| A | B |
|---|
| mid-adlantic ridge | submerged volcanic mountain range in the Atlantic Ocean. Starts at Iceland and ends at a point east of th esouthern tip of South America |
| lithosheric plate | a piece of the topmost solid part of Earth, which is composed of the crust and some of the mantle |
| pangea | a single giant landmass that existed more than 200 mya |
| ring of fire | the earthquake and volcano zone that encircles the Pacific Ocean |
| seismograph | an insroment that detects and measures seismic waves |
| richterscale | the scale used to measure the strength of erthquakes |
| ocean floor spreading | the process in which old ocean floor is pushed away from a midocean ridge by the formation of a new ocean floor |
| magma | molten rock beneath the earth's surface |
| fault | a break or crack along which rocks move |
| convergent boundary | a plate boundary at which plates come together |
| divergent boundary | a plate boundary at which plates move apart |
| convection currents | movement of air caused by differences in tepature |
| trench | a V-shaped valley on the ocean floor where old ocean floor i s subducted. |
| mantle | the layer of Earth that extends from the bottom of the crust to the core |
| molten rock | when molten lava hardens |
| hot spots | intence heat causing volcanic activity |
