| A | B |
|---|
| geology | The study of planet earth. |
| convection current | This is caused by the transfer of heat as soft rock flows through the mantle because of differences in temperature. |
| density | The amount of mass in a given space; per unit volume. |
| plates | Separate sections of the Earth's lithosphere. |
| plate tectonics | The theory stating that the plates of the Earth's lithosphere at in constant, slow motion,driven by convection currents in the mantle. |
| scientific theory | A well-tested concept that explains a wide range of observations. |
| fault | A break in the Earth's crust where slabs of rock have slipped past each other. |
| transform boundary | A plate boundary where two plates slip past each other in opposite directions. |
| divergent boundary | A plate boundary where two plates move away from each other. |
| convergent boundary | A plate boundary where two plates collide. |
| Alfred Wegener | The scientist who came up with the idea of continental drift |
| Pangaea | The name of the single landmass that broke apart 200 million years ago and gave rise to today's continents. |
| mid-ocean ridge | A long chain of mountains on the ocean floor. |
| sonar | A device that bounces sound waves off underwater objects and records the echoes. |
| sea-floor spreading | The process by which molten material adds new oceanic crust to the ocean floor. |
| deep ocean trench | A deep valley along the ocean floor through which oceanic crust slowly sinks towards the mantle. |
| subduction | The process by which the ocean crust sinks through a deep- ocean trench and back into the mantle; a convergent plate boundary. |
| fossils | A trace of an organism that has been preserved in rock. |
| rift valley | A deep valley that forms where two plates move apart. |
| continental Drift | The hypothesis that all the continents had once been joined together in a single landmass and have since drifted apart. |
