Parked at Home 2025: Carlsbad Caverns National Park

On Thursday, March 27 from 7:00 p.m. to 8:00 p.m., I watched the third Parked at Home webinar of the 2025 season. This is the fourth year of the Parked at Home series of virtual talks hosted by Blackstone River Valley National Historical Park (BLRV) and other sites in the National Park Service, along with the third year of summaries appearing on my blog. The presentations this year are interpreted into American Sign Language (ASL) by Sherrolyn King. The hour-long webinars will be uploaded to the BlackstoneNPS YouTube channel and available to view at any time. The third installment to this year’s series was Carlsbad Caverns National Park featuring park ranger Tim Bone who formerly worked at Bighorn Canyon National Recreation Area in Wyoming, Grand Portage National Monument in Northern Minnesota, Russell Cave National Monument in northern Alabama, and Blackstone River Valley and Roger Williams National Memorial in Rhode Island.

The talk began with a comparison between Blackstone River Valley and Carlsbad Caverns given by park ranger Allison Horrocks. While no caves exist at Old Slater Mill in Pawtucket, RI, she considered this site and other sites of the Industrial Revolution as places where once densely populated factory sites have “caved in”, both literally and figuratively. Draper Complex in Hopedale, MA had been a major industrial site but was demolished around 2020. A mill building in Lonsdale, Lincoln, RI burned in 2022. Other sites have withstood disaster. The Crown & Eagle Mill burned in 1975 but has since been restored, while Old Slater Mill became a textile museum in the 1920s.

During his portion of the talk, Tim Bone shared slides including fun facts, a map, and photographs to illustrate his talk, including a picture of himself dressed up as park mascot Carl S. Bat. He noted that Carlsbad Caverns are in a remote location at 30 miles from Carlsbad and 150 miles from El Paso. Visitors often fly into Albuquerque, which is an over five-hour drive from the park. Much longer than the trip to visit the caves are their history. 260 million years ago (mya), the area was part of the Delaware Sea, as evidenced by shellfish fossils found in the cave. The sea dried up to become the Permian Basin, and the Guadalupe Mountains rose from the basin. The cave system formed between four and six million years ago as sulfuric acid dissolved the limestone in the mountains and left behind gypsum rock. The formations inside the cave are currently growing at about 0.01 inch per year, or 1 inch (2.54 cm) a century.

While the cave system has forty-two miles of chambers spread across a hundred and thirty caves, only two-and-a-half miles are open to visitors. Rangers are permitted to visit four to five miles of the cave, which have names like the Big Room, Slaughter Canyon Cave, and Lechuguilla. Humans have not been exploring these caves for very long. While Native Americans have lived in the area for thousands of years and created pictographs at the cave entrance, most caves require modern ropes, ladders, and rock climbing experience for exploration. This began in 1898 when sixteen-year-old cowboy and third-grade dropout Jim White saw over a hundred thousand bats flying over the mountain and realized, “It has to be a whale of a cave down there for that many bats to call it home.” Local guano miners wanted to harvest the bat poop, which entailed carrying fifty-to-a-hundred-pound bags filled with poop onto wagons and driving to the nearest train station to send this fertilizer to California citrus groves. Jim got a job as a foreman and cave tour guide. Photographer Ray V. Davis lugged his thirty-to-fifty-pound camera and fifty-pound tripod out to the caves to take pictures. He and Jim mailed photographic slides to multiple media outlets, and the pictures were by National Geographic and New York Times, although some were initially published upside down. This led to my favorite president, Calvin Coolidge, declaring the caves a National Monument in 1923. By 1930, they were upgraded to a National Park through an act of Congress.

