Carlsbad Caverns

Carlsbad Caverns is an extensive limestone cave system in the Guadalupe Mountains of southeastern New Mexico, carved into the Permian-age Capitan reef limestone. Unlike most limestone caves, it formed largely through sulfuric acid speleogenesis: hydrogen sulfide gas rising from underlying oil and gas deposits mixed with groundwater to produce sulfuric acid, which aggressively dissolved the limestone from below over roughly the last several million years, producing unusually large chambers. Its Big Room is one of the largest single cave chambers in North America, and the cave also preserves extensive gypsum deposits left as a byproduct of the sulfuric acid dissolution process; it became a national park in 1930 and a UNESCO World Heritage Site in 1995.