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Plate Tectonics. Plate Tectonics. Theory that helps explain most geologic processes. Earth’s shell is made up of approximately 20 plates (made up of continents and oceans) Plates moving over a weak layer of hot rock. Continental Drift.
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Plate Tectonics • Theory that helps explain most geologic processes. • Earth’s shell is made up of approximately 20 plates (made up of continents and oceans) • Plates moving over a weak layer of hot rock.
Continental Drift • Alfred Wegener suggested all earth’s land masses collided 300 million years ago to form one supercontinent • He named it PANGAEA.
Wegener’s Proof • He saw a jigsaw fit between South America and Africa • Fossils of the same plants and animals on both continents.
Wegener’s Proof 3. Mountains of similar age and structure on both sides of the Atlantic Ocean
Wegener’s Proof 4. Ice sheets covered southern Africa, India, Australia, and South America 300 million years ago.
Missing Proof • Wegener could not explain what mechanism was powerful enough to move huge continents • Scientist’s never believed him
J. Tuzo Wilson • Wilson (Canadian) sparked new interest in continental drift theory. • Now known as plate tectonics (includes more than just continents, also includes ocean plates)
Plate Movements • Perhaps caused by uneven distribution of heat within the earth, causing convection currents.
Plate Movements • Convergent Boundaries • Divergent Boundaries • Transform Boundaries
