| A | B |
|---|
| Pangaea | A large landmass of all land on Earth joined together that began to break apart approximately 200 million years ago |
| Continental drift | The movement of Earth’s continents over time |
| Mid-ocean ridge | Long, narrow mountain range on the ocean floor; formed by magma at divergent plate boundaries |
| Ocean trench | A deep, underwater trough created by one plate subducting under another plate at a convergent plate boundary |
| Seafloor spreading | The process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge |
| Normal polarity | When magnetized objects, such as compass needles, orient themselves to point north |
| Reversed polarity | When magnetized objects reverse direction and orient themselves to point south |
| Plate tectonics | The theory that Earth’s surface is broken into large, rigid pieces that move with respect to each other |
| Plate | A large section of Earth’s oceanic or continental crust and the rigid upper mantle that moves around on the asthenosphere |
| Divergent plate boundary | The boundary between two plates that move away from each other |
| Transform plate boundary | The boundary between two plates that slide past each other |
| Convergent plate boundary | The boundary between two plates that move toward each other |
| Subduction | The process that occurs when one tectonic plate moves under another tectonic plate |
| Convection | The circulation of particles within a material caused by differences in thermal energy and density |
| Uplift | The process that moves large bodies of Earth materials to higher elevations |
