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The Theory of Continental Drift
• Alfred WegenerAlfred Wegener (1910)
• Formed a hypothesis that all the continents were once joined together and have drifted apart
What was Wegener’s evidence?
• Evidence from:1.1.LandformsLandforms—the continents fit together2.2.FossilsFossils—ancient plants and animals found in
many different continents3.3. ClimateClimate—Antarctica has plant fossils. Tropics have
rocks with ice scratches from glaciers- “glacial scarring”
4.4. Rock TypesRock Types- similar rocks found where continents may have once been joined together.
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.”
HESS (1960)
• Sea floor spreading • Continents were moving (as Wegener had proposed)• Evidence1.2.3.
1. The discovery of the Mid-ocean Ridge
• Scientists mapped 47,000 miles of underwater volcanic ridges by using sonar
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