Tsunami

The devastating tsunami in the Indian Ocean of December 26, 2004, alerted the world to one of the most terrifying natural phenomena on Earth. Few will forget the scenes of carnage and destruction wrought by the floodwaters as they swept across coastal areas. In fact, tsunamis have been known about for generations. The word tsunami is derived from the Japanese word meaning “harbor wave.” Tsunamis are frequently described as tidal waves; however, this view is erroneous, since they have nothing to do with tides. Tsunamis are generated by offshore earthquakes, submarine slides, and, occasionally, subaerial landslides that enter water bodies. Asteroid impact is an additional but much rarer mechanism. With the exception of asteroid impacts, the displacement of mass, whether through submarine sediment slides, the collapse of a volcanic edifice, or an earthquake that induces faulting of the seabed, leads to a large-scale displacement of water. Although most tsunamis are phenomena associated with the open ocean, some tsunamis can be generated within lakes and/or fjords due to rockslide failures. An attempt is made here to explain the processes of tsunami generation and propagation as well as what happens when tsunamis strike coastlines. A description is also given of how societies have responded to the perception of tsunami risk.