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Encyclopedia > Plate tectonics
The tectonic plates of the world were mapped in the second half of the 20th century.
The tectonic plates of the world were mapped in the second half of the 20th century.

Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere. The theory encompassed and superseded the older theory of continental drift from the first half of the 20th century and the concept of seafloor spreading developed during the 1960s. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... This article is about Earth as a planet. ... The tectonic plates of the Lithosphere on Earth. ... Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ... Age of oceanic crust. ...


The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again. This is, however, not due to cooler temperatures but due to high pressure. The tectonic plates of the Lithosphere on Earth. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... This article does not cite any references or sources. ... For other uses, see Viscosity (disambiguation). ... Shear strength in reference to soil is a term used to describe the maximum strength of soil at which point significant plastic deformation or yielding occurs due to an applied shear stress. ...


The lithosphere is broken up into what are called tectonic plates — in the case of Earth, there are seven major and many minor plates (see list below). The lithospheric plates ride on the asthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent or collision boundaries, divergent or spreading boundaries, and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of 0.65 to 8.50 centimeters per year. In plate tectonics, a convergent boundary – also known as a convergent plate boundary or a destructive plate boundary – is an actively deforming region where two (or more) tectonic plates or fragments of lithosphere move toward one another. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary), (but also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. ... A transform fault is a geological fault that is a special case of strike-slip faulting which terminates abruptly, at both ends, at a major transverse geological feature. ... This article is about the natural seismic phenomenon. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... For other uses, see Mountain (disambiguation). ... The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. ...

Contents

Synopsis of the development of the theory

Detailed map showing the tectonic plates with their movement vectors.
Detailed map showing the tectonic plates with their movement vectors.

In the late 19th and early twentieth centuries, geologists assumed that the Earth's major features were fixed, and that most geologic features such as mountain ranges could be explained by vertical crustal movement, as explained by geosynclinal theory. The observations had been made that the opposite coasts of the Atlantic Ocean — or, more precisely, the edges of the continental shelves — have similar shapes and seem once to have fitted together. Since that time many theories were proposed to explain this apparent coincidence, but the assumption of a solid earth made the various proposals difficult to explain. Image File history File links Tectonic_plates_boundaries_detailed-en. ... Image File history File links Tectonic_plates_boundaries_detailed-en. ... A is for sore ass losers like you your dumbass punk ass trick geosyncline is a largely obsolete term for a subsiding linear trough that was caused by the accumulation of sedimentary rock strata deposited in a basin and subsequently compressed, deformed, and uplifted into a mountain range, with attendant... A coastal image featured on a United States postal stamp. ... The continental shelf is an area of relatively shallow sea water that is found on the edge of each continent. ...


The discovery of radium and its associated heating properties in 1896 prompted a re-examination of the apparent age of the Earth, since this had been estimated by taking its temperature and assuming that it radiated like a black body. Such calculations assumed that, even if it started at red heat, the Earth would have dropped to its present temperature in a few tens of millions of years. With this new heat source, it was credible that the Earth was much older, and also that its core was still sufficiently hot to be liquid. General Name, Symbol, Number radium, Ra, 88 Chemical series alkaline earth metals Group, Period, Block 2, 7, s Appearance silvery white metallic Standard atomic weight (226) g·mol−1 Electron configuration [Rn] 7s2 Electrons per shell 2, 8, 18, 32, 18, 8, 2 Physical properties Phase solid Density (near r. ... Earth as seen from Apollo 17 Modern geologists consider the age of the Earth to be around 4. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ...


Plate tectonic theory arose out of the hypothesis of continental drift first proposed by Alfred Wegener in 1912 and expanded in his 1915 book The Origin of Continents and Oceans, which suggested that the present continents once formed a single land mass which had drifted apart, floating on the molten rocks of the core. But without detailed evidence and calculation of the forces involved, the theory remained sidelined. The Earth might have a solid crust and a liquid core, but there seemed to be no way that portions of the crust could move around -- although later science proved theories proposed by English geologist Arthur Holmes in 1920 that their junctions might actually lie beneath the sea. Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ... Alfred Wegener, around 1925 Alfred Lothar Wegener (Berlin, November 1, 1880 – Greenland, November 2 or 3, 1930) was a German interdisciplinary scientist and meteorologist, who became famous for his theory of continental drift (Kontinentalverschiebung or die Verschiebung der Kontinente in his words). ... CORE may refer to: The Congress of Racial Equality in the USA. The Coordinated Online Register of Electors in the United Kingdom. ... Arthur Holmes (January 14, 1890 – September 20, 1965) was a British geologist. ... This article is about the body of water. ...


The first evidence that crust plates did move around came with the discovery of variable magnetic field direction in rocks of differing ages, first revealed at a symposium in Tasmania in 1956. Initially theorized as an expansion of the global crust,[1] later collaborations developed the plate tectonics theory, which accounted for spreading as the consequence of new rock upwelling, but avoided the need for an expanding globe by recognizing subduction zones and conservative translation faults. It was at this point that Wegener's theory moved from radical to mainstream, and became accepted by the scientific community. Additional work on the association of seafloor spreading and magnetic field reversals by Harry Hess and Ron G. Mason[2][3][4][5] pinpointed the precise mechanism which accounted for new rock upwelling. Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... A car from 1956 Year 1956 (MCMLVI) was a leap year starting on Sunday (link will display full calendar) of the Gregorian calendar. ... Movements of the continents as the Earth expands. ... Age of oceanic crust. ... Harry Hammond Hess (1906-1969) was an American geologist. ... Ron G. Mason was one of the oceanographers whose pioneering Cold War geomagnetic survey work lead to the discovery of magnetic stripes around the Mid-Atlantic Ridge. ...


Following the recognition of magnetic anomalies defined by symmetric, parallel stripes of similar magnetization on the seafloor on either side of a mid-ocean ridge, plate tectonics quickly became broadly accepted. Simultaneous advances in early seismic imaging techniques in and around Wadati-Benioff zones collectively with numerous other geologic observations soon solidified plate tectonics as a theory with extraordinary explanatory and predictive power. Recent geomagnetic reversals. ... Oceanic Ridge Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the movement of waves through the Earth. ... Subduction zones mark sites of convective downwelling of the Earths lithosphere. ...


Study of the deep ocean floor was critical to development of the theory; the field of deep sea marine geology accelerated in the 1960s. Correspondingly, plate tectonic theory was developed during the late 1960s and has since been accepted all but universally by scientists throughout all geoscientific disciplines. The theory revolutionized the Earth sciences, explaining a diverse range of geological phenomena. Animated map exhibiting the worlds oceanic waters. ... Marine geology involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal margins. ...


Key principles

The division of the outer parts of the Earth's interior into lithosphere and asthenosphere is based on mechanical differences and in the ways that heat is transferred. The lithosphere is cooler and more rigid, whilst the asthenosphere is hotter and mechanically weaker. Also, 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 the Earth into (from innermost to outermost) core, mantle, and crust. The lithosphere contains both crust and some mantle. A given piece of mantle may be part of the lithosphere or the asthenosphere at different times, depending on its temperature, pressure and shear strength. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like (visco-elastic solid) asthenosphere. Plate motions range from a few millimeters per year (mm yr-1), to a more typical 10-40 mm yr-1 (Mid-Atlantic Ridge; about as fast as fingernails grow), to about 160 mm yr-1 (Nazca Plate; about as fast as hair grows).[6][7] For other uses, see Mechanic (disambiguation). ... Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... This article covers adiabatic processes in thermodynamics. ... Global earthquake epicentres, 1963–1998 The 14 major plates plus the Scotia Plate Plate tectonics map from NASA This is a list of tectonic plates on Earth. ... A viscoelastic material is one in which: hysteresis is seen in the stress-strain curve. ... Courtesy USGS The ridge was central in the breakup of Pangaea that began some 180 million years ago. ... This article discusses the anatomical nail. ...  The Nacza plate, shown in light blue The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. ... For the 1968 stage production, see Hair (musical), for the 1979 film, see Hair (film). ...


