Plate Tectonics

4. The supercontinent that formed about 200 million years ago.
9. The crust is ________ dense farther from the mid- ocean ridge.
10. ______ dense materials rise.
12. Stitched looking mountain ranges on the seafloor.
13. Energy caused by the sudden breaking of rock within the earth or an explosion.
14. Where does oceanic crust bend downward in the ocean floor?
15. This part of the Earth contains our crust and the upper part of the mantle.
17. This boundary divides.
18. The ocean floor is brand new every 200 _____ years.
20. What landform is made when two continental plates collide?

1. These are created when magma cools immediately once erupted from the ridge.
2. The _______ has convection currents which cause continental drift.
3. A break in the Earth's crust.
5. ________ theorized the continents moved.
6. The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.
7. Subduction and seafloor spreading act like a ______.
8. Movement in a gas or liquid in which the warmer parts move up and the cooler parts move down.
11. Changes in what affect the ocean floor?
16. This boundary slides.
19. What did scientists use to map out the sea floor?