National parks were treated differently in the early to mid-20^th century than they are today. During World War II, president Franklin Roosevelt received a letter suggesting that bats could be weaponized for the war effort, and he agreed this was a great idea. Bats were captured, stuck in a freezer to induce hibernation, and fitted with an incendiary device the size of a battery before being loaded into an empty bombshell. Theoretically, if the bomb was dropped onto a city, the bats would fly out to take shelter in nearby buildings. The devices would detonate, killing the bats and everything around them. This clearly phenomenal idea was known as Project X-Ray. A more successful government experiment, the Manhattan Project, created nuclear weapons, so those were used instead. Meanwhile, Carlsbad airfield had an incident where bats escaped their bombshell and burned down a nearby airplane hanger.

As for tourism, the first superintendent was Thomas Boles, who gave himself the military title of Colonel Boles event though he had never served, or as Bone put it, “Even less of a Colonel than Colonel Sanders”. Still, Boles did a lot for the park from getting highways built through the basin and adding cave infrastructure like electrical lights and trails. (Further research revealed that Boles was seemingly the only superintendent who hired women as guides at this time.) Heat from the original lights had caused algae growth, which park rangers have done their best to bleach away. The current lights are much cooler LEDs powered by nineteen miles of cable, and the lights are turned off each night. The original dirt trails were paved with asphalt in the 1950s but changed to epoxy and gravel in the 1970s when environmental scientists realized that runoff was contaminating the cave and causing its decay. Handrails were added in the 1990s to bring the cave into compliance with the Americans with Disabilities Act (ADA), which had the added benefit of preventing people from touching cave walls and formations to maintain their balance. As for the snack bar in the cave, people could initially buy coffee and fried chicken, but this was scaled back especially after a raccoon infestation forced biologists to catch and remove the raccoons one animal at a time.

Humans have had a major impact on the caves, most of which is bad and gross. Besides algae and chicken bones, the elevators installed in the caves in the 1930s and 1950s caused moisture to escape and shrink the cave pools. Rangers originally “solved” the problem by adding tap water with a hose until they learned that tap water chemicals kill microorganisms in cave pools. Starting in the 1970s, the park rangers have worked diligently to prevent moisture escape, including revolving doors in the elevator lobby and now a full airlock system. Additionally, only 2,500 people are permitted in the cave per day to cut down on acid build-up, which will make the rock formations erode more quickly. As for cave formations, visitors were once encouraged to take them home. Now broken formations of treated with care, as volunteers use “stalacti-jacks” and glue to put them back together. These volunteers also clean up hair and lint from the cave, sweeping up thirty pounds of it from the Big Room each year. Clean-up kits for rangers are stationed around the cave, and Bone admitted to having found things too disgusting for him to share the story with the public.

Bone had a few more Colonel Boles stories before the Q&A. A formation in Lower Cave is known as Colonel Boles Formation, as he would bring VIPs into the cave and tell them the columns were holding up the room before proceeding to pull a piece out from the column. The piece is now glued in place. He also hosted a “Rock of Ages” program in December, where visitors were given a guided tour of the Big Room by candlelight, and rangers would appear holding lanterns and singing the hymn “Rock of Ages”. A letter came from Washington, D.C. ordering him to stop the program, and when Boles persisted, he was reassigned to Hot Springs in Arkansas. The park continues to hold the program.

During the Q&A, Bone answered questions about bats, cave activity, and his favorite part about working in the cave. Three species of bats live in the cave: Brazilian freetail, cave myotis, and fringe myotis. The Brazilian freetail is the most common with three to five thousand bats in the colony. They hibernate in the Lake of the Clouds cave, which is about 1,040 feet below the Visitor Center. Other animals living in the cave include cave crickets and cave spiders. The cave formations grow through the drip of mineral-rich water, which takes six months to decades to descend through 7,000 feet of stone from the desert above. About ten percent of the cave is “active”, meaning that the cave formations are growing. Besides stalactites and stalagmites, other formations include draperies, cave popcorn, cave pearls, and soda straws. Finally, Bone loves have a cave as “office”. He said that he loves to “trade my flat hat for a caving helmet” and “get dirty in the cave” along with sitting in the dark, as there is “something so humbling and powerful about being in complete darkness”.