what earth layers are tectonic plates composed of
Super-Earth


pressures and temperatures of a super-Earth planet, and that the different phases of this liquid magnesium silicate would separate into layers. Further theoretical work by Valencia and others suggests that super-Earths would be more geologically active than Earth, with more vigorous plate tectonics due to thinner plates under more stress. In fact, their models suggested that Earth was itself a "borderline" case, just barely large enough to sustain plate tectonics. However, other studies determine that strong convection currents in the mantle acting on strong gravity would
9653296
Delamination (geology)


In geophysics, delamination refers to the loss and sinking (foundering) of the portion of the lowermost lithosphere from the tectonic plate to which it was attached. The outer portion of the Earth is divided into an upper, lithosphere layer and a lower, asthenosphere layer. The lithosphere layer is composed of two parts, an upper, the crustal lithosphere and lower, the mantle lithosphere. The crustal lithosphere is in unstable mechanical equilibrium because the underlying mantle lithosphere has a greater density than the asthenosphere below. The difference in densities can
16084107
Geodynamics of terrestrial exoplanets


liquid surface water. Exobiologists have not reached a consensus on whether Earth-like exoplanets have plate tectonics, but it is widely thought that the likelihood of plate tectonics on an Earth-like exoplanet is a function of planetary radius, initial temperature upon coalescence, insolation, and presence or absence of liquid-phase surface water. In order to characterize the geodynamic regime of an Earth-like exoplanet, the basic assumption is made that such a planet is Earth-like or “rocky”. This implies a three-layer
19034300
Plate tectonics


, George W. Moore of the USGS and R. C. Bostrom presented evidence for a general westward drift of the Earth's lithosphere with respect to the mantle. He concluded that tidal forces (the tidal lag or "friction") caused by the Earth's rotation and the forces acting upon it by the Moon are a driving force for plate tectonics. As the Earth spins eastward beneath the moon, the moon's gravity ever so slightly pulls the Earth's surface layer back westward, just as proposed by Alfred Wegener (see above
5129487
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
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
Post-perovskite


Post-perovskite (pPv) is a high-pressure phase of magnesium silicate (MgSiO). It is composed of the prime oxide constituents of the Earth's rocky mantle (MgO and SiO), and its pressure and temperature for stability imply that it is likely to occur in portions of the lowermost few hundred km of Earth's mantle. The post-perovskite phase has implications for the "D"′′ layer, which influences the convective mixing in the mantle responsible for plate tectonics. Post-perovskite has the same crystal structure
16618778
Mesoplates


ductile lower crust. The analogy between lithoplate tectonics and crustal deformation engaging both brittle and ductile components leads to the concept of crustal mesoplates. “Mesoplates” is a combination and contraction of two terms: “mesosphere”, as applied to the solid earth, and “tectonic plates”. “Mesosphere” (not to be confused with mesosphere, a layer of the atmosphere) is derived from “mesospheric shell”, coined by Reginald Aldworth Daly, a Harvard University geology professor. In the pre-plate tectonics era,
16010315
Crust (geology)


tectonics. The crust is a thin shell on the outside of the Earth, accounting for less than 1% of Earth's volume. It is the top component of lithosphere: a division of Earth's layers that includes the crust and the upper part of the mantle. The lithosphere is broken into tectonic plates that move, allowing heat to escape from the interior of the Earth into space. The crust lies on top of the mantle, a configuration that is stable because the upper mantle is made of peridotite and so is
15455356
John Tuzo Wilson


John Tuzo Wilson, CC, OBE, FRS, FRSC, FRSE (October 24, 1908 – April 15, 1993) was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics. "Plate tectonics" is the idea that the rigid outer layers of the Earth (crust and part of the upper mantle), the lithosphere, are broken up into numerous pieces or "plates" that move independently over the weaker asthenosphere. Wilson maintained that the Hawaiian Islands were created as a
10144210
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
Mesoplates


The term "mesoplates" has been applied in two different contexts within geology and geophysics. The first is applicable to much of the Earth's mantle, and the second to distinct layering within the Earth's crust. In 1977 researchers M. Kumazawa and Y. Fukao introduced the term "mesoplate" in the context of what they termed a "Dual Plate Tectonic Model." Their rationale is a postulated low-velocity zone near and above the 650 km discontinuity with additional properties including local low melitng temperature, active chemical migration and fractionation
16010301
Sial


In geology, the term 'sial' refers to the composition of the upper layer of the Earth's crust, namely rocks rich in silicates and aluminium minerals. It is sometimes equated with the continental crust because it is absent in the wide oceanic basins, but "sial" is a geochemical term rather than a plate tectonic term. As these elements are less dense than the majority of the earth's elements, they tend to be concentrated in the upper layer of the crust. The uppermost layer of the crust is called
19943288
Craton


