accretionary margins and make
15455279
Earth


. The combination of these processes recycles the oceanic crust back into the mantle. Due to this recycling, most of the ocean floor is less than old. The oldest oceanic crust is located in the Western Pacific and is estimated to be old. By comparison, the oldest dated continental crust is . The seven major plates are the Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, and South American. Other notable plates include the Arabian Plate, the Caribbean Plate, the Nazca Plate off the west
9155333
Intraplate deformation


Intraplate deformation is the folding, breaking, or flow of the Earth's crust within plates instead of at their margins. This process usually occurs in areas with especially weak crust and upper mantle, such as the Tibetan Plateau (Figure 1). Intraplate deformation brings another aspect to plate tectonic theory. The theory of plate tectonics states that the Earth's crust is made up of rigid plates that "float" on top of the mantle and move relative to one another. As the plates move, the crust deforms dominantly along
1362119
Ice age


around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on the earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth–Moon system; the impact of relatively large meteorites and volcanism including eruptions of supervolcanoes. Some of these factors influence each other. For example, changes in Earth's atmospheric composition (especially the concentrations of greenhouse gases) may alter the climate, while climate
15464515
Crust (geology)


repeatedly destroyed by large impacts, then reformed from the magma ocean left by the impact. None of Earth's primary crust has survived to today; all was destroyed by erosion, impacts, and plate tectonics over the past several billion years. Since then, Earth has been forming secondary and tertiary crust. Secondary crust forms at mid-ocean spreading centers, where partial-melting of the underlying mantle yields basaltic magmas and new ocean crust forms. This "ridge push" is one of the driving forces of plate tectonics,
15455361
Craton


crust at ridges and hot spots, and rapid recycling of oceanic crust at subduction zones. There are at least three hypotheses of how cratons have been formed: 1) surface crust was thickened by a rising plume of deep molten material, 2) successive subducting plates of oceanic lithosphere became lodged beneath a proto-craton in an under-plating process, 3) accretion from island arcs or continental fragments rafting together to thicken into a craton. Earth's surface was probably broken up into many small plates with volcanic islands and arcs
10217101
Tonga Trench


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 as the Pacific Plate is being subducted westward in the trench. When the Apollo 13 mission was aborted in 1970 following an explosion in an oxygen tank, the radioisotope thermoelectric generator broke up in the atmosphere and the heat source plunged in or near the Tonga Trench. Atmospheric and oceanic monitoring indicate no release of nuclear fuel
3059505
Geology of the Alps


began to move toward the European plate, oceanic trenches formed in the eastern Alps. In these, deep marine sediments were deposited, such as radiolarites and lutites. 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
1990199
Opening of the North Atlantic Ocean


in the plate and the amount of melt is governed by the fusibility of the mantle beneath. Plate tectonics can explain most of the volcanism on Earth. Active rifting, such as is formed by the Iceland plume, is driven by hotspot or mantle plume activity. From deep within the Earth, hot mantle rises to force doming of the crust. This causes thinning of the crust and lithosphere, then melting and underplating occur. Finally, there is rifting at the crest of the domed crust and volcanism occurs. In passive rifting
4880712
Aleutian subduction zone


Plate ended ~66-56 my, and the underthrusting of oceanic crust created the Aleutian trench. And yet other more complicated hypotheses exist. There are two hypotheses in the mechanism of the trench formation: tensional and compressional. The tensional hypothesis suggests that island arc loading caused the oceanic crust to create downward faulting. In other words, the trench was a part of oceanic crust once, but faulted down at depth due to the loading of island arc. The compressional hypothesis suggests that mantle convection or drag prevented oceanic crust from reaching
6082434
Mariana Islands


Mariana plate, a region which is the most volcanically active convergent plate boundary on Earth. This subduction region, just east of the island chain, forms the noted Mariana Trench, the deepest part of the Earth's oceans and lowest part of the surface of the Earth's crust. In this region, according to geologic theory, water trapped in the extensive faulting of the Pacific Plate as serpentinite, is heated by the higher temperatures of depth during its subduction, the pressure from the expanding steam results in the hydrothermal activity in
17511126
Geography of Newfoundland and Labrador


