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Oshigambo River and Etosha Pan, Namibia
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Published May 1, 2006
Etosha Pan in northern Namibia is a large, dry lakebed in the Kalahari Desert. The 120-kilometer-long (75-mile-long) lake and its surroundings are protected as one of Namibia’s largest wildlife parks. About 16,000 years ago, when ice sheets were melting across Northern Hemisphere land masses, a wet climate phase in southern Africa filled Etosha Lake. Today, Etosha Pan is seldom seen with even a thin sheet of water covering the salt pan. This astronaut photograph shows the point where the Oshigambo River runs into the salt lake during an unusually wet summer in southern Africa, in March 2006.
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Lake Poopo Water Levels
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Published April 24, 2006
Lake Poopó sits high in the Bolivian Andes, catching runoff from its larger neighbor to the north—Lake Titicaca (not shown)—by way of the Desaguadero River, which is the muddy area at the north end of the lake. Because Lake Poopó is very high in elevation (roughly 3,400 meters, or 11,000 feet above sea level), very shallow (generally less than 3 meters, or 9 feet), and the regional climate is very dry, small changes in precipitation in the surrounding basin have large impacts on the water levels and area of Lake Poopó. When the lake fills during wet periods, it drains from the south end into the Salar de Coipasa salt flat (not shown). Water levels in Lake Poopó are important because the lake is one of South America’s largest salt-water lakes, making it a prime stop for migratory birds, including flamingoes.
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Salt Dome in the Zagros Mountains, Iran
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Published April 17, 2006
The Zagros Mountains in southwestern Iran present an impressive landscape of long linear ridges and valleys. Formed by collision of the Eurasian and Arabian tectonic plates, the ridges and valleys extend hundreds of kilometers. Stresses induced in the Earth’s crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone and siltstone while leaving harder rocks, such as limestone and dolomite. This differential erosion formed the linear ridges of the Zagros Mountains. This astronaut photograph of the southwestern edge of the Zagros mountain belt includes another common feature of the region—a salt dome (Kuh-e-Namak or “mountain of salt” in Farsi).
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