Natural Acts: A Sidelong View of Science and Nature - David Quammen (1996)


Yin and Yang in the Tularosa Basin

IN THE OUTBACK OF SOUTHERN NEW MEXICO, laid down across a thousand square miles of otherwise unexceptional desert, there is a message.

It is gigantic and stark. A simple design, vaguely familiar, executed in unearthly black-and-white against the brown desert ground. You could see it from the moon with a cheap telescope. Nevertheless, it is more cryptic than Stonehenge. An army of zealous Chinese masons might have spent their lifetimes erecting such a thing—but no, that’s not where it came from. The full design includes four elements, only two of those manmade, the others attributable to natural processes of the sort that are loosely called “acts of God.” In the desert, as Moses found out, God seems to act with an especially bold hand. The constituent materials in this particular case are basalt rock and gypsum sand; black and white, rough and smooth, hard and soft; dissimilar as fire and ice. The message is drawn in high contrast. The text is clear but the meaning is not.

A dune field of startling whiteness, called the White Sands, sprawls out in giant amoeboid shape, creeping northeastward with the winds. A hardened black flow of recent volcanic lava, called the Carrizozo Malpais, stretches southwestward down the gentle incline along which gravity pulled it from its point of emergence through the earthly crust. Near an old ranch site known as Three Rivers, the leading edge of the whiteness approaches the forward lip of the blackness, leaving a gap of not many miles. Through that gap runs a narrow range road, open for public travel only one day a year. Where the road goes, and why armed men in guardhouses monitor its disuse, are questions for later. The oddities about this place will have to be taken in turn. We are in the Tularosa Basin, a sunken valley full of saltbush and lizards and history, gypsum and lava, plus more than its share of preternatural romance, lying halfway between Las Cruces and Roswell on the way to nowhere at all. We are here, first of all, for the big design.

The design: Superimposed on the desert by a convergence of geological accidents, it is an unmistakable yin and yang, a huge magnification of the Taoist emblem that stands for the paradox of dialectical oneness—two teardrops bound complementarily into a circle, dark and light, head to tail, representing the unity within which all worldly flux remains balanced. In this particular case, the emblem is as large as Long Island. From the moon or beyond, with your telescope, you might take it for a symbol of harmony. The confusion would be understandable.

An abundance of gypsum was the earliest of those geological accidents.

Gypsum is curious stuff from which to make a dune field. In scientific notation it is CaSO4 ✵ 2H2O, meaning simply the mineral calcium sulphate, bound up in crystalline form with a proportion of plain water. More familiarly, it is the main ingredient of plaster of paris. Under ideal conditions, falling out of a heavy solution, it grows into elegant daggerlike crystals called selenite, which are more or less clear or amber, depending on purity. But as erosional forces break selenite down into small granules—sand—the faces of those granules, being relatively soft, become scratched. The scratches scatter light. The result is whiteness. You hear the name White Sands, but until you make your own pilgrimage, until you lose yourself in the heart of these dunes with only a canteen and a compass, the words are unlikely to register as they should.

Take them literally. White sands. Whiteness like ivory. Like the sun-bleached skull of a lost desert cow. Whiteness like January in the Absaroka Mountains between Montana and Wyoming, 200 yards above timberline. Actually there is nothing and nowhere else quite like White Sands, the world’s largest expanse of wind-blown gypsum. Nowhere else on Earth where you can surround yourself with such profound whiteness and still be in danger of snakebite. The white dunes began forming perhaps 25,000 years ago, but the gypsum has been here much longer.

