| A | B |
|---|
| mid-ocean ridge | an undersea mountain chain where new ocean floor is produced; a divergent plate boundary |
| sonar | a device that bounces sound off underwater objects to determine the distance from that object |
| sea-floor spreading | the process by which molten material adds new oceanic crust to the ocean floor |
| deep-ocean trenches | a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle |
| subduction | the process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary |
| continental drift | the hypothesis that the continents slowly move across the Earth's surface |
| Pangaea | the name of the single landmass that broke apart 200 million years ago and gave rise to today's continents |
| fossil | a trace of an ancient organism that has been preserved in rock |
| seismic waves | vibrations that travel through Earth carrying the energy released during an earthquake |
| pressure | the force exerted on a surface divided by the area over which the force is exerted |
| the three layers of the earth | the crust, mantle, and core |
| crust | the layer of rock that forms Earth's outer surface |
| basalt | a dark, dense igneous rock with a fine texture, found in oceanic crust |
| granite | a usually light colored igneous rock that is found in continental crust |
| mantle | the layer of hot, solid material between the Earth's crust and core |
| lithosphere | a rigid layer made up of the uppermost part of the mantle and the crust |
| asthenosphere | the soft layer of the mantle on which the lithosphere floats |
| outer core | a layer of molten iron and nickel that surrounds the inner core of Earth |
| inner core | a dense sphere of solid iron and nickel at the center of the earth |
| radiation | the transfer of energy through space |
| conduction | the transfer of heat of heat within a material or between materials that are touching |
| convection | the transfer of heat by movement of a fluid |
| density | the amount of mass in a given space; mass per unit volume |
| convection current | the movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another |
