| A | B |
|---|
| Pangaea | Name of the single continent, or giant landmass that existed 200 million years ago |
| theory of continental drift | theory proposed by Alfred Wegener that the continents used to be one large continent and have drifted apart |
| midocean ridge | undersea mountain chain where new ocean floor is produced |
| sea-floor spreading | when the ocean floor is pushed away from a midocean ridge by the making of new ocean floor |
| subduction | process in which crust falls into the interior of the Earth |
| theory of plate tectonics | theory that connects the ideas of continental dirft and ocean floor spreading |
| lithosphere | top solid part of the Earth, crust and part of the mantle |
| divergent boundaries | plate boundary where plates move apart |
| convergent boundaries | plate boundary where plates move together |
| transform | plate boundary where two plates move past each other horizontally |
