Plate tectonics

1. a plate boundary where two plates move away from each other
4. a plate boundary where two plates move past each other in opposite directions
10. a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust
12. the molten mixture of rock forming, substaces, gases, and water from the mantle
13. a device that uses sound waves to measure the distance to an object
14. the force that two surfaces exert on each rock forming they rub against each other
17. a plate boundary where two plates move toward each other
18. a deep valley that forms where two plates move apart
19. the theory that pieces of earths lithosphere are in constant motion, driven by convection currents in the mantle
20. the movement of a fluid, caused by differences in temperature that transfers heat from one part of the fluid to another

2. stress that stretches rock so that it becomes thinner in the middle
3. a weak spot in the crust where magma has come to the surface
5. an undersea mountain chain where new ocean floor produced; a divergent plate boundary under the ocean
6. the process by which oceanic crust sinks beneath a deep ocean trench and back into the mantle at a convergent plate boundary
7. adds more crust to the ocean floor
8. liquid magma that reaches the surface
9. a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle
11. the shaking that results from the movement of rock beneath earth
15. a break in earths crust along which rocks move
16. the layer of hot,solid material between earths crust and core