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Causes of Plate Movement & Hot Spots

Causes of Plate Movement & Hot Spots. *These notes go on p. 15 of your INB!*. How Plates Move. convection : heating of a fluid where the hot, less dense portions rise and the cooler, denser portions sink constant motion of substance creates convection currents.

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Causes of Plate Movement & Hot Spots

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  1. Causes of Plate Movement & Hot Spots *These notes go on p. 15 of your INB!*

  2. How Plates Move • convection: • heating of a fluid where the hot, less dense portions rise and the cooler, denser portions sink • constant motion of substance creates convection currents

  3. http://www.youtube.com/watch?v=NYbTNFN3NBo mantle convection moves tectonic plates (just like a pot of water!)

  4. Stratified convection Mantle Upper mantle Outer core Inner core Boundary near 700 km separates the two convection systems. Lower mantle *draw this diagram in your notes!!! 2900 km Outer core

  5. magma is heated in the lower mantle by the outer core & rises • risen magma heats upper mantle, but is cooler than rest of lower mantle, and sinks • upper mantle magma rises to beneath the tectonic plates, moves them, then sinks as it cools

  6. Forces of Movement • ridge push & slab pull • convection currents push plates apart at ridges, and pull them back into the mantle at subduction zones • gravity helps plates sink back into mantle

  7. Hot Spots • do not occur along plate boundaries; random areas • upwelling of magma seeps through crust & build overtime (volcanic islands, seamounts, guyots) • can occur within a continent or middle of the ocean

  8. Where is this occurring? • Hawaii • Yellowstone, Wyoming • Galapagos Islands • Iceland • Canary Islands • East Africa

  9. Hawaiian Islands Show a Progression of Age of Volcanism

  10. Hawaiian Islands and Emperor Seamounts Extend >3000 km

  11. Subsidence of Volcanic Islands Creates Atolls in Tropics

  12. Further Subsidence and/or Cooler Water Creates Guyots (Flat-topped Submarine Plateaus)

  13. Volcanic Age of Seamounts Increases Away from Hawaii

  14. Estimated Extent of Ashfall from Yellowstone Eruption 630 K Years Ago

  15. How Much Ashfall from a Major Eruption at Yellowstone? Diagram from Windows into the Earth, by R. B. Smith and L. J. Siegel, 2000

  16. Simplified Cross-Section of Yellowstone Hot Spot Diagram from Windows into the Earth, by R. B. Smith and L. J. Siegel, 2000

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