Tsunamis are large seismic sea waves that can cause major destruction in coastal regions. A tsunami (Japanese for "wave in bay") is caused by underwater seismic activity, such as an earthquake.

While tsunamis are commonly called "tidal waves," this is an erroneous term; these potentially catastrophic waves have nothing to do with the tides. Tides are the up and down movements of the sea surface at the shore, caused by the gravitational attraction of the moon and sun on our marine waters. Tsunamis are caused by the movements of Earth's crustal plates. Tides rarely cause major damage unless they are associated with a storm, while tsunamis can cause major loss of life and property.

It has been known for several hundred years that tsunamis are caused by seismic movements of the ocean floor. This occurs most commonly during submarine earthquakes, underwater landslides, and perhaps volcanoes, all of which...