The mysterious mantle WHAT'S DOWN THERE?
How and why the earth detectives will pro vo miles under Canada's crust this summer
BY THE END OF THIS SUMMER, a convoy of trucks and tractors will begin moving hundreds of tons of drilling equipment to Mount Albert in the Gaspé. Set up, the big drill will cut about two miles down into the earth's crust. Some months later, a great overland tractor train will journey across the Northwest Territories from Great Bear Lake to Coppermine on the Arctic Ocean. Near Coppermine, sometime during 1963, another two-mile hole — called Muskox — is expected to go into the earth.
During 1962 and 1963, smaller rigs will put down a score of drill holes all across the country, from 1,000 to 2,000 feet deep. The drilling will all be part of a $3,000,000 three-year scientific program which a mines department scientist recently called “a colossal job of exploratory surgery on the whole country.”
The “job” will be to probe, pinprick and X-ray Canada like a patient with an undiagnosed ailment. But the earth scientists will know their objective. They want to reach, measure and analyse the mysterious mantle, the great mass of uniform rock which lies from three to forty miles under the earth's surface. This will quickly become much more than a search for the mantle. It will be the biggest detective job in the country’s history. From it should come discoveries that will enrich the future of the nation. By knowing the mantle, science can answer many vital questions: Is the earth expanding or contracting? Are we heading for another ice age? Is the earth heating up or cooling down? Where are all the major mineral resources located?
This last question alone is vital to Canada. Contrary to popular belief, we are coming close to exhausting our easily exploitable mineral resources. "It is now clear,” says the Dominion astronomer. Dr. C. S. Beals, “That we must go down ten miles, perhaps even twenty, to find the commercial minerals we will need in the future.”
The search for the mantle in Canada is part of an international adventure called the Upper Mantle Project. It is mobilizing and uniting the work of many different scientists — geologists, seismologists, geo-
physicists, astronomers, petrographers and geochemists. The National Research Council, the Department of Mines and Technical Surveys and the Geological Survey of Canada are spearheading the government effort in Canada. Most major universities are contributing under the leadership of Dr. R. J. Uffen, former head of the University of Western Ontario’s geophysics department. The project was proposed by an eminent Russian geophysicist, Dr. Vladimir Beloussov. At a science meeting in Helsinki in 1960, he said that some world program should follow the greatly successful International Geophysical Year. Why not a detailed look at the earth’s skin, and below?
The first results of this massive program won't be known till August, 1963, at the next meeting of the International Union of Geodesy and Geophysics at Berkeley, California. There Beloussov, the elected president, will report on a staggering amount of new information that sixty participating nations will have prised, bored, dug or hypothesized from the body of the earth.
Canada’s contribution will befit her great share of the earth’s surface. The most dramatic results here should come from the deep drilling at Muskox and Mt. Albert. The Muskox location, fifty miles south of Coppermine on the Arctic Ocean, was chosen because a huge saucer-shaped mass of rock has been forced like toothpaste from deep in the earth to the surface there. The earth detectives suspect that it may be joined by a long stem to the mantle proper.
“We don't really know whether it is mantle material,” says Dr. Larry Morley, chief of the geophysics division of the Geological Survey of Canada, “but we’re going down 10,000 feet to get as much information as possible.”
The great mystery of the mantle is that nobody can be sure he has ever seen it. There are a number of “intrusive areas” around the world where masses of rock at the surface are suspected to be mantle substance. At Mount Albert, about ten square miles of land is suddenly bare of all trees and vegetation. Partly because two suspected mantle elements are iron and magnesium—which, in large quantities, kill plants —the scientists feel this is
CONTINUED ON PAGE 56
continued from page 29
“What we need is an earthquake/’ said one of the Arctic scientists. Two days later, he got one
another mantle intrusion on the surface.
These tremendous earth probes will give the scientists a chance to work backwards to establish the facts. “The core from the Muskox hole." says Dr. Charles Smith, a member of the petrological sciences division of the geological survey, “will fill 400 boxes, each five feet long, and will probably contain between fifteen and twenty different types of rock. Each will be representative of rocks that cooled at different periods after the material was forced up. Knowing this, we will be able to study how the chemical elements split up as they cooled. We will know how the economic minerals have behaved during this process. We will even know how and where they have moved. Phis will enable us to work backwards and use this information as a prospecting tool."
Even after going down twe miles, the drill point at Muskox will still be thirty-five miles short of the main body of the mantle. But the Americans arc making a spectacular effort to reach the mantle directly with their giant Mohole Project. They plan to drill from an offshore platform anchored about 100 miles off the west coast of Mexico. The earth crust is many times thinner there than under dry land. They hope, by drilling about 35,000 feet down, to break into the great mass of mantle and determine, once and for all. its exact substance.
Such deep drilling will bring the scientists to the fringe of other problems, particularly heat. The earth's temperature rises by one degree centigrade for every 100 feet of depth. At 10.000, points out Dr. Smith, the atmosphere in a South African
diamond mine, which he visited recently, would be roasting hot without air conditioning. Eiven in 8,000-feet-deep mines at Kirkland Lake, the walls arc hot to touch.
At such depths, the tremendous pressure of earth might halt core drilling. The Muskox hole might be forcibly closed by plastic' rock being squeezed into it under the pressure of thousands of feet of overlaying rock. To cope with these and other difficulties, many probably unforeseen even now. the drillers will have to develop a host of new techniques and, ultimately, revolutionary machines. The gravity division of the department of mines is working on a tiny gravity-measuring machine which, if perfected, will be lowered thousands of feet into drill holes where it will report minute differences in gravity pull. “Gravity,” says Dr. C. S. Beals, chief
astronomer at the Dominion Observatory, "is typical of the problems that face us. We don’t have the faintest idea what causes it.”
Canadian university scientists are working on another equally tough problem. So far, there's no way of recording the temperature in a really deep drill hole because the wire holding the recording instrument will not carry the temperature reading accurately to the surface.
Boring or burrowing into the earth is an essential step in the search for the mantle, in much the same way as it is necessary to send men orbiting the earth in capsules to find out about space. Fortunately, knowledge of the earth’s interior can also be obtained without boring or drilling at all. During 1962, the chief seismologist at the Dominion Observatory, Dr. John Hodgson, will be working hard to gel a special grid of manned seismic stations completed. They will be 500 miles apart and equipped to record every tremor within the earth. Most will have probe holes for earth temperature instruments 1.000 to 2,000 feet down. The operators of the stations, some of which are already at work, will send daily reports to Ottawa. Their instruments are so sensitive that the first three stations, on Cornwallis, Ellesmere and Prince Patrick Islands, accurately told where the Russians exploded their last series of nuclear bombs and how big the bombs were. The stations are what one seismologist called “a great electrocardiograph machine of earth.”
To a seismologist, any shock wave tells a story of the material it has passed through. During the recent Chilean earthquakes seismic stations in Canada received some waves which had passed deeply through the earth while others, arriving much later, had rippled along the surface. Some shock waves travel only through water, others only through land. About six months ago, Columbia University scientists were trying to check some details about the extent of the continental mass projecting under the Arctic ice. “What we need is an earthquake in that area,” said
one of the scientists wistfully. The earthquake came two days later. Three northern stations relayed the information to Ottawa. The Columbia men had their answer within seventy-two hours.
1 he grid of seismic stations, about thirty in all, will enable scientists to draw underground profiles of the material between the crust and the mantle itself. Dr. Hodgson and his colleagues, without using the grid, have already discovered that thrust forces in big mountains of the world are not working as expected. The individual faults deep inside the mountains are a<" tually moving horizontally as well as vertically. The source of these faults is a major geophysical mystery. One theory, now gaining acceptance, is that all the crust is constantly on the move like an enormous, incredibly slow-moving sea. Hut how to prove this?
Dr. Morley and his colleagues of the Geological Survey are laboriously collecting rocks from all over Canada and carefully measuring their magnetic intensities. The rocks in one of their recent collection* from the Canadian Shield indicated tha the magnetic north pole lay in several di'
ferent directions. This seemed like a contradiction but actually was further proof of the movement of the earth’s crust over the mysterious mantle. “The theory is,” says Morley, “that when these rocks were emplaced in molten state, the tiny magnetic particles in them settled as they cooled and became aligned in the direction of the prevailing magnetic field, or toward the magnetic north pole.” Morley and his men calculate the ages of such rocks, then they estimate the position of the pole at that age in the earth’s history.
This sort of work is providing sometimesincredible results. Canada, the investigators now believe, was once a part of Europe. India was joined to Africa but has drifted away. One recent theory, proposed by Montana chemistry professor Ray Woodriff, even has it that the moon’s gravitational pull is powerful enough to raise^ mountains, in much the same way it presently raises tides. The entire crust of the earth may well be a thin and relatively unstable skin. As it has moved, the crust has been crumpled and twisted till now it is such a complicated mass of intermixed rocks that "it will take us one hundred^ years to sort it all out,” according to Dr. Smith.
Despite this chaotic complexity, Dr. Cliff Stockwell, a special projects scientist with the Geological Survey, is laboriously building up a vast tectonic map of all Canada —a construction plan of the crust area. It will tell where subterranean rocks are located and will give the dates the rocks were disrupted from the positions in which they solidified from the molten state.
His work will be speeded by an aero-
magnetic survey of Canada, which began last year with the federal government cooperating with the governments of Quebec and Ontario. This survey is done by airplanes equipped with magnetometers which measure the magnetic field of the earth. Since the scientists already know the magnetic susceptibility of all rocks, they merely have to measure how the emanations are distorted to know roughly what lies below.
Like much work connected with the mysterious mantle, this is not an exact science. "It’s a bit like trying to tell what’s gone on in a cabinet meeting,” says Dr. Beals, "by watching the expressions on the faces of the ministers coming out of the meeting room.” The survey will take ten years to complete. "But when it’s done,” says Dr. Morley. “It'll be just what an Xray is to a doctor, a sort of vast diagnostic picture in depth.”
Already, the earth detectives have run into some seemingly baffling problems without going an inch underground. For nstance, the Canadian Shield is known to íe about 3.5 billion years old and to predate nearly all rock elsewhere in the world. Yet there are numerous pockets of rock only a couple of hundred million years old spotted across the shield. Some of these even have fossils in them. How they got there is a mystery, now possibly explained y the theory that the shield must have ■een covered with ocean, which washed eavv deposits of sand onto it. These later turned to rock. The ocean retreated and erosion swept the shield clear again, but left the pockets of relatively new rock.
Fven when scientists get a chance to personally check such incidents from the ,oep past, they still encounter formidable • ifficulties. Dr. Victor Ben Meen. of the Royal Ontario Museum, led the first expedition to the large crater known as the Chubb east of Hudson Bay in 1951 in an attempt to determine whether it was caused by a meteor, or an old volcano. Savage weather conditions meant he had less than four weeks in which an amphibious airplane could land his crew on a near-by lake. Working rapidly, he and his colleagues analysed rocks, made seismic soundings, looked for any clue which would suggest the existence of a meteorite, perhaps thousands of feet under the crater lake. They got proof that the crater was caused by a meteor barely twenty-four hours before a blizzard forced them to leave the area.
At first look, there doesn’t seem to be much relationship between a meteor from outer space and a bunch of men digging holes in the ground. But the relationship
is close, even dramatic. “According to mathematical theory,” says Dr. S. C. Robinson, chief of the petrological sciences division of the Geological Survey of Canada, “there should be a planet between Jupiter and Mars. But there isn't. Instead, there’s a belt of asteroids, or minor planets.”
About five billion years ago. astronomers now suggest, some great cosmic accident caused the disintegration of the missing planet. Perhaps it was a collision with a comet. The planet exploded into asteroids and meteors. Chunks of this cosmic debris have been circling the sun ever since. Now and then, pieces of it hit the earth.
Some of the bits have been gigantic. One. about a mile in diameter, may have blasted out 25,000 square miles of Hudson Bay. Another may be responsible for much of the Gulf of St. Lawrence. One meteor hit eastern Siberia in 1908 and its impact was heard a thousand miles away. It destroyed 100 square miles of forest.
