<P> A tsunami (from Japanese: 津波, "harbour wave"; English pronunciation: / tsuːˈnɑːmi / tsoo - NAH - mee) or tidal wave, also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake . Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami . Unlike normal ocean waves which are generated by wind, or tides which are generated by the gravitational pull of the Moon and Sun, a tsunami is generated by the displacement of water . </P> <P> Tsunami waves do not resemble normal undersea currents or sea waves, because their wavelength is far longer . Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves, although this usage is not favoured by the scientific community because tsunamis are not tidal in nature . Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so - called "internal wave train". Wave heights of tens of metres can be generated by large events . Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean . </P>

Where does the force of a tsunami come from