It was deposited during the late Paleozoic era, gypsum-rich layers of sedimentary rock left behind from gypsum-rich seawaters as the long cycles of climate moved an ocean coast back and forth over what is now southern New Mexico. Other sediments were left in the course of other cycles, burying the gypsum beneath hundreds of feet of limestone and shale. It might have stayed there, inert and hidden, like most of the gypsum in Earth’s crust, if not for the next accident. Geological pressures that were creating the Rocky Mountains also caused this particular area to buckle upward into a high rounded plateau. Roughly 10 million years ago, another shifting of pressures caused a pair of fault lines to develop, running north-south for a hundred miles; and along these faults, the plateau fell like a startled cake. The parallel fault lines became a matched set of continuous escarpments, mountainous walls, facing each other over a sunken basin. On the east side looking west was what’s now called the Sacramento range; on the west looking east, the San Andres. In between was the Tularosa.

To the north and south also, the Tularosa was blocked by high ground. Like many valleys in the desert country of the West, it had no outlet to the sea. So when the next cycle of wetness began, this basin turned into a vast lake.

Erosional torrents flowed down from the mountains to fill it, and (because the mineral is easily eroded and highly soluble) those waters carried gypsum. The lake in its turn became gypsum-rich. Then our most recent age of relative drought dried it away to almost nothing. The waters shrank gradually back to the lowest spot in the basin, a small area toward the southwest corner, and as the big lake gave up the ghost, it also gave up the gypsum. Meanwhile groundwater flow from the upper end of the basin also carried dissolved gypsum, underground, toward the same spot. These days Lake Lucero is never more than a briny puddle, shin-deep at the end of the monsoon season. For most of the year, it is only a dry bed. But it derives a mute dignity from being the source of the White Sands.

With each cycle of evaporation—nowadays, as for thousands of years—small selenite crystals bloom magically along the puddle’s margins. Seasonal windstorms roar out of the southwest, through gaps in the San Andres Mountains, grinding the crystals to sand. And so the dunes gather themselves, rise, and move.

The nimblest of them advance about 30 feet in a year. Others travel more slowly. Today the sand is spread over an area of almost 300 square miles, enough to constitute a distinct ecosystem with its own patterns of organismic association, its (temporarily) stabilized zones of vegetation, its uniquely adapted races of animal. A whole world of life hides at the heart of the White Sands. But despite 25,000 years of shared history, there is a gypsy quality to that life. The restlessness of the dunes imposes special demands. The very ground here is in motion. We are the dunes: we cover all. You must move along with us, or get out of the way, or die. The animals, even the plants, manage to cope with that imperative in their own patient, mobile ways.

The White Sands are gliding northeastward, inexorably, toward that shape of blackness in the near distance.

The entire Tularosa Basin is tilted slightly downhill toward the southwest, like a great earthen flume. Elevations above sea level vary, from around 6,000 feet at the northern end, to 5,400 near the town of Carrizozo, down to 4,000 feet at Lake Lucero. That incline is the simplest—and least mystical—explanation for what the lava did. Vomiting suddenly up from underground one stormy day, molten black rock flowed steaming and hissing off toward exactly that point from which came the White Sands, as though some dark subterranean animus of alarming proportion were seeking to reunite itself, or maybe do battle, with its antipodal twin.

Halfway there, the lava grew cool and viscid. Wrinkled with corrugations, pocked with gas bubbles, it slowed to a sloppy halt, congealing like a runnel of candle wax. It had traveled 44 miles on a line and lapped out across 120 square miles of desert. In some places it was 100 feet deep.

The source of all this lava was a volcanic vent near the north end of the valley, a spigot-hole down to the planet’s liquid innards. The site of the vent is still marked, above the rest of the lava field, by a high cone of cinder known on the maps as Little Black Peak. Probably the lava poured out of this hole in two separate episodes, closely spaced. How long ago? The geologists can only guess. Maybe 2,000 years. Maybe less. Without question, the Carrizozo Malpais (a Spanish word for “badlands”) is one of the youngest and best preserved lava fields in the continental United States.

