| A | B |
|---|
| Earthquake | The vibrations caused by the rupture and sudden movement of rocks along a break or a crack in Earth’s crust |
| Fault | A crack or a fracture in Earth’s lithosphere along which movement occurs |
| Seismic wave | Energy generated by an earthquake that travels as vibrations on and in Earth |
| Focus | In an earthquake, the location below Earth’s surface where rocks first move along a fault releasing energy in the form of seismic waves |
| Epicenter | The location on Earth’s surface directly above an earthquake’s focus |
| Primary wave | A seismic wave that causes particles in the ground to move in a push-pull motion in the same direction that the wave travels |
| Secondary wave | A seismic wave that causes particles in the ground to move at right angles relative to the direction the wave travels |
| Surface wave | A seismic wave that causes particles in the ground to move up and down in a rolling motion |
| Seismometer | An instrument used to measure and record ground motion that can be used to determine the distance seismic waves travel |
| Volcano | A vent in Earth’s crust through which molten rock flows |
| Hot spot | A location where volcanoes form far from plate boundaries |
| Shield volcano | A large volcano with gentle slopes of basaltic lavas, common along divergent plate boundaries and oceanic hot spots |
| Composite volcano | A large, steep-sided volcano that results from explosive eruptions of andesitic and rhyolitic lavas along convergent plate boundaries |
| Cinder cone | A small, steep-sided volcano that erupts gas-rich, basaltic lava |
| Caldera | A large depression formed when a volcano’s summit collapses in on the empty magma chamber after an eruption |
| Viscosity | A measurement of a liquid’s resistance to flow |
