2. plate tectonics- theory that continents are in slow, constant motion.
3. continents- huge land masses
4. Continental Drift- the theory that the continents were once a single land mass and have broken apart and “floated” to where they are today
5. Alfred Wegener- German geologist who first came up with the Continental Drift theory in 1915
6. Pangaea- name that Wegener gave to the land mass known as the Supercontinent
7. Mid-ocean ridge- the longest mountain chain in the world
8. Sea-floor spreading- At the mid-ocean ridge, molten material rises from the mantle, then spreads out, pushing older rock to both sides of the ridge. This process, called sea-floor spreading, forms the new ocean floor.
9. magma- molten mixture of rock-forming substances, gases, and water that make up the earth’s mantle
10. lava- magma that has reached the surface; also the rock that’s formed when the liquid lava hardens
11. volcano a weak spot in the crust where magma has come to the surface Video http://www.cbsnews.com/video/watch/? id=7389841n&tag=mncol;lst;10
12. fault- a break in rock where the rocks slide past each other; a break in the earth’s crust; earthquakes occur along faults
13. earthquake- the shaking that results from the movement of rock beneath the earth’s surfacehttp://video.nationalgeographic.com/video/play er/environment/environment-natural- disasters/earthquakes/earthquake-101.html
14. uplift- the raising of the earth’s crust; usually results in mountain formation
15. intrusion- molten rock that has squeezed into existing rock and hardened Intrusion of mafic rock into granite
16. subduction- process by which the ocean floor sinks back into the mantlehttp://oregonstate.edu/media/trcnb-hiq
17. rift valley- a deep valley that forms where two plates move apart