Plate tectonics

4. mountains formed in part igneous activity associated with the subduction of oceanic lithosphere beneath a continent
5. of irregular topography on the deep ocean floor
7. the primary source of the movement of plates
9. a narrow elongated depression of the sea floor
13. plates are moving towards one another.
17. occurs when two tectonic plates move away from each other.
18. older,denser portions of oceanic lithosphere descends
19. has a greater density than continental crust
20. a continues elevated zone on the floor of all the major ocean basins

1. two oceanic plates converge
2. plates are moving up and down each other
3. what does a convergent plates make
6. what is the oceanic crust made of
8. elevated areas of the sea floor characterized by high heat flow and volcanism
10. has a less density than oceanic crust
11. what moves the crust
12. a chain of volcanic islands generally located a few hundred km from trench
14. a hypothesis, first proposed in the 1960s by harry hess
15. made the hypothesis of the sea floor spreading
16. they are made by earthquakes