A craton (, , or ; from "kratos" "strength") is an old and stable part of the continental lithosphere, which consists of the Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep lithospheric roots that extend as much as several hundred
10217095
Structure of the Earth


prime) layer. The pressure at the bottom of the mantle is ≈140 GPa (1.4 Matm). The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust. Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales. Convection of the mantle is expressed at the surface through the motions of tectonic plates. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part
1461170
Earth's magnetic field


of plate tectonics. The magnetosphere is the region above the ionosphere that is defined by the extent of the Earth's magnetic field in space. It extends several tens of thousands of kilometers into space, protecting the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation. The Earth's magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects
16080201
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
Geology of Venus


an asthenosphere—a layer of lower viscosity and mechanical weakness that allows Earth's crustal tectonic plates to move. The apparent absence of this layer on Venus suggests that the deformation of the Venusian surface must be explained by convective movements within the planet's mantle. The tectonic deformations on Venus occur on a variety of scales, the smallest of which are related to linear fractures or faults. In many areas these faults appear as networks of parallel lines. Small, discontinuous mountain crests are found which resemble those on the Moon and Mars
17338335
Geoneutrino


the Earth mantle provides internal heating to power mantle convection, which is the driver of plate tectonics. The amount of mantle radioactivity and its spatial distribution—is the mantle compositionally uniform at large scale or composed of distinct reservoirs?—is of importance to geophysics. The existing range of compositional estimates of the Earth reflects our lack of understanding of what were the processes and building blocks (chondritic meteorites) that contributed to its formation. More accurate knowledge of U, Th, and K abundances in the Earth interior would improve our understanding of present
16197068
Oceanic crust


Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the solidified and uppermost layer of the mantle. The crust and the solid mantle layer together constitute oceanic lithosphere. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial
10784995
Geology of New Zealand


New Zealand throughout its whole geological history. Most volcanism in New Zealand, both modern and ancient, has been caused by the subduction of one tectonic plate under another, this causes melting in the mantle, the layer of the earth below the crust. This produces a volcanic arc, composed of mainly basalt, andesitic and rhyolitic. Basaltic eruptions tend to be fairly placid, producing scoria cones and lava flows, such as the volcanic cones in the Auckland volcanic field, although Mount Tarawera's violent 1886 eruption was an exception.
1986860
Plate tectonics


tectonics on Europa, a satellite of Jupiter—the first sign of subduction activity on another world other than Earth. Titan, the largest moon of Saturn, was reported to show tectonic activity in images taken by the "Huygens" probe, which landed on Titan on January 14, 2005. On Earth-sized planets, plate tectonics is more likely if there are oceans of water. However, in 2007, two independent teams of researchers came to opposing conclusions about the likelihood of plate tectonics on larger super-Earths with
5129541
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
Seismic tomography


or compositional variations. Geoscientists use these images to better understand core, mantle, and plate tectonic processes. Tomography is solved as an inverse problem. Seismic travel time data are compared to an initial Earth model and the model is modified until the best possible fit between the model predictions and observed data is found. Seismic waves would travel in straight lines if Earth was of uniform composition, but the compositional layering, tectonic structure, and thermal variations reflect and refract seismic waves. The location and magnitude of these variations can be calculated
9420471
Plate tectonics


of which are the Arabian, Caribbean, Juan de Fuca, Cocos, Nazca, Philippine Sea, and Scotia. The current motion of the tectonic plates is today determined by remote sensing satellite data sets, calibrated with ground station measurements. The appearance of plate tectonics on terrestrial planets is related to planetary mass, with more massive planets than Earth expected to exhibit plate tectonics. Earth may be a borderline case, owing its tectonic activity to abundant water (silica and water form a deep eutectic). Venus shows no evidence of
5129535
Plate tectonics


Plate tectonics (from the Late Latin "tectonicus", from the "pertaining to building") is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, since tectonic processes began on Earth between 3 and 3.5 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the
5129456
Geodynamics of terrestrial exoplanets


tectonic system is these lithospheric plates become negatively buoyant at some point in their evolution, sinking into the mantle. The surface mass deficit is balanced by new plate being formed elsewhere through upwelling mantle plumes. Plate tectonics is an efficient method of heat transfer from the interior of the planet to the surface. Earth is the only planet plate tectonics is known to occur on, although evidence has been presented for Jupiter's moon Europa undergoing a form of plate tectonics analogous to Earth's. A stagnant lid regime occurs when mantle driving forces
19034302
Comparative planetary science