Its most striking characteristic is texture. The whole process of liquid rock flowing over rough terrain—cooling differentially from the outside in, piling up on itself into ropy corrugations and eddies, trapping gas bubbles under thin-lidded domes—is captured as in a snapshot. Many of the big bubbles have collapsed to chasms, tiger pits 30 feet deep. Fissures have appeared. At some places the basalt, light and brittle stuff, has been broken into shards by the crowbar of weather. But in the full scope of geologic time, weathering has scarcely begun. The crowbar has been applied but not yet the grinder, still less the emery cloth. This formation is jagged and raucous and therefore, we know deductively, very new.

Some experts date the eruption to around A.D. 500. Archeological evidence adds another interesting angle: Whenever the thing happened, apparently humans were already in the valley to witness it.

They seem to have been a pueblo-building people, sedentary agriculturalists, probably members of what now is referred to as the Mogollon culture. Eventually they disappeared, or were driven out, to be replaced by ancestors of the Mescalero Apaches, a very different bunch. No one knows just why the Mogollon folk went away. Possibly their departure was related to gradual changes in climate and water supply that were incompatible with their farming practices. Or it might have been war. Or something else.

One early commentator, writing in Science back in 1885, offered this: “A stream of no mean size seems to have once run down this valley. Not only has it now disappeared, but its bed is covered by lava and loose soil sometimes to great depths. As to the cause of the disappearance, it may have some connection with the tradition of the Indians which tells of a year of fire, when this valley was so filled with flames and poisonous gases as to be made uninhabitable.”

In 1966 the state of New Mexico set aside a small tract of the lava flow for public enjoyment and edification. A parking lot and a set of restrooms have been added, also a short loop trail out through the Malpais, complete with number-keyed features of geological and botanical interest for which commentary is supplied in a printed brochure. The place is fascinating, and largely unappreciated. To most people who visit it—and there aren’t many—it is just a rest stop on the godforsaken two-lane between Carrizozo and another sleepy town. It is called, quite aptly, Valley of Fires State Park.

Back down at White Sands, public enjoyment and edification are overseen by the U.S. Interior Department. Early in 1933 (it seems to have been one of Herbert Hoover’s last official acts) a presidential proclamation was signed, establishing White Sands National Monument. The borders of the monument encompass a sizable swatch of the dune field, though by no means all of it. Lake Lucero is included, and enough area to provide a good sampling of the different dune types and the biotic communities that exist among them, but the leading edge of the dune field is far outside the monument’s northern boundary. At large, beyond Park Service jurisdiction; off on its own reckless chase.

And surrounding these two modest administrative units—literally arching over them through the sky—is another official fiefdom, one whose appointed mission does not include edifying the public, except perhaps in the most indirect way: White Sands Missile Range. Run by the army, it is America’s largest land-area shooting gallery for the testing of aeronautical and ballistic weaponry. Forty miles wide, stretching north and south for a hundred, it overlaps the whole Tularosa Basin almost exactly. Someone decided, back in 1945, that this is what the Tularosa was good for. Hey, let’s use that big piece of empty desert on the east side of the San Andres Mountains. It’s perfect. Who will ever miss it? Virtually no one has. Outsiders don’t often come here to do their communing with God or nature. And the residents of Alamogordo, the largest town in the basin, seem generally to welcome the military dollars.

Today high-altitude research rockets go up and come down over the missile range. Cruise missiles under development by the navy and the air force are launched from bombers, finding their way with magical sentience to targets among the creosote bushes. Drone aircraft—large jet-powered skeet, guided remotely—are blasted out of the sky by the latest and best in air-defense ordnance, leaving small scraps of their debris to flutter down onto the white dunes like titanium confetti. A laser-guided artillery projectile is fired off toward another corner of desert. From Fort Bliss, down near El Paso, Pershing II missiles fly up here on their intermediate-range trajectories, sailing over White Sands as though it were Poland, heading on toward the Malpais. Ground-to-ground missiles, air-to-air, air-to-ground and vice versa, every combination a country could need or believe it needs, the names themselves resonant with mythology and mystery and stout-hearted martial precision: Nike, Talos, Tomahawk, Lance, Copperhead, Patriot, Stinger.

