Plate Tectonics

2. The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
5. A deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle.
7. A plate boundary where two plates move away from each other.
8. A book published by Alfred Wegener.
9. A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
12. A supercontinent or single landmass.
17. Another reptile fossil that has been found in places now separated by oceans.
18. Mid-Ocean ridges that are continually adding new material to the ocean floor.
19. German scientist who became curious about why some continents look as though they could fit together.
20. Any trace of an ancient organism that has been preserved in rock.

1. The way scientists mapped mid-ocean ridges in the mid-1900s.
3. A plate boundary where two plates move past each other in opposite directions.
4. A plate boundary where to plates move toward each other.
6. The theory that the continents slowly drifted over Earth's surface.
10. A break in Earth's crust along which rocks move.
11. A deep valley that forms where two plates move apart.
13. Reptile fossil that has been found in places now separated by oceans.
14. The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle.
15. A fernlike plant that lived 250 million years ago.
16. Mountain ranges that run along the middle of some ocean floors.