1. Intro Objective 10/15/12 Describe the three forces thought to move tectonic plates. Pick up worksheet from front table. Weekly Worksheet #8: What do you think causes tectonic plates to move?

3. Causes of Plate Motion 3 causes of plate motion Convection Currents Ridge Push Slab Pull

8. Causes of Plate Motion Ridge Push New magma pushes older rock at mid-ocean ridges

9. Causes of Plate Motion Slab Pull Gravity pulls down the subducting plate back into the mantle

10. Causes of Plate Motion Convection Currents Hot magma expands and rises Cool magma sinks Changes in density

11. Causes of Plate Motion Mantle Plumes An upwelling of hot magma from the core Creates volcanic “hot spots” Example: – Hawaii – Yellowstone N.P., Wyoming

12. Objective 10/15/12 Outro Describe the three forces thought to move tectonic plates. List two ways convection currents affect your life.