From one point of view, it is not so doleful as it might seem. The White Sands is a delicate ecosystem where the margin of survival is narrow, for both animals and plants, and disturbances are not easily repaired. The entire chain of life there depends on a very slow process of soil formation and preliminary vegetal growth that occurs only in flat lowland areas between the active dunes. The slightest vehicle traffic (even heavy foot traffic) leaves scars across those flats that remain visible for decades, and an abusive degree of traffic could pull the bottom out from under the whole biotic community. Park Service regulations prohibit off-road vehicular traffic within the monument, but that only covers a fraction of the dune field. Which is why Dr. William Reid, an ecologist from the University of Texas at El Paso who knows the White Sands as well as anyone, says: “Some people resent the missile range. I think it’s a great boon in disguise. It’s what saves the dunes and the interdune areas from the people in four-by-fours.” A fragile environment gets army protection from demented Sunday dirt-racers, and the occasional flaming rocket crash is, true enough, a small ecological price to pay.

So the innermost precincts of the Tularosa Basin remain unapproachable. You do not wander at will onto the White Sands Missile Range, either by truck or on foot. Fences and brusque signs warn you back. Electronic border sensors notice you. Polite security officers appear, carrying shotguns. The message is Keep out. This is secret stuff and we’re busy. Besides, you could get hurt. Then, one day each year, the gate on a certain road swings open, and hundreds of vehicles drive through.

This annual motorcade begins from the parking lot of a Kmart on the north edge of the town of Alamogordo, where the cars and the pickups and the RVs with out-of-state plates have gathered and pulled into file by 7:30 A.M. of the appointed day. It is the first Saturday in October, warm and bright, indecently good weather for a picnic or a football game, and though neither of those is the purpose today, still the atmosphere is just a bit festive. A few children have been dragged along for the occasion, by parents or grandparents, and the kids burn off their energy dodging between bumpers, just as they would amid any dull gathering of stalled cars, for a fair or a funeral. Some folks have brought hampers of food; those in the open-topped sports cars wear jaunty hats. History is the sole attraction, but most of the people here assembled have come out in order to feel good about the particular moment of history in question. A much smaller segment—and they will be distinguishable when the picket signs appear—have come out in order to feel guilty and worried and bad. Only a few of us have come out, fully premeditated, in order to feel confused and ambivalent.

The men from the Alamogordo Chamber of Commerce (cosponsors of the day’s tour, along with the missile range management) do their directing of traffic with brisk, cheerful authority. After a few years’ practice, they feel that they have this thing down to a stroll. It is the Alamogordo equivalent of a big pancake breakfast, or a sweet-pea festival, or a rattlesnake roundup: an expression, and a reinforcement, of civic pride. The 250 autos move off right on schedule. The missile range fellows are holding their fire, but only so long. Just six hours have been set aside for these pilgrims to drive out across the Tularosa, deep into missile range property, on a thin asphalt road running between the White Sands and the black lava, to a place called Trinity Site; to see the marker there, to hear the speeches; and then to get themselves back out of the line of fire.

Of course Trinity Site is the patch of woebegone desert from which Alamogordo, by metonymic incrimination, draws its greatest fame. Actually the site is sixty miles northwest of Alamogordo, shielded behind a stark upthrust of rock known as Oscura Peak. Here, on the morning of July 16, 1945, the nuclear age dawned gaudily. Robert Oppenheimer and his coven of young wizard physicists and mathematicians and engineers, from up in Los Alamos, had chosen the spot because of its sheer desolateness as a good place to test what was then still considered a dubious, improbable gadget.

The test was called Trinity. That code name had been supplied by Oppenheimer, from some free-associative inspiration about which he was ever afterward vague. In a letter, years later, he wrote: “Why I chose the name is not clear, but I know what thoughts were in my mind. There is a poem of John Donne, written just before his death, which I know and love. From it a quotation:

As West and East

In all flat Maps—and I am one—are one,

So death doth touch the Resurrection.

