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Lechuguilla Cave Lechuguilla Cave is the fifth longest cave (126.1 miles (203 km)) known to exist in the world, and the deepest in the continental United States (1,604 feet (489 m)), but it is most famous for its unusual geology, rare formations, and pristine (нетронутый) condition. The cave is named for Agave lechuguilla, a plant found near its entrance. It is located in Carlsbad Caverns National Park, New Mexico. Access to the cave is limited to approved scientific researchers, survey and exploration teams, and National Park Service management-related trips. Lechuguilla Cave was known until 1986 as a small, fairly insignificant historic site in the park's backcountry. The historic cave contained a 90-foot (27 m) entrance pit known as Misery Hole, which led to 400 feet (122 m) of dry dead-end passages. A group of Colorado cavers gained permission from the National Park Service and began digging in 1984. The breakthrough, into large walking passages, occurred on May 26, 1986. Since 1986, explorers have mapped over 126 miles (203 km) of passages and have pushed the depth of the cave to 1,604 feet (489 m), ranking Lechuguilla as the 5th longest cave in the world (4th longest in the United States) and the deepest limestone cave in the country. Cavers, drawn by the caves' pristine condition and rare beauty, come from around the world to explore and map its passages and geology. Lechuguilla Cave offered even more than just its extreme size. Cavers were greeted by large amounts of gypsum and lemon-yellow sulfur deposits. Scientific exploration has been conducted as well. For the first time a Guadalupe Mountains cave extends deep enough that scientists may study five separate geologic formations from the inside. The profusion of gypsum and sulfur (сера) lends support to speleogenesis by sulfuric acid dissolution. The sulfuric acid is believed to be derived from hydrogen sulfide which migrated from nearby oil deposits. Thus, this cavern apparently formed from the bottom up, in contrast to the normal top-down carbonic acid dissolution mechanism of cave formation. Rare, chemolithoautotrophic bacteria are believed to occur in the cave. These bacteria feed on the sulfur, iron, and manganese (марганец) minerals and may assist in enlarging the cave and determining the shapes of some unusual speleothems . Other studies indicate that some microbes may have medicinal qualities that are beneficial (целебный) to humans. Lechuguilla Cave lies beneath a park wilderness area. However, it appears that the cave's passages may extend out of the park into adjacent Bureau of Land Management (BLM) land. A major threat to the cave is proposed gas and oil drilling on BLM land. Any leakage of gas or fluids into the cave's passages could kill cave life or cause explosions. Lechuguilla Cave was shown in the BBC documentary series Planet Earth. The Denver Museum of Natural History (now known as the Denver Museum of Nature and Science) filmed one of the first documentaries in the cave titled "Lechuguilla Cave: The Hidden Giant" in 1987 featuring many of the cavers responsible for the breakthrough and initial survey work. Wikipedia, The Free Encyclopedia