Beautiful Young Lady

Elegant in phrase, lyric in tone and innocent of harsh technicalities, a broad review of modern trends in his own field is what the British Association for the Advancement of Science has come to expect of its president, at its annual get-together for exchange of news and views. This year's president, William Whitehead Watts, 75, emeritus professor of Geology at London's Imperial College, did not disappoint B. A. A. S. when it convened last week in Norwich. Professor Watts talked about Earth. "The Earth." said he, "is 'a lady of a certain age,' but she has contrived to preserve her youth and energy as well as her beauty."

If age is stagnation, Earth does not appear to be growing any older. The forces which have waved, lifted, folded, crumpled, thrust and faulted her crust seem to continue with unabated vigor. The planet trembles almost continuously, as some 8,000 earthquakes a year bear witness. Islands sink out of sight in the sea, and new ones emerge. Rain and wind level old mountains; young ones are thrust up on the shoulders of mysterious forces below. Whence comes all this energy?

Long ago the idea took root that Earth's face is squeezed and wrinkled by the contraction of cooling, but this is no longer regarded as the sole cause of unrest. A half-century ago. Dr. Watts recalled, Suess of Austria realized from geological evidence that the sea had washed back & forth on the continents in great longtime pulses, but he could not explain the underlying mechanism. After radioactivity was discovered, Joly of England and others hit on the concept of thermal pulsation: radioactivity in the solid, or nearly solid, sub-crust of Earth causes heat to be stored there until the sub-crust melts. The continental masses sink deeper into this dense, viscous pool, which in turn moves sideways, bulging and rifting ocean floors, allowing heat to escape. Then the cycle begins again. Wegener of Germany proposed that two great continents, Gondwanaland in the Southern Hemisphere and Eurasia in the Northern, cracked and sundered, slid like cakes of ice over the hot sub-crustal pool to form the present continents. Evidence: the coastlines of Western Europe and Africa and those of Eastern, North and South America almost fit like jigsaw puzzle pieces; similar fossils on the two sides seem to be remains of life that once inhabited one undivided land. During this drift mountains may have been thrust up along lines of weakness in the crust.

Terrestrial gravitation, acting unequally on unequal masses, may produce downward thrusts. But are there not forces beyond Earth causing upward thrusts? Professor Watts last week reminded his hearers that Earth is not alone in space but is clutched at by the gravitational pulls of its celestial companions:

"Is it not possible, for instance, that the tidal influence of the sun and moon which is producing so much distortion of the solid earth that the ocean tides are less than they would be otherwise, and, dragging always in one direction is slowing down the earth's rotation, may exert permanent distorting influence on the Earth itself? May it not be that such a stress . . . takes advantage of structures of weakness produced by other causes?"

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