Carlsbad Caverns Reveal More of Their Secrets

THE RESEARCHERS UNFOLD AND STEADY the lanky yellow limbs of a tripod, then attach a camera, a nondescript gray plastic case with a big glass eye. One of them takes out a stylus and taps tiny boxes on the camera’s glowing touchscreen. Soon it begins a slow, whirring orbit atop the tripod. More than a century ago, early explorers descended into Carlsbad Caverns with nothing but lanterns casting dim light into the mysterious, tempting depths. They must have been awed by the other-worldly formations—and felt the prickly fear of getting lost in an unknowable darkness. They could have used something like the guidance these researchers will soon provide: the most precise and complete maps ever made of Carlsbad Caverns National Park, a UNESCO World Heritage site that lures 500,000 visitors a year to see the largest readily accessible cave chamber in North America.

Here in the state’s remote southeast corner, researchers from the University of Arkansas are helping the National Park Service better understand what project manager Julie McGilvray calls its “cultural landscape.” The type of work they’re doing has gotten a lot of attention because of the technology’s ability to reveal what we can’t see: outlines of Mayan pyramids below dense jungle canopies and ruins of ancient cities below desert sands. The camera, a $125,000 Leica ScanStation P40, uses lidar (light detection and ranging) to bounce laser beams over every inch of the place, then combines that data with GPS coordinates to produce super-detailed 3-D views. By combining many scans at once, we can see, for the first time, the cavern in profile as it snakes down from the surface, expands into large chambers, and contracts into narrow tunnels. (From the side, it turns out, Carlsbad Caverns looks not unlike the fictional Starship Enterprise.)

The Park Service chose the University of Arkansas because of its expertise in such mapping.  Malcolm Williamson and his colleagues have used this same technology to document other World Heritage sites, including the Roman Colosseum, the ruins at Machu Picchu, and the tombs and temples of Petra. But Carlsbad Caverns is their biggest project yet. Formed millions of years ago when acidic water circulating underground dissolved the porous limestone, the chambers and tunnels acquired their spectacular features (called speleothems) when the water level dropped. Eventually, stalactites dripped from the ceiling and stalagmites formed on the floors. To capture it all, the researchers needed four trips and 24 days of scanning on four miles of trails. When they’re done, they’ll crunch more than 1.5 terabytes of data that could eventually power virtual-reality tours, so that smartphone spelunkers can plumb the caverns’ depths without ever leaving the sofa.

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Humans have been interacting with the caverns for more than 100 years, carving paths, marking trails, and mining its bat droppings for valuable fertilizer. This project will allow managers to monitor changes in the park and the relationship between people and the environment. One thing McGilvray is particularly concerned about? Dust bunnies. Lint from your clothes, stray hairs, skin cells—all the human detritus that clusters in corners. Since 1924, more than 43 million visitors have delved underground here, and the fuzz they shed adds up. So one thing McGilvray will look at is whether low barriers on the trails could keep the fuzz down while still preserving the views.

And the views! In order to capture the caverns without humans in it, the scanners start work after the park is closed. Williamson and his assistant, Vance Green, walk through the eerily empty Big Room, past a locked gate, and down the switchbacking path into a section of the caverns reserved for private (though frequent and inexpensive) ranger-led tours. They pause in the King’s Palace, a chamber with spectacularly baroque formations called draperies. It looks like outer space or the deep sea. No wonder it served as a set for such movies as The Spider, The Bat People, and The Night the World Exploded, sci-fi flops you won’t find on Netflix.

This is the last night of work for the team, so Williamson and Green are grabbing the final few scans they need. Moving along the path, stopping every 25 feet or so, they set up the camera and stand still, waiting a minute or so for it to whir around. It’s tedious work, more hurry-up-and-wait than anything else. But while they’re waiting, they’ve had time to notice interesting little features that most visitors probably speed right past. Traversing the Queen’s Chambers, they pause every once in a while to point their flashlights into a crevice where wild formations resemble worms and stars, or behind a boulder to find clusters of stalactites that fell and lodged sideways, now seeming to grow horizontally.

Even without the special access, visitors who make the pilgrimage to the Guadalupe Mountains marvel at the vastness of the famed Big Room and ooh at the draperies and other formations—soda straws, cave pools, lily pads—each carefully lit. The park recently upgraded that lighting system, and it brings new awe to one particularly dramatic section of draperies, their graceful, paper-thin folds glowing like alabaster, thanks to one perfectly placed spotlight. The Park Service hopes the new scans will help them plan future light effects.

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But the laser beams have also brought fresh surprises to historic parts of the park. Decades ago, the park had a belowground restaurant, a midcentury concrete space chamber of a lunchroom. But the grease and crumbs proved unhealthy for the caverns, so now a far smaller snack bar sells only sandwiches and bottled water. Along the cave wall, three semicircular concrete counters topped with metal signs sit disused. A thick layer of government-issue brown paint masks whatever the signs once read, but the lasers bounce right through the paint. The scanners were shocked when this revealed one kiosk’s original purpose. Clear as day, the scan shows a concrete counter, and above it a sign blaring, SEND A POSTCARD!

Yep. You could send a piece of mail postmarked from the center of the earth.

Just as they did when that sign was painted, a half century or more ago, future visitors will walk along these paths, take a ranger-guided tour, and scramble through narrow tunnels. Or maybe they’ll strap on virtual-reality headsets to take a stationary trip 1,000 feet under the earth and ages back in time.