| A | B |
|---|
| earthquake | shaking & trembling that results from the sudden movement of part of the Earth's crust |
| tsunamis | giant sea waves often produced by earthquakes |
| focus | point beneath the Earth's surface where the rocks break and move |
| epicenter | the point directly above the focus on the Earth's surface |
| seismic waves | earthquake waves |
| primary waves | seismic waves that travel the fastest |
| secondary waves | seismic waves that travel slower than the other type of wave |
| surface waves | the slowest-moving seismic waves |
| seismograph | an instrument that detects and measures seismic waves |
| seismologists | scientists who study earthquakes |
| seisomogram | record of waves |
| Richter scale | used to rate the strength of an earthquake |
| magma | hot liquid rock deep within the Earth |
| lava | hot liquid rock that reaches the Earth's surface |
| volcano | place in Earth's surface through which magma and other materials reach the surface |
| vent | opening from which lava erups |
| volcanic dust | smallest particles of rock blown into the air during volcanic eruptions |
| volcanic ash | rock particles more than .25 mm but less than 5 mm in diameter |
| volcanic bombs | larger rock particles that are a few centimeters to several meters in diameter |
| cinder cones | volcanoes made mostly of cinders and other rock particles that have been blown into the air |
| shield volcanoes | volcanoes composed of quiet lava flows |
| composite volcanoes | volcanoes built up of alternating layers of rock particles and lava |
| crater | funnel-shaped pit or depression at the top of a volcanic cone |
| caldera | formed if a crater becomes very large as a result of the collapse of its walls |
| Ring of Fire | a major earthquake and volcano zone that extends nearly all the way around the edge of the Pacific Ocean |
