by John McPhee
We moved off the gangplank and into a highway throughcut of pink granite. Love said, “Now we are on the mountain, on the Precambrian core. You have to watch closely. This fantastic geology is subtle. I-80 was not built to show it off but to take advantage of its beneficences.” There were more pink granite cuts and also some dark, shattered amphibolite that had been the country rock into which the granite intruded 1.4 billion years ago. The interstate had sliced through a section where the bright-pink granite and the charcoal-gray amphibolite met. It was as if a wall painter had changed colors there. The dark rock was full of fracture planes and cleavage planes. “That rock probably had been messed around for a long time before the granite came,” Love said. “It could be two, three billion years old. We don’t know.”
As our altitude increased, the granite roadcuts became deeper and higher and seemingly more rutilant. The rock was competent. There were no benches, and the cuts were as much as fifty metres high. Resembling marbled steak, they were shot through with veins of quartz, where, long after the granite formed, it cracked and quartz filled it in. The walls were indented with vertical parallel grooves, like giant wormtrails in some exotic sediment. These were actually fossil shot holes and unloaded guide holes from the process of presplitting. The highway builders drilled the holes and then dynamited one of three. In this manner, they—and we—reached eight thousand six hundred and forty feet, the highest point on Interstate 80 between the Atlantic and the Pacific. What appeared to be the head of a chicken sat at the top of a big granite block, as if it had been chopped off there. Only when we drew close did I glance up and see that it was Abraham Lincoln. It was, in fact, an artful likeness, resting on an outsized plinth. Years ago, this had been the summit of the Lincoln Highway, which was now incorporated in its substance, if not in its novel spirit, into the innards of the interstate.
We left I-80 there and bucked the southwest wind, crossing the surprisingly flat mountain-crest terrain on a pair of ruts in the pink granite, which had crystals the size of silver dollars. The view from that high wide surface took in a large piece of the front of the Rockies, with the Never Summer Mountains standing out clearly in Colorado, to the south, and, to the west, the bright peaks of the Snowy Range. The Snowy Range—rising white above a dark high forest—appeared to be on top of the Medicine Bow Mountains. Remarkable as it seemed, that was the case. At the ten-thousand-foot level, the bottom of the Snowy Range rests on the broad flat top of the Medicine Bows like a sloop on water, its sails flying upward another two thousand feet. In the Miocene, the high flat Medicine Bow surface at the base of the Snowy Range was the level of maximum fill. In the fifty miles between the Snowy Range and our position on top of the Laramie Range lay the gulf of the excavated Laramie Plains. Our line of sight to the tree line of the Medicine Bows had been landscape in the Miocene. From twelve thousand feet it had gently sloped to about nine thousand where we were, and as we turned and faced east and gazed on down that mostly vanished plane we could all but see the Miocene surface continuing—as Love expressed it—“on out to East G-string.”
Everywhere in the central Rockies, that highest level of basin fill touched the eminent ranges at altitudes that are now between ten and twelve thousand feet with results that are as beautiful as they are anomalous in the morphology of the world’s mountains. In the Beartooths, for example, you can ascend a glacial valley that—in its U shape and high cirques—closely resembles any hanging valley in the Pennine Alps; but after you climb from ten to eleven to twelve thousand feet you do not find a Weisshorn fingering the sky. Instead, you move into an unexpectable physiographic setting, which, after steep slopes above a dry Wyoming basin, is lush and paradisal to the point of detachment from the world. Alpine meadows with meandering brooks are spread across a rolling but essentially horizontal scene, in part forested, in part punctuated with discrete stands of conifers and small cool lakes. The Medicine Bows are also like that—and the Uintas, the Bighorns. Their high flat surfaces, with peaks that seem to rest on them like crowns on tables, make no sense unless—as you look a hundred miles from one such surface to another across a deep dividing basin—you imagine earth instead of air: the Miocene fill, the continuous terrain. The high plateaus on the shoulders of the ranges, remaining from that broad erosional plane, have been given various names in the science, of which the most prominent at the moment is subsummit surface. “There’s a plateau above Union Pass in the Wind River Range that’s twelve thousand feet and flatter than a turd on a hot day,” Love recalled, and went on to say that at such an altitude in flat country he sometimes becomes panicky—which does not happen if he is among craggy peaks, and seems to be a form of acrophobia directly related to the oddity of being in southern Iowa at twelve thousand feet.
