Geophysical Garbage Dump

Garbage--and its disposal--offers a continuing challenge to scientific ingenuity. Produced in ever-increasing amounts around the world, it is being incinerated, converted into fertilizer, used as landfill, recycled into new products or dumped carelessly into rivers and seas. Still it piles up. To keep ahead of the accumulating waste, some scientists have even suggested lofting it into perpetual solar orbit or rocketing it into the sun, where it would be consumed by nuclear fires. Now two University of Washington scientists have proposed what may be a much simpler terrestrial solution: burying civilization's debris deep within the earth.

Continental Drift. The new idea stems from discoveries that in the past few years have drastically revised classical geophysical theories. Although it was once thought that the ocean floor has remained stationary and relatively unchanged for billions of years, scientists are now certain that it is continually spreading and being renewed with fresh material welling up from a 47,000-mile-long chain of volcanically active undersea ridges. As this new rock from deep within the earth's mantle moves slowly away from the mid-ocean ridges, it carries the continents along, thereby providing the mechanism for continental drift (TIME, Jan. 5, 1970). Millions of years after leaving the ridges, the material reaches the extremely deep trenches that lie just off several of the continental coasts. There it plunges back into the earth.

The rate of movement into the trenches is almost imperceptible--no more than an inch or so a year. But Geophysicist Robert C. Bostrom and Civil Engineer Mehmet A. Sherif think that some of the more conveniently located trenches could be used as efficient geophysical garbage dumps. The trick, they explain in Nature, would be to dump packaged waste into the sea off the mouths of fast-flowing rivers, which annually wash vast amounts of mud into continental trench areas. Though the garbage would not be drawn far into the earth for many years, it would soon be buried so deep in mud that there should be little danger of pollution during the interim.

Dense Packages. Bostrom and Sherif admit that their scheme raises a number of serious technological questions. It would have to be determined, for example, whether a river deposits mud quickly enough to accommodate the projected garbage load. The plan would also be expensive, because the garbage would have to be compressed into dense, sinkable packages and transported by barge to the disposal site. Nevertheless, the two scientists, who are co-directors of the University of Washington's earthquake engineering group, are convinced that their proposal deserves serious scientific consideration. "In an age in which waste material is mass-produced," they write, "only a mass-production disposal technique can be successful."

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