| Term | Definition |
| Surface Wave | seismic wave that moves rock particles in a
backward, rolling motion and also in a side-to-side,
swaying motion |
| Primary Wave | seismic wave that causes rock particles to
move back and forth in the same direction that the wave
is traveling |
| Lithosphere | crust plus the rigid, upper mantle |
| Seismic Wave | wave generated by an earthquake |
| Focus | point below Earth’s surface where energy is first released in the form of seismic waves |
| Secondary Wave | seismic wave that moves rock particles at
right angles to the direction of the wave |
| Mercalli | scale used to measure the strength of an earthquake based upon damage. |
| Earthquake | vibrations, or shaking, produced when rocks
break along a fault |
| Epicenter | point on Earth’s surface directly above the
earthquake focus |
| Seismograph | instrument used to register seismic waves
and record the time that each arrived |
| Richter Scale | scale that compares the magnitude of an earthquake recorded by seismographs |
| Core | solid inner most part of Earth's structure, made of solid iron-nickel |
| Crust | rigid, rocky outer surface of Earth |
| Mantle | rocky layer located under the crust. Composed of silicon, oxygen, magnesium, and calcium |
| Mohorovicic Discontinuity | separates the crust and the upper mantle |
| Asthenosphere | the part of upper mantle that is flowing |
