:Richard E, Dunn, age 13, of Indianapolis, IN and Betty dean Frays age 13, of La Grange, Ill,, for their question
What causes a tidal wave?
We often hear that a faraway place has been struck by a hurricanes an earthquake or a tidal wave. When they strike without warning, these disasters claim many lives. But our scientists are busy probing their secrets. For, when we know the reasons why a disaster happens, we can often tall when it will happen and run run run to safety.
Our weather scientists know where and when to expect a hurricane and how to track its path, The angry storm may wreck a lot of property. But the people are warned in time to escape with their lives. In 1916, a warning system was started to save people from sneak attacks by deadly tidal waves.
The tidal wave gets a lot of attention from the world of science. Its secrets are probed by the experts who study earthquakes and unrest in the earth’s crust and by those who study the ocean waters and the deep sea bed. These experts tell us that the true tidal wave is not related to the high and low tides which follow an orderly pattern, It is not, as a rule, related to the wind. tossed waves. This is why they call it by another name.
The watery disaster is known as a tsunami. Sometimes a hurricane at sea will whip up a heaving wall of water and send it flooding over the land. But the true tsunami is started by a earthquake which shakes the floor of the ocean. Undersea earthquakes are common around the edges of the Pacific ocean where the earth’s crust is restless. A tsunami may be born when an earthquake rocks the Aleutian Islands or it may start in a deep trench in the sea bed more than six miles under water.
The Pacific lips in a deep basin and when its floor is shaken its
waters are upset. You know what happens when you shake a glass of water. If the bottom of the glass suddenly heaved and shook, the water would slop over the sides. On a much grander scale, this is what happens when an earthquake shakes the floor of the ocean: Masses of water pile up like heaving mountains and rush away to dash on some distant shore.
A tsunami is born when an earthquake happens under the sea. In a moment, the warning stations are flashing their signals. In mid ocean, the sea level may rise a foot or two and ships radio the news. Experts work fast to plot the path. of the tsunami for it may be rushing forward at 100 miles an hour. In five hours it may travel from the Aleutians to the Hawaiian Islands.
As it gets near to the land, the tsunami at first sucks back the water from the beaches. Then it rushes forward in a towering wall of thundering water perhaps 100 feet high. It crashes onward perhaps a mile or two, sweeping the land bare of buildings and trees. But when the people are warned in time they can go inland and escape the watery disaster.