Earth Observations taken by the Expedition 22 Crew

ISS022-E-058538 (31 Jan. 2010) --- Sir Bani Yas Island is featured in this image photographed by an Expedition 22 crew member on the International Space Station. Sir Bani Yas Island is located in the Persian Gulf near the western coastline of the United Arab Emirates (UAE). The approximately 14-kilometers x nine-kilometers island is the surface expression of a salt dome, and is one of several such islands in the Persian Gulf. During past periods of alternating wet and dry climate, sometimes involving areas with high rates of evaporation in enclosed basins, thick layers of salt minerals (such as halite ? common table salt, or gypsum ? a major component of wallboard) were deposited. These layers were subsequently buried by sediments; with enough overlaying material and depth of burial, the salt layers can begin to flow. Salt has lower density than the surrounding rock and it tends to flow upwards, pushing up the overlaying layers of rock to form a salt dome. While many salt domes retain a cap of the youngest rock layers at the surface, in some cases the underlaying salt extrudes onto the surface. This photograph illustrates the varying character of surfaces on the island. The central mountains of Jebel Wahid (center) mark the location of the Sir Bani Yas salt dome. The dome has breached the surface but exposed salt - primarily gypsum - is removed by erosion, leaving a rugged, insoluble cap formed from fragments of the overlaying sedimentary and volcanic rocks. Sand and silt derived from the Jebel Wahid area and surrounding gravel cover forms beaches along the outer edge of the island.