| A | B |
|---|
| lithosphere | combination of the Earth's crust and the top, rigid portion of the upper mantle |
| asthenosphere | portion of the upper mantle that is acutally partially melted (molten) and able to flow |
| plate | section of the Earth's lithosphere that moves due to convection currents in the asthenosphere |
| Mohorovicic Discontinuity | boundary between the Earth's crust and the upper mantle |
| outer core | its fluid motion creates the Earth's magnetic field |
| hypothesis of continental drift | stated that at one time all the continents were joined together in one supercontinent |
| HMS Challenger | expedition was responsible for discovering mid-oceanic ridges |
| SONAR | discovered trenches and confirmed length of mid-oceanic ridges |
| subduction zone | another name for trench |
| Glomar Challenger | discovered that the ocean floor is youngest near the ridges |
| hypothesis of seafloor spreading | stated that new crust is formed at the ridges and destroyed at the trenches |
| paleomagnetism | record of the direction of Earth's magnetic field due to minerals in igneous rocks |
| normal polarity | when the direction of the magnetic field in rocks matches today's alignment |
| reverse polarity | when the direction of the Earth's magnetic field is opposite of today's alignment |
| Theory of Plate Tectonics | provides the mechanism for continental drift |
| convergent boundary | place where 2 continental plates are moving together |
| divergent boundary | place where 2 continental plates are moving apart |
| transform fault | place where 2 continental plates slide horizontally past each other |
