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Plate Tectonics

Explore the fascinating theory of plate tectonics, which combines Alfred Wegener's concept of continental drift with the discovery of seafloor spreading. This framework explains how the continents fit together like puzzle pieces, driven by geological forces such as convection currents and volcanic activity. Key evidence includes matching fossil distributions, mountain ranges across oceans, and the age and depth of seafloor sediments. Learn about the types of plate boundaries (divergent, convergent, and transform) and their roles in shaping the Earth's surface.

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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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