A tsunami is a wave in the ocean caused by earthquakes or volcanic eruptions. A tsunami is a very long wave. It can be hundreds of kilometers long. It is a chain of fast moving waves caused by fast changes in the ocean. Usually, a tsunami starts suddenly. It will begin as normal waves and change to a very big wave very quickly. The waves travel at a great speed across an ocean with little energy loss. They can remove sand from beaches, destroy trees, damage houses and even destroy whole towns.
The water will draw back from the coast half of the period of the wave before it gets to the coast. If the slope of the coast is shallow, the water may pull back for many hundreds of metres. People who do not know of the danger will often remain at the shore. Tsunamis can not be prevented, but there are ways to help stop people from dying from a tsunami. Some regions with a high risk of tsunamis may use warning systems to warn the general population before the big waves reach the land. Because an earthquake that caused the tsunami can be felt before the wave gets to the shore, people can be warned to go somewhere safe.
The deadliest tsunami recorded was on December 26, 2004. It was caused by an earthquake. The earthquake was said to had magnitude 9.3 on the Richter scale. It was centered in the ocean near the coast of Sumatra, Indonesia. Over 225,000 people died from this disaster. The giant wave moved very quickly. Hundreds of thousands of people in Indonesia, Sri Lanka, Thailand, India, Somalia, and other nations, were killed or injured by it.
Tsunamis are often called tidal waves. This is misleading, because tsunamis are not related to tides.
For More Information: Tsunami K-12 Experiments & Background Information
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)