122915AlbuquerqueNmTripMP1283
SHOT 12/30/15 2:06:13 PM - A family of visitors poses for a picture while exploring the Great Sand Dunes National Park and Preserve near Alamosa, Co. Great Sand Dunes is a U.S. National Park located in the San Luis Valley, in the easternmost parts of Alamosa County and Saguache County, Colorado, United States. Originally created as Great Sand Dunes National Monument on March 17, 1932, Great Sand Dunes National Park and Preserve was established by an act of the United States Congress on September 13, 2004. The park contains the tallest sand dunes in North America, rising about 750 feet (230 m) from the floor of the San Luis Valley on the western base of the Sangre de Cristo Range, covering about 19,000 acres. Researchers say that the dunes started forming less than 440,000 years ago. The dunes were formed from sand and soil deposits of the Rio Grande and its tributaries, flowing through the San Luis Valley. Over the ages, glaciers feeding the river and the vast lake that existed upon the valley melted, and the waters evaporated. Westerly winds picked up sand particles from the lake and river flood plain. As the wind lost power before crossing the Sangre de Cristo Range, the sand was deposited on the east edge of the valley. This process continues, and the dunes are slowly growing. The wind changes the shape of the dunes daily. (Photo by Marc Piscotty / © 2015)
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