Plate tectonics

2. they are made by earthquakes
8. a chain of volcanic islands generally located a few hundred km from trench
9. the primary source of the movement of plates
10. mountains formed in part igneous activity associated with the subduction of oceanic lithosphere beneath a continent
13. two oceanic plates converge
14. what moves the crust
16. plates are moving up and down each other
19. a hypothesis, first proposed in the 1960s by harry hess
20. of irregular topography on the deep ocean floor

1. what is the oceanic crust made of
3. older,denser portions of oceanic lithosphere descends
4. a narrow elongated depression of the sea floor
5. elevated areas of the sea floor characterized by high heat flow and volcanism
6. a continues elevated zone on the floor of all the major ocean basins
7. what does a convergent plates make
11. occurs when two tectonic plates move away from each other.
12. has a greater density than continental crust
15. has a less density than oceanic crust
17. made the hypothesis of the sea floor spreading
18. plates are moving towards one another.