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objective 9
vocab
| Term | Definition |
|---|---|
| continental drift | hypothesis that continents are in constant motion |
| mantle | middle layer of earth situated between the crust above and the core below |
| pangaea | ancient supercontinent composed of land that forms todays continents |
| mid ocean ridge | mountain range located on the sea floor in the middle of the ocean |
| seafloor spreading | new oceanic crust forms at a mid ocean ridge as old oceanic crust moves away |
| convection | circulation of material caused by differences in temperature and density |
| convergent plate boundary | where two plates collide |
| lithosphere | cold, rigid outermost rock layer of earth |
| plate tectonics | theory that earths surface is made of rock plates that move with respect to each other |
| subduction | sinking of a denser plate below a more buoyant plate at a convergent plate boundary |
| transform plate boundary | where two plates slide by each other |