| A | B |
|---|
| plate tectonics | theory of formation and movement of rigid plates that cover Earth |
| subduction | where one plate is moving beneath an over-riding plate |
| convection | movement of heat by currents within a liquid or gas |
| trenches | deepest places on ocean floor;at converging plate boundaries |
| lithosphere | solid shell of earth; crust & top of mantle;100 km thick |
| asthenosphere | top of mantle that can flow; has convection currents |
| divergent plate boundary | 2 plates move apart as new crust is formed |
| convergent plate boundary | 2 plates move together |
| transform plate boundary | 2 plates slide past each other |
| hot spot | areas of volcanic activity near the center of lithospheric plates |
| ridges or rift valleys | places formed as new crust pushes up at a divergent boundary |
| Continental Drift | early theory that continents were once together in a single land mass-Pangea |
