Oceanic crust – The uppermost layer of the oceanic portion of a tectonic plate
Shield – A large stable area of exposed Precambrian crystalline rock
Supercontinent – Landmass comprising more than one continental core, or craton
Tectonic plate – Continuous section of the lithosphere of the Earth which is moving relative to adjacent plates
Terrane – Fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate
Geologists generally agree that the following tectonic plates currently exist on the Earth's surface with roughly definable boundaries. Tectonic plates are sometimes subdivided into three fairly arbitrary categories: major (or primary) plates, minor (or secondary) plates, and microplates (or tertiary plates).
These plates comprise the bulk of the continents and the Pacific Ocean. For purposes of this list, a major plate is any plate with an area greater than 20 million km2.
Pacific Plate – An oceanic tectonic plate under the Pacific Ocean – 103,300,000 km2
North American Plate – Large tectonic plate including most of North America, Greenland and a bit of Siberia – 75,900,000 km2
Eurasian Plate – A tectonic plate which includes most of the continent of Eurasia – 67,800,000 km2
African Plate – Tectonic plate underlying Africa west of the East African Rift – 61,300,000 km2
Antarctic Plate – A tectonic plate containing the continent of Antarctica and extending outward under the surrounding oceans – 60,900,000 km2
Indo-Australian Plate – A major tectonic plate formed by the fusion of the Indian and Australian plates – 58,900,000 km2 often considered two plates:
Australian Plate – A major tectonic plate, originally a part of the ancient continent of Gondwana – 47,000,000 km2
Indian Plate – A major tectonic plate once part of the supercontinent Gondwana – 11,900,000 km2
South American Plate – A major tectonic plate which includes most of South America and a large part of the south Atlantic – 43,600,000 km2
These smaller plates are often not shown on major plate maps, as the majority do not comprise significant land area. For purposes of this list, a minor plate is any plate with an area less than 20 million km2 but greater than 1 million km2.
Somali Plate – Minor tectonic plate including the east coast of Africa and the adjoining seabed – 16,700,000 km2
Nazca Plate – Oceanic tectonic plate in the eastern Pacific Ocean basin – 15,600,000 km2
Burma Plate – A minor tectonic plate in Southeast Asia – 1,100,000 km2
New Hebrides Plate – Minor tectonic plate in the Pacific Ocean near Vanuatu – 1,100,000 km2
These plates are often grouped with an adjacent major plate on a major plate map. For purposes of this list, a microplate is any plate with an area less than 1 million km2. Some models identify more minor plates within current orogens (events that lead to a large structural deformation of the Earth's lithosphere) like the Apulian, Explorer, Gorda, and Philippine Mobile Belt plates. There may be scientific consensus as to whether such plates should be considered distinct portions of the crust; thus new research could change this list.
Lwandle Plate – A mainly oceanic tectonic microplate off the southeast coast of Africa
Madagascar Plate – A tectonic plate formerly part of the supercontinent Gondwana
Rovuma Plate – One of three tectonic microplates that contribute to the Nubian Plate and the Somali Plate
Mariana Plate – A small tectonic plate west of the Mariana Trench
Philippine Mobile Belt, also known as Philippine Microplate – Complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines
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 (or have done all three).
Supercontinent – Landmass comprising more than one continental core, or craton
Rodinia – Hypothetical neoproterozoic supercontinent from between about a billion to about three quarters of a billion years ago
Ur – Proposed archaean supercontinent from about 3.1 billion years ago
Vaalbara – Archaean supercontinent from about 3.6 to 2.7 billion years ago
Ancient plates and cratons
Not all plate boundaries are easily defined, especially for ancient pieces of crust. The following list of ancient cratons, microplates, plates, shields, terranes, and zones no longer exist as separate plates. Cratons are the oldest and most stable parts of the continental lithosphere and shields are the exposed area of a craton(s). Microplates are tiny tectonic plates, terranes are fragments of crustal material formed on one tectonic plate and accreted to crust lying on another plate, and zones are bands of similar rocks on a plate formed by terrane accretion or native rock formation. Terranes may or may not have originated as independent microplates: a terrane may not contain the full thickness of the lithosphere.