The plates are around 100 km (60 miles) thick and consist of lithospheric mantle overlain by either of two types of crustal material: oceanic crust (in older texts called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The two types of crust differ in thickness, with continental crust considerably thicker than oceanic (50 km vs 5 km). Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... Sima is the name for the lower layer of the Earths crust. ... Not to be confused with Silicone. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... typical Sial material, a Precambrian granite showing potassium feldspar (felsic) matrix For the Sial tribe of Pakistan, see Sial (tribe). ... Aluminum redirects here. ...


One plate meets another along a plate boundary, and plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features like mountains, volcanoes and oceanic trenches. The majority of the world's active volcanoes occur along plate boundaries, with the Pacific Plate's Ring of Fire being most active and most widely known. These boundaries are discussed in further detail below. This article is about the natural seismic phenomenon. ... For other uses, see Mountain (disambiguation). ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. ... “The Ring of Fire” redirects here. ...


Tectonic plates can include continental crust or oceanic crust, and typically, a single plate carries both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans. The distinction between continental crust and oceanic crust is based on the density of constituent materials; oceanic crust is denser than continental crust owing to their different proportions of various elements, particularly, silicon. Oceanic crust is denser because it has less silicon and more heavier elements ("mafic") than continental crust ("felsic"). As a result, oceanic crust generally lies below sea level (for example most of the Pacific Plate), while the continental crust projects above sea level (see isostasy for explanation of this principle).  The African plate, shown in pinkish-orange The African Plate is a tectonic plate covering the continent of Africa and extending westward to the Mid-Atlantic Ridge. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ...  The Pacific plate, shown in pale yellow The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean. ... Isostasy is a term used in Geology to refer to the state of ice above stasy and is angravitational equilibrium between the Earths lithosphere and asthenosphere such that the tectonic plates float at an elevation which depends on their thickness and density. ...


Types of plate boundaries

Three types of plate boundary.
Three types of plate boundary.

Three types of plate boundaries exist, 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: Illustration by Jose F. Vigil. ... Illustration by Jose F. Vigil. ...

  1. Transform boundaries occur where plates slide or, perhaps more accurately, grind past each other along transform faults. The relative motion of the two plates is either sinistral (left side toward the observer) or dextral (right side toward the observer). The San Andreas Fault in California is one example.
  2. Divergent boundaries occur where two plates slide apart from each other. Mid-ocean ridges (e.g., Mid-Atlantic Ridge) and active zones of rifting (such as Africa's Great Rift Valley) are both examples of divergent boundaries.
  3. Convergent boundaries (or active margins) occur where two plates slide towards each other commonly forming either a subduction zone (if one plate moves underneath the other) or a continental collision (if the two plates contain continental crust). Deep marine trenches are typically associated with subduction zones. Because of friction and heating of the subducting slab, volcanism is almost always closely linked. Examples of this are the Andes mountain range in South America and the Japanese island arc.

A transform fault is a geological fault that is a special case of strike-slip faulting which terminates abruptly, at both ends, at a major transverse geological feature. ... A sinistral is a horizontal movement of blocks either side of a geological fault. ... A dextral is a horizontal movement of blocks either side of a geological fault. ... View of the San Andreas Fault on the Carrizo Plain in central California, 35°07N, 119°39W The San Andreas Fault is a geological fault that runs a length of roughly 800 miles (1300 kilometres) through western and southern California in the United States. ... Northern section of the Great Rift Valley. ... // Orogeny (Greek for mountain generating) is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within... This article is about the mountain system in South America. ... An island arc is a type of archipelago formed by plate tectonics as one oceanic tectonic plate subducts under another and produces magma. ...

Transform (conservative) boundaries

Main article: Transform boundary

John Tuzo Wilson recognized that because of friction, the plates cannot simply glide past each other. Rather, stress builds up in both plates and when it reaches a level that exceeds the strain threshold of rocks on either side of the fault the accumulated potential energy is released as strain. Strain is both accumulative and/or instantaneous depending on the rheology of the rock; the ductile lower crust and mantle accumulates deformation gradually via shearing whereas the brittle upper crust reacts by fracture, or instantaneous stress release to cause motion along the fault. The ductile surface of the fault can also release instantaneously when the strain rate is too great. The energy released by instantaneous strain release is the cause of earthquakes, a common phenomenon along transform boundaries. In plate tectonics, a transform boundary (also known as transform fault boundary, transform plate boundary, transform plate margin, strike-slip boundary, sliding boundary, or conservative plate boundary) is said to occur when tectonic plates slide and grind against each other along a transform fault. ... John Tuzo Wilson, CC , OBE , D.Sc , FRSC (October 24, 1908–April 15, 1993) was a Scottish Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics, the idea that the rigid outer layers of the Earth (crust and part of the upper... For other uses, see Friction (disambiguation). ... Stress is a measure of force per unit area within a body. ... Potential energy can be thought of as energy stored within a physical system. ... This article is about the deformation of materials. ... Rheology is the study of the deformation and flow of matter under the influence of an applied stress. ... Figure 1. ... This article is about the natural seismic phenomenon. ...


A good example of this type of plate boundary is the San Andreas Fault which is found in the western coast of North America and is one part of a highly complex system of faults in this area. At this location, the Pacific and North American plates move relative to each other such that the Pacific plate is moving northwest with respect to North America. Other examples of transform faults include the Alpine Fault in New Zealand and the North Anatolian Fault in Turkey. Transform faults are also found offsetting the crests of mid-ocean ridges (for example, the Mendocino Fracture Zone offshore northern California). View of the San Andreas Fault on the Carrizo Plain in central California, 35°07N, 119°39W The San Andreas Fault is a geological fault that runs a length of roughly 800 miles (1300 kilometres) through western and southern California in the United States. ... North America North America is a continent [1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... The Alpine Fault is clearly visible from space, running along the western edge of the Southern Alps from the southwestern coast towards the northeastern corner of the South Island. ... The North Anatolian Fault (Turkish: Kuzey Anadolu Fayı) is one of the most energetic earthquake zones in the world. ... Oceanic Ridge Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. ... Cape Mendocino in Humboldt County, California, USA, is the westernmost point on the coast of California. ...


Divergent (constructive) boundaries

Bridge across the Álfagjá rift valley near Grindavik on the Reykjanes peninsula in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates.
Bridge across the Álfagjá rift valley near Grindavik on the Reykjanes peninsula in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates.
Main article: Divergent boundary

At divergent boundaries, two plates move apart from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below. The origin of new divergent boundaries at triple junctions is sometimes thought to be associated with the phenomenon known as hotspots. Here, exceedingly large convective cells bring very large quantities of hot asthenospheric material near the surface and the kinetic energy is thought to be sufficient to break apart the lithosphere. The hot spot which may have initiated the Mid-Atlantic Ridge system currently underlies Iceland which is widening at a rate of a few centimeters per year. Image File history File links Download high resolution version (2592x1944, 1019 KB) Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates. ... Image File history File links Download high resolution version (2592x1944, 1019 KB) Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates. ... Grindavík is a fishing town at the peninsula of Reykjanes at the south-western coast of Iceland. ... Image:Reykjanes1. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary), (but also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... A triple junction is the point where three tectonic plates diverge. ... In geology, a hotspot is a location on the Earths surface that has experienced active volcanism for a long period of time. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ...


Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and the East Pacific Rise, and in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley. Divergent boundaries can create massive fault zones in the oceanic ridge system. Spreading is generally not uniform, so where spreading rates of adjacent ridge blocks are different, massive transform faults occur. These are the fracture zones, many bearing names, that are a major source of submarine earthquakes. A sea floor map will show a rather strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis. If one views the sea floor between the fracture zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear. Crest depths of the old ridges, parallel to the current spreading center, will be older and deeper (from thermal contraction and subsidence). The East Pacific Rise is a long north-south welt of seafloor spreading under the eastern Pacific Ocean from near Antarctica in the south northward to its termination at the northern end of the Gulf of California in the Salton Sea basin in southern Pennsylvania California. ... An illustration of the difference between the active transform faults between offset ridge axes, and inactive fracture zones. ... For other uses, see Submarine (disambiguation). ... A road destroyed by subsidence and shear. ...


