Brightly colored solar evaporation (salt) ponds in a desert landscape give this astronaut photo an unreal quality. The ponds sit near the foot of a long alluvial fan in the Pampa del Tamarugal, the great hyper-arid inner valley of Chile's Atacama Desert. The alluvial fan sediments are dark brown, and they contrast sharply with tan sediments of the Pampa del Tamarugal.
Nitrates and many other minerals are mined in this region. A few extraction pits and ore dumps are visible at upper left. Iodine is one of the products from mining; it is first extracted by heap leaching. Waste liquids from the iodine plants are dried in the tan and brightly colored evaporation ponds to crystallize nitrate salts for collection. The recovered nitrates are mainly used for fertilizer for higher-value crops. They are also used in the manufacture of pharmaceuticals, explosives, glass, and ceramics, as well as in water treatment and metallurgical processes. Image courtesy of NASA.