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Earth Science

Continental Drift, Sea Floor Spreading and Plate Tectonics

QuestionAnswer
In 1620, Francis Bacon… proposed that the continents once fit together but he didn’t have a way to explain it. IDEA WAS REJECTED.
In 1912, Alfred Wegener… came up with the “Theory of Continental Drift.”
Alfred Wegener’s theory said… that all the continents were once connected and have since moved apart. HE CALLED IT PANGEA.
Pangea "Allland" or supercontinent
Alfred Wegner's theory was... Rejected because he didn't have enough evidence.
In 1968,scientists found... rocks no older than 180 million years. (very young)
Evidence of sea floor spreading 1.Scientists found out by drilling that the closer you get to the Mid ocean ridge, the younger the sea floor gets 2.Earth’s magnetic poles have reversed, ion particles line up in opposite directions 3. pillow rocks erupted from mid ocean ridge (1960's)
Dr. Harry Hess's answers (1960) 1.convection currents, moved the plates. 2.The ocean floor, and the rock beneath it, are produced by magma that rises from deeper levels. The hot, less dense magma rises and cools, pushing the older crust out from the center.
How does the sea floor spread? At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material spreads out, pushing older rock to both sides of the ridge.
The ocean floor is... younger than the continents
Created by: elarocco
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