The essential characteristic of a tsunami is therefore a radical displacement of water. This displacement of water can be caused by various events, such as, earthquakes, ocean landslides, volcanic eruptions and large meteorite impacts as well as large explosions. The effect of a Tsunami depends on the severity and size of the initial causative factors and the original displacement of water mass. The effects can range from a minor and hardly noticeable ocean surge to complete devastation. Tsunamis are often not even noticed out at sea. This is due to another tsunami characteristic, namely that they "have a much smaller amplitude offshore, and a very long wavelength -often hundreds of kilometers long," (Wikipedia: Tsunami) A tsunami can reach speeds of

The reason why so many tsunamis are generated in the Pacific Ocean is mainly due to the fact that the Pacific is surrounded by plate boundaries and most of these events are the result of earthquakes which occur along the subduction boundaries.

The sense of displacement of the ocean floor is an important factor in wave generation. Tsunamis are formed when there is a vertical displacement of the ocean floor. Therefore, it is not the case that even large earthquakes will necessarily produce large tsunami. For example, the 1906 earthquake near San Francisco California had a Richter Magnitude of about 7.1, yet no tsunami was generated as a result of this event " because the motion on the fault was strike-slip motion with no vertical displacement. " ( Nelson A.)

Most of the damage caused by a tsunami is a result of the destructive power of the wave and water. There are secondary effects from the debris that is carried in the powerful water surge. Erosion from the water can also undermine the foundations of buildings and cause extensive damage and danger to those in and around them.

Another albeit less common cause of tsunami occurrences is volcanic eruptions. Volcanoes that are situated coastal areas, such as Japan, can create tsunamis. The massive explosion can displace water with the same effect as a tsunami created by an earthquake. "Explosive eruptions can rapidly emplace pyroclastic flows into the water, landslides and debris avalanches produced by

In the last 200 years tsunamis have affected the parts of the United States.

Known as Rayleigh waves (for Lord Rayleigh, who predicted their existence in 1885), these vibrations move through the ground like waves move on the surface of the ocean. They travel at 10 times the speed of sound. The waves would have reached Sri Lanka hours before the water hit." (Kenneally)

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Approximate Word count = 2299
Approximate Pages = 9 (250 words per page double spaced)