Tsunami
Tsunami (津波 Japanese big wave in port), often incorrectly called a tidal wave, is a series of massive waves that occur after an earthquake, seaquake, volcanic activity, slumpss, or meteorite impacts in or near the sea. The energy of a tsunami is constant, a function of its height and speed. Thus, as the wave approaches land, its height increases while its speed decreases. The waves travel at high speed, more or less unnoticed where crossing deep water, but increasing to a height of 30 metres and more. Tsunamis can cause severe destruction on coasts and islands.
Many cities around the Pacific, notably in Japan but also in Hawai'i, have warning systems and evacuation procedures in the event of a serious tsunami. A tsunami would be predicted by various seismologic institutes around the world and the progress monitored by satellites.
Evidence shows that megatsunamis, which are caused by significant chunks of an island collapsing into the ocean, are also possible.
When the Japanese is romanized, the word is spelled Tsunami in Hepburn, and Tunami in Nippon-shiki, Kunrei, and JSL.