The Black Canyon

Close to the south rim entrance, Tomichi Point is often the first place travelers actually look down into the canyon, and it sets the terms for everything that follows. The walls across the gap are dark, steep, and strikingly uniform for the kind of rock most Colorado overlooks show off — no neat horizontal stripes of one layer sitting on the next, the way a mesa or a road-cut through sedimentary rock reads. That is because this is not sedimentary rock at all. It is old crystalline basement — gneiss and schist, somewhere between one and a half and two and a half billion years old — recrystallized deep in the crust under heat and pressure rather than laid down bed by bed at the surface. What look at first like layers are something else: bands born of squeezing and folding while the rock was still miles underground, long before there was a canyon here to hold it up to the light. Take a minute before moving on. The rest of the sites ahead are really just closer readings of the same old page you are looking at right now.

Gunnison Point sits close enough to the rim that the drop feels immediate rather than scenic. Look straight down and the Gunnison River appears as a thin green thread, pinched between walls that barely seem to widen the whole way to the bottom. That narrowness is itself a clue about the rock. Rivers cutting through soft rock wander and widen, carving broad valleys as the banks slump and erode sideways. A river cutting through rock this old and this hard does something else: it goes down and stays down, unable to make much headway sideways against basement rock that resists weathering far better than the younger, softer rock buried elsewhere under most of the surrounding country. The shape of the gorge, in other words, is a kind of portrait of the rock’s toughness, written by the one tool patient enough to test it. Stand here a while and the canyon stops looking like a view and starts looking like a measurement — river against rock, worked out one increment at a time over a span of time that is difficult to hold in the mind for long.

This is the wall the whole rim is really built to show off — an enormous face of the same dark, ancient basement rock, but streaked through with paler bands that wander and branch rather than running straight. Those pale streaks are a second chapter, added long after the first: lighter-colored rock that was once molten, forced up into cracks in the already-solid dark rock and left to cool in place. The result is two different histories stacked in the same wall — one written slowly, under heat and pressure, deep in the crust; the other written faster, as liquid rock finding the weak seams in something that had already gone hard. Nothing about the pattern is decorative, even though it can look that way from a distance. Every pale line marks a place where the older rock had already cracked, and every dark interval between the lines marks rock that held. Give this wall more time than the others on this rim. It repays a slow look far more than a quick photograph does, and the story it is telling only gets clearer the longer you trace the lines.

Named for what you can see cutting across the rock here, this overlook is a good place to notice that the canyon walls are not one solid, unbroken slab. Look closely and the ancient rock is laced with fractures running in more than one direction, breaking the face into blocks and slabs rather than one continuous sheet. Fractures like these are part of how very old, very deep rock behaves once it is finally relieved of the enormous weight that used to sit on top of it. Rock that formed miles underground was squeezed on every side by everything above it; strip that weight away slowly, through the endless work of erosion, and the rock expands just slightly and cracks along regular lines, the way a sealed jar releases pressure once it is opened. Those fractures are also where the canyon does its slow, ongoing work today — not by the river cutting sideways anymore, but by blocks along old cracks like these eventually letting go and falling into the gorge, one rare event at a time, on a schedule far too slow for any visit to witness.

This is close to the point where the canyon pulls in tightest, rim to rim, while still holding onto real depth beneath you — the combination the whole park is best known for. Look down and there is little sense of the wall changing character as it falls away toward the river; the rock near your feet and the rock at the waterline read as the same story, not as a stack of different chapters the way a canyon cut through layered sedimentary rock usually does. That sameness is the point. Almost everything visible in this cross-section is the same ancient crystalline basement, top to bottom, which means the whole visible face is really one long passage of a single old story rather than several shorter ones piled up. Most canyons let you read time in horizontal slices, youngest at the rim, oldest at the river. Here, rim and river are close to the same age, and the depth you’re looking at is really a measure of how much of that one old rock the river has managed to remove, not how many different rocks it cut through to get there.

From here, look across the canyon for a block of rock that appears to be resting on a narrower base than its size would suggest it should need — rock balanced, rather than simply piled. It is not an accident of stacking; it is what is left after uneven erosion did its slow work on rock that was never uniform to begin with. Even ancient basement rock like this is a mix — tougher bands of one mineral makeup next to softer ones, some more resistant to weather and freeze-thaw than others. Given enough time, the softer material wears back faster, undercutting the tougher rock above it and leaving odd, top-heavy shapes standing in its place. What you are looking at, in other words, is a rough map of hardness within rock that looks uniform from a distance but is not uniform at all up close. Every balanced block and narrow pedestal on this rim is really the ancient rock grading itself, one exposed edge at a time, and this one has simply survived long enough — so far — for someone to give it a name.

The name asks you to find a shape in the rock across the canyon, and most people can, with a little squinting — a hump, a bowed neck, something animal enough to earn a name that has stuck. The shape itself is not the geology, though; it is a coincidence of the geology, the kind of pattern the human eye is quick to find in almost anything irregular. What actually produced it is the same uneven erosion at work throughout this canyon: bands of old rock with slightly different toughness wearing back at slightly different rates, over a span of time too long to picture directly, until the remaining high points happen to resemble something familiar. Once you notice that, the whole far wall opens up. Other shapes are there too, unnamed, made by exactly the same process — just without a name attached to catch the eye. Scan the wall a little further past the camel shape itself and see how many other odd silhouettes you can pick out, each one a small, accidental record of which rock here has resisted the weather best.