Swirls of turquoise and tan colored the waters off the coast of Tunisia in mid-March, 2014. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite captured this true-color image on March 17.
Typical March weather for Tunisia is unsettled, with blowing wind and some precipitation. The brisk winds loft sand and dust into the air, often blowing it across the Gulf of Gabes, sometimes in large plumes. Precipitation also washes sediment into coastal waters. In addition, the aggressive tidal flows in the shallow Gulf of Gabes - maximum depth of water is less than 200 m (656 ft)- is responsible for washing beach sand and sediment into the offshore waters.
The variation in color may be attributed to a complex set of conditions, including the depth of the sediment in the waters. When sediment lies near the surface, it appears tan. As dust and sand sinks, the reflectance characteristics change. As it sinks, sediment appears turquoise or green from space.