| A | B |
|---|
| Pangaea | super continent that existed 200 million years ago |
| Atlantic | ocean created when the super continent broke apart |
| 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 |
| magnetic stripes | bands of ocean floor that show many magnetic reversals |
| lithosphere | the crust and upper mantle |
| mantle | the largest layer inside Earth |
| crust | outermost layer of Earth |
| inner core | solid core composed of dense iron and nickel |
| outer core | liquid core composed of iron and nickel |
| asthenosphere | plastic layer below the lithosphere that can flow |
| plates | large sections of Earth's lithosphere |
| plate tectonics | theory that Earth's lithosphere is broken into sections |
| continental drift | theory that the continents move, and were once joined in a single landmass called Pangaea |
| divergent boundary | boundary between two plates that are moving apart |
| convergent boundary | boundary where two plates are moving toward each other |
| transform fault boundary | boundary where two plates are moving alongside each other |
| convection current | cycle of heating, rising, cooling and sinking in fluids |
| subduction zone | area where a denser converging plate sinks under a less dense converging plate |
| San Andreas Fault | example of a transform fault boundary, found in California |
| mid-ocean ridge | example of a divergent boundary in ocean crust |
| Great Rift Valley in Africa | example of a divergent boundary in continental crust |
| Marianas trench | deepest spot in any ocean, an example of converging oceanic plates |
| Himalaya Mountains | example of a boundary where continental crust collided |
| magnetic reversal | changes in Earth's magnetic field that result from movement in the outer core |
| a few centimeters (an inch) | the average rate the plates move per year |
| granite | the main type of rock found in continental crust |
| basalt | the main type of rock found in oceanic crust |