Atlantica – An ancient continent formed during the Proterozoic about 2 billion years ago
East European Craton – The core of the Baltica proto-plate and consists of the Fennoscandia, Volgo-Uralia and Sarmatia crustal segments
Baltic Shield, also known as Fennoscandian Shield – A segment of the Earth's crust in the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea
Junggar Plate – Geographical region in northwest China corresponding to the northern half of Xinjiang
Karelian Craton – Region comprising the Scandinavian Peninsula, Finland, Karelia, and the Kola Peninsula
Kazakhstania – A geological region in Central Asia which consists of the area roughly centered on Lake Balkhash, north and east of the Aral Sea, south of the Siberian craton and west of the Altai Mountains
Avalonia – A microcontinent in the Paleozoic era (Canada, Great Britain, and United States)
Carolina Plate – An exotic terrane from central Georgia to central Virginia in the United States
Churchill Craton – The northwest section of the Canadian Shield from southern Saskatchewan and Alberta to northern Nunavut (Canada)
Farallon Plate – An ancient oceanic plate that has mostly subducted under the west coast of the North American Plate (split into the Cocos, Explorer, Juan de Fuca, Gorda Plates, Nazca Plate, and Rivera Plates)
Hearne Craton – A craton in northern Canada which, together with the Rae Craton, forms the Western Churchill Province (Canada)
Laurentian Craton, also known as North American Craton – A large continental craton that forms the ancient geological core of the North American continent (Canada and United States)
Insular Plate – Ancient oceanic plate that began subducting under the west-coast of North America around the early Cretaceous time
Intermontane Plate – Ancient oceanic tectonic plate on the west coast of North America about 195 million years ago
Izanagi Plate – An ancient tectonic plate, which was subducted beneath the Okhotsk Plate
Nain Province – Part of the North Atlantic Craton in Labrador, Canada (Canada)
North Atlantic Craton – An Archaean craton exposed in southern West Greenland, the Nain Province in Labrador, and the Lewisian complex in northwestern Scotland
Nova Scotia Plate
Rae Craton – An Archean craton in northern Canada north of the Superior Craton (Canada)
Sask Craton (Canada)
Sclavia Craton – A late Archean supercraton thought to be parental to the Slave and Wyoming Cratons in North America, the Dharwar Craton in southern India, and the Zimbabwe Craton in southern Africa (Canada)
Slave Craton – An Archaean craton in the north-western Canadian Shield, in Northwest Territories and Nunavut (Canada)
Superior Craton – An Archean craton which forms the core of the Canadian Shield north of Lake Superior (Canada)
Wyoming Craton – A craton in the west-central United States and western Canada (United States)
^Timothy M. Kusky; Erkan Toraman & Tsilavo Raharimahefa (2006-11-20). "The Great Rift Valley of Madagascar: An extension of the Africa–Somali diffusive plate boundary?". International Association for Gondwana Research Published by Elsevier B.V.
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis, and volcanic eruptions.
A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other causing a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Benioff Zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.
Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle. These convection cells bring hot mantle material to the surface along spreading centers creating new crust. As this new crust is pushed away from the spreading center by the formation of newer crust, it cools, thins, and becomes denser. Subduction initiates when this dense crust converges with the less dense crust. The force of gravity helps drive the subducting slab into the mantle. Evidence supports that the force of gravity will increase plate velocity. As the relatively cool subducting slab sinks deeper into the mantle, it is heated causing dehydration of hydrous minerals. This releases water into the hotter asthenosphere, which leads to partial melting of asthenosphere and volcanism. Both dehydration and partial melting occurs along the 1000 °C isotherm, generally at depths of 65 – 130 km.Some lithospheric plates consist of both continental and oceanic lithosphere. In some instances, initial convergence with another plate will destroy oceanic lithosphere, leading to convergence of two continental plates. Neither continental plate will subduct. It is likely that the plate may break along the boundary of continental and oceanic crust. Seismic tomography reveals pieces of lithosphere that have broken off during convergence.
