Plate Tectonics

2. the process by which the the ocean floor sinks beneath a deep ocean trench and back into the mantle.
7. created the theory of continental drift.
9. when pieces of Earth's crust diverge on land, a deep valley called a ______ ______ forms.
11. two plates come together at a _______ boundary
13. Scientists used this in the mid 1900's to map the mid-ocean ridges.
15. The lithosphere is broken into________,which float on top of the asthenosphere.

1. Alfred Wegener created the theory of ______ drift.
3. plates move away from each other at this boundary.
4. The crust is ______dense the farther you get from the mid-ocean ridge.
5. geologists think the movement of the Earths plates is caused by convection currents in the ______.
6. if subduction happens faster than oceanic crust is formed, the ocean will_______
8. the name of the supercontinent that existed millions of years age.
10. used evidence from _______, or ancient organisms preserved in rock to support his hypothesis.
12. Molten material lines up in the direction of the poles to form_________ stripes.
14. a boundry where plates slip past each other.