The Iranian coastline is about 2,440 km long. A rugged escarpment at the edge of an interior plateau overlooks a coastal area of Tertiary rocks with ranges produced by Alpine folding and intermittent narrow coastal plains. The coastline runs parallel to the anticlinal ridges, one of which runs through the island of Qeshm. In the south (Laristan), there are numerous circular salt domes formed by diapiric intrusions from an underlying Cambrian salt horizon. Rivers that drain to the coast have short, steep courses.
The landscape is largely desert. The climate is hot and arid in summer and mild and rainy in winter. Mean annual rainfall decreases along the coast from 277 mm at Bushire to 147 mm at Bandar Abbas and less than 130 mm at Jask and Chah Bahar. Spring thunderstorms cause sudden flooding in rivers draining to the coast, and floods leave thick deposits of mud on alluvial flats around river mouths. The Persian Gulf has summer temperatures ranging from 20° in the north...