Why Mohole Was No Hole
In the fall of 1958, which was already a year of scientific wonders, plans were announced in the technical and popular press for what promised to be an amazing undertaking. A group of American geophysicists were going to drill a hole several miles beneath the sea floor all the way to the remote interior of the planet—the vast nucleus of dense, compacted rock known as the mantle.
In the late 1950s the first spacecraft were being launched, vaccines were wiping out diseases, airplanes were flying at several times the speed of sound, and ever more destructive hydrogen bombs were going off. A tunnel to the mantle seemed not only feasible but inevitable—another lesson in the limitless capabilities of American science and technology. The project, known as Mohole, was impressive not only in its daring scope and the immense array of resources it would marshal but also in the supreme self-confidence with which it was promoted. The deepest shaft ever drilled so far had ended miles above the mantle, but the intrepid researchers had faith that their ad hoc engineering would make up the shortfall. They proclaimed as much, and laymen and scientists alike believed them.
Laudatory press coverage continued unabated through the early 1960s, culminating in an article in Life by John Steinbeck, who had been an amateur oceanographer as well as a prominent novelist. His perfervid accounts of the first exploratory drillings did much to increase public support for the scheme, which reached its peak in 1962, when Congress voted to back it with an appropriation of more than $40 million. And then, abruptly, there was silence.
Once they got past the preliminary stage, the researchers ran into obstacles that even boundless enthusiasm could not overcome. Delays, malfunctions, and scandals arose; by 1966 the funding had dried up, and the project was quickly forgotten, having never come close to its goal. Soon the race to put men on the moon distracted the public. To this day no one has reached the earth’s mantle.
What happened between the early fanfare and the later obscurity? Reality intervened. The Mohole project was always more of a press campaign for funding than a plausible attempt to drill a deep hole. For all the tests and studies no expedition ever set out to excavate a shaft that would actually reach the mantle. Still, the effort did considerably advance the art of deep-sea drilling, and it set the stage for the momentous voyages of the GLOMAR Challenger , which revolutionized marine geology in the 1960s and 1970s.
Before they could make plans to drill to the mantle, of course, scientists had to know that it was there in the first place. That knowledge, and virtually everything else we know about the earth beyond its outer few miles, can be traced back to the 189Os, when what we now call geophysics began to be practiced. Before then geologists mostly confined themselves to studying the earth’s surface features. Most geologists accepted the theories of Lord Kelvin, who believed the earth to be solid to the core with a thin layer of liquid magma below the surface to account for volcanoes.
In the late nineteenth century a group of geologists called Mobilists or Fluidists challenged this view, postulating a plastic earth whose seas and continents had shifted over time as a result of underlying movements in the planet’s deep structure. Mobilist ideas would form the basis for plate tectonics and continental drift, two keystones of modern geophysics, but even as late as the 1950s no one had found conclusive evidence to support these theories, and scientific controversy continued to rage. The Mohole project was meant to resolve it.
Around the turn of the century, geophysicists began collecting the first hard data about the earth’s interior through seismology, the study of earthquakes. Shock waves from a quake travel at different speeds through different media, and layers of rock refract them just as water and glass refract light waves. By measuring the timing, strength, and direction of an earthquake’s shock waves (or ones generated artificially with an explosion) at various points around the earth, one can derive clues about what the waves have traveled through.
The first geophysicist to use this technique successfully was Richard Oldham of Great Britain in 1906. He identified a layer he called the substratum (now known as the mantle), several miles below the surface, and one several thousand miles down, which he called the core. A few years later a Croatian named Andrija Mohorovičić mapped the boundary between crust and mantle. By taking measurements on temblors, he deduced that the nature of the underlying rock changed abruptly at roughly 100,000 feet below the surface. Mohorovičić’s observations were replicated in many places around the globe, and the boundary he discovered was named the Mohorovičić discontinuity in his honor. Understandably, the name is often abbreviated to Moho by geologists. The Mohole project got its name from this discontinuity, which scientists hoped to drill through.
Oldham’s and Mohorovičić’s work led to a model of an earth with three distinct layers: a molten core, a vast mantle of dense yet plastic rock, and finally a thin, solid crust. The Moho is the boundary between the mantle and the crust. We now know that this three-layer model is a great oversimplification, but it was still widely accepted in the 1950s. The theory of continental drift was built on this base, and the Moholers hoped to find direct evidence for it by drilling down to the mantle.
Popular interest in geophysics was at a peak in the late 1950s, especially during the International Geophysical Year (IGY), which despite its name lasted eighteen months, from July 1957 through December 1958. A public relations effort meant to divert attention from the space program and the arms race to geophysics, IGY succeeded by billing itself as a model of international cooperation. Its accomplishments included Antarctic exploration, the discovery of undersea seismic faults, and measurements of the earth’s atmosphere and magnetic field. With these triumphs still fresh, the geophysical profession and the American public were eager to keep going. Moreover, early press reports kept mentioning rumors of a Soviet effort to reach the Moho, and a country already stung by Sputnik was not eager to let itself be beaten again.
The idea of drilling to the mantle actually started before IGY. One early proponent had been W. Maurice Ewing, a Texas farm boy who began doing geophysical research in the 1920s. After founding the Lamont (now Lamont-Doherty) Geological Institute at Columbia University in 1944, he used lavish federal funding to make pioneering studies in marine geology. As early as 1953 he was lobbying for a major undersea drilling effort similar to Mohole, but he didn’t get very far. Still, he planted the seeds that would blossom in a more favorable political climate.
Harry H. Hess, a sometime friend and constant rival of Ewing, was a Princeton University professor who also specialized in the study of the sea floor. During World War II his sonar skills had done much to help the U.S. Navy fight the Axis submarine fleets. Hess saw action in both the Atlantic and the Pacific and used his spare time to explore ocean-floor sediments and coral atolls. Unlike Ewing, Hess was an early convert to the theory of continental drift, and his later scientific work would go a long way toward gaining acceptance for it.
The Mohole project was first propounded by Hess and Walter Munk, a well-connected professor at the Scripps Institution who had been active in promoting IGY. Munk thought up the idea and discussed it with Hess in March of 1957. The following month they presented the scheme to an informal meeting at Munk’s house of the American Miscellaneous Society (AMSOC), a sort of ongoing scientific bull session given to free-ranging speculation and open-ended discussion. AMSOC gave the project its blessing, as did the highly prestigious International Union of Geodesy and Geophysics and the august National Academy of Sciences (NAS). In October 1958 the NAS began preparing a feasibility study with a grant from the National Science Foundation (NSF). Ewing was invited to participate, and he enthusiastically accepted.
The chairman of the feasibility study was Gordon Lill of the Office of Naval Research; Hess headed the site-selection committee, and the technical director was Willard Bascom, a freelance mining engineer. Bascom probably played a larger role in implementing the Mohole project than anyone else; he later wrote a book about it called A Hole in the Bottom of the Sea . Bascom, a can-do technician with abundant reserves of machismo who had worked with Munk in the South Pacific, was good at improvising technology to meet the needs of scientific researchers. He brought a much-needed practical sense to a project heavy with visionaries.
Bascom and others surveyed potential sites and examined the state of drilling technology to find out if the whole scheme was plausible. Bascom was as well qualified as anyone to assess the logistics of Mohole, but in the initial flush of enthusiasm neither he nor his colleagues had any real appreciation of the difficulties that faced them. They would soon find out that they were in very deep water.
History is full of examples of technological accomplishments that looked impossible when they were started. The 1940s and 1950s abounded with such triumphs, and by 1958 it was reasonable to think that no problem existed that couldn’t be solved if enough smart people put their minds to it. However, most of the great advances of that era were made possible by inventions that had not been around a decade or two before: radar, controlled atomic fission, jet engines, lasers, computers. Mohole, by contrast, would have to make do with incremental improvements in existing technology. With no high-tech boost available, it would be more a case of medium tech stretched to its limits, like putting up a thousand-story building. This may not have been clear at the beginning, but as planning and exploration went on, it became increasingly apparent to the scientists involved in the project that their plans were too grandiose.
How deep could one descend into the earth? In 1958 few had even speculated on the matter. All the deep excavations to date had been done for mining or oil drilling, and since shafts deeper than 10,000 feet were rarely worth the expense, no one had thought much about going further. With no precedent to guide them, the Moholers had to decide which of these two methods—mining or drilling—could best be adapted.
At first glance mining seems more straightforward, and some on the project advocated it. In the Soviet Union’s Mohole-type project of the late 1950s, scientists planned to dig a zigzag mine shaft on the island of Shikotan, where they said the mantle lay only 33,000 feet below ground. (This claim has since been disputed.) The project never got very far; from all indications it could not possibly have worked. The deepest mines of the 1950s extended a mere 12,000 feet below the surface, and even so they had trouble with tunnel collapse from the millions of tons of rock pressing down on them. Going three times as far was out of the question. So drilling was the only approach that offered any realistic hope. But how realistic was it?
