A tsunami is a series of large waves that move rapidly across the water. Tsunamis are caused by landslides, volcanic eruptions and earthquakes. These waves can move across the open ocean at speeds of up to 500 miles an hour.
A strong earthquake can trigger a tsunami. The wavelength of a tsunami is long, and sometimes the distance from the crest of one wave to that of another may exceed 300 miles. This long wavelength differentiates tsunamis from regular ocean waves. In deep water, tsunamis travel fast. As the tsunami nears shore, it slows down and builds up into giant waves that sometimes rise over 100 feet in height. Tsunamis often occur along the Ring of Fire, an area rich in volcanic and seismic activity.