| A | B |
|---|
| subduction | older crust sinks back into the mantle, recycling the crust of the Earth |
| seafloor spreading | a divergent boundary, which allows magma up through midocean ridges |
| older ocean floor is ... | at the edges, by the continents |
| newer ocean floor is. . . | at the midocean ridges |
| trench | break in the ocean floor, where subduction occurs |
| convergent boundaries | plates push up against one another, creating mountains |
| strike slip boundaries | boundaries that grind past each other sideways |
| the most destructive boundaries are | convergent, because of extreme pressure and friction |
| continental drift | the theory that explains the geographical location of the continents, based on the lithosphere |
| lithosphere | the top layer of the Earth's crust, made up of tectonic plates |
| Pangaea | the supercontinent |
| Wegener | developed the theory of contiental drift |
| magma | what plates float on |
| convection currents | currents that circulate based on different densities |
| seismograph | instrument that measures seismic waves |
| Ritcher Scale | scale used to compare the severity of a quake |
| magma | hot molten rock in a volcano |
| lava | hardened magma outside a volcano |
| fracture | crack in a rock |
| fault | break which rocks can move along |
| cinder cones | cones that are explosive with cinders |
| shield cones | cones that have quiet lava flows |
| composite cones | alternating rock layers, particles and lava form these cones |
| Ring of Fire | a chain of volcanoes in the Pacific Ocean |
| P waves | reach surface first |
| S waves | follow P waves |
| vent | opening which lava erupts from a volcano |
| depression | funnel shaped pit at the top of the volcano, crater shaped |
