A tsunami (image: Lukaves).A tsunami is a series of sea waves that may be triggered by earthquakes, landslides, and volcanoes. These natural hazards displace a large amount of water. This displacement creates a large wave that can affect coastal areas.

Image: A tsunami triggered by an underseas earthquake (© Lukaves).

What Causes a Tsunami?

Tsunamis can be triggered by the following events:

Earthquake:  a large earthquake can displace a large amount of water. Seismic sea waves from an earthquake can travel thousands of miles. In 2004, an earthquake off the coast of Indonesia generated a tsunami that affected coasts from Asia to Africa. Over 290,000 lives were lost in that tsunami. The 2011 Tohuku earthquake generated a tsunami that caused billions of dollars of damage in Japan. The tsunami was captured on video by many people.

Landslides and Volcanoes: seismic sea waves can also be triggered by landslides. A 1958 landslide in Alaska created a wave that was over 500 meters high. Volcanic eruptions may also trigger tsunamis.

Meteors: in the earth’s past, large meteors have struck the earth. These may also trigger a tsunami.

What Makes a Tsunami Dangerous?

A seismic sea wave is barely noticeable in the deep ocean. However, it can move at speeds up to 800 kilometers an hour. As the wave approaches land it begins to slow down and increase in height. Sometimes in coastal areas, the ocean will recede and expose the sea bed. When a drawback of water like this occurs, the tsunami will arrive within a few minutes.

As the water moves inland it begins to pick up debris. This can include cars, boats, trees, homes which can add to the destructive nature of the wave.

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NOAA Tsunami Website, NOAA.