| A | B |
|---|
| pangaea | single giant landmass that existed millions of years ago |
| continental drift | theory that states Earth once had a single landmass that broke apart into large pieces, which have since drifted apart |
| ocean-floor spreading | process in which old ocean floor is pushed away from midocean ridges to form new ocean floor |
| trench | v-shaped valley on the ocean floor where old ocean floor is subducted |
| subduction | process in which crust plunges back into the interior of the Earth |
| divergent boundary | a plate boundary at which plates move apart |
| convergent boundary | a plate boundary at which plates come together |
| transform boundary | a plate boundary at which two plates slip past one another horizontally |
| plate | a moving, irregular shaped slab on crust |