With those big crystals, the granite under our feet was about as coarse as granite ever gets, and, as a result, was particularly vulnerable to weather. Its pink feldspar, black mica, and clear glass quartz had been so exposed there for millions of years that gravels could be scraped off without the help of dynamite. The Union Pacific took advantage of this, ballasting its roadbed with pink granite for eight hundred miles. There was almost no soil in that part of the range—just twelve miles’ breadth of rough pink rock. “As you go from Chicago west, soil diminishes in thickness and fertility, and when you get to the gangplank and up here on top of the Laramie Range there is virtually none,” Love said. “It’s had ten million years to develop, and there’s none. Why? Wind—that’s why. The wind blows away everything smaller than gravel.”
Standing in that wind was like standing in river rapids. It was a wind embellished with gusts, but, over all, it was primordially steady: a consistent southwest wind, which had been blowing that way not just through human history but in every age since the creation of the mountains—a record written clearly in wind-scored rock. Trees were widely scattered up there and, where they existed, appeared to be rooted in the rock itself. Their crowns looked like umbrellas that had been turned inside out and were streaming off the trunks downwind. “Wind erosion has tremendous significance in this part of the Rocky Mountain region,” Love said. “Even down in Laramie, the trees are tilted. Old-timers used to say that a Wyoming wind gauge was an anvil on a length of chain. When the land was surveyed, the surveyors couldn’t keep their tripods steady. They had to work by night or near sunrise. People went insane because of the wind.” His mother, in her 1905 journal, said that Old Hanley, passing by the Twin Creek school, would disrupt lessons by making some excuse to step inside and light his pipe. She also described a man who was evidently losing to the wind his struggle to build a cabin:
He was putting up a ridgepole when the wind was blowing. He looked up and saw the chipmunks blowing over his head. By and by, along came some sheep, dead. At last one was flying over who was not quite gone. He turned around and said, “Baa”—and then he was in Montana.
Erosion, giving the landscape its appearance, is said to be the work of water, ice, and wind; but wind is, almost everywhere, a minimal or negligible factor, with exceptional exceptions like Wyoming. Looking back across the interstate—north up the crest of the range—among ponderosas, aspens, and limber pines we could see the granites of Vedauwoo Glen, which had weathered out in large blocks, as granite does, along intersecting planes of weakness, while wind-borne grit had rounded off the corners of the blocks. Where some had tumbled and become freestanding, grit flying close above the ground had abraded them so rigorously that the subsummit surface was, in that place, a flat of giant mushrooms. The cliffs behind them also looked organic—high piles of rounded blocks, topped in many places by narrowly balanced boulders that were undercut almost to the point of falling. Love, contemplative, appeared to be puzzling out some deep question in geomorphology. At length, he said, “When wild horses defecate, they back up to a place where other wild horses have defecated, and so on, until they build turd towers, like those, in the air. Domestic horses do not do this.”
At the Wyoming Information Center
, beside Interstate 80 just south of Cheyenne, eleven picnic tables are enclosed in brick silos, and each silo has a picture window, so that visitors to Wyoming can picnic more or less al fresco and not be blown home. On the range, virtually every house has a shelter belt of trees—and for the most part the houses are of one story. Used tires cover the tops of mobile homes. Otherwise, wind tears off the roofs. Mary Kraus, a sedimentologist from the University of Colorado, got out of her car one day in north-central Wyoming and went to work on an outcrop. The wind blew the car off a cliff. A propeller-drawn airplane that serves Wyoming is known as the Vomit Comet. When people step off it, they look like spotted slate.