cores of parent bodies which have partially or completely differentiated, then shattered. These meteorites are thus the only means of directly examining deep-interior materials and their processes. Gas giant planets represent another form of differentiation, with multiple fluid layers by density. Some distinguish further between true gas giants, and ice giants further from the Sun. In turn, a molten core may allow plate tectonics, of which Earth shows major features. Mars, as a smaller body than Earth, shows no current tectonic activity, nor mountain ridges
18390005
Geology


the global distribution of mountain terrain and seismicity. There is an intimate coupling between the movement of the plates on the surface and the convection of the mantle (that is, the heat transfer caused by bulk movement of molecules within fluids). Thus, oceanic plates and the adjoining mantle convection currents always move in the same direction – because the oceanic lithosphere is actually the rigid upper thermal boundary layer of the convecting mantle. This coupling between rigid plates moving on the surface of the Earth and the convecting mantle is called plate tectonics
11808481
Plate tectonics


plate tectonics is that on Venus temperatures are too high for significant water to be present. The Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers remain convinced that plate tectonics is or was once active on this planet. Mars is considerably smaller than Earth and Venus
5129538
Geography of El Salvador


is one of the most seismologically active regions on earth, situated atop three of the large tectonic plates that constitute the Earth's surface. The motion of these plates causes the area's earthquake and volcanic activity. Most of Central America and the Caribbean Basin rests on the relatively motionless Caribbean Plate. The Pacific Ocean floor, however, is being carried northeast by the underlying motion of the Cocos Plate. Ocean floor material is largely composed of basalt, which is relatively dense; when it collides with the lighter granite rocks of Central
9380213
Rare Earth hypothesis


for complex life to evolve (Rare Earth equation factor formula_12), tectonics must be present to generate biogeochemical cycles, and predicted that such geological features would not be found outside of Earth, pointing to a lack of observable mountain ranges and subduction. There is, however, no scientific consensus on the evolution of plate tectonics on Earth. Though it is believed that tectonic motion first began around three billion years ago, by this time photosynthesis and oxygenation had already begun. Furthermore, recent studies point to plate tectonics as an episodic
9835724
Mantle plume


postulated to rise from this layer because the "hot spots" that are assumed to be their surface expression were thought to be fixed relative to one another. This required that plumes were sourced from beneath the shallow asthenosphere that is thought to be flowing rapidly in response to motion of the overlying tectonic plates. There is no other known major thermal boundary layer in the deep Earth, and so the core-mantle boundary was the only candidate. The base of the mantle is known as the D″ layer, a seismological subdivision of
9419556
Rare Earth hypothesis


speed) cause the day and night temperatures to be too extreme. Many Rare Earth proponents argue that the Earth's plate tectonics would probably not exist if not for the tidal forces of the Moon. The hypothesis that the Moon's tidal influence initiated or sustained Earth's plate tectonics remains unproven, though at least one study implies a temporal correlation to the formation of the Moon. Evidence for the past existence of plate tectonics on planets like Mars which may never have had a large moon would counter this argument. Kasting argues that
9835736
List of longest mountain chains on Earth


of plate tectonics. Tectonic plates slide very slowly over the Earth's mantle, a lower place of rock that is heated from the Earth's interior. Several huge sections of the earth's crust are impelled by heat currents in the mantle, producing tremendous forces that can buckle the material at the edges of the plates to form mountains. Usually one plate is forced underneath the other, and the lower plate is slowly absorbed by the mantle. Where the two plates pass one another, heated rock from the mantle can burst through
18648734
Plate tectonics


of the normal-reversal patterns in the oceanic crust on one hand and known timescales derived from the dating of basalt layers in sedimentary sequences (magnetostratigraphy) on the other, to arrive at estimates of past spreading rates and plate reconstructions. After all these considerations, Plate Tectonics (or, as it was initially called "New Global Tectonics") became quickly accepted in the scientific world, and numerous papers followed that defined the concepts: The Plate Tectonics Revolution was the scientific and cultural change which developed from the acceptance of the
5129529
Martian dichotomy


lends evidence to this new hypothesis. It is believed that plate tectonic processes could have been active on Mars early in the planet's history . Large-scale redistribution of lithospheric crustal material is known to be caused by plate tectonic processes on Earth. Even though it is still not entirely clear how mantle processes affect plate tectonics on Earth, mantle convection is believed to be involved as cells or plumes. Since endogenic processes of Earth have yet to be completely understood, studying of similar processes on Mars is very difficult. The dichotomy
6069745
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
Convection


carrying heat from the interior of the earth to the surface. It is one of 3 driving forces that causes tectonic plates to move around the Earth's surface. The Earth's surface is divided into a number of tectonic plates that are continuously being created and consumed at their opposite plate boundaries. 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
3352028
Geology of Venus


