Sea Floor Spreading
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Harry Hess was an American geologist that studied mid-ocean ridges. He is famous for bringing Wegner's theory back to life in 1960
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This is called seafloor spreading. The floor spreads apart the sides of MOR creating new crust. The floors moves with continents.
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It beings in MOR, which forms along cracks in oceanic crust. Molten material that forms under the surface rises and erupts.
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Older rocks move out on both sides of the ridge. When the MM cools, it creates a slab of rock, in the middle of the ridge.
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MM may pour into the crack, and it will form a new strip of rock.
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Many hydro-thermal vents are found near rifts that cause SFS. When new rifts spread on land, water rushes in and creates new ocean
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Subduction is a process that complies with SFS. It is when ocean floor sinks under a deep-ocean trench and back into the mantle.
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As subduction takes effect, crust closer to a MOR moves away from the ridge and toward a DOT. This and SFS moves the ocean floor.
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New ocean crust is hot,but as it repels from MOR,it cools and becomes more dense.Gravity pulls down the crust below the trench.
(Picture from http://sio.ucsd.edu/...)
Tetonic plates are part of the Earth's crust. They create boundaries when two plates meet together.
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