tectonic plates. Approximately 500 million years ago the action of these plates forced parts of the oceanic crust beneath the Iapetus Ocean up and over the eastern margin of the North American plate. Sections of oceanic crust which overlie continental crust are known as ophiolites. Gros Morne National Park was designated a UNESCO World Heritage Site because it is one of the best places in the world to see the effects of plate tectonics and one of the few places where rocks formed at the Mohorovicic Discontinuity between the crust and the upper mantle of the Earth
608114
List of submarine topographical features


all oceans with the exception of the Arctic Ocean and they are most common in the North and South Pacific Oceans. There are three types of lithospheric plate boundaries: 1.) divergent (where lithosphere and oceanic crust is created at mid-ocean ridges), 2.) convergent (where one lithospheric plate sinks beneath another and returns to the mantle), and 3.) transform (where two lithospheric plates slide past each other). An oceanic trench is a type of convergent boundary at which two oceanic lithospheric slabs
19827295
Plate tectonics


be continuously added along the oceanic ridges without increasing the size of the Earth? In reality, this question had been solved already by numerous scientists during the forties and the fifties, like Arthur Holmes, Vening-Meinesz, Coates and many others: The crust in excess disappeared along what were called the oceanic trenches, where so-called "subduction" occurred. Therefore, when various scientists during the early sixties started to reason on the data at their disposal regarding the ocean floor, the pieces of the theory quickly fell into
5129517
Back-arc region


oceanic crust or continental crust. In the case of oceanic crust, most back-arc regions are subjected to tensional stresses and thus develop a spreading center where new oceanic crust is formed. The composition of this new crust is similar to MORB, although it contains higher amounts of water. 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
21774631
List of tectonic plates


This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around thick and consist of two principal types of material: oceanic crust (also called "sima" from silicon and magnesium) and continental crust ("sial" from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density
17361492
Izu–Bonin–Mariana Arc


. 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. At the south end of IBM, there is almost now convergence between the Caroline Plate and the Philippine Sea Plate. It should be noted that 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,
7387030
Kermadec-Tonga subduction zone


old oceanic plate entering the hot mantle of the Earth. The eastern boundaries of the Tonga and Kermadec Plates constitute the subduction zone of the Pacific Plate, characterized by a trench about 2,000 km in length. The trench is continuous, but has different names for different sections: Hikurangi Trench, the Kermadec Trench and the Tonga Trench. The Tonga Trench is the second deepest trench in the world at about 10,800 m, with the deepest point, Horizon Deep, being the deepest point in the Southern Hemisphere and the second deepest point
17123422
San Jose, Camarines Sur


North down to Sorsogon in the South with a total of 16 volcanoes separately spread over by about 24 km. apart and rested parallel along the 200 km. chain west of the Philippine Trench, which is the major source of earthquake in the region. The trench can be described as a long, narrow, and generally steep-sided very deep depression in the ocean floor. The axis of a trench marks, the position of a subduction zone where old oceanic lithospheric plates begin their descent into the earth's interior. In
10562581
Puget Sound faults


stresses that cause earthquakes are the motions of the tectonic plates: material from the Earth's mantle rises at spreading centers, and moves out as plates of oceanic crust which eventually are subducted under the more buoyant plates of continental crust. Western Washington lies over the Cascadia subduction zone, where the Juan de Fuca Plate is subducting towards the east (see diagram, right). This is being obliquely overridden by the North American plate coming out of the northeast, which has formed a bend in the subducting plate and in the forearc
16871893
Caribbean Plate


time by oceanic crust. The Pacific Ocean floor subducted under this oceanic crust between the continents. The CLIP drifted into the same area, but as it was less dense and thicker than the surrounding oceanic crust, it did not subduct, but rather overrode the ocean floor, continuing to move eastward relative to North America and South America. With the formation of the Isthmus of Panama 3 million years ago, it ultimately lost its connection to the Pacific. The more recent theory asserts that the Caribbean Plate came into being from an
12344075
Geochemical cycle


deep Earth and outer space. Geochemical cycles are concerned with the interactions between deep earth which consists of Earth's mantle and core, and the lithosphere which consists of the Earth's crust. Flux in geochemical cycles is the movement of material between the deep Earth and the surface reservoirs. This occurs through two different processes: volcanism and subduction of tectonic plates. Subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate and sinks into the mantle as the plates converge. This leads
4515519
Plate tectonics


crust generally lies below sea level (for example most of the Pacific Plate), while continental crust buoyantly projects above sea level (see the page isostasy for explanation of this principle). Three types of plate boundaries exist, with a fourth, mixed type, characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are: It has generally been accepted that tectonic plates are able to move because of the relative density of oceanic lithosphere
5129468
Continental crust


this reason the oldest rocks on Earth are within the cratons or cores of the continents, rather than in repeatedly recycled oceanic crust; the oldest intact crustal fragment is the Acasta Gneiss at 4.01 Ga, whereas the oldest oceanic crust (located on the Pacific Plate offshore of Kamchatka) is from the Jurassic (≈180 Ma). Continental crust and the rock layers that lie on and within it are thus the best archive of Earth's history. The height of mountain ranges is usually related to the thickness of crust. This results
10217152
Nazca Ridge


