Tsunami

Most discussions about the environment and nature have to do with safeguards against the impact that people have on those resources. How about the impact that the environment has on people? The impact of a tsunami comes to mind. Wouldn't it be nice if the folks recently hit by the destructive waves of a tsunami had some warning?

First, let's look at a tsunami itself. A tsunami produces what is commonly called a "tidal wave." Actually, the name "tidal wave" is not quite correct since the wave is not the result of the usual forces that cause the tides. The destructive waves of tsunamis have nothing to do with the moon or any other planet.

A tsunami is a "seismic sea wave" that is the result of a "submarine earthquake." In this case, the word "submarine" has nothing to do with an underwater vessel. By "submarine" earthquake, we mean an earthquake at or near the ocean floor. Before rattling buildings, bridges and other structures, a submarine earthquake first rattles the water.

Not all tsunamis result in destructive waves. Depending on the severity of the submarine earthquake, such waves may be rather small and are not destructive. However, some of these seismic disturbances can be devastating to vessels, buildings and people at or near the shoreline.

Tsunamis have been known to cause damage as far as 2,000 miles from their origin. Such damage includes knocking down a lighthouse and many other structures at great distances from the source of the tsunami.

Tsunamis travel at speeds between 300 and 500 knots. A "knot" is a nautical mile per hour. Since a nautical mile is 6,076 feet, compared to 5,280 feet in a statute mile, the speed of a tsunami is between 345 and 575 miles per hour. That is fast by any measure.

The height of the tsunami moving under the water is between 3 and 6 feet. It is not detectable in the open sea by a vessel or from overhead in an aircraft. It is not the "traveling" tsunami that is disastrous, but the tsunami reaching its destination that causes the devastation.

Tsunamis usually produce several waves that may be 10 to 40 minutes apart. The largest of the series of waves may come a few hours after the first wave. At times, the first indication of the tsunami at the shoreline is what is known as the "trough" that causes the water to recede from shore. This may be nature's way of warning us of what is to come. The destruction soon follows.

Whether a submarine earthquake results in a destructive wave is a complicated matter. The scale of the earthquake is certainly a huge factor in this equation. Both the depth and the contour of the ocean floor also play significant roles in the outcome. Certain types of "shelving" coasts are more likely to exacerbate the situation than others.

As far as warning is concerned, the severity and location of the submarine earthquake must be predicted first. Next, the "hydrology" of the area of the world that may be impacted must be evaluated. All of this has to be done in a very short period of time. You can appreciate why such things are difficult to predict.

Until next time, I wish you clear skies, fair winds, and calm seas!