Tsunami is a gigantic wave produced by a sudden change in the ocean floor as a result of earthquakes, underwater landslides, and underground volcanic eruptions. These sudden changes can happen as far away as Alaska, Japan, or South America. Violent ocean changes even in Hawaii can cause locally-generated tsunamis. A tsunami is a series of waves 10-30 minutes apart and several miles can separate them. The first wave usually is not the largest. But the later waves can form a deadly wall of water that rises more then 100 feet high as it approaches a harbor. The word "tsunami" means "harbor wave" in Japanese. In Japan, earthquakes cause these large harbor waves, leaving a lot of destruction. Now tsunamis refers to a series of waves traveling the ocean with really long wave lengths. A tsunamis is often referred to as a "tidal wave." That is not correct. True "tidal waves" are caused by the gravitational attraction of the sun and moon. The sun and moon are not the cause of a tsunami so they have no connection. Tides often have a high point and a low point in a 24 hour time span. These are real tidal waves. Most tsunamis have been 10 feet or more. There has even been a tsunami higher then 50 feet. All low areas can be struck by a tsunami. The heights of the tsunamis change and that is called runnups. Runnups are measured by the sea level. One sign of a tsunami coming is when the water disappears, exposing the ocean floor and fish. Another clue is if you see a huge gigantic wave coming at the island.

 

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