plate tectonics

2. The layer of hot, solid material between Earth'scrust and core.
4. Great landmasses surrounded by oceans
5. A trace of an ancient organism that has been preserved in rock.
10. The layer of rock that forms the Earth's outer surface.
11. A plate boundary where two plates move away from each other.
12. The amount of mass in a given space; mass per unit volume.
15. The movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another.
16. spreading, The process by which molten material adds new oceanic crust to the ocean floor.
17. A plate boundary where two plates move toward each other.
19. A rigid layer made up of the uppermost part of the mangle and the crust.
20. Scientist who hypothesized that all the continents were one joined together in a single land mass.

1. The hypothesis that the continents slowly move across the Earth's surface.
3. A plate boundary where two plates move past each other in opposite directions.
6. A dense sphere of solid iron and nickel in the center of Earth.
7. The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
8. A layer of molten iron and nickel that surrounds the inner core of Earth.
9. The soft layer of the mantle on which the lithosphere forms.
13. The study of planet Earth.
14. A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
18. The material that forms the Earth's hard surface.