Venus is a planet with striking geology. Of all the other planets in the Solar System, it is the one nearest to Earth and most like it in terms of mass, but has no magnetic field or recognizable plate tectonic system. Much of the ground surface is exposed volcanic bedrock, some with thin and patchy layers of soil covering, in marked contrast with Earth, the Moon, and Mars. Some impact craters are present, but Venus is similar to Earth in that there are much fewer craters than on the other
17338306
History of Earth


of plate tectonics continues to shape the Earth's continents and oceans and the life they harbor. Human activity is now a dominant force affecting global change, harming the biosphere, the Earth's surface, hydrosphere, and atmosphere with the loss of wild lands, over-exploitation of the oceans, production of greenhouse gases, degradation of the ozone layer, and general degradation of soil, air, and water quality. In geochronology, time is generally measured in mya (million years ago), each unit representing the period of
3941223
Earth


molten outer layer of Earth cooled to form a solid. The two models that explain land mass propose either a steady growth to the present-day forms or, more likely, a rapid growth early in Earth history followed by a long-term steady continental area. Continents formed by plate tectonics, a process ultimately driven by the continuous loss of heat from Earth's interior. Over the period of hundreds of millions of years, the supercontinents have assembled and broken apart. Roughly (Mya), one of the earliest known
9155314
Rare Earth hypothesis


global temperature regulation, and the carbon cycle. The lack of mountain chains elsewhere in the Solar System is direct evidence that Earth is the only body with plate tectonics, and thus the only nearby body capable of supporting life. Plate tectonics depend on the right chemical composition and a long-lasting source of heat from radioactive decay. Continents must be made of less dense felsic rocks that "float" on underlying denser mafic rock. Taylor emphasizes that tectonic subduction zones require the lubrication of oceans of water. Plate tectonics also provides
9835701
Geology of the United States


. Geologists usually associate volcanic eruptions with the boundaries between colliding or diverging plates. However, the focus of volcanism at Yellowstone in the Columbia Plateau Province is far inland from the subduction zone that lies along the Oregon and Washington coast. Evidence suggests that some concentrated heat source is melting rock beneath the Columbia Plateau Province, at the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary, had
17519752
List of tectonic plates


felsic granitic rocks. 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
17361493
Large igneous province


plates during subduction and the complementary ascent of plumes of hot material from lower levels. The surface of the Earth reflects stretching, thickening and bending of the tectonic plates as they interact. Ocean-plate creation at upwellings, spreading and subduction are well accepted fundamentals of plate tectonics, with the upwelling of hot mantle materials and the sinking of the cooler ocean plates driving the mantle convection. In this model, tectonic plates diverge at mid-ocean ridges, where hot mantle rock flows upward to fill the space. Plate-tectonic
19943299
Rare Earth hypothesis


and observations suggest the involvement of endogenic processes. Plate tectonics has been suggested as a hypothesis for the Martian dichotomy, and in 2012 geologist An Yin put forward evidence for active plate tectonics on Mars. Europa has long been suspected to have plate tectonics and in 2014 NASA announced evidence of active subduction. In 2017, scientists studying the geology of Charon confirmed that icy plate tectonics also operated on Pluto's largest moon. Kasting suggests that there is nothing unusual about the occurrence of plate tectonics in large rocky planets and liquid water on
9835726
Plate tectonics


layers of the Earth are divided into the lithosphere and asthenosphere. The division is based on differences in mechanical properties and in the method for the transfer of heat. The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confused with the "chemical" subdivision of these same layers into the mantle (comprising both
5129461
Planetary habitability


has been offered as a rough dividing line for habitable planets. However, a 2008 study by the Harvard-Smithsonian Center for Astrophysics suggests that the dividing line may be higher. Earth may in fact lie on the lower boundary of habitability: if it were any smaller, plate tectonics would be impossible. Venus, which has 85% of Earth's mass, shows no signs of tectonic activity. Conversely, "super-Earths", terrestrial planets with higher masses than Earth, would have higher levels of plate tectonics and
7511722
Theory


likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics)...One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that
12113025
Earth science


physical and chemical processes in the earth's crust. Beneath the Earth's crust lies the mantle which is heated by the radioactive decay of heavy elements. The mantle is not quite solid and consists of magma which is in a state of semi-perpetual convection. This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics. Plate tectonics might be thought of as the process by which the Earth is resurfaced. As the result of seafloor spreading, new crust and lithosphere is
15740341
Mesosphere (mantle)


includes the D' zone which lies just above the core-mantle boundary at approximately . The base of the lower mantle is at about 2700 km. "Mesosphere" (not to be confused with mesosphere, a layer of the atmosphere) is derived from “mesospheric shell”, coined by Reginald Aldworth Daly, a Harvard University geology professor. In the pre-plate tectonics era, Daly (1940) inferred that the outer Earth consisted of three spherical layers: lithosphere (including the crust), asthenosphere, and mesospheric
11385805
Plate tectonics


of magnetic striping discovered on this planet. Some scientists interpreted these as requiring plate tectonic processes, such as seafloor spreading. However, their data fail a "magnetic reversal test", which is used to see if they were formed by flipping polarities of a global magnetic field. Some of the satellites of Jupiter have features that may be related to plate-tectonic style deformation, although the materials and specific mechanisms may be different from plate-tectonic activity on Earth. On 8 September 2014, NASA reported finding evidence of plate
5129540
Lithosphere


