| A | B |
|---|
| stress | A force that acts on rock to change its shape or volume. |
| tension | Stress that stretches rock so that it becomes thinner in the middle. |
| compression | Stress that squeezes rock until it folds or breaks. |
| shearing | Stress that pushes masses of rock in opposite directions, in a sideways movement. |
| normal fault | A type of fault where the hanging wall slides downward; caused by tension in the crust. |
| reverse fault | A type of fault where the hanging wall slides upward; caused by compression in the crust. |
| strike-slip fault | A type of fault in which rocks on either side move past each other sideways with little up or down motion. |
| plateau | A large landform that has high elevation and a more or less level surface. |
| earthquake | The shaking that results from the movement of rock beneath Earth’s surface. |
| focus | The point beneath Earth’s surface where rock first breaks under stress and causes an earthquake. |
| epicenter | The point on Earth’s surface directly above an earthquake’s focus. |
| P wave | A type of seismic wave that compresses and expands the ground. |
| S wave | A type of seismic wave in which the shaking is perpendicular to the direction of the wave. |
| surface wave | A type of seismic wave that forms when P waves and S waves reach Earth’s surface. |
| seismograph | A device that records ground movements caused by seismic waves as they move through Earth. |
| Modified Mercalli scale | A scale that rates the amount of shaking from an earthquake. |
| magnitude | The measurement of an earthquake’s strength based on seismic waves and movement along faults. |
| Richter scale | A scale that rates an earthquake’s magnitude based on the size of its seismic waves. |
| moment magnitude scale | A scale that rates earthquakes by estimating the total energy released by an earthquake. |
| seismogram | The record of an earthquake’s seismic waves produced by a seismograph. |
