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

  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 How Plates Move

 mantle convection moves tectonic plates (just like a pot of water!) NFN3NBo

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

1.magma is heated in the lower mantle by the outer core & rises 2.risen magma heats upper mantle, but is cooler than rest of lower mantle, and sinks 3.upper mantle magma rises to beneath the tectonic plates, moves them, then sinks as it cools

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

 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

 Where is this occurring?  Hawaii  Yellowstone, Wyoming  Galapagos Islands  Iceland  Canary Islands  East Africa

Hawaiian Islands Show a Progression of Age of Volcanism

Hawaiian Islands and Emperor Seamounts Extend >3000 km

Subsidence of Volcanic Islands Creates Atolls in Tropics

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

Volcanic Age of Seamounts Increases Away from Hawaii

Estimated Extent of Ashfall from Yellowstone Eruption 630 K Years Ago

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

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