
Tsunamis are triggered by disturbances on the ocean floor that displace water and upset the equilibrium of the surrounding ocean. Undersea earthquakes, landslides, and erupting volcanoes are the main causes. In deep water, the height of a tsunami wave may be less than 4 feet and hardly noticeable on the surface where normal swells are that large or larger, but the wave length, or the trough between waves in a tsunami train, can be 50 miles or more. Once a tsunami is propagated, the long wave travels at 500 to 600 miles per hour. As the wave nears land and the water shallows, the leading edge slows down and the trailing wave closes the gap and compresses the water into a wave that can build to a height of 100 feet or more as it sweeps ashore. The destructive power of a large tsunami hitting the shoreline is hard to imagine. A tsunami is usually made up of more than one wave. A train of two, three, or four waves can strike land at intervals of 10 to 30 minutes or longer. The first wave is usually not the largest. The second or third wave is often the biggest and most destructive. Very little is left standing after a large tsunami sweeps ashore. The wave’s power smashes buildings, uproots trees, and sucks everything back out to sea when it recedes. The scene is one of complete devastation. If you live near the ocean, take tsunami warnings seriously. Head inland as directed by local authorities. Do not go to the beach to see what a tsunami looks like. By the time you find out, it will be too late.