It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the sea-floor spreading hypothesis was found. Airborne geomagnetic surveys showed a strange pattern of symmetrical magnetic reversals on opposite sides of ridge centers. The pattern was far too regular to be coincidental as the widths of the opposing bands were too closely matched. Scientists had been studying polar reversals and the link was made by Lawrence W. Morley, Frederick John Vine and Drummond Hoyle Matthews in the Morley-Vine-Matthews hypothesis. The magnetic banding directly corresponds with the Earth's polar reversals. This was confirmed by measuring the ages of the rocks within each band. The banding furnishes a map in time and space of both spreading rate and polar reversals. The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... The Earths Magnetic Field reverses at intervals, ranging from tens of thousands to many millions of years, with an average interval of ~250,000 years. ... Recent geomagnetic reversals. ... Lawrence Morley (Canada), along with Vine and Matthews (UK), contributed significantly to geology by relating the magnetic properties of ocean crust to the processes involved in the theory of plate tectonics. ... Frederick J. Vine (born in 1939) is a marine geologist and geophysicist and was a key contributor to the theory of plate tectonics. ... Drummond Hoyle Matthews (February 5, 1931–July 20, 1997) was a British marine geologist and geophysicist and a key contributor to the theory of plate tectonics. ...


Convergent (destructive) boundaries

Main article: Convergent boundary

The nature of a convergent boundary depends on the type of lithosphere in the plates that are colliding. Where a dense oceanic plate collides with a less-dense continental plate, the oceanic plate is typically thrust underneath because of the greater buoyancy of the continental lithosphere, forming a subduction zone. At the surface, the topographic expression is commonly an oceanic trench on the ocean side and a mountain range on the continental side. An example of a continental-oceanic subduction zone is the area along the western coast of South America where the oceanic Nazca Plate is being subducted beneath the continental South American Plate. In plate tectonics, a convergent boundary – also known as a convergent plate boundary or a destructive plate boundary – is an actively deforming region where two (or more) tectonic plates or fragments of lithosphere move toward one another. ... The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ...  The South American plate, shown in purple The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge. ...


While the processes directly associated with the production of melts directly above downgoing plates producing surface volcanism is the subject of some debate in the geologic community, the general consensus from ongoing research suggests that the release of volatiles is the primary contributor. As the subducting plate descends, its temperature rises driving off volatiles (most importantly water) encased in the porous oceanic crust. As this water rises into the mantle of the overriding plate, it lowers the melting temperature of surrounding mantle, producing melts (magma) with large amounts of dissolved gases. These melts rise to the surface and are the source of some of the most explosive volcanism on Earth because of their high volumes of extremely pressurized gases (consider Mount St. Helens). The melts rise to the surface and cool forming long chains of volcanoes inland from the continental shelf and parallel to it. The continental spine of western South America is dense with this type of volcanic mountain building from the subduction of the Nazca plate. In North America the Cascade mountain range, extending north from California's Sierra Nevada, is also of this type. Such volcanoes are characterized by alternating periods of quiet and episodic eruptions that start with explosive gas expulsion with fine particles of glassy volcanic ash and spongy cinders, followed by a rebuilding phase with hot magma. The entire Pacific Ocean boundary is surrounded by long stretches of volcanoes and is known collectively as The Ring of Fire. Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... For the mountain in California, see Mount Saint Helena. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... // Orogeny (Greek for mountain generating) is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within...  The Nacza plate, shown in light blue The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. ... “Cascades” redirects here. ... A cinder is a fragment of cooled pyroclastic material (lava or magma). ...


Where two continental plates collide the plates either buckle and compress or one plate delves under or (in some cases) overrides the other. Either action will create extensive mountain ranges. The most dramatic effect seen is where the northern margin of the Indian Plate is being thrust under a portion of the Eurasian plate, lifting it and creating the Himalayas and the Tibetan Plateau beyond. It has also caused parts of the Asian continent to deform westward and eastward on either side of the collision. Perspective view of the Himalaya and Mount Everest as seen from space looking south-south-east from over the Tibetan Plateau. ... Tibet Autonomous Region, Qinghai Province and Sichuan Province of China lie on the Tibetan Plateau. ...


When two plates with oceanic crust converge they typically create an island arc as one plate is subducted below the other. The arc is formed from volcanoes which erupt through the overriding plate as the descending plate melts below it. The arc shape occurs because of the spherical surface of the earth (nick the peel of an orange with a knife and note the arc formed by the straight-edge of the knife). A deep undersea trench is located in front of such arcs where the descending slab dips downward. Good examples of this type of plate convergence would be Japan and the Aleutian Islands in Alaska. Aleutians seen from space The Aleutian Islands (possibly from Chukchi aliat, island) are a chain of more than 300 small volcanic islands forming an island arc in the Northern Pacific Ocean, occupying an area of 6,821 sq mi (17,666 km²) and extending about 1,200 mi (1,900...

Oceanic / Continental
Continental / Continental
Oceanic / Oceanic

Plates may collide at an oblique angle rather than head-on (e.g. one plate moving north, the other moving south-east), and this may cause strike-slip faulting along the collision zone, in addition to subduction. Image File history File links Oceanic-continental_convergence_Fig21oceancont. ... Image File history File links Oceanic-continental_convergence_Fig21oceancont. ... Plate tectonics: convergence of two continental plates. ... Plate tectonics: convergence of two continental plates. ... Image File history File links Oceanic-oceanic_convergence_Fig21oceanocean. ... Image File history File links Oceanic-oceanic_convergence_Fig21oceanocean. ... Geologic faults, fault lines or simply faults are planar rock fractures, which show evidence of relative movement. ...


Not all plate boundaries are easily defined. Some are broad belts whose movements are unclear to scientists. One example would be the Mediterranean-Alpine boundary, which involves two major plates and several micro plates. The boundaries of the plates do not necessarily coincide with those of the continents. For instance, the North American Plate covers not only North America, but also far northeastern Siberia, plus a substantial portion of the Atlantic Ocean.


Driving forces of plate motion

Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere. Dissipation of heat from the mantle is acknowledged to be the original source of energy driving plate tectonics. The current view, although it is still a matter of some debate, is that excess density of the oceanic lithosphere sinking in subduction zones is the most powerful source of plate motion. When it forms at mid-ocean ridges, the oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes more dense with age, as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows it to sink into the deep mantle at subduction zones, providing most of the driving force for plate motions. The weakness of the asthenosphere allows the tectonic plates to move easily towards a subduction zone. For other uses, see Density (disambiguation). ...


Although subduction is believed to be the strongest force driving plate motions, it cannot be the only force since there are plates such as the North American Plate which are moving, yet are nowhere being subducted. The same is true for the enormous Eurasian Plate. The sources of plate motion are a matter of intensive research and discussion among earth scientists.


Two and three-dimensional imaging of the Earth's interior (seismic tomography) shows that there is a laterally heterogeneous density distribution throughout the mantle. Such density variations can be material (from rock chemistry), mineral (from variations in mineral structures), or thermal (through thermal expansion and contraction from heat energy). The manifestation of this lateral density heterogeneity is mantle convection from buoyancy forces.[8] How mantle convection relates directly and indirectly to the motion of the plates is a matter of ongoing study and discussion in geodynamics. Somehow, this energy must be transferred to the lithosphere in order for tectonic plates to move. There are essentially two types of forces that are thought to influence plate motion: friction and gravity. Seismic tomography uses digital seismographic records to image the interior of the Earth. ... Mantle convection is the slow creeping motion of Earths rocky mantle in response to perpetual gravitationally unstable variations in its density. ... For other uses, see Friction (disambiguation). ... Gravity is a force of attraction that acts between bodies that have mass. ...


Friction

Basal drag
Large scale convection currents in the upper mantle are transmitted through the asthenosphere; motion is driven by friction between the asthenosphere and the lithosphere.
Slab suction
Local convection currents exert a downward frictional pull on plates in subduction zones at ocean trenches. Slab suction may occur in a geodynamic setting wherein basal tractions continue to act on the plate as it dives into the mantle (although perhaps to a greater extent acting on both the under and upper side of the slab).

Convection in the most general terms refers to the movement of currents within fluids (i. ...

Gravitation

Gravitational sliding: Plate motion is driven by the higher elevation of plates at ocean ridges. As oceanic lithosphere is formed at spreading ridges from hot mantle material it gradually cools and thickens with age (and thus distance from the ridge). Cool oceanic lithosphere is significantly denser than the hot mantle material from which it is derived and so with increasing thickness it gradually subsides into the mantle to compensate the greater load. The result is a slight lateral incline with distance from the ridge axis.
Casually in the geophysical community and more typically in the geological literature in lower education this process is often referred to as "ridge-push". This is, in fact, a misnomer as nothing is "pushing" and tensional features are dominant along ridges. It is more accurate to refer to this mechanism as gravitational sliding as variable topography across the totality of the plate can vary considerably and the topography of spreading ridges is only the most prominent feature. For example:
1. Flexural bulging of the lithosphere before it dives underneath an adjacent plate, for instance, produces a clear topographical feature that can offset or at least effect the influence of topographical ocean ridges.
2. Mantle plumes impinging on the underside of tectonic plates can drastically alter the topography of the ocean floor.
Slab-pull 
Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at trenches[9]. There is considerable evidence that convection is occurring in the mantle at some scale. The upwelling of material at mid-ocean ridges is almost certainly part of this convection. Some early models of plate tectonics envisioned the plates riding on top of convection cells like conveyor belts. However, most scientists working today believe that the asthenosphere is not strong enough to directly cause motion by the friction of such basal forces. Slab pull is most widely thought to be the greatest force acting on the plates. Recent models indicate that trench suction plays an important role as well. However, it should be noted that the North American Plate, for instance, is nowhere being subducted, yet it is in motion. Likewise the African, Eurasian and Antarctic Plates. The overall driving force for plate motion and its energy source remain subjects of ongoing research.

A lava lamp illustrates the basic concept of a mantle plume. ...

External forces

In a study published in the January-February 2006 issue of the Geological Society of America Bulletin, a team of Italian and U.S. scientists argued that the westward component of plates is from Earth's rotation and consequent tidal friction of the moon. As the Earth spins eastward beneath the moon, they say, the moon's gravity ever so slightly pulls the Earth's surface layer back westward. It has also been suggested (albeit, controversially) that this observation may also explain why Venus and Mars have no plate tectonics since Venus has no moon, and Mars' moons are too small to have significant tidal effects on Mars.[10] This is not, however, a new argument.


It was originally raised by the "father" of the plate tectonics hypothesis, Alfred Wegener. It was challenged by the physicist Harold Jeffreys who calculated that the magnitude of tidal friction required would have quickly brought the Earth's rotation to a halt long ago. Many plates are moving north and eastward, and the dominantly westward motion of the Pacific ocean basins is simply from the eastward bias of the Pacific spreading center (which is not a predicted manifestation of such lunar forces). It is argued, however, that relative to the lower mantle, there is a slight westward component in the motions of all the plates. Sir Harold Jeffreys (22 April 1891 – 18 March 1989) was a mathematician, statistician, geophysicist, and astronomer. ...


Relative significance of each mechanism

Plate motion based on Global Positioning System (GPS) satellite data from NASA JPL. Vectors show direction and magnitude of motion.
Plate motion based on Global Positioning System (GPS) satellite data from NASA JPL. Vectors show direction and magnitude of motion.

The actual vector of a plate's motion must necessarily be a function of all the forces acting upon the plate. However, therein remains the problem of to what degree each process contributes to the motion of each tectonic plate. Image File history File links Global_plate_motion. ... Image File history File links Global_plate_motion. ...


The diversity of geodynamic settings and properties of each plate must clearly result in differences in the degree to which such processes are actively driving the plates. One method of dealing with this problem is to consider the relative rate at which each plate is moving and to consider the available evidence of each driving force upon the plate as far as possible.


One of the most significant correlations found is that lithospheric plates attached to downgoing (subducting) plates move much faster than plates not attached to subducting plates. The Pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Ring of Fire) and moves much faster than the plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates. It is thus thought that forces associated with the downgoing plate (slab pull and slab suction) are the driving forces which determine the motion of plates, except for those plates which are not being subducted.


The driving forces of plate motion are, nevertheless, still very active subjects of on-going discussion and research in the geophysical community.


Major plates

The main plates are

Notable minor plates include the Indian Plate, the Arabian Plate, the Caribbean Plate, the Juan de Fuca Plate, the Nazca Plate, the Philippine Plate and the Scotia Plate.  The African plate, shown in pinkish-orange The African Plate is a tectonic plate covering the continent of Africa and extending westward to the Mid-Atlantic Ridge. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... The Antarctic plate is shown in blue on this map The Antarctic Plate is a continental tectonic plate covering the continent of Antarctica and extending outward under the surrounding oceans. ... Categories: Plate tectonics | Geology stubs ...  The Indian plate, shown in red Due to continental drift, the India Plate split from Madagascar and collided with the Eurasian Plate resulting in the formation of the Himalayas. ...  The Eurasian plate, shown in green The Eurasian Plate is a tectonic plate covering Eurasia (a landmass consisting of the traditional continents of Europe and Asia) except that it does not cover the Indian subcontinent, the Arabian subcontinent, and the area east of the Verkhoyansk Range in East Siberia. ... For other uses, see Asia (disambiguation). ... For other uses, see Europe (disambiguation). ...  The North American plate, shown in brown The North American Plate is a tectonic plate covering most of North America, extending eastward to the Mid-Atlantic Ridge and westward to the Cherskiy Range in East Siberia. ... North America North America is a continent [1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... This article is about Siberia as a whole. ...  The South American plate, shown in purple The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ...  The Pacific plate, shown in pale yellow The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean. ...  The Indian plate, shown in red Due to continental drift, the India Plate split from Madagascar and collided with the Eurasian Plate resulting in the formation of the Himalayas. ... The Arabian plate is shown in bright yellow on this map The Arabian Plate is a continental tectonic plate covering the Arabian peninsula and extending northward to Turkey. ... Detail of tectonic plates from: Tectonic plates of the world. ... A map of the Juan de Fuca Plate The Juan de Fuca Plate, named after the explorer, is a tectonic plate arising from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate. ...  The Nacza plate, shown in light blue The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. ...  The Philippine plate, shown in dull red The Philippine Plate is an oceanic tectonic plate beneath the Pacific Ocean to the east of the Philippines. ...  The Scotia plate, shown in blue-green towards the bottom of the map The Scotia Plate is an oceanic tectonic plate bordering the South American Plate on the north, the South Sandwich microplate to the east, and the Antarctic Plate on the south and west. ...


The movement of plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent that contains most or all of the continents. The supercontinent Rodinia is thought to have formed about 1 billion years ago and to have embodied most or all of Earth's continents, and broken up into eight continents around 600 million years ago. The eight continents later re-assembled into another supercontinent called Pangaea; Pangea eventually broke up into Laurasia (which became North America and Eurasia) and Gondwana (which became the remaining continents). In geology, Rodinia (from the Russian родина, or motherland) refers to one of the oldest known supercontinents, which contained most or all of Earths then-current landmass. ... For other uses, see Pangaea (disambiguation). ... Laurasia was a supercontinent that most recently existed as a part of the split of the Pangaean supercontinent in the late Mesozoic era. ... For other uses of Gondwana and Gondwanaland, see Gondwana (disambiguation). ...

Related article

Global earthquake epicentres, 1963–1998 The 14 major plates plus the Scotia Plate Plate tectonics map from NASA This is a list of tectonic plates on Earth. ... Download high resolution version (1280x838, 359 KB) --216. ...

Historical development of the theory

Continental drift

For more details on this topic, see Continental drift.

Continental drift was one of many ideas about tectonics proposed in the late 19th and early 20th centuries. The theory has been superseded and the concepts and data have been incorporated within plate tectonics. Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ...


