Of Plates and an Elephant

Throughout most of the Nth and Keith centuries, geologists the world over labored like the fabled blind men and the elephant. In that instructive tale, a group of blind men come upon an elephant. Of course they cannot see, so each reaches out with his hands to determine the nature of the animal before them. One grasps the trunk and cries, "It's just like a snake"; another finds a leg and shouts, "No, it's like a tree.' Needless to say, the poor fellows can't agree who is right.

As the author John McPhee has pointed out, this fable accurately describes the state of geologic science only a few short years ago.' By the 1950s, many parts of the geologic elephant had become known - the tail, the right hind foot, the trunk. But no one had a theory that could unite these assorted parts into a reasonable-looking animal. To be sure, many ideas were proposed. One popular theory suggested that the Earth is contracting, thrusting up mountains like wrinkles on a raisin. Another postulated that mountain belts rise up out of long troughs filled with thick deposits of sediments called geosynclines. In 1911, Austrian geologist Alfred Wegener, using fossil evidence, proposed that the continents had once been joined together but had for unknown reasons since drifted apart. All of these ideas had merit and were based on careful, accurate field observations; but each had serious flaws that prevented its universal acceptance.

With the advent of deep-diving nuclear submarines following World War 11, a new interest was sparked in understanding the world's oceans. Major funding was applied to research on these previously neglected regions covering three-quarters of the globe. It was like giving the blind men a stepladder to reach areas of the elephant that they were only vaguely aware of before. Since that time, oceanographic research vessels have crisscrossed the oceans taking samples, trailing arrays of scientific equipment, and carefully mapping the hitherto unsuspected hills and valleys of the ocean floor. During the 1950s and 1960s, a number of major discoveries about the oceans took most geologists completely by surprise. New evidence overwhelmingly favored plate tectonics, a theory that finally united geosynclines, Wegener's drifting continents, and many

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