The word tsunami comes from a Japanese word meaning “harbor wave.” Tsunamis are not caused by tides. Tsunamis can be generated by earthquakes, volcanic eruptions, landslides and meteorite impacts. Earthquakes of magnitude 7.0 and higher produce most tsunamis.
Tsunami waves come in a series. The distance between crests often exceeds 60 miles. They can travel at more than 500 mph. In deep water they may be only a few inches high at the surface and will pass beneath a boat undetected. When the waves approach shallow water, they slow down and build in height. A tsunami can hit shore as a huge wave hundreds of feet high. Most of the time, they arrive as a deadly, turbulent surge of whitewater.