Plate Tectonic Theory

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Plate Tectonic Theory A revolution in geology began almost 100 years ago with the hypothesis that the continents have not always been in their present-day positions after the breakup of a supercontinent known as Pangaea. But the evidence of continental drift included the fit between the coastlines of continents is stronger when the fits is made along the true edge of the continent. In addition, geologic feature such as mountain ranges, ancient glacial deposits, and rock types match very closely on both sides of the Atlantic Ocean, which know separates these continents. Matching fossils can be found on both sides of the ocean. Many are from plants and animals that could not have crossed a wide body of water and that could have thrived at different at different latitudes than the present location of the fossil. According to plate tectonics, the lithosphere has fragmented into several large plates. These plates essentially float on an underlying layer of hot, ductile rock called the asthenosphere. The asthenosphere is in slow, but constant, motion and this forces the more rigid lithospheric plates to move around, collide, split apart, or slide past each other. At present there are six major lithospheric plates and many smaller ones. Plate tectonics unifies the processes of continental drift, seafloor spreading, mountain building, faulting, earthquakes, and volcanism into the tectonic cycle. The tectonic cycle creates and recycles oceanic crust on a time scale of roughly 200 million years. Continental crust lasts much longer, and its recycling involves processes such as weathering and erosion. The release of heat from Earth's interior creates huge convection cells, which are at least partly responsible for driving plate motion. Convection brings hot rock up from deep in the mantle and recycles cold rock back into the mantle. Many unanswered questions
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