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In 1910 a scientist by the name by Alfred Wegner had a thoery of continental drift. Continental drift is how the continents floated apart and became a different continent. Before continental drift there was a landmass and it all just drifted apart. A fossil is any trace of ancient organismsthat have been preserved in a rock. Wegner found evidence from the fossils. He found evidence from the climate. He also found evidence from the landforms.Unfortunatly, wegner could not provide a satasfactory explantation for the force that pushes or pulls the continents. The mid ocean ridge is the longest chain of mountians in the world.In the 1900s scientists mapped the mid ocean ridge using a sonar. A sonar is a device that bounces sound waves off under the water. At the mid ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. this process is sea floor spreading. He got evidence from molten material. They found molten material called alvin all down the bottom of the mid ocean ridge. He had evidence from magnetic stripes. Deep ocean trenches is a deep canyon in the ocean floor.Where ever there is a treanch, there is subduction. A subduction is the process by which the ocean floor sinks beneath a deep ocean trench. At a deep ocean trench, subduction allows part of the ocean floor to sink baack into the mantle, over tens of millions of years. the theory of plate tectonics explains the formation , movement, and subductionof the earths plates. A transform boundary is a place where teo plates slip past each other in opposing directions.