Tsunamis

Tsunamis, commonly called tidal waves, are really seismic sea waves generated by earthquakes. In the open sea they travel very fast, perhaps 600 miles per hour, but have almost no effect there because of the low height and great length of the waves.

But as the waves approach land, it is a different story. The waves pile up as the ocean depth lessens; destructive surges as much as 100 feet high can result. Sometimes sea level drops in the minutes before a tsunami strikes, but since it doesn't always, this is not a satisfactory warning of an approaching tsunami.

The Pacific Ocean has many tsunamis; in the Atlantic only one has been reported. It accompanied the great Lisbon earthquake of 1755. Its devastation to a portion of this best of all possible worlds formed an episode in Voltaire's Candide.

One of the worst tsunamis of recent years was generated by an Aleutian earthquake in 1946. The tsunami killed 159 people in Hawaii and destroyed nearly 500 homes. Another similar incident occurred in 1957. This time the establishment of a tsunami warning system prevented loss of life in Hawaii, but there was 3 million dollars in property damage there.