Updated February 21, 2017 | Factmonster Staff
Source: The Federal Emergency Management Agency (FEMA)

A tsunami (pronounced soo-nahm-ee) is a series of huge waves that happen after an undersea disturbance, such as an earthquake or volcano eruption. Tsunami is from the Japanese word for “harbor wave.”

The waves travel in all directions from the area of disturbance, much like the ripples that happen after throwing a rock. The waves may travel in the open sea as fast as 450 miles per hour. As the big waves approach shallow waters along the coast they grow to a great height and smash into the shore. They can be as high as 100 feet. They can cause a lot of destruction on the shore. They are sometimes mistakenly called “tidal waves,” but tsunami have nothing to do with the tides.

Hawaii is the state at greatest risk for a tsunami. They get about one a year, with a damaging tsunami happening about every seven years. Alaska is also at high risk. California, Oregon and Washington experience a damaging tsunami about every 18 years.

Did You Know?

On Dec. 26, 2004, a 9.0 magnitude earthquake—the largest earthquake in 40 years—occurred off the west coast of the Indonesian island of Sumatra. The earthquake triggered a tsunami in the Indian Ocean, the deadliest in world history. More than 226,000 died and twelve countries felt the devastation. Hardest hit were Indonesia (particularly the province of Aceh), Sri Lanka, India, Thailand, and the Maldives. Millions were left homeless by the disaster.

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