plate tectonics

2. boundaries- What boundaries is where two plates slip past each other,moving past each other?
3. is any trace of any trace of an ancient organism that has been preserved in rock.
8. ocean ridge-When does sea floor spreading begin?
9. drift-Wegener's idea that continents slowly moved over Earth's surface became known as?
11. its when wegener made a what about the continents were once joined together in a single landmass and have since drifted apart?
12. supercontinent,or single landmass,about 300 million years ago.
13. thing did wegener infer lived on a single landmass
18. oceans- what ocean is expanding?
19. boundaries- what boundaries is two plates that move slowly away from each other?
20. floor spreading-what adds more crust to the ocean floor?

1. boundaries-What boundaries is where two plates collide?
4. the process by which the ocean floor sinks beneath a deep ocean trench and back into a mantle is called?
5. was the name of the scientist?
6. these pieces became the what?
7. As the plates move what do they do?
10. did scientist mapped mid ocean ridges using?
14. floor- part of what sinks back into the mantle at deep ocean trench?
15. and shape-the processes of subduction and sea floor spreading can change what?
16. valley-where peices of Earth's crust diverge on land,a deep valley called a ?
17. ocean trench-At what trench does the oceanic crust bend downward?