| A | B |
|---|
| SEISMIC WAVE | A vibration that travels through Earth carrying the energy released during an earthquake. |
| PRESSURE | The amount of force pushing on a surface or area. |
| CRUST | The layer of rock that forms Earth's outer surface. |
| MANTLE | The layer of hot, solid material between Earth's crust and core. |
| LITHOSPHERE | A rigid layer made up of the uppermost part of the mantle and the crust. One of four spheres into which scientists divide Earth. |
| 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 in the center of Earth. |
| HEAT TRANSFER | The movement of energy from a warmer object to a cooler object. |
| RADIATION | The direct transfer of energy through empty space by electromagnetic waves. |
| TRANSFORM BOUNDARY | The transfer of heat from one substance to another by direct contact of particles of matter. |
| 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. |
| PANGAEA | The name of the single landmass that broke apart 225 million years ago and gave rise to today's continents. |
| CONTINENTAL DRIFT | The hypothesis that the continents slowly move across Earth's surface. |
| FOSSIL | The preserved remains or traces of living things. |
| MID-OCEAN RIDGE | The undersea mountain chain where new ocean floor is produced; a divergent plate boundary. |
| SONAR | A system that determines the distance of an object under water by recording echoes of sound waves; gets its name from SOund NAvigation and Ranging. |
| SEA-FLOOR SPREADING | The process by which molten material adds new oceanic crust to the ocean floor. |
| DEEP-OCEAN TRENCH | A deep valley along the ocean floor through 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. |
| PLATE | A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust. |
| SCIENTIFIC THEORY | A well-tested concept that explains a wide range of observations. |
| PLATE TECTONICS | The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle. |
| FAULT | A break or crack in Earth's lithosphere along which the rocks move. |
| TRANSFORM BOUNDARY | A plate boundary where two plates move past each other in opposite direction. |
| DIVERGENT BOUNDARY | A plate boundary where two plates move away from each other. |
| RIFT VALLEY | A deep valley that forms where two plates move apart. |
| CONVERGENT BOUNDARY | A plate boundary where two plates move toward each other. |
