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Theory of Continental Drift
Cornell Notes Pg. 95
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The Theory of Continental Drift
Alfred Wegener (1910) Formed a hypothesis that all the continents were once joined together and have drifted apart
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What was Wegener’s evidence?
Evidence from: Landforms—the continents fit together Fossils—ancient plants and animals found in many different continents Climate—Antarctica has plant fossils. Tropics have rocks with ice scratches from glaciers. Rock Types- similar rocks found were continents may have once been joined together.
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Wegener’s DATA
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Pangaea Continents were joined together in one land mass
“The super continent” 245 mya
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Which way are the continents moving today?
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Plate Tectonics Timeline
page 98
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The Theory of Sea Floor Spreading
Page 99
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Sea Floor Spreading Harry Hess (1960)
as the ocean floor spreads apart, new crust material rises from the mantle and creates new sea floor to fill the “hole.”
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HESS (1960) Sea floor spreading
Continents were moving (as Wegener had proposed) Evidence 1. 2. 3.
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1. The discovery of the Mid-ocean Ridge
Scientists mapped 47,000 miles of underwater volcanic ridges by using sonar
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Map of Mid-ocean Ridges
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2. Ocean floor shows Magnetic Poles reversing
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3. Ocean floor samples—older crust is further away from ridges
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