The earliest documentation of Jewel Cave was a mining claim filed by brothers, Frank and Albert Michaud in October 1900. They initially described the spot as a hole where humans couldn’t fit in, and that cold air was coming out of it. They used dynamite to blow up the entrance, allowing for the discovery of the calcite-filled cave.
In 1966, caving pioneer Herb Conn deemed Jewel Cave a “breathing cave.” That explains the cold air described by the Michauds. In breathing caves, airflow changes due to differences in atmospheric pressure between the inside and outside the cave. The process is called barometric ventilation.
Today, Jewel Cave National Monument, situated in Custer County, South Dakota, is a 1,273-acre site and home to 220.01 miles of mapped cave passageways (Mammoth Cave has 426 miles) that are set to increase amid active exploration.
Jewel Cave, which is currently the fifth-longest cave in the world, got its name after the sparkling gypsum crystals lining its walls.