. Earth's lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. The lithosphere is subdivided into tectonic plates. The uppermost part of the lithosphere that chemically reacts to the atmosphere, hydrosphere, and biosphere through the soil forming process is called the pedosphere. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle. The Lithosphere-Asthenosphere boundary is defined by a difference in response to stress: the lithosphere remains rigid
15455483
Low-velocity zone


but as ULVZ) has been detected in a thin ≈50 km layer at the core-mantle boundary. These LVZs may have important implications for plate tectonics and the origin of the Earth's crust. The LVZ has been interpreted to indicate the presence of a significant degree of partial melting, and alternatively as a natural consequence of a thermal boundary layer and the effects of pressure and temperature on the elastic wave velocity of mantle components in the solid state. In any event, a very limited amount of melt (about 1%
11956110
Stiperstones


over time the movement of the tectonic plates landed at this site, combined with the movement of the earth it crumpled the layers and the softest layers were then eroded away. After mining stopped, the undisturbed remnants provided a range of wildlife habitats: birds nest in the old buildings, bats roost in the old mine tunnels, and reservoirs and ponds are ideal for aquatic life. The Bog Visitor Centre is the main facility for visitors to the Stiperstones. It is housed in the former village school and retains its old interior design
13209989
Lithosphere


must exist a strong, solid upper layer (which he called the lithosphere) above a weaker layer which could flow (which he called the asthenosphere). These ideas were expanded by Reginald Aldworth Daly in 1940 with his seminal work "Strength and Structure of the Earth." They have been broadly accepted by geologists and geophysicists. These concepts of a strong lithosphere resting on a weak asthenosphere are essential to the theory of plate tectonics. There are two types of lithosphere: The thickness of the lithosphere is considered to be the
15455485
List of tectonic plates


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. 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
17361495
True polar wander


which is where different parts of the Earth's crust move in different directions because of circulation in the mantle. The effect should further not be confused with the effect known as geomagnetic reversal that describes the repeated proven reversal of the magnetic field of the Earth. Paleomagnetism is used to create tectonic plate reconstructions by finding the paleolatitude of a particular site. This paleolatitude is affected both by true polar wander and by plate tectonics. To reconstruct plate tectonic histories, geologists must obtain a number of dated paleomagnetic samples. Because true polar wander
18510505
History of Earth


mantle was faster. Although a process similar to present-day plate tectonics did occur, this would have gone faster too. It is likely that during the Hadean and Archean, subduction zones were more common, and therefore tectonic plates were smaller. The initial crust, formed when the Earth's surface first solidified, totally disappeared from a combination of this fast Hadean plate tectonics and the intense impacts of the Late Heavy Bombardment. However, it is thought that it was basaltic in composition, like today's oceanic crust, because
3941237
Tectonics


which connect offset segments of mid-ocean ridges. Strike-slip tectonics also occurs at lateral offsets in extensional and thrust fault systems. In areas involved with plate collisions strike-slip deformation occurs in the over-riding plate in zones of oblique collision and accommodates deformation in the foreland to a collisional belt. In plate tectonics the outermost part of the Earththe crust and uppermost mantleare viewed as acting as a single mechanical layer, the lithosphere. The lithosphere is divided into separate "plates" that move relative to each other on
3562101
Eoarchean geology


lid at its infant stages. The earth's condition during Archean to Proterozoic (including Eoarchean era) serves as a crucial linkage between Hadean magma ocean to present-day plate tectonics. Various interpretations have been suggested to explain the prevalent tectonic style corresponding to Eoarchean geology. However it can be, in general, classified into two tectonic models, which are vertical tectonics and plate tectonics. Explanation on the release of large amount of mantle heat is the prominent concern. Most of the evidences shows a probability that pre-plate tectonics
503132
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
Super-Earth


make the crust stronger and thus inhibit plate tectonics. The planet's surface would be too strong for the forces of magma to break the crust into plates. New research suggests that the rocky centres of super-Earths are unlikely to evolve into terrestrial rocky planets like the inner planets of the Solar System because they appear to hold on to their large atmospheres. Rather than evolving to a planet composed mainly of rock with a thin atmosphere, the small rocky core remains engulfed by its large hydrogen-rich envelope. Theoretical models show
9653297
Olympic-Wallowa Lineament


