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Continental Drift

Continental Drift. Evidence: Fossils. Evidence: Rock Sequences. Evidence: Glaciation. Evidence: Glaciation (cont’d). Evidence: Rock Types/Climates. glacial till & striations (scratches on rock) = polar climate sand dunes = desert climate coral reefs = tropical climate.

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Continental Drift

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  1. Continental Drift

  2. Evidence: Fossils

  3. Evidence: Rock Sequences

  4. Evidence: Glaciation

  5. Evidence: Glaciation (cont’d)

  6. Evidence: Rock Types/Climates • glacial till & striations (scratches on rock) = polar climate • sand dunes = desert climate • coral reefs = tropical climate

  7. Evidence: Rock Types/Climates

  8. Evidence: Polar Wander??

  9. “Uh-Oh!”: Problems with Continental Drift….

  10. …an alternate explanation? 1928: Arthur Holmes suggested fluids rise toward the crust, spread, and sink again. 1930: Wegner dies, unable to adapt Holmes’ idea to his theory.

  11. Mantle/Crust Structure

  12. Earth’s Structure

  13. A New Hope: Sea-floorSpreading

  14. Testing the model….

  15. Paleomagnetic reversals….

  16. The seafloor spreading model is confirmed!

  17. Today’s model:

  18. Boundaries: Converging

  19. Boundaries: Diverging

  20. Boundaries: Transform

  21. Convection currents: drag and move the lithospheric plates above the asthenosphere (three sources of heat produce the convection curents): cooling of Earth’s core radioactivity within the mantle/crust cooling of mantle So, what causes plates to move?

  22. ConvectionCells

  23. ConvectionCells

  24. SUMMARY OF P.T.: • The plate tectonic model suggests: (1) continents can move across the surface of the globe (2) patterns of volcanism can change and shift across the globe as plates and their boundaries evolve and move (3) new oceans may grow (4) oceans basins close and are deformed to produce mountains

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