What is a Tsunami?

What is a Tsunami? Tsunamis (pronounced soo-ná-mees), also known as seismic sea waves (mistakenly called “tidal waves”), are a series of enormous tsunami waves created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite.

A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet or more.



Where do Tsunamis occur?

From the area where the tsunami originates, waves travel outward in all directions. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger than the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.

All tsunamis are potentially dangerous, even though they may not damage every coastline they strike. A tsunami can strike anywhere along most of the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska, and Hawaii.

Earthquake-induced movement of the ocean floor most often generates tsunamis. If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued. Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline.

Drowning is the most common cause of death associated with a tsunami. Tsunami waves and the receding water are very destructive to structures in the run-up zone. Other hazards include flooding, contamination of drinking water, and fires from gas lines or ruptured tanks.

Learn about floods that can result from tsunamis

Remembering one of the biggest Tsunamis

The 2004 Indian Ocean Earthquake was an underwater earthquake that was centered off the coast of Sumatra, Indonesia. The earthquake created a disastrous Tsunami that destroyed the coastlines of eleven countries. The Tsunami killed over 225,000 people and was one of the most deadliest Tsunamis in the history of natural disasters.

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