Tsunamis

Environmental Science

Tsunamis

A tsunami (soo-NAH-mee) is a series of waves that occur in an ocean or other large body of water and that are caused by some activity that displaces big amounts of water. Tsunami is the Japanese word for "harbor wave."

Earthquakes that occur on the seafloor or in coastal areas usually cause tsunamis.

The energy generated by the earthquake is transmitted through the water. In deep oceans the energy in these seismic sea waves can travel virtually unnoticed because the wave height may be only twelve inches. When this energy reaches the shallow waters of coastlines, bays, or harbors, it forces the water into a giant wave. Some tsunamis may reach heights of 100 feet or more.

Although a relatively rare event, since 1992 tsunamis have claimed over 2,000 lives worldwide. Earthquakes in Japan, Indonesia, and Nicaragua caused the tsunamis.

Damage to cities along coastlines has been in the millions of dollars.

The phenomenon we call a tsunami is a series of waves of extremely long

wavelength and period generated in a body of water by an impulsive disturbance that

displaces the water. Although English-speaking people often refer to tsunamis as “tidal

1) waves”, they are not caused by the tides and are unrelated to them.

Tsunamis are primarily associated with earthquakes in oceanic and coastal regions.

When an earthquake occurs, the energy travels outward in all directions from the source.

This can be illustrated by throwing a pebble into a small, still pond. The pebble represents a meteorite or some other energy source, and the pond represents the ocean.

The ripples that travel out in all directions from the focus, or the point where the pebble hit the water, represent the energy that creates a sea wave. Notice how the waves become larger as they reach shore, where the water is shallower.

Detecting tsunamis is a very difficult thing to do. When a wave begins in the deep ocean waters, it may only have a height of about twelve to twenty-three inc...

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...yone enters. Administer first aid only if you know what to do.

*Stay tuned to local radio and TV stations, especially NOAA Weather Radio, for evacuation orders if a Tsunami Warning has been issued. Do NOT return to low-lying areas until the tsunami threat has passed and the "all clear" is announced.

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The map above shows the areas where tsunamis have occurred in the past five years and the number of people who consequently died.

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