| A | B |
|---|
| Pangaea | the name of the single landmass that broke apart 200 million years ago and gave rise to today's continents. |
| fossil | the preserved remains or traces of an organism that lived in the past. |
| continental drift | the hypothesis that the continents slowly move across Earth's surface. |
| mid-ocean ridge | the undersea mountain chain where new ocean floor is produced; a divergent plate boundary. |
| sea-floor spreading | the process by which molten material adds new oceanic crust to the ocean floor; occurs along the boundary between diverging plates. |
| deep-ocean trench | a deep valley along the ocean floor through which oceanic crust slowly sinks toward the mantle. |
| subduction | the process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary. |
| plate | a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust. |
| plate tectonics | the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle. |
| fault | a break or crack in Earth's lithosphere along which the rocks move. |
| boundary | the limit/edge |
| transform boundary | a plate boundary where two plates move past each other in opposite directions. |
| divergent boundary | a plate boundary where two plates move away from each other. |
| rift valley | a deep valley that forms where two plates move apart. |
| convergent boundary | a plate boundary where two plates move toward each other. |
