Tsunami is an unusually large sea wave produced by a seaquake or undersea volcanic eruption. Some meteorological conditions, such as deep depressions that cause tropical cyclones, can generate a storm surge, called a meteotsunami, which can raise tides several meters above normal levels. The displacement comes from low atmospheric pressure within the centre of the depression. As these storm surges reach shore, they may resemble (though are not) tsunamis, inundating vast areas of land.
Tsunami (pronounced soo-NAH-mee) is a Japanese word. Tsunamis are fairly common in Japan and many thousands of Japanese have been killed by them in recent centuries. Tsunami waves can be very long (as much as 60 miles, or 100 kilometers) and be as far as one hour apart. They are able to cross entire oceans without great loss of energy. An earthquake generates a tsunami if it is of sufficient force and there is violent movement of the earth causing substantial and sudden displacement of a massive amount of water.
The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Here are some measures should be taken to avoid trouble if caught in a tsunami:
- When in coastal areas, stay alert for tsunami warnings.
- Plan an evacuation route that leads to higher ground.
- Never stay near shore to watch a tsunami come in.
- Do not return to an affected coastal area until authorities say it is safe.