| A | B |
|---|
| plate tectonics | theory that describes the formation, movements and interactions of the earth's plates |
| continental drift | based on a hypothesis by Alfred Wegener that the continents have moved, or drifted, from one location to another over time |
| mid-ocean ridge | a long chain of volcanic mountains on the ocean floor with a deep central valley |
| divergent boundary | a boundary between two lithospheric plates that are moving apart (sometimes called spreading centers) |
| rift valley | a deep valley at the center of a mid-ocean ridge |
| rift | a crack along the valley |
| convergent boundary | boundary between two plates that are moving toward each other, or converging |
| subduction boundary | boundary between plates when the oceanic plate plunges beneath the overriding plate |
| deep-sea trench | a long, deep trench that forms along a subduction boundary -- These trenches are the deepest parts of the ocean floor. |
| collision boundary | boundary that forms when two continents collide and are welded into a single, larger continent |
| transform boundary | a boundary between two plates that are sliding past each other |
| mantle convection | a process through which heat from the Earth's inner and outer cores is transferred through the mantle |
| ridge push | when cooling, subsiding rock exerts a force on spreading lithospheric plates that could help drive their movements |
| slab pull | the force that the sinking edge of a plate exerts on the rest of the plate |
| Pangea | a giant land mass - all the continents welded together - thought to exist about 250 million years ago |
| craton | an expanse of ancient rock at the core of each continent |
| terrane | large block of lithospheric plate that has been moved, often over a distance of thousands of kilometers, and attached to the edge of a continent |
