An earthquake (also known as a quake, or tremor) is a violent movement of the rocks in the Earth's crust. Earthquakes are usually quite brief, but may repeat over a long period of time. They are the result of a sudden release of energy in theEarth's crust. This creates seismic waves, waves of energy that travel through the Earth.
There are large earthquakes and small earthquakes. Big earthquakes can take down buildings and cause death and injury.