The document defines key terms related to plate tectonics and continental drift including: plate tectonics, continents, continental drift, Pangaea, mid-ocean ridge, sea-floor spreading, magma, lava, volcano, fault, earthquake, uplift, intrusion, subduction, and rift valley. Continental drift is the theory that the continents were once joined together and have since drifted apart. Sea-floor spreading at mid-ocean ridges causes the ocean floors to expand and push older sections downward.

1. VOCABULARY

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 surface
http://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 mantle
http://oregonstate.edu/media/trcnb-hiq

17. rift valley-
 a deep valley that forms where two plates
move apart