Wednesday, May 18, 2016


A Tsunami is a series of ocn waves that sends surges of water, sometimes rching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widesprd destruction when they crash ashore.

These awe-inspiring waves are typically caused by large, unders rthquakes at tectonic plate boundaries. When the ocn floor at a plate boundary rises or falls suddenly it displaces the water above it and launches the rolling waves that will become a tsunami.

Most tsunamis, about 80 percent, happen within the Pacific Ocn’s “Ring of Fire,” a geologically active ar where tectonic shifts make volcanoes and rthquakes common.

Tsunamis may also be caused by underwater landslides or volcanic eruptions. They may even be launched, as they frequently were in rth’s ancient past, by the impact of a large meteorite plunging into an ocn.

Tsunamis race across the s at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace they can cross the entire expanse of the Pacific Ocn in less than a day. And their long wavelengths mn they lose very little energy along the way.

In deep ocn, tsunami waves may appr only a foot or so 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 precipitously.

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

A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves rch shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable loions.

Some tsunamis do not appr on shore as massive brking waves but instd resemble a quickly surging tide that inundates coastal ars.

The best defense against any tsunami is rly warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations hdquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at s. Similar systems are proposed to protect coastal ars worldwide.

Info: National Geographic

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