By 1915, Alfred Wegener was making serious arguments for the idea in the first edition of The Origin of Continents and Oceans. In that book, he noted how the east coast of South America and the west coast of Africa looked as if they were once attached. Wegener wasn't the first to note this (Abraham Ortelius, Francis Bacon, Benjamin Franklin, Snider-Pellegrini, Roberto Mantovani and Frank Bursley Taylor preceded him), but he was the first to marshal significant fossil and paleo-topographical and climatological evidence to support this simple observation (and was supported in this by researchers such as Alex du Toit). However, his ideas were not taken seriously by many geologists, who pointed out that there was no apparent mechanism for continental drift. Specifically, they did not see how continental rock could plow through the much denser rock that makes up oceanic crust. Wegener could not explain the force that propelled continental drift. South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... Abraham Ortelius. ... For other persons named Francis Bacon, see Francis Bacon (disambiguation). ... Benjamin Franklin (January 17 [O.S. January 6] 1706 – April 17, 1790) was one of the most well known Founding Fathers of the United States. ... In 1858, Snider-Pellegrini made these two maps. ... Roberto Mantovani (* March 25, 1854 in Parma, † January 10, 1933 in Paris) was an violinist and scientist from Italy. ... Frank Bursley Taylor, [b. ... For other uses, see Fossil (disambiguation). ... Alex du Toit (1878-1948) was a geologist from South Africa, and an early supporter of Alfred Wegeners theory of continental drift. ...


Wegener's vindication did not come until after his death in 1930. In 1947, a team of scientists led by Maurice Ewing utilizing the Woods Hole Oceanographic Institution’s research vessel Atlantis and an array of instruments, confirmed the existence of a rise in the central Atlantic Ocean, and found that the floor of the seabed beneath the layer of sediments consisted of basalt, not the granite which is the main constituent of continents. They also found that the oceanic crust was much thinner than continental crust. All these new findings raised important and intriguing questions.[11] William Maurice Doc Ewing (May 12, 1906 – May 4, 1974) was an American geophysicist and oceanographer. ... The Woods Hole Oceanographic Institution (WHOI) is a private, nonprofit research and higher education facility dedicated to the study of all aspects of marine science and engineering and to the education of marine researchers. ...


Beginning in the 1950s, scientists including Harry Hess, using magnetic instruments (magnetometers) adapted from airborne devices developed during World War II to detect submarines, began recognizing odd magnetic variations across the ocean floor. This finding, though unexpected, was not entirely surprising because it was known that basalt—the iron-rich, volcanic rock making up the ocean floor—contains a strongly magnetic mineral (magnetite) and can locally distort compass readings. This distortion was recognized by Icelandic mariners as early as the late 18th century. More important, because the presence of magnetite gives the basalt measurable magnetic properties, these newly discovered magnetic variations provided another means to study the deep ocean floor. When newly formed rock cools, such magnetic materials recorded the Earth's magnetic field at the time. A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... For other uses, see Submarine (disambiguation). ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ...


As more and more of the seafloor was mapped during the 1950s, the magnetic variations turned out not to be random or isolated occurrences, but instead revealed recognizable patterns. When these magnetic patterns were mapped over a wide region, the ocean floor showed a zebra-like pattern. Alternating stripes of magnetically different rock were laid out in rows on either side of the mid-ocean ridge: one stripe with normal polarity and the adjoining stripe with reversed polarity. The overall pattern, defined by these alternating bands of normally and reversely polarized rock, became known as magnetic striping.


When the rock strata of the tips of separate continents are very similar it suggests that these rocks were formed in the same way implying that they were joined initially. For instance, some parts of Scotland and Ireland contain rocks very similar to those found in Newfoundland and New Brunswick. Furthermore, the Caledonian Mountains of Europe and parts of the Appalachian Mountains of North America are very similar in structure and lithology. For other uses, see strata (novel) and strata title. ... This article is about the country. ... This article is about the Canadian province of Newfoundland and Labrador. ... This article is about the Canadian province. ... The Caledonian orogeny is a mountain building event recorded in the mountains and hills of northern Scotland, Ireland, England, Wales, and west Norway. ... The Appalachian Mountains are a vast system of mountains in eastern North America. ... Structural geology is the study of the three dimensional distribution of rock bodies and their planar or folded surfaces, and their internal fabrics. ... Petrology is a field of geology which focuses on the study of rocks and the conditions by which they form. ...


Floating continents

The prevailing concept was that there were static shells of strata under the continents. It was observed early that although granite existed on continents, seafloor seemed to be composed of denser basalt. It was apparent that a layer of basalt underlies continental rocks.


However, based upon abnormalities in plumb line deflection by the Andes in Peru, Pierre Bouguer deduced that less-dense mountains must have a downward projection into the denser layer underneath. The concept that mountains had "roots" was confirmed by George B. Airy a hundred years later during study of Himalayan gravitation, and seismic studies detected corresponding density variations. Pierre Bouguer (February 16, 1698 – August 15, 1758) was a French mathematician. ... George Biddell Airy Sir George Biddell Airy (July 27, 1801–January 2, 1892) was British Astronomer Royal from 1835 to 1881. ...


By the mid-1950s the question remained unresolved of whether mountain roots were clenched in surrounding basalt or were floating like an iceberg.


In 1958 the Tasmanian geologist Samuel Warren Carey published an essay The tectonic approach to continental drift in support of the expanding earth model. Samuel Warren Carey (1911 – 2002) was an Australian geologist who was an early advocate of the theory of continental drift. ...


Plate tectonic theory

Significant progress was made in the 1960s, and was prompted by a number of discoveries, most notably the Mid-Atlantic ridge. The most notable was the 1962 publication of a paper by American geologist Harry Hess (Robert S. Dietz published the same idea one year earlier in Nature. However, priority belongs to Hess, since he distributed an unpublished manuscript of his 1962 article already in 1960). Hess suggested that instead of continents moving through oceanic crust (as was suggested by continental drift) that an ocean basin and its adjoining continent moved together on the same crustal unit, or plate. In the same year, Robert R. Coats of the U.S. Geological Survey described the main features of island arc subduction in the Aleutian Islands. His paper, though little-noted (and even ridiculed) at the time, has since been called "seminal" and "prescient". In 1967, W. Jason Morgan proposed that the Earth's surface consists of 12 rigid plates that move relative to each other. Two months later, in 1968, Xavier Le Pichon published a complete model based on 6 major plates with their relative motions. Harry Hammond Hess (1906-1969) was an American geologist. ... Robert Sinclair Dietz (September 14, 1914 - May 19, 1995) was Professor of Geology at Arizona State University. ... Robert Roy Coats (1910-1995) was born in Toronto, Canada, and grew up in Marshalltown, Iowa and Seattle, Washington. ... W. Jason Morgan (* 10th October 1935 in Savannah, Georgia, USA) is a US geophysicist who has made seminal contributions to the theory of plate tectonics and geodynamics. ... Xavier Le Pichon (born June 18, 1937) is a French geophysicist. ...


Explanation of magnetic striping

Seafloor magnetic striping.

The discovery of magnetic striping and the stripes being symmetrical around the crests of the mid-ocean ridges suggested a relationship. In 1961, scientists began to theorise that mid-ocean ridges mark structurally weak zones where the ocean floor was being ripped in two lengthwise along the ridge crest. 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, later called seafloor spreading, operating over many millions of years continues to form new ocean floor all across the 50,000 km-long system of mid-ocean ridges. This hypothesis was supported by several lines of evidence: A theoretical model of the formation of magnetic striping. ... A theoretical model of the formation of magnetic striping. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ...

  1. at or near the crest of the ridge, the rocks are very young, and they become progressively older away from the ridge crest;
  2. the youngest rocks at the ridge crest always have present-day (normal) polarity;
  3. stripes of rock parallel to the ridge crest alternated in magnetic polarity (normal-reversed-normal, etc.), suggesting that the Earth's magnetic field has reversed many times.

