| A | B |
|---|
| asthenosphere | a layer of plastic rock; solid rock that flows slowly when under pressure |
| continental crust | material that makes up the continental landmasses |
| continental drift | movement of continents to new position |
| convection | transfer of heat through the movement of heated fluid material |
| convection current | cycle of warm material moving up and cooler material moving down; warm material less dense than cooler material |
| convergent boundary | the direct collision between two plates moving toward each other |
| divergent boundary | two plates moving away from each other |
| island arc | molten rock rsulting from subducted plate rises to the surface along the trench and forms a chain of volcanic islands |
| lithosphere | made of continental and oceanic crust and part of the earth's upper mantle |
| Mid-Atlantic Ridge | undersea mountain range with a steep, narrow valley running down the center |
| mid-ocean ridges | system of undersea ridges winding around the earth |
| oceanic crust | material on the ocean floor that forms the ocean floor |
| Pangaea | Word for single great landmass; means "All Lands" |
| Panthalassa | Word for single great ocean; means "All Seas" |
| plate tectonics | describes continental movement and proposes possible reasons for why and how they move |
| rift valley | narrow valley that is formed in mid-ocean ridges as plates separate |
| seafloor spreading | valley in the center of rift is a fracture in the floor of the ocean. Plates are moving away from this fracture. |
| subduction zone | region along a plate boundary where one plate is forced under another plate |
| suspect terrane | theory that suggests continents are a patchwork of lands with different properties |
| terrane | pieces of land, each with its own distinct geologic history |
| transform fault boundary | two plates are ginding past each other. Do not move smoothly. |
