Karst is unique landscape formed by the underground erosion of rocks such as limestone and marble that dissolve in water. Rainwater, made acidic by carbon dioxide from the atmosphere and soil, slowly infiltrates cracks in limestone and marble, dissolving the rock and enlarging the openings. If these openings become large enough for humans to enter, they are termed caves. Caves, however, form only a tiny part of most karst areas. Karst openings support unique ecosystems that include plants, bacteria, crickets, spiders, fish, and small mammals adapted to this dark, but little changing environment.

Caves and karst develop slowly over tens of thousands of years or longer. Areas of karst landscape require careful management, as sensitive underground features can be damaged by surface activities such as road building or logging that alter the underground flow of water and air.