The Great Sand Dunes

History of the Great Sand Dunes

Colorado

On the eastern side of the remote, high-mountain San Luis Valley, between the Blanca Massif and Crestone Needle, are the Great Sand Dunes, the tallest sand dunes in North America. The dunes cover approximately 39 square miles and rise to almost 750' above the valley floor.

The dunes are the product of the wind and rain eroding the San Juan and Sangre de Cristo Mountains that ring the San Luis Valley. They have collected here because the prevailing winds across the valley blow in this direction and meet winds blowing in the opposite direction. The sand drops to the valley floor and is held in place by water flowing from the Sangre de Cristo's. So over the course of millenia, the dunes have built up to where they are today. And tomorrow they will be different because the wind still blows, the sand still moves and the deposits of sand still grow.