Lil’ Lechuguilla: a Carlsbad Cavern passage with no usable map for 43 years

The first explorers of Lil' Lechuguilla, a section of Carlsbad Caverns National Park in New Mexico, left their survey markers in the cave, but their maps and data were lost, so for 43 years the passage was effectively abandoned. In 2019 survey teams went back and found a large chamber of gypsum and calcite. A park guide told the story for the Inside Earth newsletter of fall 2020.

A section the park had lost

Lil' Lechuguilla was first discovered in 1976. It opens off the Guadalupe Room, the second largest chamber in Carlsbad Cavern. According to the park's resources department, the original survey was so poor that its data were erased years ago, which gave a pair of survey trip leaders and their teams the chance to remap it. Since only one team had been there 43 years earlier, the area was nearly pristine and every map would be new. One team explored the section early in 2019, and a four-person team, calling itself the Guad Squad, began on November 7 where the first team had stopped.

Gypsum, calcite and a pit

After scrambling down and through a large breakdown slope, the team reached an area of solid limestone covered in delicate gypsum that looked like snow, a winter wonderland underground. The room holds a gypsum chandelier, a rare cave formation; the only other caves in the Guadalupe Mountains known to have them are Lechuguilla Cave and Cottonwood Cave.

Gypsum chandeliers. NPS photo.

After survey station 26 was set, a team member moved ahead and called back, "This room is huge!" The chamber had ceilings at least 43 feet (13 m) high, and its floor was a pile of calcite rafts as much as 20 feet (6 m) high. Calcite rafts form only on the surface of a calm pool and sink when a droplet strikes them, so a pile that tall means the chamber was flooded for a very long time. The room also held:

• Selenite blades. Very delicate, transparent crystals a couple of inches long that form underwater where the pool water has a high concentration of selenite, which supports the idea that the chamber filled with water and then drained.
• Gypsum stalagmites. These are rare because they do not form like ordinary stalagmites: dripping water erodes layers of gypsum already on the floor, sometimes leaving conical mounds, and since gypsum is highly soluble the evidence is often erased.
• A large pit, now called the BFP, at the end of the room's long axis and over 30 feet (9 m) deep. Another team is to return to explore its depths.

Selenite blades. NPS photo.

Corroded limestone. NPS photo.

Past the room the team found a passage with an almost nonexistent floor; the openings in it might connect to the bottom of the pit, in which case a hand line would be enough to reach the bottom instead of rappelling. Only the people who surveyed the cave 43 years earlier know what lies at the bottom, but their data are gone, so credit for the discovery now goes to today's explorers.

Sources

• National Park Service, Carlsbad Caverns National Park, Lil' Lechugilla, article from the Inside Earth newsletter, Fall 2020, by a park guide; rewritten in hubnx's own words, with the cavers' names and photos of people left out.