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Continental Drift Alfred Wegener • Proposed that the continents were once joined as a supercontinent called Pangaea. • Pangaea= Greek for “all the Earth” Wegener’s Evidence for Continental Drift 1. Similar Rock Types Wegener found rocks of similar composition and age on Africa and S. America Wegener’s Evidence 2. Fossil Evidence Same species of land animals found on opposite sides of Atlantic Ocean Wegener’s Evidence 3. Climate Evidence Coal deposits and fern fossils in Antarctica Glacial deposits in India, S. America, Africa, Australia hint: These locations must have once been at a different latitude (further north or south!) Wegener’s Evidence 4. Mountain Belts Similar mountain ranges on different continents now separated by water Wegener’s ideas were rejected because… he couldn’t explain how or why the continents drifted Possible explanations • Rotation of Earth • Physicists “No way!” • Continents plow through ocean crust • Fractures? Proof of Continental Drift 1940’s-50’s using SONAR & magnetometers: Mid-Ocean Ridges (MOR’s) = spreading centers Deep-Sea Trenches