Japan8217;s killer tsunamis

Earthquakes,volcanic eruptions,underwater explosions even from nuclear detonation meteorite impacts and other disturbances can cause tsunamis.

Scientists continue to study the nature of these seismic sea waves as they are yet to be completely decoded.

Tsunamis were called tidal waves but that definition is now archaic because tsunami have nothing to do with tides. Tsunami produces waves of water that move inland and the inland movement of water is much greater and lasts for a longer period,giving the impression of an incredibly high tide.

Tsunamis race across the sea at up to 500 miles 805 kilometres an hour,the same pace of a jet plane. At that pace they can cross the entire expanse of the Pacific Ocean in less than a day.

In deep ocean,tsunami waves may appear only a foot high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do,which causes them to rise very high.

A tsunamis trough,the low point beneath the wave,often reaches shore first. When it does,it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami,because the waves crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives.