Geologists drilling `ultradeep' holes hope for scientific pay dirt
Geologists are gearing up to turn Earth into a pincushion. Around the world, scientists are laying plans to bore a new series of ``ultradeep'' holes into the continental crust to help unravel some basic riddles of geology.Skip to next paragraph
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West German scientists are looking at two possible sites to spud a 46,000-foot (14,000-meter) hole beginning in 1988. A national continental drilling program is getting under way in the United States which includes plans for a possible 33,000-foot (10,000-meter) probe in the Appalachians -- the deepest ever drilled in North America.
The Soviet Union, long the leader in the field, is expanding its ambitious deep-drilling program. Canada, too, is weighing plans to begin rummaging around in its continental basement.
All this is expected to lead to a great leap forward in geology over the next decade, aiding scientists in understanding such fundamental things as the origins of continents, how mountain chains form, and the forces that give birth to minerals.
``It will answer questions that have been raised and argued about literally for centuries,'' says G. Arthur Barber, president of a 24-university consortium overseeing a US drilling program, referring mainly to the American effort. ``Here we've been spending billions sending sensors out into space, yet we don't know what's eight miles beneath our feet.''
It is this knowledge gap that is driving the deep-drilling activity. The past few decades have seen a wealth of geologic information unearthed: The theory of plate tectonics -- that continents drift around the world atop a soupy layer of molten rock -- explains much of the earth's general geology today. So, too, have scientists gleaned much from a successful deep-sea drilling program. But the continental crust remains largely an unexplored frontier.
``We think this is one of the major areas that earth scientists have yet to come to grips with,'' says Benjamin Morgan of the US Geological Survey (USGS).
What is known has been inferred from surface rocks and studying eroded riverbeds or holes drilled by the oil and gas industry, which are usually in the wrong place and not deep enough for geologists. Lately, scientists have gained new insights by using seismic devices to create fuzzy ``snapshots'' of the earth's crust. Now, however, they need to drill into the basement rock itself to test these theories and to retrieve other information.
The nascent US continental drilling program is being funded by the National Science Foundation, the US Department of Energy, and the USGS. Some $7 million will be spent on boreholes this year.
The most ambitious proposal being considered is the 6.5-mile-deep hole in the Appalachian Mountains, near the Georgia-South Carolina border. The area is believed to mark the leading edge of a sheet of crystalline rock that was pushed over sedimentary rock during a great continental collision between Africa and North America 270 million years ago. The deep hole would test this theory.
It may also, says University of South Carolina geologist Robert Hatcher, open a window on the evolution of continents and the formation of mountains here and around the world.
Funding for the $40 million-plus project has not been approved yet. But an advisory committee of the National Academy of Sciences has suggested it receive high billing in the national drilling program. At present, Dr. Hatcher and colleagues are boring shallow holes to test rock samples. Work on the deep hole itself could begin within three years, though garnering federal funding in these deficit-ridden times may be as tough as chipping granite with a wooden mallet.