ABSTRACT
In spite of the large extent of karst in Iran, the number and lengths of caves are less than might be expected. There are many highland karst aquifers without any cave systems yet known, while big springs emerge at their bases of erosion. Several levels of caves are expected in the karst mountains of Iran, as a result of the rapid rates of uplifting and local valley incision. There are two main reasons for the small number of known caves. First, most of the karst areas are high mountains with steep slopes, so that many cave entrances have been filled in by talus or transported sediments or have been blocked by entrance breakdown in the high-risk earthquake regions of Iran. Second, many springs with high discharges are of the vauclusian type, with no explorable dry cave systems. Conduit systems of these springs, which have developed at higher levels in the past, cannot presently be seen on the surface. The short length of caves is also to be expected as the rapid rates of uplift and incision reduce the time for cave development at any one level. Water in the cave conduits leaks to lower levels and prevents further cave development. Also, recharge is mainly diffuse flow in the majority of the karst sites, so cave development is only initiated where branches of diffuse flow join each other beneath the surface.
