Chap. 17 Plate Tectonics

6. huge pieces of crust and rigid upper mantle that fit together at their edges to cover Earth's surface
8. a region where two plates slide horizontally past each other
10. a long narrow depression formed when continental crust begins to separate
11. is an imaginary line on a map that shows points that have the same age, that is they formed at the same time
12. a device that can detect small changes in magnetic field
13. two tectonic plates are moving toward each other
14. a single landmass that broke apart 200 mya
15. a process where older portion of the sea-floor sinks, the weight of the uplifted ridge is thought to push the oceanic plate toward the trench formed at the subduction zone

1. a hypothesis developed by Alfred Wegener that proposed that Earth's continents had once been joined as a single landmass that broke apart and sent the continents adrift
2. the theory that explains how new oceanic crust is formed at ocean ridges, slowly moved away from ocean ridges and destroyed at deep ocean trenches
3. the weight of the relatively cool, dense subducting plate pulls the trailing slab into the subduction zone
4. process where two plates collide, the denser plate eventually descends below the other less dense plate
5. regions where two tectonic plates are moving apart
7. happens when the flow in the outer core changes, and Earth's magnetic field changes direction
9. is the study of history of Earth's magnetic field