Hundreds, perhaps thousands of years ago the inhabitants of northern China drilled 2,000 feet in search of brine, natural gas, and petroleum (which was used for medicinal purposes). That record was unsurpassed until the nineteenth-century American oil boom, which prompted engineers to improve their drilling methods. The traditional approach involved chiseling the bedrock by jerking a weighted blade on a long chain or rope. At the turn of the century, a technique that had previously been used only in drilling for water was adapted for petroleum drilling. A rotary drill at the end of a hollow steel pipe was lowered into the hole, and thin mud was pumped at high pressure through the pipe and out an exit near the drill bit. The mud sealed the hole, lubricated the bit, and shot the debris back through the top, making it unnecessary to stop drilling to haul out crushed rock. By the 188Os drillers had reached 3,000 feet; by the turn of the century they had surpassed 5,000; and by the eve of the Mohole project there were a few experimental or exploratory holes as deep as 25,000 feet.
These holes had all been drilled on land, and even the deepest ones reached only a fraction of the way to the mantle. It was not plausible to think about penetrating 100,000 feet of rock, which would have been necessary to reach the Moho. (The proposed Russian site on Shikotan, which might have required a shallower hole, was off limits to American scientists, of course.) Drilling at sea looked much more promising, because in some places the mantle pokes up to within a few miles of the ocean floor. However, marine drilling posed considerable problems of its own.
It was still a fairly new technology when Mohole was first conceived. Underwater oil exploration began in the late 1930s and early 1940s in the Gulf of Mexico, and at first it involved nothing more than mounting a drill on stilts over twenty or thirty feet of water. As more and more offshore deposits were discovered in the 1950s, the oil industry developed techniques to drill holes under several hundred feet of water. It quickly became apparent that stationary platforms attached to the sea floor were not economical for depths greater than a hundred feet, so the industry experimented with floating platforms, barges, submersibles, and specialized drilling ships.
The progress that had been made was encouraging, but it was still nowhere near what was needed to drill to the Moho. To get to where the mantle comes closest to the sea floor requires going far out in the ocean instead of hugging the continental shelf. To drill the Mohole from a floating platform would require sinking a pipe through at least 10,000 feet of water before even hitting bottom. The entire length of the pipe, known as a drill string, would have to exceed 30,000 feet, perhaps half of which would have nothing but water to support it.
To make matters worse, geologists estimated that the rock at the bottom of the Mohole could be as hot as four hundred to a thousand degrees Fahrenheit, depending on the location. Nevertheless, Mohole enthusiasts were not dissuaded; any technology they lacked, they repeatedly insisted, could be improvised along the way.
After choosing undersea drilling, the Mohole committee had to decide what type of platform to use. It settled on a self-propelled drilling ship, because it would be the most convenient for getting to and from the possible sites, some of which were quite remote. By early 1959 the choices had been narrowed to three: a spot near the Hawaiian chain; one close to Guadalupe Island, off the coast of Baja California; and one north of Puerto Rico. Most of the team favored Guadalupe, because it had fair weather and was within easy reach of San Diego.
While they were selecting a site, the team also had to come up with a design for a drilling ship. That type of craft, built with an oil derrick amidships, had only recently been invented, and oil companies were carefully guarding their design secrets. Maurice Ewing, who had many contacts in the industry, tried to sell oil executives on the project, forecasting a wealth of profitable geological information. Most were skeptical at first, but Ewing was persistent and persuasive. After official confirmation of the Soviet project added a patriotic motive, four firms agreed to let the Mohole team use one of the most advanced drilling ships of the day— CUSS I , an acronym for Continental, Union, Shell, and Superior, which had been performing deep-sea drilling research since 1956.
Early in 1961 the Mohole team elected to drill the first experimental hole off Guadalupe. Water depth at the site would be more than 10,000 feet, easily twenty times that at the deepest undersea oil well yet drilled. This presented the drillers with two related problems: stabilizing the ship and keeping the drill string in one piece. A 10,000-foot span of unsupported pipe has almost no inherent rigidity and can easily break; furthermore, its weight alone can be enough to break it from the derrick.
The stability problem was solved by an ingenious dynamic positioning system that used radar and under-water sonar sensors to detect movement and a brace of swiveling outboard motors (controlled with a joystick by a pilot who monitored the system) to push the ship back into place. Robert Taggart, a naval architect, and Chad Ohanian, an electronics engineer, developed this system, which has since been widely adopted by the oil industry; it was by far the Mohole project’s most important payoff. The weight of the drill pipe was made manageable by use of a telescopic construction, the diameter decreasing with increasing depth.
CUSS I made three voyages between late February and late April. The first two were short shakedown excursions off San Diego in which the crew familiarized itself with the rig and drilled in depths of more than 3,000 feet. The shakedowns went well, with only one minor accident, involving a wrecked drill bit. The crucial third voyage took the ship to the waters off Guadalupe.
In late March of 1961 CUSS I put to sea with a small contingent of geologists, some drilling engineers, a crew of roughnecks lent by various oil companies, and John Steinbeck. The novelist was fascinated by the balletic precision with which the crew handled the rig and the array of sophisticated positioning equipment used to stabilize the ship. Bascom was in charge of the drilling. He was a good choice. He quickly won the respect of drilling crews and was able to communicate his enthusiasm to the nonscientists on board.
Bascom exuded confidence and easily convinced Steinbeck that the new drilling rig was equal to the demands of the program. Inwardly, though, Bascom was far less sanguine. He knew that his equipment was entirely unproven and that a single mistake would probably scuttle the project. He was betting everything, and he realized that hundreds of scientists considered the endeavor an ill-conceived public relations bubble and wanted him to fail.
In spite of choppy seas and a malfunction in the positioning system, Bascom, ever the gambler, chose to stick to the schedule. The crew lowered the drill and succeeded in boring hundreds of feet into the seabed at depths exceeding 10,000 feet, extracting a valuable collection of deep sediment samples. The basic equipment devised for the experiment surpassed all expectations, and the expedition returned in triumph to be feted by scientific organizations all over the globe.
The scientific achievements of CUSS I were considerable, but the holes it had drilled hadn’t come close to the Mohorovičić discontinuity. There was no way they could have, for CUSS I had been built only as an experimental vessel to test the apparatus. It had nowhere near the capacity needed to store the tons and tons of pipe that would be required to drill six miles down. Besides, drilling through loose sea-floor sediment was the easy part. Penetrating the basalt between it and the mantle would take much more rugged equipment. To go forward with the project would mean building a new, much bigger ship.
And that would cost lots of money. Preliminary grants and corporate donations had paid for CUSS I , but a ship capable of actually drilling the Mohole would require an entirely different level of funding. Estimates of the cost kept going up, but even in the earliest stages it was clear that it would be at least $15 million. By 1962 the price tag had passed $40 million, and when the project was finally abandoned, in 1966, it was more than $110 million. Government financing would obviously be needed.
Many Mohole advocates, mindful of the importance of public support, wanted to go right ahead and drill to the mantle, with no more exploratory missions to eat up funds. Others, including Bascom, privately wondered if the available technology was equal to the task. Bascom suggested that the project proceed in stages, like the lunarlanding program.
The ostensible reason was to let participants get used to the novel equipment and perhaps improve it, but in fact Bascom doubted that the Mohole would ever be completed and may have wanted to do as much geological research as possible before the money ran out. In a recent interview Bascom said that the entire Mohole venture was misguided and technically unfeasible and that a better goal would have been to drill many shallow holes in the ocean floor and examine the sediment they yielded—which was in fact done several years later.
Whatever Bascom’s motives at the time, his plea for a phased approach failed, and his own bid for a government contract was rejected (and in characteristically reckless Bascomian fashion, he had mortgaged his home to set up a deep-sea drilling company). Instead, in March of 1962 the NSF signed a preliminary contract with Brown & Root, a giant Texas construction firm. From that point on, none of AMSOC’s original Mohole committee —Ewing, Hess, Munk, and Bascom—played any significant role in the project except to complain about how everybody else was screwing it up.
Brown & Root had very little experience in the construction of oil platforms and none whatever in the field of floating derricks, but it did meet one very important qualification for government funding: It had bankrolled Vice President Lyndon B. Johnson throughout his political career. Controversy erupted over the NSF’s award of the contract, with congressional hearings and grandstanding politicians galore. Participants in the project quarreled over whether to use one ship or two and whether to perform a series of tests or go for broke immediately. In the summer of 1963 a new scheme was announced in which the drilling ship would be replaced by a derrick on a platform supported by two submarines. Meanwhile, charges of incompetence, mismanagement, and conflict of interest flew back and forth.
By 1964 the project had become so bogged down in internecine disputes that it dropped from public attention. Early in 1965 the NSF announced plans to revive Mohole at a new site off the Hawaiian Islands, but as costs kept rising with nothing to show, the public grew weary of tossing money into the ocean. In January 1966 a House subcommittee recommended cutting off funds for Mohole. That spring LBJ, now President and ever loyal to his friends, urged Congress to restore the money. But then it came out that the family of one of Brown & Root’s principals had just given $25,000 to Johnson’s campaign fund. The ensuing row damaged the President’s credibility, and in August Congress voted against any further appropriation. Mohole was dead.
The members of the original AMSOC Mohole crew had mixed experiences after their involvement with the project ended. Bascom wrote his book and fruitlessly pursued federal research grants. Ewing and Hess became embroiled in the great debate over continental drift, which Mohole had been intended to solve. Hess drew fresh encouragement from other deep-sea explorations that conclusively demonstrated sea-floor spreading, a central tenet of the theory. Ewing bitterly fought a losing battle with continental-drift proponents until the end of the 1960s, much to the detriment of his reputation. Munk stayed at Scripps and went on to have a long and distinguished career, eventually winning many awards and medals, including one named after Ewing.
Though Mohole was the first project to attempt deep-sea drilling, its failure did not mean the end of the technique. In 1962, a little more than a year after CUSS I ’s voyage, an expedition organized by Cesare Emiliani of the University of Miami conducted a deep-sea drilling project off Puerto Rico on a drilling ship called Submarex . The expedition was far less publicized than Mohole but gathered much more geological data and probably did more to establish ocean drilling.
Then, in 1966, in the wake of the Mohole fiasco, a number of research institutes, including Scripps, Woods Hole, Lamont-Doherty, and the Institute of Marine Science, applied for an NSF grant to pursue a much more modest program of deep-sea drilling. A year later the group bought a very large drilling ship from the Global Marine Corporation. It was called the GLOMAR Challenger , after its builder, and it used the dynamic positioning that Bascom had developed for CUSS I . Through the late 1960s and 1970s the GLOMAR Challenger drilled a total of six hundred holes in the ocean floor at points all over the globe, some through more than 20,000 feet of water. Its findings revolutionized marine geology and provided an immense body of evidence supporting the theories of continental drift and plate tectonics.
In the 1970s and early 1980s geological formations known as ophiolites were discovered under the oceans. They contain masses of periodotite, which the mantle is believed to be made of, and evidence suggests that they may have been forced up from the mantle through rifts in the earth’s surface at great mid-ocean ridges. But the “living” mantle has yet to be reached, and thirty-five years after Mohole was first conceived, the most advanced deep-drilling equipment is still probably not up to the task.
In contemplating the high hopes and failed aspirations of the Moholers, one is tempted to ask, What if? What if the $60 million swallowed up by Brown & Root had gone into basic research on deep drilling? Could the Moho have been reached?
Maybe not. According to Roger Campbell, of Lamont-Doherty, who has extensive experience in the field, the biggest problem in reaching the depths required to pierce the mantle is the vertical movement of the drilling ship in response to ocean swells. A ship can rise and fall more than fifty feet, causing the drill string to fail long before it can penetrate three miles of solid rock. Vertical stabilizing equipment developed by Hughes Aircraft could make a modern Mohole possible, but it has not yet been made available to scientists. Without such equipment the challenges facing deep-sea drilling crews are just as daunting as they were thirty years ago.
So perhaps the Mohole was beyond the capabilities of 1960s American technology. But when one considers that astronauts reached the moon in 1969 with computers that are incredibly slow by today’s standards and with guidance systems built from impossibly bulky and inefficient electronic circuitry, it’s not implausible that an allout, cost-is-no-object assault on the Mohole could have succeeded. In 1959 the advances in rocketry required for a moon shot were far greater than the advances in deep drilling required to reach the mantle.
Of course, no such effort was or is likely, because geophysics has never been on an even footing with the space program. Geophysicists have no government agency of their own and no tie-in with the military, and their accomplishments lack the glamour and inspirational value of walking on the moon. The Moholers were forced to juryrig apparatus out of production equipment instead of having it made to order, and thus they were able to make only small improvements. Lack of money, and ultimately the lack of a mandate from the government and the public, doomed them. The Mohole was presented to the public as a single isolated feat of exploration, like a bathyscaph descent or an Everest expedition, when in fact the funding requirements were much greater. To have any chance of success, the project should have been sold as part of a comprehensive program of sea-floor exploration.
Someday someone will reach the mantle, but the problems involved in doing so remain formidable, and the age of enthusiasm that spawned the first Mohole project has long since passed. The mantle will hold its secrets for a great while yet.
