CAVE (מְעָרָה֒, H5117, cave; חֹרִ֖ים, holes; Gr. σπηλαῖον, cave) a hollow extending beneath the surface of the earth. Caves have been used by mankind of all ages for habitation (Gen 19:30), refuge (Josh 10:16) and burial (John 11:38), and many legends and superstitions are attached to them. Some caves have been cut by wave action (sea caves), other scoured by wind action, particularly in desert regions (eolian caves) and still others result from glacial melt-water (glacial caves). The largest and most common types of caves, both worldwide and in the Holy Land in particular, are solution caves which result from the action of underground water. Most of these caves are in limestone because no other rock equally abundant at the earth’s surface is so readily dissolved. Calcite (calcium carbonate), which is the chief constituent of limestone, including the Judean Limestone which crops out over large areas of Israel and Jordan, is dissolved by ground water containing carbon dioxide. Some of this carbon dioxide is taken up by rain water falling through the air, but much comes from the air in soil containing decaying humus which contains 300 times more carbon dioxide than the air of the atmosphere. As dissolved carbon dioxide reacts with water to form carbonic acid, water passing through soil rich in humus may become strongly acidic. It is by the action of this water that most caves in limestone have been formed. Particularly in dense, jointed limestone, water is concentrated along restricted planes rather than being disseminated throughout the rock. In this way much solution takes place along joints and bedding planes by the reaction of the carbonic acid in the ground water with the calcium carbonate to give a solution of calcium bicarbonate.

Caves are formed just below the water table in regions where the water table remained stable for a long time. They have a characteristic pattern of passages which are usually horizontal, even where the limestone beds are steeply inclined, except in regions where the originally horizontal attitude of the cavern network has been tilted during later mountain building deformation. The development of most caves just below the water table, in rocks saturated with water, rather than at random depths within the water saturated part of the earth’s crust, is prob. the result of a nonlinear relation between calcium carbonate solution and the partial pressure of carbon dioxide. The result is that the mixing of water percolating down from the surface with slowly moving ground water below the water table constantly produces an undersaturated solution capable of dissolving more calcium carbonate.

Most caverns are composed essentially of horizontal and some vertical passageways. Passage width and height varies from upwards of 30 meters to the smallest penetrable dimensions. Where not modified by collapse, the cave cross sections are tubular or rectangular in shape, but others are irregular in cross section. The pattern of their ground plan varies: a grid of intersecting passageways is referred to as a network cave, a dentritic branching pattern of increasingly smaller passages make up a branching cave and one tube with numerous twists and turns is an angulate cave. The vertical passageways are the active recharge points of ground water into the limestone. Often these are roughly cylindrical vertical shafts with smooth walls and heights of 100 meters or more.

Collapse of the roof of a cavern or the downward solution of limestone or other soluble materials (e.g. dolomite—calcium magnesium carbonate, or gypsum—hydrated calcium sulphate), results in the development of depressions at the surface commonly referred to as sinkholes. Typically they are circular and 10-20 meters deep and often of the order of 100 meters in diameter. Coalescence of sinkholes is common, particularly the coalescence of a linear series. In this way access from the surface to some caverns is provided.

Lowering of the water table makes the caverns accessible and in many the process of deposition of calcite dominates over solution. As water drips from the cavern ceilings, it evaporates, loses carbon dioxide, and calcium carbonate (calcite) is precipitated. Progressively icicle-like forms, stalactites, develop hanging down from the ceiling. Calcite precipitated when water drips to the floor is built up as stalagmites. Continued precipitation of calcite may result in the meeting of stalactites and stalagmites to form columns.

The abundance of limestone cropping out in Israel and Jordan—the Judean Limestone made up mainly of massive hard beds of limestone and dolomite with some softer chalky marls, shales and gypsiferous strata—and the semi-arid climate, resulted in an abundance of caves throughout the region. With the successive downward movement of the Jordan Rift Valley (earthquakes q.v.) the base level of the streams draining into this tectonic depression has been lowered and the water table lowered. The resultant cutting down of valleys exposed caves on valley sides, such as the cave of Adullam in which David took refuge (1 Sam 22:1), and insured that the caves were relatively dry so that they could be used for habitation (Gen 19:30) or for burial (23:19). The branching pattern of some caves made them suitable for places of burial, particularly if the entrance was small and could easily be sealed (John 11:38, 39). The network pattern of many cave systems together with the columns and stalagmites make them ideal places of refuge (1 Sam 13:6), even for large numbers (22:2) and for surprise (1 Sam 24), with small entrances easy to hide or defend and other exits available for escape. The fig. use of caves as places of refuge is given in Isaiah 2:19. See Dead Sea Scrolls.

Bibliography R. W. Fairbridge (ed.) The Encyclopedia of Geomorphology (1968), 652, 653, 1036-1039; E. M. Blaiklock (ed.), The Zondervan Pictorial Bible Atlas (1969), 438-452; D. J. Easterbrook, Principles of Geomorphology (1969), 256-265.