Earthquake: n. a vibration or movement of a part of the Earth's surface, due to the faulting of rocks, to volcanic forces, etc.

An earthquake is a shaking of the ground caused by the sudden breaking and shifting of the earth’s rocky outer shell. Shifting tectonic plates can cause earthquakes. An earthquake can releases up to ten thousand times more energy than the first atomic bomb. An earthquake or some type of tremor occurs every thirty seconds. Many last a few seconds, and some occasionally last several minutes.

       Earthquakes can also lead to other natural disasters. For example, an earthquake can cause an avalanche, tsunami/tidal wave, volcanic eruption, and floods. They can also destroy towns, cities, and lives.

       Seismographs or seismometers measure earthquakes. Tremors felt by the earthquakes move a needle with a pin on the end. The pin moves back and forth. The wider the line gets, the worse the earthquake is. Readings from stations widely spaced out are compared to pinpoint the exact origin of the earthquake. This has become an effective early warning system to help predict tsunamis that will occur in the Pacific Ocean.

Earthquakes in the United States occur mostly in California, because of the San Andreas Fault. The fault forms a “gash” across the California desert.