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Plate Movement
| Term | Definition |
|---|---|
| crust | Earth's outer layer; the coolest and least dense layer of Earth. See also core, and mantle. |
| mantle | The layer of Earth beneath the crust. It is about 2,900 km (1,800 mi) thick, and makes up about 83 percent of Earth's interior. See also core, and crust. |
| outer core | A layer of molten iron and nickel that surrounds the inner core of Earth. |
| inner core | A dense sphere of solid iron and nickel at the center of Earth. |
| latitude | The distance north or south of the equator measured in degrees. See also longitude. |
| longitude | The distance east or west of the prime meridian in Greenwich, England; measured in degrees. See also latitude |
| oceanic ridge | A mountain-like landform that develops when tectonic plates move apart or separate and a new ocean lithosphere forms. |
| sea-floor spreading | The process by which molten material adds new oceanic crust to the ocean floor. |
| divergent boundary | A plate boundary where two plates move away from each other. |
| convergent boundary | A plate boundary where two plates move toward each other. |
| transform boundary | A plate boundary where two plates move past each other in opposite directions. |
| subduction | The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary |
| ocean trench | An undersea valley that represents on of the deepest parts of the ocean |
| tectonic plate | A piece of Earth's crust that, according to plate tectonics, is pushed by movement in the asthenosphere. |
| lithosphere | The cool, solid outer shell of Earth. It consist of the crust and the rigid uppermost part of the mantle and is broken up into segments, or plates. |
| fracture | The breakage of a rock into two or more pieces. |
| elasticity | The ability of rock to be stretched and then return to its original position once the stress has been removed. |
| stress | The amount of force being applied to a rock or surface |
| strain | Change in volume, size, or shape that results from stress |
| plate boundary | A place where pieces of the broken lithosphere meet. Boundary types include convergent, divergent, and transform |
| continental crust | Crust that contains mostly land, ranging from 15 to 70 kilometers (9 to 43 miles) thick. |
| oceanic crust | The thin, dense and young outer layer of Earth's lithosphere that forms the floor of the ocean basins. |
| friction | A force that opposes the motion of objects, which are in contact. |
| rift valley | The valley formed by a diverging plate boundary |