| A | B |
|---|
| continental drift | land masses have moved horizontally |
| continental drift | proposed by Alfred Wegener in 1912 |
| Pangea | "all land" |
| Mesosaurus | reptile found in South America and Africa |
| Glossopteris | ancient fern found fossilized on many present day continents |
| glacial deposits | found on land masses located in the tropics today |
| similar rock structures | found on margins of different continents today |
| accurate topographic seafloor maps | made in the 1950's when echo sounding technology became available |
| seafloor spreading | theory proposed in 1960 by Harry Hess |
| seafloor spreading | hot, less dense magma forces plates apart at mid-ocean ridges |
| Glomar Challenger | found, in 1968, that seafloor rocks are young |
| ocean floor rock | made of basalt, youngest at mid-ocean ridges |
| magnetometer | records magnetic orientation of the Earth |
| ocean floor rock | shows changes in magnetic polarity |
| plate tectonics | combined ideas of continental drift and seafloor spreading |
| plate tectonics | crust and upper mantle move as rigid "rafts" on the mantle |
| lithosphere | name for the crust and upper mantle |
| asthenosphere | deeper and denser part of the mantle |
| divergent boundary | place where two plates are moving away from each other |
| examples of divergent boundaries | Mid-Atlantic Ridge, Great Rift Valley, Red Sea |
| convergent boundary | place where two plates are colliding |
| subduction zone | area where an ocean plate sinks under another plate and descends into the mantle |
| examples of continental plate collisions | Himalayas, Appalachians |
| examples of subduction zone | Aleutian Islands, Japan, Philippenes, Andes |
| deep-sea trench | forms when two ocean plates collide |
| island arcs | form when volcanic activity results from subduction of an ocean plate |
| transform faults | occur when two plates slide past one another |
| examples of transform faults | San Andreas Fault, at right angles to the Mid-ocean ridges |
| convection current | cycle of heating, rising, cooling, and sinking |
| convection current | mechanism believed responsible for driving plate movement |
| fault block mountains | created by tension forces creating a series of normal faults |
| rift valleys | created by the separation of plates |
| Rodinia | supercontinent believed to exist before Pangea; 750 million years ago |
