"Just erosion": A walk in Bisti/De-Na-Zin
Strolling 75 million years back in time
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“Geologically speaking, Bisti really is not all that interesting,” my friend, a geologist, explained to me as we entered the Bisti/De-Na-Zin Wilderness in northwestern New Mexico. “It’s just erosion.”
“Huh?” I reply, preparing a snide retort about scientists and their lack of aesthetic appreciation. Then I look across the barren, drab plain, squinting to make out a line of featureless buttes in the distance, and utter the best response I can muster: “Hmmph!”
We walk, the three of us. The January wind blows fierce and cold. The sky is brilliant blue. In the absence of trails, maps, objectives, or prominent landmarks, we find ourselves drawn to a barbed-wire fence and walk alongside it until it turns to the north. Look. Out there: Topography. We meander across ash-gray, flora-free soil toward a line of low hills.
When we finally arrive, I stop and ogle the voluptuous curves of what time and water and wind left behind and later erosion—just erosion—shaped and revealed.
My revery is shattered by the geologist’s shout, “Look at that! Oh, wow. Check that out.” He’s pointing in several different directions at once, his geologic apathy apparently cured. “That’s insane. Look at that petrified tree!”
The tree trunk—or rather, the minerals that now remembered the tree—lay where it fell some 75 million years ago, when this was the shore of a shallow, salty inland sea and the climate was warm and wet. When big bugs fluttered through the canopy of widely spaced conifer, while possum-like marupiala, crocodilian scutes, and dinosaurs—from the “Bisti Beast,” a horned-headed tyrannosaurus-like creature to ol’ Dineobellator notohesperus, a terrifyingly quick relative of the velociraptor—cruised through verdant ferns, ficus, and willows growing among shallow, brackish ponds.
The sea receded, the dinosaurs perished, the forest fell, the climate gradually became more arid, the earth erupted and ash rained down on what is now the San Juan Basin. The memory of the swamp’s flora is contained within the Fruitland coal formation, which is exhumed and burned to generate electricity in the massive power plants 30 miles north of here. The sea’s plankton became petroleum and methane, trapped in shales and sandstones.
In much of the Basin, these memories lay hidden beneath a scrubby, nearly featureless plain. But in Bisti, water and wind have worn away the terrestrial vestments, laying bare the geological soul of the landscape and sculpting it into Dali-esque forms. The petrified log provides an un-erodible cap for its own display pedestal. Mushroom-shaped and phallic formations jut lewdly into a bright blue sky. Watercourses cut deep grooves into sensuous, black-ochre hillsides. In some places the water has actually tunneled through the buttes. Varying shades of gray give way to umber red where the underground coal beds caught fire and burned long ago, leaving behind deceptively light chunks of slag.
We continue to wend our way through this surreal world for a couple of hours or maybe millions of years. We get disoriented at one point, and bicker about which direction we should go for a moment before shutting up and just walking along a wash. As we approach the parking area, we are baffled to see several cars there, and a party of four or five heading our direction.
I stifle my disappointment at seeing fellow humans who, like us, seem wildly out of place here. I say nothing, but inside I’m screaming:
Nothing to see here, folks! It’s just erosion.
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