Ch 8 Plate Tectonics Review

4. bends in rock that form when compression shortens and thickens earth's crust
6. magma that exits a volcano and is exposed to air or water
10. the sinking movement of ocean floor back into the mantle
11. the boundary at which plates slip past each other
12. a single number that geologists use to assign to an earthquake based on the earthquake's size
13. long, zipperlike chains of undersea mountains
14. an opening in the earth's crust through which material is forced upwards during a volcanic eruption
16. traces of organisms preserved in rock
18. a triangle shaped hill formed as material from volcanic eruptions piles up around the volcanic vent
19. He developed the continental drift hypothesis
21. undersea valleys that are the deepest parts of the ocean
23. a volcano that poses little threat of eruption but could reawaken someday
24. a break in the rock of earth's crust or mantle
25. a molten mixture of rock-forming substances, gases, and water from the mantle
27. a cyclical movement of fluid in the mantle
28. a volcano that poses very little threat of eruption

1. seismic waves produced by earthquakes are measured by this device
2. a structure that forms in earth's crust when molten material, or magma, reaches earth's surface
3. the supercontinent that broke up into the continents we know today
5. vibrations that travel through earth carrying energy released by earthquakes and volcanoes
7. the most dangerous volcanoes that could erupt at any moment
8. the hypothesis that all of the continents had once been together and drifted apart
9. scientists use these to measure plate motions
15. the boundary at which plates come together
17. the process by which molten rock flows up through a crack in earth's crust and hardens into solid strips of new rock on both sides of the crack
20. the boundary at which plates move apart
22. the shaking and trembling that results from plate movements
26. the force that acts on rock to change its shape or volume