What is a Tsunami?

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Scientific Explanation of a Tsunami

Tsunami is a Japanese word that translates into English as “harbor wave”. However, a tsunami is not just one wave, but is a series of waves, sometimes referred to as a “wave train”.

A tsunami is formed in a body of water, such as an ocean or sea, by an event that causes enough of a disturbance so that a vertical displacement of the water column occurs.

  • Tsunami:  A tsunami is not just one wave, but a series of waves.
  • Earth Geography: Learn about the earth’s structure, which explains why many natural hazards occur.
  • Public Outreach: Resources concerning the ocean and its conservation.
  • Weather: Weather resources from a variety of different sites concerned with a number of different topics including tsunamis.
  • Goddard: Environmental resources, including a number on tsunamis and other disasters.

Causes of a Tsunami

Tsunamis can be caused by a number of natural phenomena including earthquakes, volcanic eruptions, or landslides. Even an explosion, whether natural or man-made, can cause a tsunami. It is also possible for space debris, such as a meteorite or an asteroid, to cause a tsunami.

An earthquake-induced tsunami is caused by the shifting of the sea floor. A tectonic earthquake; that is, one that is caused by changes in the earth’s crust, but happening under the sea, causes the water above the area where the movement occurred to be displaced. As it attempts to get back to normal, in accordance with gravitational pull, the sea floor either raises or lowers, which can cause the tsunami.

Subduction earthquakes can also cause tsunamis. These occur when shifting happens over fault lines. For example, along the edges of the Pacific Ocean, oceanic plates, which are denser than continental plates, slip under the continental plates. This process is known as subduction, and can be particularly known for causing a tsunami.

Undersea volcanoes can also cause tsunamis. These volcanoes erupt much as those on land do. When they do, they cause a displacement of the water, which results in tsunami waves being formed.

Earthquakes on land or under water can also cause undersea landslides. When the debris that is loosened by the landslide moves the water, a tsunami can be formed by the water trying to reclaim the space taken over by the landslide debris, or by being pushed to another area.

Although very rare, meteorites or asteroids impacting with the earth could cause tsunamis. The asteroid or meteorite hitting the ocean water would cause a ripple effect, just as if a pebble were thrown into a pond, lake, or river.

  • Causes: Earthquakes, volcanic eruptions, landslides, explosions, and (rarely) space debris can all cause a tsunami to occur.
  • Earthquakes: Resources about earthquakes, the damage they can cause and the tsunamis they create.
  • Subduction earthquake: This type of earthquake can also cause tsunamis, and in fact is known for its propensity to do so.
  • Undersea landslides: These can occur when earthquakes on land or underwater loosen debris, which then falls into the water.
  • Meteorites or asteroids: Although rare, these could cause a tsunami. The effect would be similar to a pebble being thrown into a pond.

Effects of a Tsunami

A tsunami isn’t a rainstorm and you should bring your umbrella inside if you expect one to hit. When a tsunami reaches land, the effects can be disastrous. Coastlines are ravaged or even destroyed. People lose their lives, either by drowning, which causes the majority of tsunami deaths or by being injured. Injuries can occur by violent contact with debris that has been washed ashore by the tsunami or that has been loosened or uprooted and is floating in the water.

Tsunami waves act just like regular waves, hitting land and then receding. However, upon a tsunami wave receding, a strong suction action is caused. This action can result in debris being carried or pulled into populated areas, causing not only injury but destruction to existing property and landscape.

Oftentimes, the debris being tossed and moved about destroys homes and buildings. This causes people in the affected area to become homeless. As a result, they are exposed to the climate, insects, and other environmental problems.

Flooding is also a major effect of a tsunami. The flood waters can destroy or contaminate water and food supplies, making them unsuitable for human consumption.

  • Tsunami Questions: Now that you know all about tsunamis, test your cognition. See if you can answer ten important questions.
  • Surviving a Tsunami —Lessons from Chile, Hawaii, and Japan. This is a report published by the US Geologic Survey, and printed as a circular. It gives survivors’ descriptions of the effects of the tsunami which occurred as a result of a 9.5 earthquake in Chili on May 22, 1960.
  • The Orphan Tsunami of 1700— This tsunami was thought to be caused by parent earthquake that occurred in the United States. Several cities in Japan were affected.
  • Survivor Pictures: These are photographs from Pacific Tsunami Museum, showing survivors of the April 1, 1946 Pacific tsunami. 
  • Emergency Preparedness and Response: Information from the Center for Disease Control gives instructions and advice on how to prepare for a tsunami and how disaster personnel are to respond when one occurs.
  • Results from Aid Efforts: As a result of the aid given to tsunami survivors of Indian Ocean tsunami in 2004, improvements were made to rural areas of Aceh, Indonesia. These improvements actually raised the residents’ quality of life.
  • Extreme Weather: A project to do with students to teach them about weather and weather forecasts. Is there a tsunami coming your way?