Chapter 17

3. Plates slide away from mid-ocean ridges.
6. Formed when two continents collide.
8. Movement in the mantle caused by heat; drives plate motion.
10. An underwater mountain chain where new crust is created.
12. The theory that Earth’s outer layer is broken into moving plates.
13. Heat from Earth’s center that powers convection.
14. Boundary where plates slide past each other.
16. Sudden shaking caused by plate movement.
17. Where two tectonic plates meet.
18. A supercontinent that included all land on Earth long ago.
22. Earth’s outer layer.
23. Ocean rocks are youngest near ridges and older farther away.
25. When coastlines (like South America and Africa) fit together like puzzle pieces.
27. Scratches and deposits from glaciers that show past movement of continents.
30. A sinking plate pulls the rest of the plate with it.
32. Patterns in seafloor rocks showing Earth’s magnetic field has changed over time.
33. Remains of plants/animals found in rocks that show continents were once connected.

1. Thin, dense crust found under oceans.
2. A deep valley in the ocean formed by subduction.
4. Boundary where plates move apart (new crust forms).
5. The process where new ocean crust forms at mid-ocean ridges and moves outward.
7. The idea that continents move slowly over time.
9. Large pieces of Earth’s crust that move.
11. Crust + upper mantle (rigid layer).
15. Melted rock beneath Earth’s surface.
19. Soft layer beneath lithosphere that flows slowly.
20. Helps move plates downhill from ridges.
21. Melted rock that reaches Earth’s surface.
24. One plate sinks under another.
26. The layer beneath Earth’s crust.
28. Scientist who proposed continental drift.
29. Boundary where plates move toward each other.
31. An opening where magma reaches the surface.