The Chubb meteor, which the Ontario Museum’s Dr. Meen investigated, must have created an almost perfect simulation of a fifty-megaton nuclear explosion; it blasted a two-mile-wide crater which by Meen’s measure, was more than 1.300 feet deep. It must have cracked the earth’s crust, perhaps clear down to the mantle thirty miles below.
If the meteors are remnants of an exploded planet, then they likely consist of the same materials as earth itself. They are certainly of two basic types, one consisting of rock like our hypothetical mantle material, the other consisting of nickel and iron, the material that’s supposed to make up the core of the earth.
"So. theoretically.” says one scientist, "all we have to do is analyse these fragments and we’ll be finding out exactly what’s deep inside our own planet.” The concept has eerie undertones. When Dr. Jim Harrison, director of the Geological Survey of Canada, was showing a visitor a large piece of core-type meteorite in his Ottawa laboratory recently, he pointed out how highly polished the iron was along a line where it had been cut for demonstration purposes. The visitor struck the fragment with his fist and produced a strong ringing sound, like a large gong being struck. "It gives me the feeling that it's man-made." the visitor said. “It gives its the feeling.” said Harrison, “that there are worlds out there similar to ours.”
Unfortunately, meteor fragments are very scarce, even though, as Dr. Peter Millman of the National Research Council has calculated, about 100 meteorites hit Canada every year. So far, scientists have
only located about one fall every ten years. One U. S. scientist financed years of research by selling bits of a large fragment he found, at prices of up to $1,000 for chunks weighing 200 pounds or so.
Sometimes, the competition to get fragments can be fierce—and funny. When a meteorite exploded and fell high over Alberta in early March, I960, Dr. R. E. Folinsbee, of the geology department of the University of Alberta, jumped into his car and set out for the scene. The frag ments had fallen over a wide area, three miles long and four miles wide, but Folinsbee wanted every piece of it.
To his chagrin, the biggest piece had been picked up by a farmhand who had traded pieces of it to a local barman for a wild night on the town. “It’s a sign of the times,” said one scientist, “that it’s now possible to get drunk on earth at the expense of the solar system.”
Though analysing meteorites is not a satisfactory way of checking the earth’s interior, it will be used for a long time to come. The difficulties of getting into the earth are formidable, as the Americans are already discovering. When they put down two exploratory holes, both over 600 feet, in Pacific bedrock off the western American coast recently, as preludes to the giant Mohole Project, they found after the drills were temporarily withdrawn, that they couldn’t find the holes. Six hundred feet is one-fiftieth of the distance they must go down. So Mohole is stalled, awaiting a solution.
Regardless of difficulties, though, all the mantle project scientists are elated at the prospects ahead. Says Dr. W. F. van Steenburgh, director-general of the scientific services division of the department of mines. “Till now, the atom people have had it all their own way. Now it's our turn.”
When the earth scientists meet in Berkeley at the end of 19 63, they will discuss vast problems, and projects, looming in the future. Some Russian scientists have speculated that the Arctic ice cap might be melted to create a northern sea for navigation and commerce. The Americans feel this is madness. They say it would cause the most fearsome ice age ever known, which would overwhelm Siberia and the North American continent.
Other scientists are talking about the chances of tapping and harnessing the almost limitless heat power of the earth which would make polar ice melting projects quite feasible and which could drastically change the world’s climate.
Whether these men reach the mantle by 1964 or not, the search for it won’t stop till answers are found to its mysteries. T he answers may come from deep in the earth, or they may fall on us from outer space. “The first man on the moon could give us vital information in the search,” says one geological survey scientist.
The scientists aren't letting a trick pass in their search. Dr. Bob Barager, geologist at the Yellowknife office, hits alerted all civil and private pilots in the Yukon to watch for unexplained dark marks on the snow and on frozen lakes. In this way, he hopes to track down meteorites that have fallen unseen, and so pick up one more clue in the detective story that leads to the mysterious mantle, iç