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A tsunami (from Japanese 津波 meaning wave in port) (the term tidal wave is generally synonymous, but not in scientific usage, as tsunamis are not related to tides) is one or a series of waves that occur after an earthquake, seaquake, volcanic activity, slumps, 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 can increase to a height of 30 metres and more as they approach the coastline. Tsunamis can cause severe destruction on coasts and islands.

Many cities around the Pacific, notably in Japan but also in Hawaii, 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.

No such system can protect against a sudden tsunami. A devastating tsunami occurred off the coast of Hokkaido in Japan as a result of an earthquake on July 12July 12 is the 193rd day (194th in leap years) of the year in the Gregorian Calendar, with 172 days remaining. Events 1690 William of Orange's army wins the Battle of the Boyne as reckoned under Gregorian calendar. 1759 British cannon start firing on Fren, 19931993 is a common year starting on Friday and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003 Events January January 1 Czechoslovakia divides. Establishment of independent Slovakia and Czech Republic.. As a result, 202 people on the small island of Okushiri lost their lives, and hundreds more were missing or injured.

Evidence shows that megatsunamiA megatsunami is a large form of tsunami that is usually caused by a truly gigantic landslide, such as a collapsing island, into a vast body of water like an ocean or sea. The defining characteristic for a megatsunami is that it is more than 100 meters his, which are caused by significant chunks of an island collapsing into the ocean, are also possible.

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