“Most people today don’t realize the power of wind and sand,” Love said. “Roads are paved. But in the first fifty years of the Lincoln Highway you didn’t like to travel west in the afternoon. You’d lose the finish on your car. Your windshield became so pitted you could hardly see out.” The Highway Department has not yet paved the wind. On I-80, wind will capsize tractor-trailers. When snow falls on Wyoming, its travels are only beginning. Snow snows again, from the ground up, moves along the surface in ground blizzards that can blind whole counties. Ground blizzards bury houses. In roadcuts, they make drifts fifty feet deep. The wind may return ahead of the plows and take the snow away. The old-timers used to say, “Snow doesn’t melt here; it just wears out.” Interstate 80 has been closed by snow in Wyoming in every month but August—sometimes closed for days. Before Amtrak dropped its Wyoming passenger service, people stranded on I-80 used to abandon their cars and make their escape by train. The most inclement stretch of 80 is east of Rawlins where it skirts the tip of the Medicine Bows, where anemometers set on guardrails beside the highway frequently catch the wind exceeding the speed limit.
Now, looking from mountains to mountains west over the Laramie Plains—his gaze bridging fifty miles of what had fairly recently been solid ground—Love said he thought the role of the wind had been much greater than hitherto suspected in the Exhumation of the Rockies. Water, of course, was the obvious agent for the digging and removal of the basin fill, as a look at the Mississippi Delta would tend to confirm. Many miles off the coast there, you could drill down into the muck and after fifteen thousand feet the bit would still be in the Miocene. He continued, “We know, however, the approximate volume of sediment from the Powder River Basin, the Bighorn Basin, the Wind River Basin, the Laramie Basin, and so forth. We can say it all went downhill to the Mississippi Delta. But go to the delta. Look at the volumes. There’s an enormous discrepancy. You add up what’s down there in the Gulf and what was removed here, and they don’t square. A great deal more has been removed from here than is down there. Streams only account for about half the material that was taken up and out of here. Since it is not all in the delta, where did it go? So much has been taken away that it’s got to be explained in some other manner. I think the wind took it. My personal feeling is that a lot of it blew eastward to the Atlantic. Possibly some went to Hudson Bay. We don’t know. These are problems we are trying to grapple with at the present time. How much did the wind take? Again, we don’t know, but in one dust storm several years ago a great deal of debris from Kansas and Nebraska and Colorado went into the Atlantic—a storm that lasted only a couple of days.”
Such storms are frequent, and this one was not unusual in size or duration. It is noteworthy because its effects were studied and published, in the Journal of Sedimentary Petrology. When the dust appeared above the coast of Georgia—as thick haze—it attracted the attention of researchers at the Skidaway Institute of Oceanography, near Savannah. The cloud of particles was two miles in height, and satellite photographs showed its other dimensions: four hundred thousand square miles. With air-sampling-and-measuring equipment, the Skidaway people collected particles. They reported in that one storm enough dust to account for twenty-five per cent of the annual rate of sedimentation—from all rivers as well as the air—in the proximate North Atlantic. Moreover, about eighty-five per cent of it was a clay mineral called illite. Silts coming out of east-coast rivers include very little illite, and yet illite is predominant among the sediments of the ocean floor. By Skidaway’s calculations, that one storm’s deposits in the ocean amounted to a million tons.
Moving even farther from the interstate on the subsummit surface, we came upon a granite pyramid, sixty feet high, sixty feet wide at the base. It had been designed by the architect H. H. Richardson and weighed six thousand tons—enough to prevent its blowing over. We stood in its lee. The wind was coming in pulses that made percussions in the ears. The incongruity of this monument was in direct proportion to its stark isolation. It was Uncle Pete’s version of Interstate 80’s Abraham Lincoln. It commemorated the brothers Oakes and Oliver Ames—Massachusetts shovel-makers, railroad financiers—whose Credit Mobilier of America made construction contracts with itself in enjoying the fruits of subsidy of the Union Pacific Railroad. If you belonged to the United States Congress, you could buy shares of Credit Mobilier stock for fifty per cent of their value. Near the apex of the east side of the pyramid was Oliver’s face in a portrait plaque, sculptured in 1881 by Augustus Saint-Gaudens, whose William Tecumseh Sherman stands in Manhattan’s Grand Army Plaza and Robert Gould Shaw in Boston Common. Saint-Gaudens’ plaque of Oakes Ames was on the west side of the pyramid, facing the wind. The monument had been built beside the Union Pacific at the railroad’s highest point, but the railroad’s highest point was somewhere else now; the alignment had been changed in 1901, and the track was three or four miles away. The original roadbed had become so indistinct that a geologist was required to point out where it had been, which he did. Oakes’ nose had been shot off with a high-powered rifle. Oliver’s nose had been shot away, too, and a large part of his face. Love remarked that Greek, Roman, and Saracen vandals broke off the noses from pieces of sculpture. Probably the Vandals did, too.
