What causes tsunami?
The latest tsunami in Japan is just one of the greatest tsunami ever happened in the whole world. These tsunamis never happened in a sudden. But what really causes tsunamis?
The number one cause of tsunamis is underwater earthquakes. They can also be caused by other sudden movements on the ocean floor, such as volcanic eruptions, underwater landslides, and large meteorite impacts. This sudden movement in the ocean floor displaces the water above it forming harbor waves or a tsunami itself. Tsunamis occur when water is displaced in some way, but they also have to form and reach the shore. Once a large amount of water is displaced, a wave forms. Part of the wave travels out to the ocean, but the other part heads toward land. It is often hard to notice tsunamis when they are farther out in the ocean because they are not very high in deep water; they reach larger heights in shallower waters. Even far out from shore, tsunamis are hundreds of kilometers in length. Tsunamis also travel faster in the sea but their speed reduces to when they reach shallow waters. A large tsunami can have multiple waves that hit shore hours apart .
Most tsunamis occur in the Pacific Ocean near Asia because of the position of the tectonic plates and the topography of the ocean floor. It is believed that the tectonic plates bump at each other causing tectonic earthquakes.
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