The term cave is given to a naturally formed underground cavity. The term usually implies that the opening is large enough for a person to enter and may indicate a length further than sunlight reaches. Some caves measure a few hundred feet while others extend for many miles and reach hundreds of feet in depth. Caves can be found in many parts of the world and in every state in the United States.
Caves are geological features and form in a variety of ways.
The most common caves are solutional caves, often called limestone caves for the common type of soluble rock in which they form. This is the type of cave seen in the Journey into Amazing Caves movie in the canyon areas and the cave diving scenes. Both the terrestrial and underwater caves in the film are solutional or limestone caves. Most limestone caves form through the dissolution of soluble rocks by a weak, naturally occurring acid in groundwater. The minerals which make up the rock actually dissolve into groundwater, like sugar into hot tea, but much more slowly.