Caves, or caverns, are among the most fragile ecosystems on the planet and are impacted by human activity and environmental degradation. There are approximately 17,000 caves in the United States, according to the US Geological Survey. Caverns are found throughout the United States, except in Rhode Island and Louisiana. Caves range from single, small rooms to interconnecting passageways that extend outward for miles. Among the largest caverns in the United States are Mammoth Cave, Jewel Cave, Wind Cave and Lechuguilla Cave.
Caves contain spectacular mineral formations called speleothems.
Mammoth Cave extends more than 285 miles underneath south-central Kentucky and is the world’s longest cave system. Some of the cave’s natural features include beautiful gypsum flowers, delicate gypsum needles and rare mirabilite flowers, which are minerals shaped like blossoms. More than 130 animal species call this diverse ecosystem home. Several endangered animals – bats, blind fish, freshwater mussels and Kentucky cave shrimp – are found here. The cave was designated a World Heritage site in 1981 and a biosphere reserve in 1990 by the United Nations World Heritage Centre.
Located in South Dakota near the town of Custer in the southwest corner of the state, Jewel Cave contains more than 160 miles of underground passageways and is the world’s second-longest cave system. Strong winds blow through the cave because of barometric pressure changes at the entrance, and airflow studies indicate much of the cave remains undiscovered. Some unusual cave formations include delicate strands of gypsum and sparkling calcite crystals that look like jewels. During the winter months, more than 1,000 bats hibernate inside the cave. President Theodore Roosevelt designated the cave a national monument in 1908.
Located north of Hot Springs, South Dakota, in the southwest corner of the state, Wind Cave is named after the strong winds at its entrance. The cave’s complex, maze-like passageways extend more than 136 miles, making it the third-longest cave in the United States and the fifth-longest cave in the world. The cave is best known for its outstanding natural display of boxwork — thin blades of calcite that resemble a honeycomb. President Roosevelt created Wind Cave National Park in 1903 to protect the cave.
Lechuguilla Cave in Carlsbad, New Mexico, is the deepest cave in the United States, extending down 1,604 feet. Surveyors have mapped more than 120 miles of cave passageways. Records maintained by the National Speleological Society rank the cave as the fourth-longest in the United States and the seventh-longest in the world. Never-before-seen cave formations include 20-foot gypsum chandeliers; rusticles, rust formations that resemble icicles; and subaqueous helicites, mineral formations that change their axis from vertical to horizontal while growing. The cave is closed to the general public. Access is limited to authorized scientific researchers, survey and research teams and National Park Service personnel and requires a special permit.
- US Geological Survey: Geology of Caves
- National Park Service: Mammoth Cave
- National Park Service: Mammoth Cave — Animals
- UNESCO World Heritage Centre: Mammoth Cave National Park
- National Park Service: Jewel Cave
- National Park Service: Jewel Cave — Animals
- National Park Service: Wind Cave
- National Park Service: Wind Cave — Cave / Karst Systems
- National Park Service: Wind Cave: Speleothems — Boxwork
- National Park Service: Carlsbad Caverns — Lechuguilla Cave
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