A tsunami is a series of ocean waves usually caused by earthquakes or underwater landslides. Tsunami waves may travel up to 600 miles an hour in open water. As they enter shallow water near land, they get higher and can cause great loss of life and property damage. Experts believe a tsunami could hit some areas of the Pacific coast with as little as five minutes warning. In low-lying areas without a tsunami warning system, an earthquake may be the only sign a tsunami is approaching. Contact your local emergency management office to find out if there is a tsunami warning system in your area.