Plate Tectonics

4. ridge an undersea mountain chain where new ocean floor is produced (usually at a divergent boundary)
7. current the movement of fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another
8. the transfer of heat within a material or between materials that are touching
9. the name of the single land mass that broke apart and gave rise to today's continents
10. boundary a plate boundary where two plates move away from each other
12. Weak, partially melted layer composed of semi-molten rocks
15. trench a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle
17. tectonics the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle
19. valley a deep valley where two plates move apart
20. the transfer of heat by movement of fluid

1. core a dense sphere of solid iron (Fe) and nickel(Ni) at the center of the Earth
2. A rigid layer made up of the uppermost part of the mantle and the crust.
3. boundary a plate boundary where two plates move toward each other
5. the layer of hot, solid material between Earth's crust and core.
6. drift the hypothesis that the continents slowly move across Earth's surface
11. a trace of an ancient organism that has been preserved in rock
13. the transfer of energy through space
14. the process by which molten materials add new oceanic crust to the ocean floor
16. the layer of rock that forms Earth's outer surface.
18. core a layer of molten iron (Fe) and nickel (Ni) that surrounds the inner solid core of the Earth