by John McPhee
The 1955 Wyoming map set a standard for state geologic maps in the detail of its coverage, in its fossil dating, in its delivery of the essence of the region—a standard set anew in the 1985 edition. In the words of Malcolm McKenna, of the American Museum of Natural History, “Most maps are patched together from various papers and reports. Dave has looked at all the rock. It’s all in one mind. Most geologic maps are maps of time, not rocks. They will say something like ‘undifferentiated Jurassic’ and omit saying what the rocks are. There is little of that on Dave’s map. Mapping is below the salt now. Yet you can’t look at satellite photos for everything. You’ve got to have high-resolution basic mapping. You have to keep your hand in with the real stuff. When the solid foundations aren’t there, geologists are talking complete mush. Dave is making sure the foundation is there. He does not write about geology from a distance. He does not sit in high councils figuring out how the earth works. He is field-oriented. Some geologists think field work is wheeling their machines out into the yard. Dave has his hand on the pulse. He knows geology from having found it out himself. He has set an example of the way geology is done—one hell of an example. To compete with Dave, you’d have to do a lot of walking.”
Love once picked up a mail-order catalogue and saw an item described as “Thousand Mile Socks.” He sent for them skeptically but later discovered that there was truth in the catalogue’s claim. They were indeed thousand-mile socks. He had rapidly worn them out, but that was beside the point.
Years ago, almost anybody going into geology could look forward to walking some tens of thousands of miles and seriously studying a comparable number of outcrops. Geology, by definition, was something you did in the field. You sifted fine dirt for fossils the eye could barely see. You chiselled into lithified mud to remove the legs of dinosaurs. You established time-stratigraphic relationships as you moved from rock to rock. You developed a sense of structure from, among other things, your own mapping of strikes and dips. In the vernacular of geology, your nose was on the outcrop. Through experience with structure, you reached for the implied tectonics. Gradually, as you gathered a piece here, a piece there, the pieces framed a story. Feeling a segment of the earth, you were touching a body so great in its dimensions that you were something less than humble if you did not look upon your conclusions as tentative. Like many geologists, Love became fond of the Hindu fable of the blind men and the elephant, because the poem in a few short verses allegorized for him the history and the practice of his science. “We are blind men feeling the elephant,” he would say, almost ritually, as a way of reminding anyone that the crust is so extensive and complicated—and contains so little evidence of most events in earth history—that every relevant outcrop must be experienced before a regional outline can so much as be suggested, let alone a global picture.
In recent years, the number of ways to feel the elephant has importantly increased. While the science has assimilated such instruments as the scanning transmission electron microscope, the inductively coupled plasma spectrophotometer, and the 39Ar/40Ar laser microprobe—not to mention devices like Vibroseis that thump the earth to reflect deep structures through data reported by seismic waves—the percentage of geologists has steadily diminished who go out in the summer and deal with rock, and the number of people has commensurately risen who work the year around in fluorescent light with their noses on printouts. This is the age of the analog geologist, who, like a watch with a pair of hands, now requires a defining word. For David Love, the defining word is “field.” Whereas all geologists were once like him, they are no longer, and his division of the science is field geology. He is the quintessential field geologist—the person with the rock hammer and the Brunton compass to whom weather is just one more garment to wear with his thousand-mile socks, the geologist who carries his two-hundred-gigabyte hard disk between his ears. There are young people following in his steps, people who still go out to scuff their boots and fray their jeans, but they have become greatly outnumbered by their contemporaries who feed facts and fragments of the earth into laboratory machines—activity that field people describe as black-box geology. Inevitably, some touches of tension have appeared between these worlds:
“Who is the new structural geologist?”
“Dorkney.”
“Is he a field-oriented person?”
“He’s a geophysicist, but he’s a good guy.”
“That would be difficult.”
Black-box geologists—also referred to as office geologists and laboratory geologists—have been known to say that field work is an escape mechanism by which their colleagues avoid serious scholarship. Their remarks may rarely be that overt, but the continuing relevance of field geology is not—to say the least—universally acknowledged. Some laboratory geologists, on the other hand, are nothing less than eloquent in expressing their symbiosis with people of wide experience out in the terrain. “I spend most of my time working on computers and waving my arms,” the geophysicist Robert Phinney once said to me, adding that he required the help of someone’s field knowledge as a check, and without it would be in difficulty. “Without such people there would be no such thing as a geological enterprise,” he went on. “Every box of samples that comes into the lab should include a worn-out pair of field boots. There’s a group of senior geologists who have met on the outcrops and share a large body of knowledge. They paste together different perceptions of the world by visiting each other’s areas. When I meet them, I chat them up like the guys at the corner store, because what I do is conceptual and idealized, and I’d like to know that it relates to what they have seen. These people are generally above fifty. Their kind is being diminished, which is a major intellectual crime. It has to do with the nature of science and what we’re doing. Reality is not something you capture on a blackboard.”