. The broadest and fullest context of the OWL is the global system of plate tectonics, driven by convective flows in the Earth's mantle. The primary story on the western margin of North America is the accretion, subduction, obduction, and translation of plates, micro-plates, terranes, and crustal blocks between the converging Pacific and North American plates. (For an excellent geological history of Washington, including plate tectonics, see the Burke Museum web site.) The principal tectonic plate in this region (Washington, Oregon
12246576
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
Upper mantle (Earth)


and numerous other factors. The upper mantle can only flow very slowly. However, when large forces are applied to the uppermost mantle it can become weaker, and this effect is thought to be important in allowing the formation of tectonic plate boundaries. Although there is a tendency to larger viscosity at greater depth, this relation is far from linear and shows layers with dramatically decreased viscosity, in particular in the upper mantle and at the boundary with the core. Because of the temperature difference between the Earth's surface and outer core
17196344
Polflucht


Polflucht (from German, "flight from the poles") is a geophysical concept invoked in 1915 by Alfred Wegener to explain his ideas of continental drift. He suggested that a differential gravitational force (horizontal component of centrifugal or Eötvös force) and the Earth's flattening would cause continental masses to drift slowly towards the equator. The hypothesis was expanded by Paul Sophus Epstein in 1920 but the force is now known to be far too weak to cause plate tectonics. The strength of the layers of the Earth's crust is much
8361393
History of Earth


weeks. Under the influence of its own gravity, the ejected material became a more spherical body: the Moon. Mantle convection, the process that drives plate tectonics, is a result of heat flow from the Earth's interior to the Earth's surface. It involves the creation of rigid tectonic plates at mid-oceanic ridges. These plates are destroyed by subduction into the mantle at subduction zones. During the early Archean (about 3.0 Ga) the mantle was much hotter than today, probably around , so convection in the
3941236
Geology of the Pacific Northwest


, the fissures that fed flows and cone-building eruptions. Calderas, great pits formed by explosive volcanism, and low shield volcanoes, and rhyolite hills are also part of the landscape here, but many are obscured by later lava flows. Evidence suggests that some concentrated heat source is melting rock beneath the Columbia Plateau Province. At the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary
15164547
Cataclysmic pole shift hypothesis


connected with plate tectonics, the well-accepted geological theory that the Earth's surface consists of solid plates which shift over a viscous, or semifluid asthenosphere; nor with continental drift, the corollary to plate tectonics which maintains that locations of the continents have moved slowly over the face of the Earth, resulting in the gradual emerging and breakup of continents and oceans over hundreds of millions of years. Pole shift hypotheses are not the same as geomagnetic reversal, the periodic reversal of the Earth's magnetic field (effectively switching the north
1791851
Nature


tropical to subtropical region. Precipitation varies widely with location, from several metres of water per year to less than a millimetre. 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several gradually migrating tectonic plates. The interior remains active, with a thick layer of plastic mantle and
2035111
Mantle (geology)


Lithosphere underlying ocean crust has a thickness of around 100 km, whereas lithosphere underlying continental crust generally has a thickness of 150-200 km. The lithosphere and overlying crust make up tectonic plates, which move over the asthenosphere. The Earth's mantle is divided into three major layers defined by sudden changes in seismic velocity: The lower ~200 km of the lower mantle constitutes the D" (D-double-prime) layer, a region with anomalous seismic properties. This region also contains LLSVPs and ULVZs. The top of
3501315
Rare Earth hypothesis


and plate tectonics may be brief or entirely absent. A planet that is too large will retain too dense an atmosphere like Venus. Although Venus is similar in size and mass to Earth, its surface atmospheric pressure is 92 times that of Earth, and surface temperature of 735 K (462 °C; 863 °F). Earth had a similar early atmosphere to Venus, but may have lost it in the giant impact event. Rare Earth proponents argue that plate tectonics and a strong magnetic field are essential for biodiversity,
9835700
Aravalli Range


of upward thrust caused by the stopping of movement of the tectonic plates in the Earth's crust below them. The Aravalli Range joins two of the ancient earth's crust segments that make up the greater Indian craton, the Aravalli Craton which is the Marwar segment of earth's crust to the northwest of the Aravalli Range, and the Bundelkand Craton segment of earth's crust to the southeast of the Aravalli Range. Cratons, generally found in the interiors of tectonic plates, are old and stable parts of the continental lithosphere that has
14923773
Geology of Venus