The Nazca Ridge is a submarine ridge, located on the Nazca Plate off the west coast of South America. This plate and ridge are currently subducting under the South American Plate at a convergent boundary known as the Peru-Chile Trench at approximately 7.7 cm/yr. The Nazca Ridge began subducting obliquely to the collision margin at 11°S, approximately 11.2 Ma, and the current subduction location is 15°S. The ridge is composed of abnormally thick basaltic ocean crust, averaging 18 ±3 km thick. This crust is buoyant
2144591
Makran Trench


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 Makran region, the Arabian Plate subducts beneath the Eurasian Plate at ~4cm/yr. This subduction is associated with an accretionary wedge of sediments which has developed since the Cenozoic. To the west, the Makran Trench
18637563
Earth's crustal evolution


Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface. The variation in composition within the Earth's crust is much greater than that of other terrestrial planets. Mars, Venus, Mercury and other planetary bodies have relatively quasi-uniform crusts unlike that of the Earth which contains both oceanic and continental plates. This unique property reflects the complex series of crustal processes that have taken place throughout the planet's history, including the ongoing process of plate tectonics. The proposed mechanisms
8421005
Oceanic trench


under the volcanic arc as deeply as are diagnostic of convergent plate boundaries and their deeper manifestations, subduction zones. Trenches are related to but distinguished from continental collision zones (such as that between India and Asia forming the Himalaya), where continental crust enters a subduction zone. When buoyant continental crust enters a trench, subduction eventually stops and the area becomes a zone of continental collision. Features analogous to trenches are associated with collisions zones, including sediment-filled foredeeps, such as those the Ganges River and Tigris-Euphrates rivers
15455271
Banda Arc


The Banda Arc (main arc, Inner, and Outer) is a set of island arcs that exist in eastern Indonesia. It manifests the collision of a continent and an intra-oceanic island arc. The presently active arc is located on what appears to be oceanic crust whereas the associated subduction trench is underlain by continental crust. The convergence of the Indo-Australian plates and Eurasia and resulted in the formation of the Sunda and Banda island arcs. The transitional zone between the arcs is located south of Flores Island and is
11041738
Crust (geology)


ocean spreading centers, where the adiabatic rise of mantle causes partial melting. Tertiary crust is more chemically-modified than either primary or secondary. It can form in several ways: The only known example of tertiary crust is the continental crust of the Earth. It is unknown whether other terrestrial planets can be said to have tertiary crust, though the evidence so far suggests that they do not. This is likely because plate tectonics is needed to create tertiary crust, and Earth is the only planet in our Solar System with plate
15455355
Island arc


plate which meets the descending plate containing normal oceanic crust along the Benioff zone. The sharp bending of the oceanic plate downward produces a trench. There are generally three volcanic series from which the types of volcanic rock that occur in island arcs are formed: This volcanic series is related to the age of the subduction zone and the depth. The tholeiitic magma series is well represented above young subduction zones formed by magma from relative shallow depth. The calc-alkaline and alkaline series are seen in mature subduction zones, and are related
728748
Oceanic trench


Oceanic trenches are topographic depressions of the sea floor, 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. Trenches are generally parallel to a volcanic island arc, and about from a
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Sea


the process is accompanied by friction as the plates grind together. The movement proceeds in jerks which cause earthquakes, heat is produced and magma is forced up creating underwater mountains, some of which may form chains of volcanic islands near to deep trenches. Near some of the boundaries between the land and sea, the slightly denser oceanic plates slide beneath the continental plates and more subduction trenches are formed. As they grate together, the continental plates are deformed and buckle causing mountain building and seismic activity. The Earth's deepest trench is
18965552
Plate tectonics


