03 Mar Bend’s Underground Scene
A tour beneath Central Oregon’s volcanic surface
With the occasional muted squeak, windshield wipers whisked away what few raindrops flecked the glass as Nick, our versed Wanderlust naturalist tour guide, steered our tour van down China Hat Road. There were about ten of us onboard, headed to Boyd Cave for a spelunking tour this early, chilly Sunday morning. With CB-loudspeaker mic in hand, Nick doled out some history along the way: local logging lore, the dates and names of a few wildfire scars the road traversed through, and the volcanic significance of Central Oregon as a whole.
By the time our 20-minute ride was over, a clear patch of blue sky had opened up, giving the sun a chance to compete with the icy morning breeze brought on by the final vestiges of last night’s winter rainstorms. During the summer months, cavers are advised to dress warmly for their subterranean adventure, since the temperature below ground remains a near-constant 45 degrees year round. This day, however, most of us chose to shed a layer or two before donning our hardhats and headlamps.
We clustered around Nick near a hole in the desert that was nearly unnoticeable, were it not for the two silvery handrails that curved awkwardly up from the miniature abyss, and the squat, rusty metal fence that enclosed it. To our west stood Coyote Butte, a smallish cinder cone covered in yellow grass, its red mine-pit scar gaping open at the base. The horizon beyond wore a ragged skirt of silver and blue clouds, which were roiling down from the enshrouded Cascades Mountains, in our direction—the next wave of this morning’s leftover showers.
Nick gave us a geology primer before we set out. Every bit of rock around us, he explained, came from the Newberry Volcano complex. Each knobby butte in the immediate area, including Coyote, was a cinder cone that sprung from the flanks of the massive shield volcano ten miles to our south, each supplied by Newberry’s own far-reaching magma reservoir.
The very cave into which we would descend was part of Newberry’s “sewer system,” quipped Nick. Lava tubes are a form of natural geologic plumbing that disperse magmas far and wide from their volcanic vents of origin; Boyd Cave helped pump Newberry lavas out into the desert bordering Bend’s eastern flank. It was an effective system, considering some flows made it as far as Smith Rock, 40 miles to the north.
Our lesson concluded, and we filed down into the hole via a steel stairway so steep it could easily be mistaken for a ladder. At the bottom, some 20 feet down, the air was damp but still. The group shuffled around on a fine, sandy silt, clicking our headlamps on and testing their efficiency by shining them into the darkness beyond the dimly skylit cave floor. Then, with our intrepid tour guide leading the way, we headed in.
“Lava tubes are formed much in the same way that a river of water freezes over in the winter,” explained Nick as we padded our way downhill, into the earth. “The surface lava in the channel air-cools, solidifies and forms an insulating roof layer, which allows the lava to retain more of its heat. That superheated lava then melts the underlying rock, deepening and widening the channel. When the magma vent upstream runs dry, the lava drains out, and a lava tube cavern is left behind.”
It must have been a massive amount of lava, considering the ceiling at most points was at least ten feet above our heads. Much of the cave floor is covered with a pellicle of powder, deposited by thousands of years of surface water tricking down through the cracks in the ceiling, pulling fine sand from the desert down with it. At one point Nick pointed out a shiny, waxlike heap of bat dung on a small rock shelf; we weren’t the only creatures finding respite from the elements in Boyd Cave.
In some spots we had to pick our way down narrow rocky chutes or shimmy sideways between boulders that had long ago collapsed from the ceiling. The occasional outstretched hand was offered as we helped one another scramble over, across or around the trickier parts when needed. More than a few times someone caught their hardhat on a low overhang, creating a hollow, plasticky “thud.”
We arrived at a section where the cave’s ceiling hung so low, only a few feet of open space was left. One couple in the party chose to stay behind; Nick left them a spare flashlight. The rest of us squirmed our way a dozen or so feet through the dust under the gap, returning to our feet once the ceiling yawned open to its usual height.
A few minutes later we were at the tube’s terminus. The party stopped and clicked off our headlamps’ power switches to get a feel for what perfect dark and perfect quiet was like. “Wave your hand in front of your face,” Nick’s voice echoed quietly. “Can you see anything?” We couldn’t. In the silence we heard only hints of breathing and the occasional rustle of clothes when someone shifted.
With a series of clicks the flashlights snapped back on, and our group made its way back towards the entrance. After navigating back under the army-crawl gap, we reunited with our temporarily abandoned companion-couple and eventually arrived back at the steep steel staircase.
By this time the sun had crept higher into the sky, allowing a wide beam of light to pierce down through the hole, onto the sand. A few shimmering motes of dust waltzed through the air in slow-motion. One by one we gripped the handrails of the stairs, squinted into the sun, and pulled ourselves upwards, back into the vibrant world above.