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Transcript of Plate Tectonics
Francisco Alfred Wegener Alfred Wegener Alfred Wegener was a German meteorologist and geophysicist who developed the first theory of continental drift and formulated the idea that a super-continent known as Pangaea existed on the Earth millions of years ago. Theory Of Continental Drift states: parts of the Earth's crust slowly drift atop a liquid core What In The World Is Pangea?! the hypothetical landmass that existed when all continents were joined, from about 300 - 200 million years ago. the landmass can be broken into two continents... laurasia- -gonwandland northern hemisphere (North America, Europe, Asia) southernmost hemisphere (Australia, Africa, South America, India, Arabia, Antarctica) Evidence? ..prove Pangea -identical plant and animal fossils found in rocks in Africa and South America
-rocks show similar strata and ages
-coal found underneath Antarctica's surface but coal can only form in warm and wet environments. -Plate Tectonics- same: different: How Is Continental Drift The and from Always moving, their names, and locations Float on liquid core .vs. actually pieces of Earth's crust. The plates collide while the continents move apart. Tectonic Plates continental: oceanic: Tectonic plates are huge fragments of Earth’s lithosphere, which consists of the crust fused with the upper mantle. They move over a more ductile, or plastic, layer of the mantle called the asthenosphere. African Plate North American Plate South American Plate Eurasian Plate Australian Plate Antarctic Plate Pacific Plate Seafloor Spreading Zone a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Fault Zones convergence zone: divergent zone: transform boundaries: crust is extended, thinned, and fractured by the upwelling of hot mantle material. The crust buoys up, producing a mid-ocean ridge, and lava is extruded through a central rift valley to create new oceanic crust. Seamount volcanoes may also arise. collide at convergent boundaries. Where oceanic crust meets continental crust, the latter may be compressed and thickened, resulting in mountain-building. The dense oceanic plate sinks beneath the lighter continental plate, forming an ocean trench, and volcanic activity occurs as the crust descends into the mantle. Where two ocean plates meet, the oldest, most dense plate is subducted and an arc of volcanic islands is formed parallel to the trench. arise where plates are moving past each other. No crust is created or destroyed, nor is there any volcanic activity. They can occur where segments of a divergent boundary are offset, and extensive fracture zones can result. the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic and sinks into the mantle as they converge. Subduction Zone (trenches) Pacific Ring Of Fire An area where a large number of earthquakes and volcanic eruption occur in the basin of the Pacific Ocean. In a 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes Hot Spot -Hawaiian Islands- A geologic 'hot spot' is an area in the middle of a crustal plate where volcanism occurs. The molten magma breaks through the crustal plate (theories describe this as either from a weak/thin part of the plate or a particularly hot part of the molten magma). If the hot spot is under the seafloor (as it is in Hawaii) it produces undersea volcanoes. Some of these volcanoes build up to the surface of the ocean and become islands. Over millions of years the plate may move across the 'hot spot' and the original volcano become extinct but a new volcano will begin to form in the area of the 'hot spot.' Bibli-ogra-phy! http://www.moorlandschool.co.uk/earth/pangea.htm http://library.thinkquest.org/17701/high/pangaea/ http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html
http://oceana.org/en/explore/marine-science/tectonics-and-the-ocean-floor The Earth’s rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle. The plates are made of rock and drift all over the globe; they move sideways and up and down. Over long periods of time, the plates also change in size. Their margins are added to, crushed together, or pushed back into the Earth’s mantle. These plates are from 80 to 400 km thick. Oceanic plates contain minerals that are denser than those of continental. These minerals contain elements such as Iron, Magnesium, and Calcium. Oceanic plates are generally around 5 or 6 kilometers thick, and shape the ocean basins. Formed by the spreading of the ocean floor, oceanic plates feature volcanic oceanic ridges. Along the oceanic ridges, erupting magma spills out, cools, and forms new, denser oceanic crust.