lay of the land

stormy

“Geology is the youngest science. Perhaps this is because it is so imprecise. Physicists and chemists solve problems to the sixth decimal place on their computers. Biologists poke and dissect in the laboratory, studying a thin slice of time—the present. Geologists walk around on the little of the earth we see and scratch their heads about the rest. They check their watches for lunchtime, interrupting a conversation about events that occurred 375 million years ago, plus or minus 5 million years. Scientists don’t like imprecision—it smacks of fiction. Perhaps this is why geology is so young; few scientists dared to deal a deck with so many cards missing.”

-Bill Fiero, Geology of the Great Basin (1986)

Somewhere northwest of Reno, in the rolling sage-scrub habitat characteristic of much of the Great Basin, range ecologist Pat Shaver stands atop a tongue of granitic rubble protruding from a hill, hands in his pockets. He has picked this spot purposefully—it is a premeditated stop on his geomorphological tour of the area. He is wearing blue jeans, cowboy boots, sunglasses, a long-sleeved field shirt tucked behind a gleaming brass buckle. Though he sports a baseball cap on this particular afternoon, the occasional ten-gallon has been known to grace his hairless, New Mexican pate. His snow-white moustache matches his shirt, its handlebars trailing off his chin and fluttering in the wind. Here, on this east-facing pediment overlooking the suburb of Lemmon Valley, redolent of sage and golden currant, he is searching for a teachable moment. He is trying, at the very least, to make a point. He addresses a young group of plant surveyors squinting in the sun.

“What are we standing on right now?” Someone raises a hand, offers a word—”peed”-something.  “Piedmont is the landscape, that’s correct. The landscape is what we can see, right? Plants, roads, buildings, fields, all that. So we’re on a piedmont slope—we’re surrounded by piedmont slope here. How about the landform? Remember, landscapes are composed of numerous landforms. What do you think?”

There are tentative responses: Fan apron? Fan skirt? Inset fan? Ballena? The plant surveyors are testing out newly acquired terms, trying to wrap their heads around the nuance between basins and bolsons, flats and fans, plains and terraces. They all connote various damages inflicted on rock by water, wind, and gravity; they describe alluvial processes, colluvial processes that shape terrain and wear it away and carry it off to other places. The differences in definition are largely a product of time. A landform subject to millennia of weathering might emerge altogether changed, and thus given a new name. It is sometimes compositionally the same, but older, more degraded, slouching. Different. Sometimes parent material or altered climatic conditions are brought to bear, but mostly it is time, in the geologic sense, that transforms terminology to fit the landform.

Shaver hears his answer. “I would agree with fan apron. This is all post-alluvial, right? There’s no longer water moving through here, clearly. Hasn’t been for quite some time. So this stuff we’re on right now is old, older probably than anything else around us. These are the remnants of a range, eroded down toward that bolson floor, where all the houses are. I’d say this is a fan apron, but what could happen to it given another couple thousand years? Given all these other aprons around us?” He pauses, waits for the uptake. “That’s right, they could accrete into fan piedmont, a kind of smoothed-over version of the aprons.”

With knowledge of a region’s parent material, its climatological tendencies, and its overarching geology, one finds the inherent landforms conforming, in their maturation, to certain archetypes. Over many thousands of years, for example, an inset fan in the Great Basin will more than likely peter out into a fan remnant, which eventually settles in its old age as a ballena. Just as biologists differentiate young and old in their argot—eft to newt, kit to fox, larva to imago—so geologists do the same. Thus the headwall becomes a cirque, and the cirque becomes an arête, or a pyramid peak. Seamounts, shield volcanoes, island arc. Inset fan, fan remnant, ballena. Names for landforms through the ages. In Nevada’s physiographic province, ranges are uplifted, beset by erosion, and leveled into basins with a regularity and uniformity that is stunning to behold. The senescence of the land here is in a large sense predictable, but this in no way diminishes its beauty.

Again, someone raises a hand, voices a nagging concern: “So, I guess what I want to know is…why? Why do we need to differentiate between fan aprons and skirts?” There are titters in the crowd. Shaver has anticipated this.

“Good,” he says, nodding. “Good question. The purpose of learning your landforms—and geomorphology in general—is to better understand the landscape you’re working with. You guys will be dealing mostly with plant surveys, soil samples, stuff on the surface. But those landscape features are sitting on landforms, and the more you know about landforms, the more complete your picture is of the overall story. Landforms tell you about alluvial and other erosional processes, they tell you about time scales, they tell you about the past and also the future. If you know what kind of landform you’re looking at, you know quite a bit about how it got there, possibly how long it’s been there, and what it’ll look like in several thousand years. And these kinds of details inform your survey work. They inform land-use decisions. Geomorphology tells us a great deal about the land, what it’s been through and why it looks the way it does, and what it might do in the future. So, does that make sense?”

A wave of nods answers his query. In classrooms, Shaver is fond of saying, “In the Basin and Range, geomorphology is right there in your face.” Driving through the province, one can’t help but find its varied landforms on prodigious display, leering from roadcuts and drawing the otherwise understimulated eye, but whether one knows what one is looking at is clearly a matter of Mohs scale-subjectivity. Where one observer sees a hill, another, perhaps more geomorphologically inclined one sees a distal complex of coalescent fans, or maybe a constructional surface comprising individual alluvial fans and interfan valleys. Nomenclature aside, it is the noticing, the observing, that makes all the difference. As Bill Fiero wrote, geology “offers us the ability to play Sherlock Holmes and partially decipher the past…[a] mountain, canyon, or cliff is no longer merely a scene. The view becomes an exciting mystery story, and we become the investigators seeking answers.”

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