Back on the interstate and just west of Abraham Lincoln, the rock became younger again, as we left the Precambrian range core and encountered the same Pennsylvanian red sandstone that had leaned on the mountain on the other side. It was rich red, and the cuts were very big as the road plunged through them in christie turns, running down the mountains through Telephone Canyon. Somewhere overhead had been the first telephone wire ever strung across the Rockies. The President of the United States, with a dozen horses and companions, rode up Telephone Canyon on his way to Cheyenne in 1903. His mustache was an airfoil with a fineness ratio that must have impressed the Wright brothers. He wore a three-gallon hat. His paunch at the time was under control. The interstate trail was more than a little wild then, but manifestly so was he. The red rock is of so much beauty there, and competence, that people collect it for building material, banging it free from the shattered roadcuts and loading it into pickups, much as ranchers did when they first came to the Laramie Plains and ascended the mountains in wagons and collected the rock to build their homes. It is a porous and permeable, fine-grained, hard, brittle sandstone; and because it rests on impermeable granite water moves through it downhill. Released in a fault zone at the bottom, the water leaps to the surface in artesian fountains—the springs that established Laramie. The bright-red roadcuts, ten and twenty metres high, were capped with a buff-colored limestone, which had been deposited in tropical waters on top of the Pennsylvanian sand. After a mountain range rises under layers of flat-lying rock and bends them upward until they all but stand on end, the slopes of the eroding mountains will descend more gently than the dip of the molested strata. And so, as we plunged down Telephone Canyon, the interstate was tilting less than the rock of the roadcuts, and the red sandstone yielded gradually, interstitially, to the younger limestones, until the sandstone was gone altogether and we were moving through the floor of an ocean. It was full of crinoids, brachiopods, and algal buttons, which had lived near the equator in a place like the Bismarck Archipelago or an arm of the Celebes Sea.
The canyon opened to the plains—a broad dry sea of the interior Rockie
s—and soon we were on Grand Avenue, Laramie, passing the University of Wyoming, whose buff buildings on wide soft lawns could never be said to resemble roadcuts, notwithstanding the crinoids in their walls, the brachiopods and algal buttons. We passed Love’s home, on Eleventh Street, and his office on the campus, adjacent to a life-size two-story sculpture of Tyrannosaurus rex, the toughest-looking critter in the history of the earth, a native, needless to say, of Wyoming. We passed St. Matthew’s Episcopal Cathedral, which also—as Love had reason to regret—contained in its walls brachiopods, crinoids, and algal buttons. He once taught Sunday school there. He took the kids outside and showed them the fossils in the church walls. He described the environment in which the creatures had lived. He mentioned the age of the rock. He explained how things evolve and the fit prosper. Here endeth his career in sedimentary theology.
A few miles north of town, we passed the quarry out of which had emerged not only the university and St. Matthew’s Cathedral but also the Ivinson Home for Aged Ladies and the Albany County Courthouse. “It’s a limey sandstone, slightly fossiliferous,” he said. “It holds up pretty well.” We continued north along the foot of the Laramie Range and then turned east into the mountains, climbing a canyon downsection until we had returned to Precambrian time. The rock in this place was even older than the neighboring subsummit granite, and some of it was chatoyant: flashing like a cat’s eye. It flashed every color in the spectrum. The rock was anorthosite, nearly fifteen per cent aluminum, Love said. When the bauxites of the Caribbean run out, anorthosite will be a source of aluminum. “Anorthosite is tough, has a high melting point, and doesn’t fracture easily,” he continued. “Hence it might be useful for containing atomic waste.” Anorthosite is rare on earth. It began forming during the Archean Eon and predominantly dates from an age of the later Precambrian known as Helikian time. Yet the high Adirondacks are largely anorthosite. The choice they present is to seal up our spent nuclear fuel inside them or dismantle them one at a time to make beer cans. Anorthosite is more plentiful elsewhere. It is most of what you are looking at when you are looking at the moon.