Science: Ocean Frontier

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Fossil Volcanoes. Geologists and oceanographers who look to the ocean's bottom have found that the ocean is a gigantic museum, where geological specimens are preserved like flies in amber. Among the most interesting of these geological fossils are the guyots, the flat-topped extinct volcanoes that dot the Pacific floor. How did they get down there, the oceanographer asks. Did their weight force them into the earth's crust, like corks pushed into putty? Did the ocean increase in volume and rise above them?

A recent discovery is evidence that an enormous volcanic eruption may have darkened the sky when man was in his stone-chipping stage. Cruising down the west coast of South America, Lament's Vema discovered a layer of clean white volcanic ash up to twelve inches thick. Other explorations have found layers of similar ash in many parts of the Pacific and Atlantic. Dr. Ewing suspects that all the ash came from a series of stupendous eruptions along the spine of the Andes, estimates the date as 68,000 years ago. It must have been a black time for paleolithic man.

Mysterious Trenches. An ocean-bottom problem that fascinates all oceanographers is the origin of the deep troughs that are found mostly in the Pacific. The deepest ones, e.g., the Tonga Trench, the Marianas Trench, have narrow V bottoms that are clear of sediment. They are uneasy parts of the earth's crust. Deep-focus earthquakes rumble out of them, and generally volcanoes spout near by.

Dr. Revelle suspects that the trenches may be part of the mechanism by which continents grow. The first step, he thinks, is for a slow current in the earth's plastic mantle to start flowing horizontally and then curve downward (see diagram). Where it makes the dive, it drags down a strip of the crust, forming a V-bottomed trench which after many millions of years fills with sediment. Eventually the downward current in the mantle stops flowing. Since the mantle rock at its sides is heavier, it moves in, forcing upward the dragged-down crust and the sediments in the trough. Final result is that the former trench pokes above the sea, appearing as an arc of islands set with volcanoes, like Japan, or a curving shore of young mountains, like California.

Only a small part of the ocean bed is yet known in any detail. Recent surveys have shown that large areas of the bottom are covered thickly with rounded, blackish nodules that have grown as crusts around some nucleus, sometimes a shark's tooth. They are mostly iron and manganese oxides, but they often contain considerable amounts of copper, nickel and cobalt. "The amounts are absolutely staggering," says Dr. Henry Menard of Scripps. One 10-million-sq.-mi. area in the Pacific, he estimates, has nodules worth hundreds of thousands of dollars per square mile.

New Imp. Today oceanography is working to perfect its tools. There are intelligent buoys, which can be anchored at sea, and queried by radio for oceanographic and meteorological data. Other buoys sink to the bottom, where they can record currents, take pictures of their surroundings. They will be brought to the surface months later by a small charge of TNT exploded near by, which triggers their ballast-release mechanism.