Commonly (and incorrectly) known as a tidal wave, a Tsunami involves long period ocean waves generated by earthquakes and other geological or tectonic disturbances below sea level. Tsunamis can travel at speeds of up to 500 knots through the open ocean. While they may be of low height in deep water, the shoaling process as they approach land can increase the tsunami to heights of over 35 feet or more in bays or other restricted areas.