high res (2.6 M) low res (105 K)
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ISS011-E-11543 (3 August 2005) --- Algodones Dunefield, CA is featured in this image photographed by an Expedition 11 crew member on the international space station. Fans of the Star Wars series of films may recognize the Algodones Dunefield – also known as the Imperial Dunes - as portions of the imaginary planet of Tatooine. While not planetary in scale, this dune field located at the junction of three states (Arizona and California in the USA; Baja California del Norte in Mexico) is a distinctive feature of North America. The field is approximately 72 kilometers long by 10 kilometers wide (45 miles by 6 miles) and extends along a northwest-southeast line that correlates to the prevailing northerly and westerly wind directions. The dune field is designated a wilderness area, with the only manmade structure being the All American Canal that cuts across the southern portion from west to east (right side of view). A checkerboard pattern of farms in the Colorado River floodplain is visible on the Mexican side of the border (far right). Wisps of clouds obscure the Cargo Muchacho Mountains (top). Distinctive dune forms pointed out by NASA geologists in this image include transverse mega-dunes and linear dunes. The transverse dunes, appearing much like a large tank tread along the long axis of the dune field, are the largest features and were formed by strong and constant northwesterly winds. A fine pattern of smaller dunes has formed along the crests and windward (northwestern) sides of these large dunes and point to continuing sediment transport activity. Networks of small dunes along the western side of the dune field suggest that wind direction here is more variable and perhaps influenced by the large transverse dunes themselves. Long linear dunes extending northwest-southeast are visible along the western edge of the dune field. The presence of vegetated drainage networks along the northeastern border of the field, and the relative lack of dunes themselves, suggest that rapid dune migration is not occurring along this margin. The majority of dune migration today occurs at a rate of approximately 0.3 meter/year (1 foot/year) along the southeast margin of the dune field.
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