By explaining both the zebralike magnetic striping and the construction of the mid-ocean ridge system, the seafloor spreading hypothesis quickly gained converts and represented another major advance in the development of the plate-tectonics theory. Furthermore, the oceanic crust now came to be appreciated as a natural "tape recording" of the history of the reversals in the Earth's magnetic field. The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ...


Subduction discovered

A profound consequence of seafloor spreading is that new crust was, and is now, being continually created along the oceanic ridges. This idea found great favor with some scientists, most notably S. Warren Carey, who claimed that the shifting of the continents can be simply explained by a large increase in size of the Earth since its formation. However, this so-called "Expanding earth theory" hypothesis was unsatisfactory because its supporters could offer no convincing mechanism to produce a significant expansion of the Earth. Certainly there is no evidence that the moon has expanded in the past 3 billion years. Still, the question remained: how can new crust be continuously added along the oceanic ridges without increasing the size of the Earth? Movements of the continents as the Earth expands. ...


This question particularly intrigued Harry Hess, a Princeton University geologist and a Naval Reserve Rear Admiral, and Robert S. Dietz, a scientist with the U.S. Coast and Geodetic Survey who first coined the term seafloor spreading. Dietz and Hess were among the small handful who really understood the broad implications of sea floor spreading. If the Earth's crust was expanding along the oceanic ridges, Hess reasoned, it must be shrinking elsewhere. He suggested that new oceanic crust continuously spreads away from the ridges in a conveyor belt-like motion. Many millions of years later, the oceanic crust eventually descends into the oceanic trenches — very deep, narrow canyons along the rim of the Pacific Ocean basin. According to Hess, the Atlantic Ocean was expanding while the Pacific Ocean was shrinking. As old oceanic crust is consumed in the trenches, 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, Hess' ideas neatly explained why the Earth does not get bigger with sea floor spreading, why there is so little sediment accumulation on the ocean floor, and why oceanic rocks are much younger than continental rocks. Princeton University is a private coeducational research university located in Princeton, New Jersey. ... Robert Sinclair Dietz (September 14, 1914 - May 19, 1995) was Professor of Geology at Arizona State University. ... The U.S. Coast and Geodetic Survey was established by President Thomas Jefferson in 1807 as the Survey of the Coast. ... The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. ...


Mapping with earthquakes

During the 20th century, improvements in and greater use of seismic instruments such as seismographs enabled scientists to learn that earthquakes tend to be concentrated in certain areas, most notably along the oceanic trenches and spreading ridges. By the late 1920s, seismologists were beginning to identify several prominent earthquake zones parallel to the trenches that typically were inclined 40–60° from the horizontal and extended several hundred kilometers into the Earth. These zones later became known as Wadati-Benioff zones, or simply Benioff zones, in honor of the seismologists who first recognized them, Kiyoo Wadati of Japan and Hugo Benioff of the United States. The study of global seismicity greatly advanced in the 1960s with the establishment of the Worldwide Standardized Seismograph Network (WWSSN) to monitor the compliance of the 1963 treaty banning above-ground testing of nuclear weapons. The much-improved data from the WWSSN instruments allowed seismologists to map precisely the zones of earthquake concentration world wide. Seismographs (in Greek seismos = earthquake and graphein = write) are used by seismologists to record seismic waves. ... This article is about the natural seismic phenomenon. ... Subduction zones mark sites of convective downwelling of the Earths lithosphere. ... A Benioff zone (also Benioff-Wadati zone or Wadati-Benioff zone) is a deep active seismic area in a subduction zone. ... Professor Kiyoo Wadati was an early seismologist at the Central Meteorological Observatory of Japan, researching deep (subduction zone) earthquakes. ... This article or section does not cite its references or sources. ...


Geological paradigm shift

The acceptance of the theories of continental drift and sea floor spreading (the two key elements of plate tectonics) may be compared to the Copernican revolution in astronomy (see Nicolaus Copernicus). Within a matter of only several years geophysics and geology in particular were revolutionized. The parallel is striking: just as pre-Copernican astronomy was highly descriptive but still unable to provide explanations for the motions of celestial objects, pre-tectonic plate geological theories described what was observed but struggled to provide any fundamental mechanisms. The problem lay in the question "How?". Before acceptance of plate tectonics, geology in particular was trapped in a "pre-Copernican" box. For other uses, see Astronomy (disambiguation). ... Copernicus redirects here. ... ‹ The template below has been proposed for deletion. ...


However, by comparison to astronomy the geological revolution was much more sudden. What had been rejected for decades by any respectable scientific journal was eagerly accepted within a few short years in the 1960s and 1970s. Any geological description before this had been highly descriptive. All the rocks were described and assorted reasons, sometimes in excruciating detail, were given for why they were where they are. The descriptions are still valid. The reasons, however, today sound much like pre-Copernican astronomy. Nature, Science and PNAS In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. ...


One simply has to read the pre-plate descriptions of why the Alps or Himalaya exist to see the difference. In an attempt to answer "how" questions like "How can rocks that are clearly marine in origin exist thousands of meters above sea-level in the Dolomites?", or "How did the convex and concave margins of the Alpine chain form?", any true insight was hidden by complexity that boiled down to technical jargon without much fundamental insight as to the underlying mechanics. Alp redirects here. ... Perspective view of the Himalaya and Mount Everest as seen from space looking south-south-east from over the Tibetan Plateau. ... // The Dolomites (Italian: Dolomiti; German: Dolomiten; Friulian: Dolomitis) are a section of the Alps. ...


With plate tectonics answers quickly fell into place or a path to the answer became clear. Collisions of converging plates had the force to lift the sea floor to great heights. The cause of marine trenches oddly placed just off island arcs or continents and their associated volcanoes became clear when the processes of subduction at converging plates were understood.


Mysteries were no longer mysteries. Forests of complex and obtuse answers were swept away. Why were there striking parallels in the geology of parts of Africa and South America? Why did Africa and South America look strangely like two pieces that should fit to anyone having done a jigsaw puzzle? Look at some pre-tectonics explanations for complexity. For simplicity and one that explained a great deal more look at plate tectonics. A great rift, similar to the Great Rift Valley in northeastern Africa, had split apart a single continent, eventually forming the Atlantic Ocean, and the forces were still at work in the Mid-Atlantic Ridge. Northern section of the Great Rift Valley. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... Courtesy USGS The ridge was central in the breakup of Pangaea that began some 180 million years ago. ...


We have inherited some of the old terminology, but the underlying concept is as radical and simple as was "The Earth moves" in astronomy.


Biogeographic implications on biota

Continental drift theory helps biogeographers to explain the disjunct biogeographic distribution of present day life found on different continents but having similar ancestors.[12] In particular, it explains the Gondwanan distribution of ratites and the Antarctic flora. Biogeography is the science which deals with patterns of species distribution and the processes that result in such patterns. ... A group of organisms is said to have common descent if they have a common ancestor. ... For other uses of Gondwana and Gondwanaland, see Gondwana (disambiguation). ... Families Struthionidae (ostriches) Rheidae (rheas) Casuariidae (emus etc. ... Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale Minke whale...


Plate tectonics on other planets

Venus

See also: Geology of Venus

Venus shows no evidence of active plate tectonics. There is debatable evidence of active tectonics in the planet's distant past; however, events taking place since then (such as the plausible and generally accepted hypothesis that the Venusian lithosphere has thickened greatly over the course of several hundred million years) has made constraining the course of its geologic record difficult. However, the numerous well-preserved impact craters has been utilized as a dating method to approximately date the Venusian surface (since there are thus far no known samples of Venusian rock to be dated by more reliable methods). Dates derived are the dominantly in the range ~500 Mya - 750Mya, although ages of up to ~1.2 Gya have been calculated. This research has led to the fairly well accepted hypothesis that Venus has undergone an essentially complete volcanic resurfacing at least once in its distant past, with the last event taking place approximately within the range of estimated surface ages. While the mechanism of such an impressionable thermal event remains a debated issue in Venusian geosciences, some scientists are advocates of processes involving plate motion to some extent. A global view of Venus made from a mosaic of radar images from the Magellan spacecraft, centred at 90 degrees longitude. ... Tycho crater on Earths moon. ... Dating methods include: radiometric dating methods: K-Ar potassium/argon Rb-Sr rubidium/strontium argon/argon U-Th-Pburanium/thorium/lead carbon-14 dating other methods: tree-ring Issues with dating: Atmospheric helium concentration is inconsistent with an evolutionary time scale. ...


