Thursday, July 15, 2010

White Sands, New Mexico, USA

White Sands, New Mexico, originally uploaded by MsLitello.

The desert is located in Tularosa Basin New Mexico. Its white sands are not composed of quartz, unlike most desert sands, but of gypsum and calcium sulfate. Unlike other desert sands, it is cool to the touch, due to the high rate of evaporation of surface moisture and the fact that the sands reflect, rather than absorb, the sun's rays. At 1185 meters above sea level, there are approximately 442 total square kilometers of dune fields and is known to be the world's largest surface deposit of gypsum.[3]
Gypsum is one of the most common mineral compounds found on Earth but is rarely seen on the surface, as it dissolves easily in water. The origin of this desert dates back to around 100 million years ago, during which it was covered by a shallow sea. As its waters gradually receded, saltwater lakes were left behind, which eventually evaporated in the sun. In addition to the salt, gypsum was also laid down in thick deposits on the old seabed.
The Sacramento and San Andres Mountains, with the Tularosa Basin between them, took shape approximately 250 million years ago. Giant upheavals in the Earth's crust distorted the land along with the gypsum deposits, forcing them high into the air about 70 million years ago.[4] Rainfall and melt water came from the mountains causing the gypsum to percolate out and the concentrated solutions were washed down the mountainsides. The gypsum solution accumulated in Lake Lucero, the lowest part of the Tularosa Basin. Water in the lake does not have any means of escaping except by evaporation, which leaves behind thin layers of crystallized gypsum, or selenite. Weathering then reduced these crystals to fine, sandy grains. Winds then carried the grains farther up the basin, and the grains piled in steep dunes that often reach as high as 15 m (50 ft). The winds carved more dunes and, while at the same time, carried small amounts of the gypsum grains by distances of up to 9 m (30 ft) a year.
This constant movement still occurs today, and with the added alkaline and the little amount of rainfall makes it difficult for plants to grow here leaving the desert desolate as it appears today.
source: Wikipedia

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