Plate Tectonics

1. ridge The undersea mountain mountain chain where new ocean floor is produced; a divergent plate boundary
4. boundary A plate boundary where two plates grind against each other, moving it different directions
6. boundary A plate boundary where two plates move away from each other
8. A soft layer of the mantle on which the lithosphere floats
11. zone The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary
12. A break or crack in the Earth's lithosphere along which rocks move
14. A rigid layer made up of the uppermost part of the mantle and the crust
15. boundary A plate boundary where two plates move toward each other
17. Thickest layer of the Earth; it consists of two layers - the lithosphere and the asthenosphere
19. spreading The process by which molten material adds new oceanic crust to the ocean floor
20. The layer of rock that forms the Earth's outer surface

2. currents Cause the plates to move; between the lithosphere and the asthenosphere
3. Wegener German Scientist who developed the Theory of the Continental Drift in 1912.
5. core Dense ball of solid material at the center of he Earth
7. The name of the single landmass that broke apart about 225 million years ago
9. valley A deep valley where two plates move apart
10. Drift Alfred Wegener's hypothesis that the continents were once one huge land mass but have since then drifted apart
13. A deep canyon on the ocean floor
16. core A layer of molten iron and nickel that surrounds the inner core of the Earth
18. of Plate Tectonics Theory that pieces of the Earth's lithosphere are in motion,driven by convection currents in the mantle