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Continental Drift and Sea-floor Spreading

Continental Drift and Sea-floor Spreading. Chapter 4, Sec.2. Alfred Wegner. Theory of Continental Drift Noticed “puzzle-like” fit of continents. Support for Continental Drift:. Same fossils on different continents Similar types of rocks Grooves left by glaciers. Mesosaurus fossils

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Continental Drift and Sea-floor Spreading

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  1. Continental Drift and Sea-floor Spreading Chapter 4, Sec.2

  2. Alfred Wegner • Theory of Continental Drift • Noticed “puzzle-like” fit of continents

  3. Support for Continental Drift:

  4. Same fossils on different continents • Similar types of rocks • Grooves left by glaciers

  5. Mesosaurus fossils Glossopteris fossils

  6. Pangaea • Means “all earth” • Huge super continent • Occurred about 245 m.y.a

  7. SEA-FLOOR SPREADING

  8. More Support for Continental Drift • Discovered underwater mountain chains in Atlantic Ocean • Called Mid-Atlantic Ridge • Mountains on other ocean bottoms also

  9. Tectonic plates move away from each other • Magma rises to fill in the gap • Magma from the asthenosphere (not outer core)

  10. Newest sea-floor at the ridge • Older sea-floor pushed to the edges

  11. NORTH AMERICA SOUTH AMERICA

  12. Earth’s magnetic field

  13. When the magnetic poles of Earth switch – it’s called a magnetic reversal • Recorded by the molten rock at ocean ridges

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