Tsunami the Terrible

Beneath the black waters of the Aleutian Deep the earth moved. Some 15,000 feet down and 70 miles southeast of Unimak Island (see cut), nature was building a mountain which living men might never see. But the secondary results were visible enough: 1) quivering squiggles which are the seismographic record of earthquake violence; 2) a series of tsunami* ringing out from the earthquake center, carrying death & destruction to Hawaii, spreading alarm across the Pacific.

Tsunami follow any submarine earthquake which causes a fissure or crack in the earth's crust. When a part of the ocean bottom drops away or when there is an underwater landslide, water surges in from all sides to fill the void.

At first the waves are low and confused but as they work their way out they pick up momentum and rhythm, become long, heaving swells of tremendous power. The waves which hit Hawaii were moving at approximately 400 miles an hour. Since the waves washed ashore at twelve-minute intervals, the crest-to-crest distance must have been about 80 miles.

In the open ocean the long swells may pass almost unnoticed, since they do not rise to breaker height until the trough begins to scrape sea bottom. Then, as speed is reduced by friction, the water piles up into steep, precipitous peaks. Last week in Hawaii eyewitnesses guessed the tsunami ran as high as 100 feet. Best estimate: 45 feet. Either way, they were enough to smash the city of Hilo on the exposed northeast side of the island of Hawaii, kill some 200 of its inhabitants, deposit 14 feet of silt in its harbor and wriggling fish in its coconut palms.

Many jittery readers, wondered whether the Bikini atomic-bomb test had been given a secret preview. Answer: a definite no. It would take many times 20,000 tons of TNT (the equivalent of the atomic bomb to be dropped at Bikini) to match the earthquake in the Aleutian Deep.

* Tsunami (pronounced (tsu-nah'-mee) is a Japanese term favored by seismologists over the popular but inaccurate "tidal wave." Literal translation: seismic sea-wave.

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