That still does not make Trinity; but in another, better known devotional poem Donne opens, ‘Batter my heart, three person’d God.’ Beyond this, I have no clues whatever.” Such an arcane and obfuscatory explanation was, for Robert Oppenheimer, utterly characteristic.

A different Los Alamos scientist was directly in charge of the Trinity operation, but the two senior officials present were Oppenheimer, the laboratory director, and General Leslie Groves. Groves was a portly career soldier from the Army Corps of Engineers, a man with a large ego and an abrasive personality who had been thwarted in his hope of seeing overseas duty during World War II and who wound up instead, to his dismay, in command of the Manhattan Project. Groves’s original mandate seems to have been limited, a simple engineering task in the corps tradition: to build the laboratories in which others would build the Bomb. But by degrees, in the wartime confusion, he filled a vacuum to become supreme potentate of the entire effort. It was Groves who had picked Robert Oppenheimer to run Los Alamos, the final-stage lab where the details of the weapon’s design were worked out—picked him despite advice from the FBI that Oppenheimer was a security risk. Groves chose to ignore the FBI charges, but not without letting Oppenheimer know he had heard them. Which gave the general a certain leverage. Despite (or perhaps partly because of) that leverage, the two men had settled into a harmonious and effective working relationship.

In character, background, capabilities, these two couldn’t have been more dissimilar. Oppenheimer was an intellectual of broad interests and surprisingly disparate eruditions, who read the classics of Greek and Sanskrit and Spanish literature, loved poetry, carefully studied the work of Karl Marx to see for himself what was there. He had come out of Harvard and done graduate and postdoctoral work at some of the best universities of Europe. He was an epicure. During the 1930s he had been active in leftist causes, generous financially and with his time, never quite a card-carrying Communist but sympathetic with much that the party was doing. Leslie Groves was an engineer and a soldier, period. Son of an austere Presbyterian minister who was himself also an army man, a chaplain to the Fourteenth Infantry, Groves grew up on military posts and went to West Point. Like his father, he was something of a martinet. He was bullish and direct-minded and good at pushing straightforward jobs to completion; not so good at dealing with people. Impatient with psychological complexity. He knew nothing at all about nuclear physics when he was picked to ramrod the A-bomb project, but he never allowed that to dampen his confidence in his own authority. Sometimes he was obtuse; sometimes, in the view of certain scientists, he behaved like a boob. Groves’s military deputy on the project said later: “He’s the biggest sonovabitch I’ve ever met in my life, but also one of the most capable individuals.…I hated his guts and so did everyone else but we had our form of understanding.” Groves was a large man, well upholstered in flesh. Robert Oppenheimer was gangly and emaciated. Both of them could be arrogant, both could be quick to judge. By objective criteria, they should have been expected to loathe and distrust each other wholeheartedly. But it didn’t unfold that way. As an unlikely partnership, the physicist and the soldier also evidently had their own form of understanding.

And so Trinity happened, a great success.

Originally the test firing was scheduled for four o’clock on the morning of July 16, a Monday. By Saturday afternoon the bomb had been assembled on the site—its plutonium core inserted delicately into the larger casing—and hoisted up to the top of its 100-foot girder tower. Electrical detonators were connected at sixty-four points along the outside of the metal sphere, small taps plugged onto the surface, a tangle of crisscrossing wires, as though the monstrous and inscrutable thing were having its mind read by electroencephalograph. What was it thinking? What did it know? Notwithstanding the elaborate electronics, that could be found out only the hard way. Before sundown on the last afternoon, Robert Oppenheimer himself climbed the tower, alone, for a last look at this device he had guided into being. About the same time, General Groves arrived at the site. Then the weather turned bad.

