| A | B |
|---|
| plate tectonics | theory that the Earth has 12 plates floating on the mantle |
| subduction | at convergent boundaries; one plate dives under another |
| convection | movement of heat currents due to changes in density |
| trenches | at convergent boundaries; deepest places on ocean floors |
| asthenosphere | liquid portion of the matle on which plates move |
| lithosphere | solid shell of earth; crust and upper mantle |
| ridges/rift valleys | formed where magma comes to the surface and new crust is formed; on ocean floor |
| Continental Drift | theory that continents were all attached and eventually moved apart |
| Pangea | original "super" continent |
| divergent | two plates moving away from each other |
| convergent | two plates moving toward each other |
| transform | two plates sliding past each other |
| Richter Scale | used to determine magnitude of earthquakes |
| Mercalli Scale | determines earthquake destruction by eyewitness accounts |
| island arcs | chain of islands fromed as one plate subducts under another |
| folding | bending of rock due to seismic activity |
| fault | crack in the rock where movement occurs |
| hot spot | areas of volcanic activity in weak areas of lithospheric plates |
| magnetic reversal | the switching of north and south poles |
| age patterns in oceanic rock | the closer one gets to the mid-Atlantic ridge, the younger the rock; shorelines contain the oldest rock |
