What is a Tsunami

A tsunami is a series of ocean waves with very long wavelengths and wave periods. This wavelength can range from 10 to hundreds of kilometres in length and the wave periods can be up to an hour. Tsunamis are caused by large-scale disturbances of the ocean that is triggered by earthquakes, landslide, volcanic eruptions, explosions or rarely, meteorites. In the past, tsunamis have been called "tidal waves" or "seismic sea waves". Recently, scientists discourages people to call it "tidal waves" because tsunamis are unrelated to the tides. Even "seismic sea waves" is also misleading because tsunamis are not only triggered by earthquakes but also by other events stated above.

The term tsunami came from Japanese words: tsu and nami, which means harbor and wave respectively.

In deep water, tsunami waves can only be one to two feet tall and ships in the middle of the ocean will not even notice it. As the waves encounter shallow water, they slow down and the wave height increase dramatically. Tsunamis can travel at speeds of up to 600 miles per hour in deep water.

Tsunami Wave Animation

propagation of tsunami

When a tsunami happens, the first wave the hits a coastal area may not be the largest in the series. Also, one coastal community may experience no damaging wave activity, while another nearby community might experience very large, destructive waves. The flooding can extend inland by half a mile or more and cover large tracts of land with water filled with all sorts of debris.

One thing to note, is that there is no such thing as tsunami season. It can occur any day of the year and any time of the day.