Located 35 miles northeast of Alamosa, Colorado, nestled against the Sangre de Cristo Mountains, sits the Great Sand Dunes National Park and Preserve. The park features huge sand dunes, the tallest in North America.
The dunes comprise about 11% of a massive sand deposit that covers more than 330 square mile.
Most of the sand is created by the freeze and thaw in the mountains 65 miles to the west of the dunes, and the action of the snow melt each spring. The steams of snow melt carry the sand out into the valley, and the prevailing winds move it across the valley.
The dunes are estimated to be from 12,000 to a million years old. I realize this is a big span, but I'm not doing the research, so we'll go with it.
The dunes remain stable because the prevailing winds keep pushing them up against the Sangre de Cristo's, but cannot lift the sand over the mountains. Any sand that does reach the mountains is washed back down by the snow melt. As a result the dunes are continually reshaped, but never move very far in any direction.
If you'd like more info, use this link >>> Great Sand Dunes National Park
