| A | B |
|---|
| inner core | inner-most layer of Earth; pressure keeps this layer a solid; iron and nickel |
| outer core | heat makes this layer a liquid; molten metal; responsible for the Earth's magnetic field |
| asthenoshpere | The "softer" layer of the mantle |
| lithosphere | the "rock hard" layer of the mantle that also includes the crust |
| oceanic crust | outer-most layer that can be as little as 5 km think; consists mainly of basalt |
| continental crust | outer-most layer that can be up to 70 km think; consists mainly of granite |
| heat transfer | the movement of heat from warmer things to cooler things |
| radiation | the movement of heat through SPACE |
| conduction | the movement of heat through one object, or from one object to another when they TOUCH |
| convection | the movement of heat through a LIQUID or GAS; depends on density, heating, cooling, and gravity |
| continental drift | Wegener's theory that the present-day continents were once a super-continent (Pangaea) and have since drifted apart |
| Pangaea | The supercontinent that formed in the Paleozoic Era and broke apart throughout the Mesozoic Era |
| sea-floor spreading | Hess's theory that new sea floor emerges at mid-ocean ridges and hardens, pushing the older floor outwards |
| subduction | the process in which crust becomes dense enough to sink back down into the mantle |
| mid-ocean ridges | under-water mountain chains; where sea floor spreading occurs |
| sonar | process of using sound waves to map out the ocean floor |
| deep-sea trenches | under-water valleys where subduction occurs |
| plate tectonics | J. Tuzo Wilson's theory that the Earth's lithosphere is divided into plates that move over the Earth's surface because of convection currents in the mantle |
| convergent boundary | a tectonic plate boundary where plates collide, or come together |
| divergent boundary | a tectonic plate boundary where plates divide, or move apart |
| transform boundary | a tectonic plate boundary where plates slide past each other |
