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Plate Tectonics
| Term | Definition |
|---|---|
| tectonic/crustal plates | large, moving pieces of Earth's lithosphere that rest on the asthenospere; commonly carries both oceanic and continental crust |
| Continental Drift | a hypothesis made by Alfred Wegener in 1912; continents were once joined together but moved apart over time |
| Pangaea | supercontinent that included all of the landmasses on Earth; began breaking apart about 200 million years ago |
| plate tectonics | theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle |
| divergent boundary | boundary along which two tectonic plates move away from each other; the sea floor spreads apart and new crust is formed |
| convergent boundary | boundary along which two tectonic plates move toward each other; characterized by subduction or continental collision; crust is usually destroyed |
| transform boundary | boundary along which two tectonic plates scrape past each other; characterized by earthquakes; crust isn't created or destroyed |
| hot spot | an area where a column of hot material rises from deep within the mantle; lithosphere above is heated, causing volcanic activity at the surface |
| subduction | the process by which denser crust sinks beneath less dense crust |
| rift valley | a deep valley formed as tectonic plates move away from each other at a divergent boundary |
| mid-ocean ridge | an underwater mountain range where new ocean crust is formed by volcanic activity along a divergent boundary |
| ocean basin | a great depression occupied by the ocean on the surface of the lithosphere |