grabens of different geological units, indicating that these are the oldest parts of the planet. It was once thought that the tesserae were continents associated with tectonic plates like those of the Earth; in reality they are probably the result of floods of basaltic lava forming large plains, which were then subjected to intense tectonic fracturing. Venus's crust appears to be thick, and composed of silicate rocks. Venus's mantle is approximately thick, its chemical composition is probably similar to that of chondrites. Since Venus is a terrestrial planet,
17338339
Henry Robert Frankel


drifted" across the ocean bed. The idea of continental drift was subsumed by the theory of plate tectonics in the mid-20th century. Plate tectonics explains that the continents move by riding on plates of the Earth's lithosphere. Frankel's four volume work, "The Continental Drift Controversy" ("Volume 1: Wegener and the Early Debate; Volume 2: Paleomagnetic Support for Shifting Continents; Volume 3: Initiation of Seafloor Spreading; and Volume 4: Evolution into Plate Tectonics"), published in 2012 by Cambridge University Press
18379983
Nature


tectonic plates. Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other planets. The moon formed roughly 20 million years later. Initially molten, the outer layer of the Earth cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources. The highly energetic chemistry is believed to have produced a self-replicating molecule around
2035116
Lid tectonics


plate tectonics (which can also be described as "mobile lid tectonics"). The presence of a stagnant lid above a convecting mantle was recognised as a possible stable regime for convection on Earth, in contrast to the well-attested mobile plate tectonics of the current eon. A lid tectonic regime arises because the cold upper lithosphere is too viscous to participate in the underlying flow of the mantle. The lid's yield strength is high enough where the lid cannot brittley fail. This relationship relies heavily on the ratio of
22194479
Plate tectonics


is also referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual shrinking (contraction) or gradual expansion of the globe. Tectonic plates are able to move because the Earth's lithosphere has greater mechanical strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection; that is, the slow creeping motion of Earth's solid mantle. Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography (the ridge
5129459
Plate tectonics


longitudinal grid of the Earth itself. Ironically, these systematic relations studies in the second half of the nineteenth century and the first half of the twentieth century underline exactly the opposite: that the plates had not moved in time, that the deformation grid was fixed with respect to the Earth equator and axis, and that gravitational driving forces were generally acting vertically and caused only local horizontal movements (the so-called pre-plate tectonic, "fixist theories"). Later studies (discussed below on this page), therefore
5129485
Geological history of Earth


and Mars as well. The Earth of the early Archean () may have had a different tectonic style. During this time, the Earth's crust cooled enough that rocks and continental plates began to form. Some scientists think because the Earth was hotter, that plate tectonic activity was more vigorous than it is today, resulting in a much greater rate of recycling of crustal material. This may have prevented cratonisation and continent formation until the mantle cooled and convection slowed down. Others argue that the subcontinental lithospheric mantle is too buoyant
6516638
Origin of water on Earth


soon after the formation of Earth. This presents somewhat of a paradox, as the cool early Earth hypothesis suggests temperatures were cold enough to freeze water between about 4.4 billion and 4.0 billion years ago. Other studies of zircons found in Australian Hadean rock point to the existence of plate tectonics as early as 4 billion years ago. If true, that implies that rather than a hot, molten surface and an atmosphere full of carbon dioxide, early Earth's surface was much as it is today. The action of plate tectonics traps
89046
Plume tectonics


the Earth's crust. In it's more modern form born during the seventies of the 20th Century, it tries to reconcile in one single geodynamic model the horizontalistic concept of Plate tectonics, and the verticalistic concepts of mantle plumes, by the gravitational movement of plates away from major domes of the Earth crust. The existence of various supercontinents in Earth history and their break-up has been associated recently with major upwellings of the mantle. It is classified together with mantle convection as one of the mechanism that are used to explain
3199828
Geothermal gradient


of present-day at approximately 3 billion years ago, resulting in larger temperature gradients within the Earth, larger rates of mantle convection and plate tectonics, allowing the production of igneous rocks such as komatiites that are no longer formed. Temperature within the Earth increases with depth. Highly viscous or partially molten rock at temperatures between are found at the margins of tectonic plates, increasing the geothermal gradient in the vicinity, but only the outer core is postulated to exist in a molten or fluid state, and the temperature at the Earth
4324805
Earth


would have been produced, increasing the rates of mantle convection and plate tectonics, and allowing the production of uncommon igneous rocks such as komatiites that are rarely formed today. The mean heat loss from Earth is , for a global heat loss of . A portion of the core's thermal energy is transported toward the crust by mantle plumes, a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce hotspots and flood basalts. More of the heat in Earth is lost through plate tectonics, by mantle
9155330
Erosion and tectonics


Earth's landscape is a product of two factors: tectonics, which can create topography and maintain relief through surface and rock uplift, and climate, which mediates the erosional processes that wear away upland areas over time. The interaction of these processes can form, modify, or destroy geomorphic features on the Earth's surface. The term tectonics refers to the study of the Earth's surface structure and the ways in which it changes over time. Tectonic processes typically occur at plate boundaries which are one of three types: convergent boundaries
3288668
Tectonic weapon


