A heard of deer grazing on the springtime plains of the Colorado Great Sand Dunes National Park and Preserve.
Wildlife of the park and preserve includes pikas, bighorn sheep, black bears, mountain lions, beavers, badgers, bison, pronghorn, birds such as ptarmigan, peregrine falcons, owls, eagles, and herons, and reptiles such as lizards and snakes. Fish encountered in the park’s streams include the Rio Grande cutthroat trout and suckers. Insects such as beetles are common as well.
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 (7,700 ha). 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. Source: wiki