. The relative movement of the plates typically ranges from zero to 100 mm annually. Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction, or one plate moving under another, carries the lower one down into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the lithosphere remains the same. This prediction of plate tectonics
5129458
Himalayas


rocks settled on the ocean floor and the volcanoes that fringed its edges. Since both plates were composed of low density continental crust, they were thrust faulted and folded into mountain ranges rather than subducting into the mantle along an oceanic trench. An often-cited fact used to illustrate this process is that the summit of Mount Everest is made of marine limestone from this ancient ocean. Today, the Indian plate continues to be driven horizontally at the Tibetan Plateau, which forces the plateau to continue to move upwards. The Indian plate
17169010
Philippine Trench


and displaced, by Benham Plateau on the Philippine Sea Plate. The Philippine trench is hypothesized to be younger than 8–9 million years ago. The central part of the Philippine fault formed during the Plio-Pleistocene times is considered to be an active depression of the Earth's crust. The trench formed from a collision between the Palawan and Zamboanga plates. This caused a change in geological processes going from a convergent zone to a subduction zone. The subduction zone is located west to east of the Philippine Islands. The rate of subduction
19555575
Geology of the Pacific Northwest


than a simple subduction zone. Not far off the coast of the North Pacific lies a spreading ridge; a divergent plate boundary made up of a series of breaks in the oceanic crust where melted mantle rises and freezes, creating new ocean crust. On one side of the spreading ridge new Pacific Plate crust is made, then moves away from the ridge. On the other side of the spreading ridge the Juan de Fuca and Gorda Plates move eastward. There are some unusual features at the Cascade subduction zone. Where the Juan
15164528
Hjort Trench


The Hjort Trench is a linear topographic depression south of Macquarie Island in the southwest Pacific Ocean. Geologically, the depression is considered to be the seafloor expression of an ocean-ocean subduction zone, where the Australian plate is thrusting beneath the Pacific Plate. As the southernmost portion of the Macquarie Ridge Complex, the Hjort Trench lies in an area of diagonal convergence produced by the transform fault evolution of the Emerald Fracture Zone. Frequent seismic events, most less than 20 km deep, characterize the transpression along this plate boundary. The
7306912
Coral reef


islands are volcanic in origin. Others have tectonic origins where plate movements lifted the deep ocean floor. In "The Structure and Distribution of Coral Reefs", Charles Darwin set out his theory of the formation of atoll reefs, an idea he conceived during the voyage of the "Beagle". He theorized that uplift and subsidence of the Earth's crust under the oceans formed the atolls. Darwin set out a sequence of three stages in atoll formation. A fringing reef forms around an extinct volcanic island as the island and ocean
5548000
Felix Andries Vening Meinesz


the same on land and at sea, which was in agreement with the principle of isostasy. Vening Meinesz was especially intrigued by the oceanic trenches. The coexisitence of active volcanism, large negative gravity anomalies and the sudden difference in terrain elevation could only be explained by assuming the Earth's crust was somehow pushed together at these places. As a geophysicist, he was prejudiced that the crust was too rigid to deform at that scale in such a way. His discoveries could be explained only with the development of the theory of plate
10917790
History of Earth


, Siberia and Gondwana. During periods when continents move apart, more oceanic crust is formed by volcanic activity. Because young volcanic crust is relatively hotter and less dense than old oceanic crust, the ocean floors rise during such periods. This causes the sea level to rise. Therefore, in the first half of the Paleozoic, large areas of the continents were below sea level. Early Paleozoic climates were warmer than today, but the end of the Ordovician saw a short ice age during which glaciers covered the south pole, where
3941284
Mid-Atlantic Ridge


includes a deep rift valley that runs along the axis of the ridge along nearly its entire length. This rift marks the actual boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava and producing new crustal material for the plates. Near the equator, the Mid-Atlantic Ridge is divided into the North Atlantic Ridge and the South Atlantic Ridge by the Romanche Trench, a narrow submarine trench with a maximum depth of , one of the deepest locations of the Atlantic Ocean. This trench,
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Sea


ten kilometres (three to six miles) thick. The relatively thin lithosphere floats on the weaker and hotter mantle below and is fractured into a number of tectonic plates. In mid-ocean, magma is constantly being thrust through the seabed between adjoining plates to form mid-oceanic ridges and here convection currents within the mantle tend to drive the two plates apart. Parallel to these ridges and nearer the coasts, one oceanic plate may slide beneath another oceanic plate in a process known as subduction. Deep trenches are formed here and
18965551
Tonga Trench


dive was part of the Five Deeps Expedition. The objective of this expedition is to thoroughly map and visit the deepest points of all five of the world's oceans by the end of September 2019. 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
3059509
Earth


