The development of limestone cave systems in the dimensions of length and depth

Karst caves are defined as solutional cavities >5–16 mm in diameter and discussion is limited to cases where such continuously extend to a surficial input or output or both. Three opposed sets of general genetic hypotheses ('the classical hypotheses') have been presented for such caves, arguing that the majority develop (1) in the vadose zone, (2) in the phreatic zone, or (3) proximate and parallel to a water table. It is contended here that vadose, phreatic, and water-table caves are all of common occurrence and may be linked in one genetic theory. A four state model is proposed in which ideal phreatic and water-table caverns are end members; in a given massif of soluble rock the state (cave type) that develops is a function of the frequency of fissures penetrable by groundwater. The water-table type is the high frequency end member. Fissure frequency increases with passage of time after onset of karstification and gradational features may also develop to modify phreatic types. Vadose caves may be of 'drawdown' type (following an initial phreatic path) or 'invasion' type (developing a new path through rock drained by earlier caves). Extensive cave systems may comprise vadose, phreatic, and (or) water-table components developed contemporaneously.