Throughout Sunday night the Trinity gadget sat atop its steel tower in the midst of a desert storm, a raucous overture of thunder and lightning and wind-driven rain. No one seems to have gotten an hour’s sleep except Leslie Groves. Oppenheimer paced and fretted. One bolt of lightning striking the tower might not have detonated the bomb, but it certainly would have destroyed the electrical circuitry and caused a major delay. Any delay now was dreaded, because Harry Truman at Potsdam was eager for news about this far-fetched atomic weapon, and the test results would tell him how to deal with Stalin concerning the continuing war against Japan. But lightning wasn’t the only meteorological problem. There was also concern that storm clouds would carry large doses of fallout onto population centers downwind. Amarillo was 300 miles away, and more immediately, the small town of Carrizozo lay just east across the Tularosa Basin. Groves woke from his nap and consulted with Oppenheimer.

Then around 4 A.M. the rain stopped. The countdown resumed. A young scientist named Joe McKibben, responsible for the remote electrical signals, threw a switch at minus 45 seconds that locked the whole system into an automatic timer. Though not unstoppable, the event was now progressing on its own robotic momentum, without active human control. In the command bunker and back at the base camp, people lay down on their bellies with their feet toward the tower, a position of backward obeisance. At 5:29:45 A.M. Mountain War Time, the wrapper of high explosives squeezed down on the plutonium core. Neutrons ricocheted, atoms split; a chain reaction ensued.

The report that General Groves sent off at once to Potsdam said: “For a brief period there was a lighting effect within a radius of 20 miles equal to several suns at midday; a huge ball of fire was formed which lasted for several seconds. This ball mushroomed and rose to a height of over 10,000 feet before it dimmed. The light from the explosion was seen clearly at Albuquerque, Santa Fe, Silver City, El Paso, and other points generally to about 180 miles away…. Amassive cloud was formed which surged and billowed upward with tremendous power, reaching the sub-stratosphere at an elevation of 41,000 feet, 36,000 feet above the ground, in about five minutes, breaking without interruption through a temperature inversion at 17,000 feet which most of the scientists thought would stop it.…Huge concentrations of highly radioactive materialsresulted from the fission and were contained in this cloud.” That account, concrete and dispassionate, reached Truman by courier. In a quiet moment sometime afterward, Robert Oppenheimer offered his own version of the moment: “A few people laughed, a few people cried. Most people were silent.” Then he quoted another bit of poetry.

The command bunker and the base camp are long since gone. Oppenheimer and Groves are gone. Hiroshima and Nagasaki are not the same cities they were. But Trinity Site was just a spot out in the desert, and so it remains.

On the first Saturday of October, four decades later, you can still see the frizzled steel stumps left behind when the tower was vaporized. You can still pick up a chirpy reading on a Geiger counter. You can hear speeches by the commander of the missile range and the president of the Chamber of Commerce, and you can join in a prayer with an army chaplain who says: “…and guide us, Lord, that we may then begin beating our plowshares into…uh, beating our swords into plowshares.” The confusion is understandable. You can even chat with Joe McKibben, the man who threw that last switch, now a retirement-age gentleman in casual clothes with a friendly and slight dotty manner, who happens to be back for the tour this year himself. McKibben is genial about answering questions, but there is an unreachable look in his eyes.

He says: “Well, you have to wonder how it would have gone if some things had been different.”

There is one more stop on the Tularosa circuit; one more element in the Tularosa design. This one could easily be overlooked, so watch carefully for a small sign along the two-lane that runs north out of Alamogordo toward Carrizozo. Again you will be about halfway from White Sands to the Malpais, but with no motorcade surrounding you now, no men waving you forward with flashlights, no guard stations or crossbars. You stay alert for an inconspicuous junction, at the corner of which sits the bulky white shape of what once was a merry establishment. The building is boarded up; lettering on the window says 3 RIVERS AND DEVIANTS M/C CLUBHOUSE. PRIVATE. BEWARE OF DOG. An M/C, in case you need telling, is a motorcycle club. The 3 Rivers boys and the Deviants (evidently a syncretic group) are not presently in session. But that’s your landmark to turn right.