Such sentiments notwithstanding, within university geology departments black-box people tend to outvote field people on questions of curriculum and directions of research, and to outperform them in pursuit of funds. “The black-box era has been caused by the availability of money for esoteric types of work,” Love remarked one day. “The Department of Defense, the National Science Foundation, and so forth have had money to spend on—let’s say—un—usual quests. The experience you get from collecting rocks in the field is lost to the lab geologist. For example, there’s a boom in remote-sensing techniques—in satellite imagery. From that, you get a megapicture without going into the field. But it’s two-dimensional. To get the third dimension—to study what’s underground—they consult another sacred cow, which is geophysics. They can make a lot of these interpretations in the office. They can go off the mark easily, because for field relationships they often rely on data collected years ago. They use samples from museums, or samples collected by somebody else—perhaps out of context. I’m afraid I’m rather harsh about it, but we see misinterpretations, because of lack of knowledge of field relationships. Many of the megathinkers are doing their interpretations on the basis of second- and third-hand information. The name of the game now is ‘modelling.’ A lot of it I can’t see for sour owl shit. How can you write or talk authoritatively about something if you haven’t seen it? It isn’t adequate to trust that the other guy is correct. You should be able to evaluate things in your own right. Laboratory geology is where the money is, though. The money is in the black box. I think eventually it will get out. You can’t blame the kids for doing this kind of office research when they’re financed. I don’t want to do it myself. Putting the geologic scene into a broad perspective is for me more satisfying. I want to know what’s over the next hill.”
He was saying some of this in the Mt. Leidy Highlands one day when we were sitting on an outcrop at ninety-two hundred feet and looking at a two-hundred-and-seventy-degree view that ran across the pinnacled Absarokas to a mountain of lava of Pleistocene age and then on up the ridgeline of the Continental Divide to the glaciers and summits of the Wind River Range, thirty-eight feet higher than the Tetons. Th
e skyline sloped gently thereafter, flattened, and became the subsummit surface of Miocene age, the level of maximum burial. There followed, across the southern horizon, the whole breadth of the Gros Ventre Mountains, with afternoon light on bright salmon cliffs of Nugget sandstone, at least four hundred feet high. The eye moved west over other summits and ultimately came to rest on the full front of the Tetons. We looked at it all for a considerable time in silence. Love said he liked this place because he could see so much from it, and had stopped here many times across the decades, to lean against a piñon pine and sort through the country, like an astronomer with the whole sky above him sorting through the stars. He also said, reflectively, “I guess I’ve been on every summit I can see from here.”
Below us was Dry Cottonwood Creek. It ran southeast several miles, and then turned through a tight bend to head west toward the Tetons. We could see other streams almost identical in configuration, like a collection of shepherd’s crooks. “The land tilted east, and then south, before it tilted west,” Love said. “This is the tilting block that stops at the foot of the Tetons. The barbed streams are evidence that the hinge is east of us here. The hinge is probably the Continental Divide. We can learn a lot from streams. They’re so sensitive. They respond to the slightest amount of tilting. I think this is underestimated.” Pointing down to some sandstone ledges along the bank of Dry Cottonwood Creek, he said that Indians had frequently camped there because long ago the stream was so full of trout you could reach in under the ledges and catch them with your hand. He asked if I knew why the water was so clear. “There’s no shale upstream,” he said. “No fines to contaminate it. If you look at a stream, you can see in the sediments the whole history of a watershed. It’s as plain as the lines on the palm of your hand.”
On the way up to the lookoff, we had stopped at a spring, where I buried my face in watercress and simultaneously drank and ate. Love said that F. V. Hayden, the first reconnaissance geologist in Wyoming Territory, also happened to be a medical doctor, and he went around dropping watercress in springs and streams to prevent scurvy from becoming the manifest destiny of emigrants. Hayden, who taught at the University of Pennsylvania, led one of the several groups that in 1879 combined to become the United States Geological Survey. When he came into the country in the late eighteen-fifties, he was so galvanized by seeing the composition of the earth in clear unvegetated view that he regularly went off on his own, moved hurriedly from outcrop to outcrop, and filled canvas bags with samples. This puzzled the Sioux. Wondering what he could be collecting, they watched him, discussed him, and finally attacked him. Seizing his canvas bags, they shook out the contents. Rocks fell on the ground. In that instant, Professor Hayden was accorded the special status that all benevolent people reserve for the mentally disadvantaged. In their own words, the Sioux named him He Who Picks Up Rocks Running, and to all hostilities thereafter Hayden remained immune.
I remarked at the spring that Love was having nothing to drink.
He said, “If I drink, I’ll be thirsty all afternoon.”
And now, on the high outcrop, turning again from the Eocene volcanic Absarokas to the Wind River Range (the supreme expression in Wyoming of the Laramide Orogeny) and on to the newly risen Tetons (by far the youngest range in the Rockies), I mentioned the belief of some geologists that of all places in the world the Rocky Mountains will be the last to be deciphered in terms of the theory of plate tectonics.
“I don’t think I would necessarily agree,” Love said. “I think it is one of the more difficult ones, yes. I’ve thought a lot about it. At this stage, I’m uncomfortable with a direct tie-in. Until we have a detailed chronology of all the mountains, how can we plug them into a megapicture of plate tectonics? I don’t want to give a premature birth to anything.”
Plate-tectonic theorists pondering the Rockies have been more than a little inconvenienced by the great distances that separate the mountains from the nearest plate boundaries, where mountains theoretically are built. The question to which all other questions lead is, What could have hit the continent with force enough to drive the overthrust and cause the foreland mountains to rise? In the absence of a colliding continent—playing the role that Europe and Africa are said to have played in the making of the Appalachians—theorists have lately turned to the concept of exotic terranes: island arcs like Japan slamming up against the North American mainland one after another, accreting what are now the far western states, and erecting in the course of these collisions the evidential mountains. Whatever the truth in that may be, a tectonic coincidence very much worth noting is that the development of the western mountain ranges begins at the same time as the opening of the Atlantic Ocean. In the middle Mesozoic, as the Atlantic opens, the North American lithosphere, like a great rug, begins to slide west, abutting, for the most part, the Pacific Plate. A rug sliding across a room will crumple up against the far wall.
“We’re about a thousand miles from the nearest plate boundary,” Love was saying. “We should not tie in the landscape here with events that have taken place along the coast. This doesn’t neutralize or dispose of the theory of plate tectonics, but applied here it’s incongruous—it’s kind of like a rabbit screwing a horse. There is no evidence of plates grinding against each other here. The thrust sheets are probably symptoms of plate-tectonic activity fifty million years ago, but the chief problem is that tectonism is not adequately placed in a time framework here. Almost everybody now agrees that there is tremendous significance to plate tectonics—also that the concept is valid. Most people don’t argue about that anymore. Our arguments come in the details. We should dissect all these mountain ranges before we get diarrhea of the pen trying to clue them in to plate theory. There’s nothing wrong with ideas, with working hypotheses, but unsubstantiated glittering generalities are a waste of time. Most of the megathinkers are basing sweeping interpretations on pretty inadequate data. There are swarms of papers being written by people who have been looking at state and federal and worldwide geologic maps and coming to sweeping conclusions on how mountains were formed and what the forces involved were. Until we know the anatomy of each mountain range, how are we going to say what came up when—or if they all came up in one great spasm? You can’t assume they’re all the same. In order to know the anatomy of each mountain range, you have to know details of sedimentary history. To know the details of sedimentary history, you have to know stratigraphy. I didn’t know until recently that stratigraphy is dead. Many schools don’t teach it anymore. To me, that’s writing the story without knowing the alphabet. The geologic literature is a graveyard of skeletons who worked the structure of mountain ranges without knowing the stratigraphy. In Jackson Hole in the late Miocene, you had a lake that collected six thousand feet of sediment, half of which was limestone that was chemically precipitated. There had to be a source. It came from broad exposures of Madison limestone in the ancestral Teton–Gros Ventre uplift, chemically dissolved and then precipitated with cool-climate fossils. Therefore, that lake lay under a cool, humid climate. First, a basin had to be created in which the material was deposited—a basin ultimately thirteen thousand feet deep to accommodate all the lake and river sediments we find there, which puts it two miles below sea level at a time when the region is supposedly uplifting. All this is basic to structure, and the structure is basic to tectonics. The Owl Creek Mountains and the Uinta Mountains trend east-west. Why? Why are their axes ninety degrees from what you would expect if the tectonic force came from the west? You can do a torsion experiment with a rubber sheet and get folds in various directions—you can get east-west uplifts in the rubber sheet—but I would not say that is conclusive. You have mountains foundering. You have thrusting in the Laramide and sinking forty to fifty million years later, causing parts of basins to tilt this way and that like broken pieces of piecrust. The Granite Mountains were once as high as the Wind Rivers. Why did they go down? How did they go down? I don’t think we’re ready yet to put together a real megapicture. The 1985 g
eologic map of Wyoming consists of eighty-five-per-cent new mapping since 1955. The amount remapped shows how much new information was acquired in thirty years. The Big Picture is not static. It will always include new ideas, new tectonics, new stratigraphy. This information is an essential part of the megathinking of the plate-tectonics people, and twenty-five, fifty, a hundred years from now it will be very different.”
West of Rawlins on Interstate 80, Love and I in the Bronco came into a region a good deal flatter than most of Iowa, with so little relief that there were no roadcuts for more than fifty miles. Among dry lakebeds dimpling the Separation Flats, our altitude was seven thousand feet, yet the distant horizon was close to the curve of the earth. In this unroughened milieu, we passed a sign informing us that we were crossing the Continental Divide. So level is the land there that the divide is somewhat moot. Cartographers seem to have difficulty determining where it is. Its location will vary from map to map. Moreover, it frays, separates, and, like an eye in old rope, surrounds a couple of million acres that do not drain either to the Atlantic or the Pacific—adding ambiguity to the word “divide.”
With respect to underlying strata, we were running along the crest of an arch between two sedimentary basins, although nothing on the surface suggested that this was so, for the basins were completely filled. The flats to our left were the Washakie Basin, to our right the Great Divide Basin—each like a bowl brimming over with Eocene alluvial soup. Younger deposits—maybe a mile’s thickness —had long since been washed or blown away, leaving a fifty-million-year-old surface on which anything modern might fall.
A shepherd on horseback stood out against the sky, more so than his sheep. Even from a distance, he looked cold and uncomfortable. On this robust May afternoon, gray clouds, moving fast, were beginning to throw down hail. Love turned off the interstate, and the vehicle bucked south for a couple of miles in drab brown ruts that suddenly turned bright, almost white, as the ground jumped forward in time roughly fifty million years. This patch of thirty or forty acres was all that remained locally of a volcanic-ash fall that had covered large parts of Wyoming, Colorado, Kansas, and Nebraska and had reached as far as Texas. Radiometric dating has established the event at six hundred thousand years before the present—far along in Pleistocene time, and an extremely recent date in the history of the world when you reflect that the age of the earth is more than seven thousand times the age of that ash fall, just as the United States of America is more than seven thousand times as old as something that happened in the middle of last week. The ash—consisting of very small shards of glass—had travelled about two hundred miles downwind from its volcanic source. Two hundred miles downwind from Mt. St. Helens, in the state of Washington, the amount of ash that has accumulated as a result of Mt. St. Helens’ recent eruptions is three inches. The ash here at the Continental Divide was sixty feet thick. A hundred and more miles northwest are remnants of the same fallout, suggesting the dimensions of the great regional blanket of six hundred thousand years ago, now almost wholly lost to erosion. Love said cryptically, “We have to assume it fell on saint and sinner alike.” It had not been milled around by streams. It was a pure ash, distinctly wind-borne, containing no sand, no clay. He said that some woolly-mammoth bones had been found not far away, and with them as a minor exception this ash marked the only firm Pleistocene date in an area of twenty thousand square miles. After settling, it had not consolidated—as volcanic ash sometimes will, forming welded tuff. (The Vesuvian air-fall ash that settled on Pompeii also flew too high to weld. Rising rapidly like smoke, it actually pooled up against the stratosphere. Pliny said it looked like a flat-topped Italian pine. The geologic term for such an event is “Plinian eruption.”) A couple of hundred miles northwest of us were the paint pots and fumaroles, the geysers and calderas of Yellowstone. Love said that this Lava Creek ash represented one of the great outpourings in Yellowstone history. The hail now was pelting us. It collected like roe on the brim of his Stetson. Love seemed to regard it as a form of light rain, as something that would not last even for six hundred thousand nanoseconds and was therefore beneath notice.