) properties. The outer layer is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity. The thickness of the crust varies from about under the oceans to for the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, and it is of the lithosphere that the tectonic plates are composed. Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which
9155327
Plate tectonics


, Matthews and Morley a few years later. The discovery of magnetic striping called for an explanation. In the early 1960s scientists such as Heezen, Hess and Dietz had begun to theorise that mid-ocean ridges mark structurally weak zones where the ocean floor was being ripped in two lengthwise along the ridge crest (see the previous paragraph). New magma from deep within the Earth rises easily through these weak zones and eventually erupts along the crest of the ridges to create new oceanic crust. This process, at first denominated the
5129526
Continental crust


billion cubic kilometers of continental crust, but this quantity varies because of the nature of the forces involved. The relative permanence of continental crust contrasts with the short life of oceanic crust. Because continental crust is less dense than oceanic crust, when active margins of the two meet in subduction zones, the oceanic crust is typically subducted back into the mantle. Continental crust is rarely subducted (this may occur where continental crustal blocks collide and overthicken, causing deep melting under mountain belts such as the Himalayas or the Alps). For
10217151
Sunda Trench


The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian-Capricorn plates subduct under a part of the Eurasian Plate. It is long. Its maximum depth is the deepest point in the Indian Ocean. The trench stretches from the Lesser Sunda Islands past Java, around the southern coast of Sumatra on to the Andaman Islands, and forms the boundary between Indo-Australian Plate and Eurasian plate (more specifically, Sunda
2720614
Tectonic–climatic interaction


usually at great depth. Yellowstone National Park is a hot spot located within the center of a continent. Divergence of continental plates (i.e. the Atlantic Mid-Ocean ridge complex) creates magmas very near the surface of the Earth. A plume of heat from the mantle will melt rocks, creating a hot spot, which can be located at any depth in the crust. Hot spots in oceanic crust develop different magmatic plumbing systems based on plate velocities. Hawaii and the Madeira Archipelago (off the West coast of Africa) are
7733508
Seafloor spreading


seafloor forms and spreads apart from the mid-ocean ridge it slowly cools over time. Older seafloor is, therefore, colder than new seafloor, and older oceanic basins deeper than new oceanic basins due to isostasy. If the diameter of the earth remains relatively constant despite the production of new crust, a mechanism must exist by which crust is also destroyed. The destruction of oceanic crust occurs at subduction zones where oceanic crust is forced under either continental crust or oceanic crust. Today, the Atlantic basin is actively spreading at the
15455323
Ophiolite


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. The hot, positively buoyant ocean crust from the extension won't subduct, instead obducting onto the island arc as an ophiolite. As compression persists, the ophiolite is emplaced onto the
9932207
Caroline Plate


formation and current status as an independent plate are uncertain. There is a very slow rate of spreading between the Caroline and Philippine plates but the Caroline Plate apparently moved together with both the Philippine and New Guinea plates during the Neogene. The Caroline Ridge, to the north, meets the Caroline Plate at the Sorol Trough at which there some evidence of oblique extension; the Caroline Ridge, however, is, although of uncertain origin, made of oceanic crust and probably the product of a hotspot. The presence of a trench and
16750828
Subduction


Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle. Regions where this process occurs are known as "subduction zones". Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries. Plates include both oceanic crust and continental crust. Stable subduction zones involve the oceanic lithosphere of one plate sliding beneath the continental or oceanic lithosphere
15455932
Volcano


A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-oceanic ridge, such
14164426
Izu–Bonin–Mariana Arc


region to the north. The forearc region is very narrow and the intersection of backarc basin spreading axis with the arc magmatic systems is complex. 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
7387044
Hydrothermal vent


A hydrothermal vent is a fissure on the seafloor from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart at spreading centers, ocean basins, and hotspots. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents. Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, hydrothermal vents may form features called black smokers or white smokers. Relative
3118568
Earth science


created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. 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
15740342
Pacific Plate


The southern part of Zealandia, which is to the east of this boundary, is the plate's largest block of continental crust. The northern side is a convergent boundary subducting under the North American Plate forming the Aleutian Trench and the corresponding Aleutian Islands. The Pacific Plate is almost entirely oceanic crust, but it contains some continental crust in New Zealand, Baja California, and coastal California. The Pacific Plate has the distinction of showing one of the largest areal sections of the oldest members of seabed geology being entrenched into eastern Asian
1922347
Biosphere


