What is a Tsunami?
Tsunamis are large, often destructive sea waves, usually caused by earthquakes below the ocean, volcanic eruptions, or underwater landslides. To the Japanese phrase meaning “harbor wave,” tsunamis can devastate the infrastructure of coastal cities and can be very deadly. Though tsunamis are often misleadingly called tidal waves for their resemblance to a rising tide, tsunamis are unrelated to the tides. Still, they are caused by movements in the earth, usually far below the ocean. Landslides in the ocean have caused some of the most giant tsunamis in history, known as megatsunamis.
Tsunami waves have a much longer wavelength than regular waves, reaching hundreds of kilometers in length. In contrast, the height (amplitude) of the waves remains just above average, slowly building until it reaches the shallow waters along the coast. Before the giant wave hits the coast, the water drastically recedes as a drawback. The giant wall of water then travels at high speeds toward land, crashing and destroying everything in its path. The tsunami then recedes to the ocean, pulling with it much of the debris of the structures it has destroyed.
The slow build-up of the waves is one factor that makes tsunamis challenging to predict. Earthquakes, considered the leading cause of tsunamis, are also not absolute predictors of a tsunami because some large earthquakes do not result in a tsunami, and some small earthquakes do. Most tsunamis occur around the Pacific Ocean because of the high level of seismic activity in this Pacific Ring of Fire.
Worst Tsunamis In History
March 11, 2011, Japan – After the 9.0 magnitude earthquake in Japan, the country was hit with tsunamis 33 feet high to as tall as 97 feet tall, killing about 20,000 people.
December 26, 2004, Indonesia – The most destructive tsunami in recorded history, the Asian tsunami of 2004 devastated eleven countries, killing 230,000 people around the Indian Ocean and reaching about 98 feet in height.
July 9, 1958, Lituya Bay, Alaska – The Lituya Bay megatsunami is the tallest recorded tsunami in history, reaching heights of 1,720 feet.
August 26, 1883, Indonesia – The eruption and collapse of the Krakatoa volcano in Indonesia caused a series of tsunamis, reaching 135 feet and killing over 36,000 people.
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