You drive east for another five miles on dirt, into the foothills of the Sacramento Range. You park and begin walking, up the crest of a sharp north-south ridge. Another sign shows you the way. Welcome to the Three Rivers Petroglyph Site, famous among archeologists of the Southwest and unknown to almost everyone else.

A community of the Mogollon people, those pacific agriculturalists, lived here at the start of the present millennium for a span of about four hundred years. Their village was down lower in the Three Rivers drainage; this exposed ridge seems to have served as a lookout, from which they could spot game or approaching enemies far out in the Tularosa Basin. The view is indeed good. Gazing westward across the desert, you can see the great white shape of gypsum and the great black shape of lava. You can see the barren upthrust that is Oscura Peak, and if a fireball 10,000 feet high were suddenly to blossom behind it, you would sure as hell see that too. Mogollon scouts may have spent many hours and weeks and years up on this boulder-toothed ridge, watching. After four centuries, though, the whole community disappeared.

Probably they migrated north, out of the Tularosa. They could have been fleeing a drought. Or their exodus may have been linked to that dolorous remnant of collective memory, the one telling about “a year of fire, when this valley was so filled with flames and poisonous gases as to be made uninhabitable.” Maybe they saw something distressful. A sudden thunderous ebullition of cinder and smoke and liquidy black rock, for instance. Or who knows what.

All they left behind were a few potsherds, a few fallen adobe pit-houses, and about five thousand rock carvings, scratched and chipped onto the boulder faces along that ridge.

Some of these carvings are far more artful than others. Some are vividly representational—a bighorn sheep impaled by three arrows—and some aren’t. There are a few human figures, but no romantic and elegant portrayals of prowess in battle or hunting; mainly large ovoid heads, wide-eyed and jug-eared. No warriors on horseback. Aside from those arrows in the bighorn, weaponry is conspicuously absent. Animal portraits abound, especially birds and horned mammals and even a few fish. Also there are carven images of tracks: bear paws, bird prints as though in mud, human foot shapes. The preponderance of the petroglyphs on the ridge, though, are abstract designs.

Among these, the most common motif, appearing in many variations, is a circle or several concentric circles surrounded by a ring of dots. Similar circle-and-dot patterns are known from Mogollon petroglyph sites throughout the Southwest, but they seem to have held a special fascination for the artists at Three Rivers. You can see in them almost anything you might choose: a circle of family members, the solar system, the nucleus and electrons of an atom.

Walking the ridge trail up among these carvings, you find another arresting motif. Having made a lucky detour off the main path, watching for rattlesnakes as you step, you notice it first on the western side of a large dark boulder cropping out high on the ridge’s westernmost knob. This design is more elaborate and sophisticated than others, even beautiful, and something about it stops you short:

It recurs, in its variations, a dozen times on the ridge. In a few instances it is less squarish, more curvilinear; in several it is done with linked or interlocking spirals. Despite transmutations, in each the essence is unmistakable.

Evidently the people at Three Rivers had a concept of yin and yang. They drew rock pictures of dialectical oneness. They cherished some notion—maybe it was only wishful—of a unity within which all worldly flux remains balanced.

What did that mean to them? Obviously, we don’t know. They watched and they drew and then they departed. But the yin-and-yang notion is easily reduced to truism, and these figures, like the dotted circles, can be taken to represent almost anything. John Donne’s idea, for instance: “As West and East…are one, / So death doth touch the Resurrection.” Or another idea, maybe in this case more applicable: “For they have sown the wind, and they shall reap the whirlwind.”

Now suddenly a pair of turkey vultures wheel into view above you, cruising on thermals that rise off the west slope of the Three Rivers ridge. With typical lazy grace, they are scouting for a meal. One of the vultures sweeps closer to scrutinize you.

This bird pauses, holding position not 30 feet over your head, like a kite on a short string. It seems unsure whether to take you for a pile of dead meat. And you are sitting quite still. The confusion is understandable.