Earth's oceans. In fact, single-celled life forms have been found in the deepest part of the Mariana Trench, by the Challenger Deep, at depths of . Other researchers reported related studies that microorganisms thrive inside rocks up to below the sea floor under of ocean off the coast of the northwestern United States, as well as beneath the seabed off Japan. Culturable thermophilic microbes have been extracted from cores drilled more than into the Earth's crust in Sweden, from rocks between . Temperature increases with increasing depth into the
4613361
Samoa hotspot


The Samoa hotspot is a volcanic hotspot located in the south Pacific Ocean. The hotspot model describes a hot upwelling plume of magma through the Earth's crust as an explanation of how volcanic islands are formed. The hotspot idea came from J. Tuzo Wilson in 1963 based on the Hawaii volcanic island chain. In theory, the Samoa hotspot is based on the Pacific Tectonic Plate traveling over a fixed hotspot located deep underneath the Samoan Islands. The Samoa hotspot includes the Samoan Islands (American Samoa and Samoa), and extends to the
19333759
Puerto Rico Trench


The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench is associated with a complex transition between the Lesser Antilles subduction zone to the south and the major transform fault zone or plate boundary, which extends west between Cuba and Hispaniola through the Cayman Trough to the coast of Central America. The trench is long and has a maximum depth of or 5.20 miles in the Brownson Deep, which is the deepest point in the Atlantic Ocean and the deepest point not in the Pacific Ocean
16454359
Oceanic trench


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. Globally, forearcs have the lowest heatflow from the interior Earth because there is no asthenosphere (convecting mantle) between the forearc lithosphere and the cold subducting plate. The inner trench wall marks the edge of the overriding
15455278
Geography of Japan


Plate and Okinawa Plate to the south. The Pacific Plate moves under the Okhotsk Plate to the north. These subduction plates have pulled Japan eastward and opened the Sea of Japan by back-arc spreading around 15 million years ago. The Strait of Tartary and the Korea Strait opened much later. La Pérouse Strait formed about 60,000 to 11,000 years ago closing the path used by mammoths which had earlier moved to northern Hokkaido. The subduction zone is where the oceanic crust slides beneath the continental crust or other oceanic plates. This is
15572858
Kutai Basin


been moving north and subducting under Eurasia. The collision of the Indian continent with Eurasia halted subduction and uplifted the Himalayas. In between the continents of India and Australia, the oceanic crust is still subducting under the Sunda plate, forming the Sunda trench and Sunda Arc. Australia and Australian derived micro-plates collided with the Sunda plate and Pacific plate in the Pliocene, creating a complex of subduction zones and island arcs. The Philippine plate has been obliquely subducting the Sunda plate for most of the Cenozoic. The complex interaction of
8032985
Back-arc basin


a buoyant feature in the subduction zone, which locally slows down subduction and induce the subducting plate to rotate adjacent to it. This rotation is associated with trench retreat and overriding plate extension. For back-arc extension to form, a subduction zone is required, but not all subduction zones have a back-arc extension feature. Back-arc basins are found in areas where the subducting plate of oceanic crust is very old. The age need to establish back-arc spreading is oceanic lithosphere that is 55 million years old
12527808
Johnson Cann


report "Strengthening University Earth Sciences" he moved to the University of Leeds where he was Chairman of the School of Earth Sciences from 1989 to 1995. While Professor at Leeds he also held a visiting position as an Adjunct Scientist at the Woods Hole Oceanographic Institution in the United States. In 1987 he instigated, and subsequently led, the Natural Environment Research Council's British Mid-Ocean Ridge Initiative (BRIDGE), a major UK investigation of the creation of the Earth's crust in the deep oceans. For his contributions to
8516102
2013 Saravan earthquake


separates two forms of plate collision. To the northwest, continental crust portions of the Arabian and Eurasian Plates are colliding, resulting in compressive faulting. To the southeast, dense oceanic crust of the Arabian Plate is subducting underneath the Eurasian Plate at the Makran Trench. Iran lies on the fault line between the Arabian plate and the Eurasian plate. The collision of these two plates cause most of the earthquakes that strike Iran. The specific area of the fault that lies below the Sistan and Baluchestan Province is referred to as the Makran
18569119