| A | B |
|---|
| continental drift | the idea that Earth's continents move from one part of Earth to another |
| fossil | preserved remains, imprints, or traces of an organism |
| trench | deep, narrow ocean canyhon that forms where one plate is subducted below another plate |
| lithosphere | brittle outer layer of Earth that includes the crust and top part of the upper mantle |
| asthenosphere | hot layer of Earth's upper mantle that flows very slowly |
| mid-ocean ridge | long, narrow chain of underwater mountains |
| rift | deep valley that runs along the crest of the mid-ocean ridge |
| subduction | process in which the edge of one plate sinks below the edge of another plate |
| sea-floor spreading | new oceanic crust forms, spreads from the ridge, and is subducted at trenches |
| magma | melted rock formed inside Earth |