The Farallon Trench was a subduction related tectonic formation located off the coast of the western California continental margin during the late to mid Cenozoic era, around 50 miles southeast of modern-day Monterey Bay. The time duration of subduction began from around 165 Ma when the Farallon Plate replaced the Mezczlera promontory, until the San Andreas Fault straightening around 35 Ma. As data accumulated over time, a common view developed that one large oceanic plate, the Farallon Plate, acted as a conveyor belt, conveying accreted terranes onto the North American west coast. 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. Rapid subduction under the southwestern North America continent began 40 to 60 million years ago (Ma), during the mid Paleocene to mid Eocene epochs. This convergent subduction margin created a distinctive geomorphologic feature called an oceanic trench, which occurs at a convergent plate boundaries as a heavy metal rich, lithospheric plate moves below a light silica rich continental plate. The trench marks the position at which the flexed subducting slab begins to descend beneath and deform the continental plate margin. By 43 Ma, during the Eocene, worldwide plate motions changed and the Pacific Plate began to move away from North America and subduction of the Farallon Plate slowed dramatically. By around 36 Ma, the easternmost part of the East Pacific Rise, located between the Pioneer and Murray fracture zones at that time, approached the trench and the young, hot, buoyant lithosphere appears to have clogged part of the subduction zone, resulting in widespread dramatic uplift on land. The eventual complete subduction of this plate, consequential contact of the Pacific Plate with the California continental margin, and creation of the Mendocino Triple Junction (MTJ), took place around 30 to 20 Ma. The partial complete subduction and division of the Farallon Plate by the Pacific Plate, created the Juan de Fuca Plate to the north and the Cocos Plate to the south. The final stages of the evolution of California's continental margin was the growth of the San Andres transform fault system, which formed as the Pacific Plate came into contact with the continental margin and the MTJ was formed. As subduction of the Pacific Plate continued along this margin, and the contact zone grew, the San Andres proportionally grew as well.
The Greenland Plate is a supposed tectonic plate bounded to the west by Nares Strait, a probable transform fault, on the southwest by the Ungava transform underlying Davis Strait, on the southeast by the Mid-Atlantic Ridge, and the northeast by the Gakkel Ridge, with its northwest border is still being explored. The Greenland craton is made up of some of the oldest rocks on Earth. The Isua greenstone belt in southwestern Greenland contains the oldest known rocks on Earth dated at 3.7–3.8 billion years old.The Precambrian basement of Greenland formed an integral part of the Laurentian Shield that is at the core of the North American continent. Greenland was formed in two rifting stages from the main body of North America. The first, during the Cretaceous period formed Baffin Bay. Baffin Bay is the northwestern extension and terminus of the North Atlantic-Labrador Sea rift system that started forming 140 million years ago in the Early Cretaceous epoch. The Labrador Sea started opening 69 million years ago during the Maastrichtian age but seafloor spreading appears to have ceased by the Oligocene epoch, 30–35 million years ago. Correlations between tectonic units in Canada and Greenland have been proposed, however, the pre-spreading fit of Greenland to Canada is still not accurately known.Since the closure of the North Atlantic–Labrador Sea rift, Greenland has moved roughly in conjunction with North America; thus, there are questions as to whether the Greenland Plate should be still considered a separate plate at all. The area between Greenland and Baffin Island is, however, seismically very active, being the location of the epicenter of many earthquakes including a 7.3-magnitude earthquake in 1933. As of 2009, scientists have been unable to correlate the seismicity with particular geological structures or geophysical anomalies. It has been suggested that seismicity in the region is related to the stresses associated with post-glacial rebound.
The Iberian Plate with the microcontinent Iberia encompassed not only the Iberian Peninsula but also Corsica, Sardinia, the Balearic Islands, and the Briançonnais zone of the Penninic nappes of the Alps. Nowadays, the Iberian plate is a part of the Eurasian plate.
The Indian Plate or India Plate is a major tectonic plate straddling the equator in the eastern hemisphere. Originally a part of the ancient continent of Gondwana, India broke away from the other fragments of Gondwana 100 million years ago and began moving north. Once fused with the adjacent Australia to form a single Indo-Australian Plate, recent studies suggest that India and Australia have been separate plates for at least 3 million years and likely longer. The Indian Plate includes most of South Asia—i.e. the Indian subcontinent—and a portion of the basin under the Indian Ocean, including parts of South China and western Indonesia, and extending up to but not including Ladakh, Kohistan and Balochistan.
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. 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. Knowledge of the now-subducted Izanagi Plate is limited to Mesozoic magnetic lineations on the Pacific Plate that preserve the record of this subduction.
