| A | B |
|---|
| trench | a deep valley feature on the sea floor |
| subduction | the process by which one plate is pushed below another |
| divergent boundary | a place where plates move apart. |
| convergent boundary | a place where two plates come together. |
| Pangaea | "all lands"-the single land mass when all continents were joined |
| Mid-Ocean Ridge | The continuous chain of underwater mountains around the earth |
| theory of plate tectonics | the earth's lithosphere is broken into moving plates |
| asthenosphere | a zone of magma in the upper mantle of the earth |
| convection current | the movement of material caused by differences in temperature |
| hot spots | (plumes) columns of molten rock that rise from places deep in the mantle |
| transform fault | a boundary where plates slide past each other |
| lithosphere | the crust or "rock" layer of the earth |
| island arc | a group of volcanic islands formed by subduction |