The question remains why Venus, a planet with a similar size as the Earth, shows no evidence for plate tectonics. The best accepted explanation is that on Venus temperatures are too high for water to be present.[citation needed] 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. A shear zone is a tabular zone of rock that has been crushed and brecciated by many parallel fractures due to shear strain. ...


Mars

See also: Geology of Mars

Unlike Venus, the crust of Mars has water in it and on it (mostly in the form of ice). This planet is considerably smaller than the Earth, but shows some indications that could suggest a similar style of tectonics. The gigantic volcanoes in the Tharsis area are linearly aligned like volcanic arcs on Earth; the enormous canyon Valles Marineris could have been formed by some form of crustal spreading. False colour view of a landslide in Zunil crater The geology of Mars, also known as areology (from Greek: Ἂρης, Arēs, Ares; and λόγος, logos, knowledge), refers to the study of the composition, structure, physical properties, history and the processes that shape the planet Mars. ... Clouds hover over the volcano peaks of the Tharsis region in this color mosaic image. ... Valles Marineris cuts a wide swath across the face of Mars Valles Marineris (Latin for Mariner Valley, named after the Mariner 9 Mars orbiter of 1971-72 which discovered it. ...


As a result of observations made of the magnetic field of Mars by the Mars Global Surveyor spacecraft in 1999, large scale patterns of magnetic striping were discovered on this planet. To explain these magnetisation patterns in the Martian crust it has been proposed that a mechanism similar to plate tectonics may once have been active on the planet.[13][14] Further data from the Mars Express orbiter's High Resolution Stereo Camera in 2007 clearly showed an example in the Aeolis Mensae region.[15] Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... Concept model of the Mars Express spacecraft Main Engine Thrust for braking manouevre on Venus Express. ...


Galilean satellites

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. Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ...


Titan

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.[16]


Metaphoric uses

Sometimes the idea of moving tectonic plates is used metaphorically, e.g. "a tectonic shift" in a BBC TV news program describing the political effects of Ariel Sharon's illness on 4 January 2005. This article is an overview article about the Crown chartered British Broadcasting Corporation formed in 1927. ...   (Hebrew: , also known by his diminutive Arik אָרִיק) (born February 27, 1928) is a former Israeli politician and general. ... is the 4th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ...


In the late 1980s, Québec theatre director Robert Lepage created a large international production called Tectonic Plates, which used this image to illustrate the rifts between Europe and America and the drifting of various destinies, relative to one another. Robert Lepage (born December 12, 1957 in Quebec City) is a playwright, actor and film director from Quebec City, Quebec, and is one of Canadas most honoured theatre artists. ...


See also

This is a list of articles related to plate tectonics and tectonic plates. ... Global earthquake epicentres, 1963–1998 The 14 major plates plus the Scotia Plate Plate tectonics map from NASA This is a list of tectonic plates on Earth. ... See plate tectonics for a more complete discussion Tectonic plate interactions are of three different basic types: Divergent boundaries are areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys. ... A is for sore ass losers like you your dumbass punk ass trick geosyncline is a largely obsolete term for a subsiding linear trough that was caused by the accumulation of sedimentary rock strata deposited in a basin and subsequently compressed, deformed, and uplifted into a mountain range, with attendant... Plume tectonics is a relatively new theory in Geophysics, which studies the movements of Mantle plumes under Tectonic plates at the depth of 2900km in the earth. ...

References

  1. ^ 1958: The tectonic approach to continental drift. In: S. W. Carey (ed.): Continental Drift – A Symposium. University of Tasmania, Hobart, 177-363 (expanding Earth from p. 311 to p. 349)
  2. ^ Ron Mason's key work Oceanography 18, 1.]
  3. ^ Oceanography 16, 3.
  4. ^ Mason, R.G. and A.D. Raff, (1961): Magnetic survey off the west coast of the United States between 32°N latitude and 42°N latitude. Bull. Geol. Soc. Am., 72, 1259–1266.
  5. ^ Raff, A.D. and R.G. Mason, (1961): Magnetic survey off the west coast of the United States between 40°N latitude and 52°N latitude. Bull. Geol. Soc. Am., 72, 1267–1270.
  6. ^ Speed of the Continental Plates
  7. ^ Hancock, Paul L.; Skinner, Brian J. & Dineley, David L. (2000), The Oxford Companion to The Earth, Oxford University Press, ISBN 0-19-854039-6
  8. ^ http://www.pnas.org/cgi/content/full/97/23/12409 Toshiro Tanimoto and Thorne Lay, Mantle dynamics and seismic tomography, PNAS, November 7, 2000, vol. 97 no. 23 pp. 12409–12410
  9. ^ Conrad, C.P. and Lithgow-Bertelloni C. 2002. How Mantle Slabs Drive Plate Tectonics, Science, Vol. 298. no. 5591, pp. 207 - 209
  10. ^ Richard A. Lovett, Moon Is Dragging Continents West, Scientist Says, National Geographic News January 24, 2006 http://news.nationalgeographic.com/news/2006/01/0124_060124_moon.html
  11. ^ Maurice Ewing and the Lamont-Doherty Earth Observatory Living Legacies, Laurence Lippsett. Retrieved 14 October 2006.
  12. ^ S. J. Moss and M. E. J. Wilson, 1998, Biogeographic implications of the Tertiary palaeogeographic evolution of Sulawesi and Borneo, Biogeography and geological evolution of SE Asia
  13. ^ Connerney, J.E.P.; Acuña, M.H.; Wasilewski, P.J.; Ness, N.F.; Rème, H.; Mazelle, C.; Vignes, D.; Lin, R.P.; Mitchell, D.L. & Cloutier, P.A.; 1999: Magnetic Lineations in the Ancient Crust of Mars, Science 284, p. 794-798.
  14. ^ Connerney, J.E.P.; Acuña, M.H.; Ness, N.F.; Kletetschka, G.; Mitchell, D.L.; Lin, R.P. & Rème, H.; 2005: Tectonic implications of Mars crustal magnetism, Proceedings of the National Academy of Sciences 102, p. 14970-14975.
  15. ^ Tectonic signatures at Aeolis Mensae, European Space Agency, 28 June 2007
  16. ^ Soderblom, L.A., et al.; 2007: Topography and geomorphology of the Huygens landing site on Titan, Planetary and Space Science 55, Issue 13, p. 2015-2024
  • McKnight, Tom (2004) Geographica: The complete illustrated Atlas of the world, Barnes and Noble Books; New York ISBN 0-7607-5974-X
  • Oreskes, Naomi ed. (2003) Plate Tectonics: An Insider's History of the Modern Theory of the Earth, Westview Press ISBN 0-8133-4132-9
  • G. Schubert, DL Turcotte, and P. Olson (2001) Mantle Convection in the Earth and Planets, Cambridge University Press, Cambridge, ISBN 0-521-35367-X
  • Stanley, Steven M. (1999) Earth System History, W.H. Freeman and Company; pages 211–228 ISBN 0-7167-2882-6
  • Tanimoto, Toshiro and Thorne Lay (2000) Mantle dynamics and seismic tomography, Proc. Natl. Acad. Sci. USA, 10.1073/pnas.210382197 http://www.pnas.org/cgi/content/full/97/23/12409 Accessed 03/29/06.
  • Thompson, Graham R. and Turk, Jonathan, (1991) Modern Physical Geology, Saunders College Publishing ISBN 0-03-025398-5
  • Turcotte, DL and Schubert, G. (2002) Geodynamics: Second Edition, John Wiley & Sons, New York, ISBN 0-521-66624-4
  • Winchester, Simon (2003) Krakatoa: The Day the World Exploded: August 27, 1883, HarperCollins ISBN 0-06-621285-5

Oxford University Press (OUP) is a highly-respected publishing house and a department of the University of Oxford in England. ... The National Geographic Society was founded in the USA on January 27, 1888, by 33 men interested in organizing a society for the increase and diffusion of geographical knowledge. ... is the 24th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Lamont-Doherty Earth Observatory (LDEO) is a world-class research institution specializing in the Earth sciences and is part of Columbia University. ... Palaeogeography is the study of the ancient geography of the Earths surface. ... Sulawesi (formerly more commonly known as Celebes, IPA: a Portuguese-originated form of the name) is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands. ... Borneo is the third largest island in the world and is located at the centre of Maritime Southeast Asia. ... Seismic tomography uses digital seismographic records to image the interior of the Earth. ... An Australian based componey that produces Geothermal Power uning Hot Dry Rocks (HDR) It is supported by the Australian goverment Geodynamics Category: ... For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ... is the 239th day of the year (240th in leap years) in the Gregorian calendar. ... Year 1883 (MDCCCLXXXIII) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 12-day slower Julian calendar). ...

