2. Hess reasoned that if the ocean floor was moving away from either side of the mid- ocean ridge. Then it must be colliding somewhere else, such as the edge of a continent.

3. The area where the plates meet is called a Plate Boundary. There are 3 types of plate boundaries.

4. 1. Divergent Boundaries: This is where two plates are moving away from one another and new oceanic crust is forming.

6. Underwater mountain ranges are formed at the divergent boundary.

8. 2. Convergent Boundaries: As seafloor spreading moves plates apart at one boundary, those plates push into neighboring plates. Causing a collision of plates.

10. Collisions between oceanic crust and continental crust, will cause the oceanic crust to subduct, under the continental crust.

12. This type of plate collision forms a trench & Continental Volcanoes.

16. Neither plate is subducted. Instead the colliding edges are crumpled and uplifted, producing large mountain ranges.

19. One side will subduct, causing a very deep trench. The plate that is subducted melts and the molten rock rises to the surface along the trench which causes a long chain of volcanic islands.

23. This is when two plates grind past each other horizontally. When enough friction builds up an earthquake will occur.