How Do Tsunamis Start?

Tsunamis start from any large, sudden displacement of water. This includes earthquakes, landslides, volcanic eruptions and the breaking of coastal ice, such as in glaciers or icebergs. Rarely, a large body from space, such as a meteorite, can cause a tsunami.

Most often, tsunamis start from underwater earthquakes that happen along tectonic plate lines. Earthquakes that shift one side up or down significantly cause a sudden change in where that volume of water is located, which in turn creates a large wave. The wave then continues until it reaches land. Other underwater causes include underwater landslides or landshifts, which are often caused by earthquakes. These underwater causes are usually the most dangerous.