| A | B |
|---|
| Pangaea | super continent that existed 200 million years ago |
| Alfred Wegener | scientist who thought that the continents were once one super continent |
| sea-floor spreading | theory that new ocean crust is formed at the mid ocean ridges by molten lava |
| lithosphere | crust and upper mantle |
| mantle | the largest layer inside Earth |
| crust | outer most layer of Earth |
| inner core | solid core composed of dense iron and nickel |
| outer core | outer layer composed of iron and nickel |
| asthenosphere | layer below the lithosphere |
| plate tectonics | theory that Earth's crust and upper mantle are broken into sections |
| continental drift | theory that the continents move |
| divergent boundary | boundary between two plates that are moving apart |
| convergent boundary | boundary where two plates are moving toward each other |
| transform boundary | boundary where two plates are moving past each other |
| convection current | cycle of heating, rising, cooling and sinking |
| mid-ocean ridge | example of a divergent boundary in ocean crust |
| convection currents | heat that radiates outward from the core to move the plates |