A tectonic weapon is a hypothetical device or system which could create earthquakes, volcanoes, or other seismic events in specified locations by interfering with the Earth's natural geological processes. It was defined in 1992 by Aleksey Vsevolovidich Nikolayev, corresponding member Russian Academy of Sciences: "A tectonic or seismic weapon would be the use of the accumulated tectonic energy of the Earth's deeper layers to induce a destructive earthquake". He added "to set oneself the objective of inducing an earthquake is extremely doubtful". Theoretically, the tectonic weapon
8571439
Outline of oceanography


parts of the ocean floor, typically formed when one tectonic plate slides under another. Plate tectonics – The scientific theory that describes the large-scale motions of Earth's lithosphere Seamount – A mountain rising from the ocean seafloor that does not reach to the water's surface Subduction zones – A geological process at convergent tectonic plate boundaries where one plate moves under the other Submarine calderas – Volcanic calderas that are partially or fully submerged under the water of a larger ocean or lake, sometimes forming a reef, bay or harbor. Paleoceanography
15988923
Scientific theory


), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics)...One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that have not yet been observed. From the American Association for the Advancement of Science: A scientific theory is a well-substantiated explanation of
20123917
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
Geology


. The development of plate tectonics has provided a physical basis for many observations of the solid Earth. Long linear regions of geologic features are explained as plate boundaries. For example: Transform boundaries, such as the San Andreas Fault system, resulted in widespread powerful earthquakes. Plate tectonics also has provided a mechanism for Alfred Wegener's theory of continental drift, in which the continents move across the surface of the Earth over geologic time. They also provided a driving force for crustal deformation, and a new setting for the observations of
11808482
Slab (geology)


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. Their motion can cause dynamic uplift and subsidence of the
18481627
Oceania


almost entirely oceanic crust. The oldest member disappearing by way of the plate tectonics cycle is early-Cretaceous (145 to 137 million years ago). Australia, being part of the Indo-Australian plate, is the lowest, flattest, and oldest landmass on Earth and it has had a relatively stable geological history. Geological forces such as tectonic uplift of mountain ranges or clashes between tectonic plates occurred mainly in Australia's early history, when it was still a part of Gondwana. Australia is situated in the middle of the
2647745
Volcanology of Mars


turbulently over the span of several weeks and thought to be one of the youngest lava flows on Mars. 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. Martian volcanoes are more analogous to terrestrial
9723494
Xiong'er Volcanic Belt


these tectonic settings, but seems to have more of a mixture of the two which has caused much confusion about the origin of the belt. Understanding what type of tectonic setting the Xiong'er Volcanic Belt formed in is crucial for the reconstruction of the Supercontinent Columbia and for making models of plate movement in the Earth's past. If the Xiong'er Volcanic belt represents a rift, then that will indicate that the southern edge of the North China craton faced another continent while it was a part of the Supercontinent Columbia, but if it is
4751485
Juan de Fuca Plate


The Juan de Fuca Plate is a tectonic plate generated from the Juan de Fuca Ridge and 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. The Juan de Fuca plate system has its origins with Panthalassa's oceanic
17296312
Bay of Bengal


chain of mud volcanoes, which are occasionally active. Great Andaman is the main archipelago or island group of the Andaman Islands, whereas Ritchie's Archipelago consists of smaller islands. Only 37, or 6.5%, of the 572 islands and islets of the Andaman and Nicobar Islands are inhabited. The lithosphere of the earth is broken up into what are called tectonic plates. Underneath the Bay of Bengal, which is part of the great Indo-Australian Plate and is slowly moving north east. This plate meets the Burma Microplate at
3608322
Heaven and Earth (book)


what happens in the galaxy" and that climate is driven by the sun, the Earth's orbit and plate tectonics rather than the levels of atmospheric greenhouse gases such as carbon dioxide. Plimer says his book is for the "average punter in the street" who can "smell something is wrong in the climate debate but can't put a finger on what." Critics have regularly questioned Plimer about his commercial interests in the mining industry, but he defends the independence of his views, saying that these commercial interests do not
22116804
Pangaea


different climatic pressures were placed on the life on Pangaea. Although plate tectonics was paramount in the formation of later land masses, it was also essential in the placement, climate, environments, habitats, and overall structure of Pangaea. What can also be observed in relation to tectonic plates and Pangaea, is the formations to such plates. Mountains and valleys form due to tectonic collisions as well as earthquakes and chasms. Consequentially, this shaped Pangaea and animal adaptations. Furthermore, plate tectonics can contribute to volcanic activity, which is
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