Plate Tectonics

5. waves of energy that travel through Earth's crust and interior
6. a long area where one tectonic plate sinks beneath another
8. the process by which ocean crust spreads apart along each side of a mid-ocean ridge
12. the gradual movement of the continents across Earth’s surface over time
15. a puzzle piece-like section of the lithosphere that moves over the asthenosphere carrying pieces of continental and oceanic crust
16. the outermost layer of Earth that forms Earth's surface
17. a trace of an ancient organism preserved within a layer or rock
18. the movement of fluid caused by differences in temperature
19. an area where two plates slide past each other in opposite directions
20. a rigid layer composed of the crust and the upper mantle
22. the place on Earth's surface directly over the focus of an earthquake
23. the place deep inside Earth where a shift in Earth's crust occurs, causing an earthquake

1. an area where two or more tectonic plates move toward one another and collide
2. the downward movement of one of Earth's plates beneath another plate
3. an area in the ocean that has an upwelling of molten material associated with seafloor spreading
4. the layer of the mantle on which the lithosphere floats
7. an area where two or more tectonic plates move away from one another
9. a crack and Earth's crust
10. an area of lowland with steep walls formed at divergent boundaries
11. the theory that pieces of the lithosphere are constantly moving due to convection currents in Earth's mantle
13. a rigid layer composed of the crust and the upper mantle
14. the thick region between Earth's core and crust
21. a well-tested, widely accepted explanation that combines several hypotheses and observations