Encyclopedia of Caves

except in a few extremely arid regions. Figure 1 shows the variety of sources for the water responsible for the development of caves. Most of the caves are dissolved by the movement of groundwater in contemporary drainage basins. In coastal regions, the mixing of fresh groundwater with saltwater produces an aggressive solution that can dissolve out caves. Some caves (for example, the large caves of the Black Hills of South Dakota) are formed from hot water rising up from deep within the rock. Carlsbad Caverns in New Mexico and other caves of the Guadalupe Mountains have been formed by sulfuric acid derived from the oxidation of hydrogen sulfide migrating upward from the oil fields to the east. In summary, caves form in a great variety of rocks by a great variety of geological and chemical processes. Each has its importance to geology. However, the common theme that binds this diverse collection of cavities together is their interest to human explorers and their use as habitat by cave-adapted organisms.