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Plate Tectonics

Plate Tectonics. …or the bump and grind of the planet Joe Cocker – Woodstock…. It seems oddly related, but I don’t know how. Alfred Wegner, 1912. Looked at a map of the world and saw it as a puzzle. Continental Drift Alfred Wegner came up with the idea of Pangea.

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Plate Tectonics

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  1. Plate Tectonics • …or the bump and grind of the planet • Joe Cocker – Woodstock…. It seems oddly related, but I don’t know how

  2. Alfred Wegner, 1912 • Looked at a map of the world and saw it as a puzzle

  3. Continental Drift Alfred Wegner came up with the idea of Pangea • Continents seem to fit together like pieces of a puzzle

  4. Continental DriftFossils • Similar distribution of fossils such as the Mesosaurus

  5. Continental DriftMountains • Mountain ranges match across oceans

  6. Continental DriftGlaciation • Glacial ages and climate evidence

  7. Continental Drift ModelProblems • Alfred Wegener • Presented research to professionals • Did not provide a plausible mechanism to explain how continents drifted

  8. In the 1960’s a discovery - Mid-Atlantic Ridge - Series of ridges and volcanic activity in the center of the Atlantic Ocean

  9. Seafloor Spreading • Continental drift reexamined in 1960’s with new information • New theory developed – Seafloor spreading • Supporting evidence for seafloor spreading • World seismicity (like your map) • Volcanism • Age of seafloor • Paleomagnetism • Heat flow • Theory combining continental drift and seafloor spreading termed “Plate Tectonics”

  10. Spreading at the Mid-Ocean ridges • Evidence: • Mud depth gets deeper as you move away • Rocks get older • Magnetic reversals - Paleomagnetism

  11. Evidence for Seafloor SpreadingWorld Seismicity • Earthquake distribution matches plate boundaries

  12. Evidence for Seafloor SpreadingVolcanism • Volcanoes match some plate boundaries; some are hot spots

  13. Seafloor SpreadingHeat Flow

  14. Seafloor SpreadingConvection Currents • In 1960, proposed as driving force to move continents

  15. Theory of Plate Tectonics • John Tuzo Wilson combined ideas of continental drift and seafloor spreading into “Plate Tectonics”

  16. Rifts at Mid-Ocean ridges • So - Magma comes up because the sea floor is spreading • Creates rifts – parallel ridges • This was all called, oddly enough… Sea Floor Spreading

  17. Divergent Plate BoundariesExamples East African Rift Mid-Atlantic Ocean Ridge

  18. If it can spread….. • It can CRUNCH

  19. Subduction • Happens when Oceanic Crust (denser) dives beneath Continental Crust (not as dense) • You also get Deep Ocean Trenches

  20. Crunches • When 2 continental plates collide – rocks bend and fold, mountains are made

  21. Sooo… the continents slide around • Called Continental Drift

  22. The continents are really on Giant Plates • So the whole thing is called Plate Tectonics and it depends on 2 ideas: CONTINENTAL DRIFT AND SEAFLOOR SPREADING

  23. Hot Spots…Hawaii

  24. Plate Boundaries Cartoons – 4 frames per cartoon • 1) Divergent Boudary • 2) Transform Boundary • 3) Convergent Boundary – Continental-Continental • 4) Convergent Boundary – Continental-Oceanic • 5) Convergent Boundary – Oceanic-Oceanic

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