The Lwandle Plate is one of three tectonic microplates, along with the Rovuma Plate and Victoria Plate, that make up the African Plate with the Somali Plate and the Nubian Plate. Its discovery is very recent, so the velocity of the plate is neither well known nor well understood. Many experiments are ongoing to quantify this. The Lwandle Plate lies between 30°E and 50°E, sharing a boundary with the Nubian, Somali, and Antarctic Plates.The Lwandle Plate is largely oceanic, lying off the southeast coast of Africa. It is currently believed that the southern part of Madagascar forms part of the Lwandlean Plate, with one of the plate boundaries cutting through the island.
The following outline is provided as an overview of and topical guide to geology:
Geology – one of the Earth sciences – is the study of the Earth, with the general exclusion of present-day life, flow within the ocean, and the atmosphere. The field of geology encompasses the composition, structure, physical properties, and history of Earth's components, and the processes by which it is shaped. Geologists typically study rock, sediment, soil, rivers, and natural resources.
The Seven Summits are the highest mountains of each of the seven continents. Climbing to the summit of all of them is regarded as a mountaineering challenge, first achieved on 30 April 1985 by Richard Bass. The Seven Summits achievement has become noted as an exploration and mountaineering accomplishment.
The Shan–Thai or Sibumasu Terrane is a mass of continental crust extending from Tibet into Southeast Asia sharing a similar geological history. The Shan–Thai Terrane rifted from Australia in the Permian and collided with the Indochina terrane in the Triassic. It extends from Malaysia, through peninsular Thailand, Myanmar, West Yunnan, to Lhasa.Shan–Thai is c. 4,000 km (2,500 mi) long and bounded by the Indochina terrane to the east and the South Chine terrane to the north. It is one of a series of continental blocks or terranes that were rifted off eastern Gondwana during the Ordovician (495 to 443 Ma), long before the formation of Pangaea. Today these blocks form south-east Asia but the different timing of their journeys has given them distinct geologic histories.Shan–Thai was an archipelago on the Paleo-Tethys Ocean spread over several latitudes. It can therefore be subdivided into several portions with different palaeo-geographical histories. The internal "Thai" elements, bordering the Indochina block, are of Cathaysian type and characterised by palaeo-tropical warm-water facies. The external "Shan" part has Gondwanan cold-water facies whilst the central "Sibumasu" part is transitional between the other two.
The internal parts of Shan–Thai merged with Laurasia 265 Ma when the Nan-Uttaradit suture closed.
Oceanic basins separated the other elements of Shan–Thai until the Late Triassic–Early Jurassic Late Indochina Orogeny.The collision between India and Eurasia during the Oligocene and Miocene resulted in clockwise rotation of south-west Asia, severe deformation of south-east Asia, and the extrusion of Shan–Thai and Indochina blocks. These two blocks are still crisscrossed by the faults from this collision.
A submarine, undersea, or underwater earthquake is an earthquake that occurs underwater at the bottom of a body of water, especially an ocean. They are the leading cause of tsunamis. The magnitude can be measured scientifically by the use of the moment magnitude scale and the intensity can be assigned using the Mercalli intensity scale.
Understanding plate tectonics helps to explain the cause of submarine earthquakes. The Earth's surface or lithosphere comprises tectonic plates which average approximately 50 miles in thickness, and are continuously moving very slowly upon a bed of magma in the asthenosphere and inner mantle. The plates converge upon one another, and one subducts below the other, or, where there is only shear stress, move horizontally past each other (see transform plate boundary below). Little movements called fault creep are minor and not measurable. The plates meet with each other, and if rough spots cause the movement to stop at the edges, the motion of the plates continue. When the rough spots can no longer hold, the sudden release of the built-up motion releases, and the sudden movement under the sea floor causes a submarine earthquake. This area of slippage both horizontally and vertically is called the epicenter, and has the highest magnitude, and causes the greatest damage.
As with a continental earthquake the severity of the damage is not often caused by the earthquake at the rift zone, but rather by events which are triggered by the earthquake. Where a continental earthquake will cause damage and loss of life on land from fires, damaged structures, and flying objects; a submarine earthquake alters the seabed, resulting in a series of waves, and depending on the length and magnitude of the earthquake, tsunami, which bear down on coastal cities causing property damage and loss of life.
Submarine earthquakes can also damage submarine communications cables, leading to widespread disruption of the Internet and international telephone network in those areas. This is particularly common in Asia, where many submarine links cross submarine earthquake zones such as the Pacific Ring of Fire.
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