The island of Bahrein has a coastline 126 km long, and is accompanied by more than 30 small islands. Bahrein is linked to Saudi Arabia by a causeway. The island is low-lying and rocky, a dome structure with a central core of Eocene limestones, sandstones, and marls, the land rising to Jabal Dukhan, an interior hill with a summit 135 m above sea level (Willis 1967), surrounded by in-facing escarpments. There is a broad coastal fringe of unconsolidated Quaternary silts, quartzose dune sands, carbonate sands in beaches and beach ridges, shell deposits, and evaporites. The southern half of the island is a barren sandy plain with some salt marshes, and the northern half is a broad plateau with settlements and gardens irrigated from artesian wells. Groundwater seeping from Saudi Arabia is under sufficient pressure to generate submarine freshwater springs off the north coast.
The climate is hot and humid. Bahrein has 19° in January and 36° in July, and the mean annual rainfall is...