About 200 salt diapirs (plugs) have been known in the region of the Persian Gulf. numerous are still active. Karst rocks are represented by a rock salt, less frequently by gypsum and anhydrite. Karst developed especially in relics of planated surfaces. Karst forms are completely comparable with karsts in classical carbonate rocks. Different forms can be distinguished: karren, solution pipes, solution dolines, solution-collapse dolines, uvala-like to polje-like depressions, blind valleys, canyon-like forms, ponors, springs and caves. Two World longest caves in salt were discovered and explored here. Long caves are developed especially in a watertable, large ones in plugs near the seacoast. Caves are often outlets of closed depressions (polje-like). Some caves at bottoms of collapse-solution dolines or swallow holes are subvertical. Karst processes are caused dominantly by dissolution of salt, less frequently of gypsum. The process of subrosion of halite under gypcretes plays the main role. Deep circulation of meteoric waters was proved in some plugs.

Four classes of different thickness of cap rock can be distinguished, each with its special superficial and underground karst forms: 1. salt outcrops, 2. thin cap rock (0,5-2 m), 3. cap rock of moderate thickness (5-30 m), 4. cap rock of great thickness (more than 30 m). The most important factors affected by cap rock thickness are as follows: the density of recharge points, the amounts of concentrated recharge which occur at each recharge point, the rate of lowering the ground surface of salt karst, the dissolution capacity of water and the size and amount of load transported by underground flood-streams into cave systems. The thickness of cap rock above the cave does not influence the cave itself; more important seems to be the thickness of cap rock in the recharge area of the cave and the type of recharge into the salt environment. Another important factor is the thickness of overburden above the cave, which negatively correlates with intensity of breakdown. Wide passages in some caves are developed as result of intensive deposition of bedload, which expel the stream into the side of the passage and are due to enhanced corrosion in the few decimetres high zone above the bottom of passage.