This causes air to shift throughout the cave network. Local storms also lead to pressure changes at the surface that can create breezes within the cave. Like many caves, Mammoth cave stays at a pretty constant 53 degrees Fahrenheit, and is extremely humid. When a heavy summer rain brings a rush of warm water into the cave, the moist cave air condenses and an eerie fog forms in cave tunnels near the underground river and cave openings. During such fogs, Meiman imagines the early explorers in the cave, not understanding why fog had suddenly clouded their lantern light.
Floods bring more than just fog.
The cave environment is very low in nutrients, explains Tom Poulson, a biology professor from the University of Illinois. Occasional large floods renew the organic matter that feeds crustaceans and plankton, which in turn feed larger cave species like blind cave fish. They also have enhanced senses to maneuver in the dark. Cave crayfish live well over 100 years, while their counterparts on the surface live only 10. Pearson says the often illusive, nearly colorless cave fish standout against the darkness of the cave when a beam of light catches them.