External links

Wikimedia Commons has media related to:
Plate tectonics

Image File history File links Commons-logo. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... The tectonic plates of the Lithosphere on Earth. ... This article does not cite any references or sources. ... The mesosphere refers to the lower mantle in the region between the asthenosphere and the outer core. ... Earth cutaway from core to exosphere. ... Earth cutaway from core to exosphere. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 450,000 years For current global climate change, see Global warming. ... The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. ... Instrumental global surface temperature measurements; see also [http://www. ... Comparison of ground based (blue) and satellite based (red: UAH; green: RSS) records of temperature variations since 1979. ... The temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. ... The website of the National Oceanic and Atmospheric Administration contains detailed data of the annual land and ocean temperature since 1880. ... This article is devoted to temperature changes in Earths environment as determined from geologic evidence on multi-million to billion (109) year time scales. ... Aviation contributes to global warming in a number of ways, the most significant of which is the combustion of kerosene (a fossil fuel) in flight. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. ... Global dimming is the gradual reduction in the amount of global direct irradiance at the Earths surface that was observed for several decades after the start of systematic measurements in 1950s. ... Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. ... Wikinews has related news: Scientists warn thawing Siberia may trigger global meltdown A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ... The Keeling Curve is a graph measuring the increase in the levels of carbon dioxide in the atmosphere since 1958. ... Land Use, Land-Use Change and Forestry (LULUCF) is a term often used in climate change topics. ... Tokyo, a case of Urban Heat Island. ... Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average cloud conditions and cloud-free conditions. ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... Global cooling in general can refer to a cooling of the Earth. ... Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 El Niño and La Niña (also written in English as El Nino and La Nina) are major temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... 400 year history of sunspot numbers. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting and predicting climate change, where they are commonly called Global Climate Models. ... The politics of global warming looks at the current political issues relating to global warming, as well as the historical rise of global warming as a political issue. ... The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty produced at the United Nations Conference on Environment and Development (UNCED), informally known as the Earth Summit, held in Rio de Janeiro in 1992. ... IPCC is the science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans, based mainly on... The global warming controversy is a dispute regarding the nature and consequences of global warming. ... This article lists scientists and former scientists who have stated disagreement with one or more of the principal conclusions of the mainstream scientific assessment of global warming. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. ... Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 20 centimeters per century (2 mm/year). ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ... This article or section does not cite any references or sources. ... The National Assessment on Climate Change (NACC) was a massive multidisciplinary effort to study and portray in regional detail the potential effects of human-induced global warming on the United States. ... As recent estimates of the rate of global warming have increased, so have the financial estimates of the damage costs. ... Shutdown or slowdown of the thermohaline circulation is a possible effect of global warming. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... Global monthly average total ozone amount Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earths stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earths... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ... For other uses, see Wildfire (disambiguation). ... Global carbon dioxide emissions 1800–2000 Global average surface temperature 1850 to 2006 Mitigation of global warming involves taking actions aimed at reducing the extent of global warming. ... Kyoto Protocol Opened for signature December 11, 1997 in Kyoto, Japan Entered into force February 16, 2005. ... CDM directs here. ... Joint implementation (JI) is an arrangement under the Kyoto Protocol allowing industrialised countries with a greenhouse gas reduction commitment (so-called Annex 1 countries) to invest in emission reducing projects in another industrialised country as an alternative to emission reductions in their own countries. ... The United Kingdoms Climate Change Programme was launched in November 2000 by the British government in response to its commitment agreed at the 1992 United Nations Conference on Environment and Development (UNCED). ... The European Climate Change Programme (ECCP) was launched in June 2000 by the European Unions European Commission. ... Emissions trading (or cap and trade) is an administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. ... Emissions trading schemes (also known as ‘cap and trade’ schemes) are one of the policy instruments available for reducing carbon dioxide (CO2) and other greenhouse gases. ... A carbon tax is a tax on energy sources which emit carbon dioxide into the atmosphere. ... Until recently, most carbon offsets were commonly done by planting trees. ... This article deals with carbon credits for international trading. ... A carbon dioxide (CO2) sink is a carbon reservoir that is increasing in size, and is the opposite of a carbon dioxide source. The main natural sinks are (1) the oceans and (2) plants and other organisms that use photosynthesis to remove carbon from the atmosphere by incorporating it into... For the physical concepts, see conservation of energy and energy efficiency. ... Efficient energy use, sometimes simply called energy efficiency, is using less energy to provide the same level of energy service. ... Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ... Renewable energy commercialization involves three generations of technologies dating back more than 100 years. ... // Renewable energy development covers the advancement, capacity growth, and use of renewable energy sources by humans. ... The soft energy path is an energy use and development strategy delineated and promoted by some energy experts and activists, such as Amory Lovins and Tom Bender; in Canada, David Suzuki has been a very prominent (if less specialized) proponent. ... The G8 Climate Change Roundtable was formed in January 2005 at the World Economic Forum in Davos. ... The issue of human-caused, or anthropogenic, climate change (global warming) is becoming a central focus of the Green movement. ... Adaptation to global warming covers all actions aimed at reducing the negative effects of global warming. ... This article is about the physical universe. ... This article is about Earth as a planet. ... Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... Earth cutaway from core to exosphere. ... Geological time scale. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... For the geological process, see Weathering or Erosion. ... Air redirects here. ... This article is about life in general. ... For other uses, see Biosphere (disambiguation). ... For the definition, see Life. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... For other uses, see Plant (disambiguation). ... For the fictional character, see Fungus the Bogeyman. ... Fauna is a collective term for animal life of any particular region or time. ... For other uses, see Animal (disambiguation). ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, speech lit. ... The evolutionary history of life and the origin of life are fields of ongoing geological and biological research. ... For other uses, see Wilderness (disambiguation). ... For the journal, see Ecology (journal). ... A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... For other uses, see Universe (disambiguation). ... This article is about matter in physics and chemistry. ... Green people redirects here. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ...


  Results from FactBites:
 
Plate Tectonics Earth Planet Model Patent (1840 words)
Each plate member (12) is formed of a durable, lightweight plastic material and molded in raised and indented relief to illustrate such tectonic features as subduction zones, collision zones, mid-ocean ridges, island chains, island arcs, continental shelves, terrestrial and ocean floor topography, and the like.
Plates (12) are attached to the exterior of a base globe (14) forming, as a whole, the surface layer of Earth, or lithosphere.
Plate tectonics is quickly becoming the unifying, or central, theme of Earth science and geology school curriculum across the nation and, indeed, around the world.
An Introduction to Plate Tectonics (2104 words)
According to the plate tectonic model, the surface of the Earth consists of a series of relatively thin, but rigid, plates which are in constant motion.
Plate movement takes place laterally away from the plate boundary, which is normall marked by a rise or a ridge.
As one of the plates is subducted beneath the other it begins to melt at a depth of between 90 and 150 km and the resulting magma rises to the surface above the subduction zone to form a chain or arc of volcanoes.
  More results at FactBites »

 
 

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