Tsunamis have occurred on many occasions all around the world. Volcanic eruptions, landslides, earthquakes, and other natural disasters have caused these massive waves. A tsunami is a towering ocean wave generated by tectonic displacements such as undersea earthquakes, landslides, cosmic collisions, or volcanic eruptions. There is a common misconception that a tsunami is a tidal wave. Although the impact of a tsunami on a coastline may change depending upon the tidal level at the time when one occurs, tsunami waves are unrelated to tides. In the open, the water level may rise and fall several feet as a tsunami passes by. But as a tsunami approaches the coastline, it can form a deadly wall of water that rises more than 100 feet high. .

             The most frequent cause of tsunamis is earthquakes. A tsunami that is caused by an undersea earthquake is also called seismic sea wave. When the sea floor abruptly deforms and vertically displaces the overlying water a tsunami can be generated. Consequently, as the displaced water mass tries to return to its original position, waves are created. On July 9, 1958, the largest tsunami waves produced by a landslide occurred at Lituya Bay in Alaska. The tsunamis of Krakatoa have been the cause of over 36,000 human fatalities. Tsunami waves that have been responsible for crossing entire oceans have almost always come from submarine faulting associated with extremely large earthquakes. Tsunami-producing earthquakes usually exceed 6.5 on the Richter scale. Since 1819, about 40 tsunamis have struck the Hawaiian Islands. Most tsunamis occur in the Pacific Ocean because of the seismic activity around its perimeter.

             As the water depth decreases, the tsunami slows whereas the energy current stays almost constant despite its being reliant on both the wave speed and height. Tsunamis usually have wavelengths equal to the water depth (up to several thousand meters) at the point of origin.