| A | B |
|---|
| continental drift | hypothesis: the continents once formed a single landmass, broke up, and drifted to their present locations |
| mid-ocean ridge | a long, undersea mountain chain; a steep, narrow valley at its center; forms as magma rises from the asthenosphere; creates new oceanic lithosphere (sea floor) |
| sea-floor spreading | the process by which new oceanic lithosphere (sea floor) forms as magma rises to Earth's surface and solidifies at a mid-ocean ridge |
| paleomagnetism | study of the alignment of magnetic minerals in rock (relating to the reversal of Earth's magnetic poles); magnetic properties that rock acquires during formation |
| plate tectonics | the theory that explains how large pieces of the lithosphere, called plates, move and change shape |
| lithosphere | the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle |
| asthenosphere | the solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it |
| divergent boundary | the boundary between tectonic plates that are moving away from each other |
| transform boundary | the boundary between tectonic plates that are sliding past each other horizontally |
| rifting | the process by which Earth's crust breaks apart; can occur within continental crust or oceanic crust |
| terrane | a piece of lithosphere that has a unique geologic history and that may be part of a larger piece of lithosphere, such as a continent |
| supercontinent cycle | the process by which supercontinents form and break apart over milllions of years |
| Pangaea | The supercontinent that formed 300 million years ago and that began to break up beginning 250 million years ago |
| Panthalassa | the single, large ocean that covered Earth's surface during the time the supercontinent Pangaea existed |
| mountain range | a series of mountains that are closely related in orientation, age, and mode of formation |
| folded mountain | a mountain that forms when rock layers are squeezed together and uplifted |
| fault-block mountain | a mountain that forms where faults break Earth's crust into large blocks and some blocks drop down relative to other blocks |
| dome mountain | circular/elliptical elevation or structure; stratified rock slopes downward from the point of folding |
