Michael A. Stecker

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Great Sand Dunes National Park
Found in southern Colorado at the edge of the snow-covered Rocky Mountains, Great Sand Dunes National Park (formerly a Monument) covers approximately 39 square miles of the San Luis Valley. These dunes of pure golden sand reach heights of 700 feet above the valley floor, making them the tallest in the U.S.A.

The Great Sand Dunes National Park in southern Colorado lies at the southeastern end of the San Luis Valley, nestled against the western slope of Sangre de Cristo Mountains. It's closest town is Alamosa, 38 miles to the southwest. At a greater distance, the dunes are northeast of Pagosa Springs, east of Creede, and southeast of Gunnison, Colorado. The mountains immediately to the east of the dunes are the Sangre de Cristo Range. Among their highest peaks are (from north to south) Cleveland Peak, 13,414; Mount Herard, 12,200; Mount Zwischen, 12,006 and Carbonate Mountain, 12,308 feet.


Their Formation
These dunes were created by winds blowing sand toward the northeast across the San Luis Valley, where they were deposited at the foot of the high Sangre de Cristo Mountains. Although the dunes seem misplaced, they are here because the key ingredients for making dunes -- sand, wind, and time -- exist. For centuries, the Rio Grande meandered through the San Luis Valley carrying sand and other sediments and depositing them in its riverbed and along its shores. Most of the sand was eroded bits and pieces of the San Juan Mountains brought to the Rio Grande by tributary streams. Some of it was eroded particles of rock left in the valley by alpine glaciers during the Ice Age. In time, the Rio Grande changed its course, and these large dry deposits of sand were exposed to the winds that swept across the broad, flat valley. The prevailing winds, blow the sands toward the northeast where they are deposited at the foot of the steep Sangre de Cristo Mountains. Seeking a way over this barrier, the winds surge upward through low mountain passes, carrying the lighter particles but leaving the heavier sand at the foot of the mountains. In this way, over thousands of years, the Great Sand Dunes were created. As if never quite satisfied, the winds return day after day, sculpting new delicate patterns in the dunes.


Great Sand Dunes National Park lies northeast of Alamosa, Colorado at the foot of the Sangre de Cristo Mountains