Caves Speleology

Caves — naturally occurring underground spaces large enough for human entry — contain some of Earth's most extreme environments and remarkable geological formations. The world's longest known cave system is Mammoth Cave (Kentucky, 676 km of mapped passages, 400 million years old). The deepest cave is Veryovkina Cave (Georgia/Caucasus, 2,212m deep — the deepest known point underground). Son Doong (Vietnam) is the world's largest single cave chamber — so large it contains its own weather system (clouds form inside) and a jungle. Cave geology produces extraordinary formations: stalactites and stalagmites (calcite deposited by dripping water — the mnemonic: 'stalactites hold tight to the ceiling, stalagmites might reach the ceiling'); cave pearls (concentrically layered calcite spheres in cave pools); cave popcorn; boxwork (Carlsbad Caverns); and cave ice. Cave ecosystems (troglobites — obligate cave-dwellers) include eyeless fish, depigmented crayfish, and blind cave crickets adapted to permanent darkness and food scarcity. Lechuguilla Cave (New Mexico) contains 240km of passages with selenite crystal formations up to 9m long — and microbes in its extreme environment are being studied for antibiotic resistance.