A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, usually an ocean, but can occur in large lakes. Tsunamis are a frequent occurrence in Japan; approximately 195 events have been recorded. Owing to the immense volumes of water and the high energy involved, tsunamis can devastate coastal regions.
Where the ocean is deep, tsunamis can travel unnoticed on the surface at speeds up to 500 miles an hour (800 kilometers an hour), crossing an ocean in a day or less. Scientists are able to calculate arrival time of a tsunami in different parts of the world based on knowledge of water depths, distances, and when the event that generated the tsunami occurred.
Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides and other mass movements, meteorite ocean impacts or similar impact events, and other disturbances above or below water all have the potential to generate a tsunami.
Signs of a Tsunami can include water Drawback, slight rumble can be heard, and the ground might shake. As the waves approach shore, the water near the shore will recede dramatically, leaving fish, seaweed coral and such like. (following a 'sucking sound'. A clear rumble should be heard. The fast moving waves will start to get higher as the seafloor gets shallower near the coastline. This forms a 20m wall of waves (a tsunami) and the waves will crash onto shore and rush inland. Sometimes, warnings are given to the country and surrounding countries.
