* The topmost layer‚ about 500 meters (1‚650 feet) thick‚ includes lavas made of basalt. Oceanic crust differs from continental crust in several ways: it is thinner‚ denser‚ younger‚ of different chemical composition‚ and formed above the subduction zones. Continental Lithosphere * The continental crust is 20 to 70 kilometers thick and composed mainly of lighter granite. The density of continental crust is about 2.7 grams per cubic centimeter. It is thinnest in areas like the Rift Valleys
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Earthquakes occur both on land and sea.They may occur at areas where plates collide (subduction zones/ convergent plate margins) ; where plates slide past eachother along fault lines (transform plate margins) or due to volcanic eruption. Earthquakes may be of three different categories: * Tectonic – movement in the earth’s crust due to sudden movement along fault lines. * Plutonic - occurs deep within the subduction zone of colliding plates. * Volcanic – earthquakes accompanied by molten lava
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CONTINENTAL DRIFT THEORY In the early 20th century‚ German scientist Alfred Wegener published a book explaining his theory that the continental landmasses‚ far from being immovable‚ were drifting across the Earth. He called this movement continental drift. Wegener noticed that the coasts of western Africa and eastern South America looked like the edges of interlocking pieces of a jigsaw puzzle. He was not the first to notice this‚ but he was the first to formally present evidence suggesting
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are now many kilometres apart. Climatological Evidence shows that places as far apart as Antarctica‚ North America and the UK all contain coal deposits of a similar age that were formed in tropical conditions. They are no longer in tropical climate zones and must have drifted apart since the Carboniferous period. Biological Evidence shows that similar fossil formations are found on either side of the Atlantic. Plant remains from humid swamps that later formed coal deposits have been found in India
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usually involves a continental plate and an oceanic plate. The oceanic plate is denser than the continental plate so‚ as they move together‚ the oceanic plate is forced underneath the continental plate. The point at which this happens is called the subduction zone. As the oceanic plate is forced below the continental plate it melts to form magma and earthquakes are triggered. The magma collects to form a magma chamber. This magma then
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displace the overlying water. It is very unlikely that they can form at constructive or conservative plate boundaries. This is because constructive or conservative boundaries do not generally disturb the vertical displacement of the water column. Subduction zone related earthquakes generate the majority of all tsunamis. Tsunamis have a small wave height offshore‚ and a very long wavelength (often hundreds of kilometers long)‚ which is why they generally pass unnoticed at sea‚ forming only a slight swell
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Jaesung Lee Geography 1 Professor Thomas Orf Chapter 14 Questions 1) The first evidence Wegner was able to find was the remarkable number of close affinities of geologic features on both sides of the Atlantic Ocean. He found the continental margins of the subequatorial portions of Africa and South America fit together with jigsaw-on-like precision. He also determined that the petrologic records on both sides of the Atlantic show many distributions- such as ancient coal deposits-that would
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pressures higher than normal Rocks can | |be subjected to these higher temperatures and pressures as they become buried deeper in the Earth. Such burial usually takes place | |as a result of tectonic processes such as continental collisions or subduction. In most cases‚ the overall chemistry of the | |metamorphic rock is very similar to that of the parent rock. A quartz sandstone‚ for example‚ will metamorphose into a rock that
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occurring on the earth’s surface and in its interior * Core: earth’s innermost zone. It’s extremely hot and has a solid middle surrounded by a liquid core of molten or semisolid lava * Mantle: thick zone surrounding the core. Mostly solid rock but under the outermost part lies the asthenosphere (hot‚ partly melted pile-able rock that flows and can be deformed like soft plastic) * Crust: outermost and thinnest zone of the earth. Consists of continental crust which underlines the continents and
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two converging plates is known as a destructive plate margin‚ as it is responsible for more violent seismic activity‚ volcanoes and high mountain ranges. Destructive Plate Margins Destructive plate margins can either result in collision zones or subduction zones. When a plate of oceanic lithosphere comes into contact with a continental plate the oceanic plate is subducted beneath the continental plate due to the higher density of the oceanic crust. This can sometimes form what is known as a volcanic
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