Great Sand Dunes

Abstract

Great Sand Dunes is located in the Rio Grande Rift where subsidence creates a depositional basin that supplies sediment to an aeolian system. Prevailing winds from the southwest blow across the San Luis Valley transporting sand to the Sangre de Cristo mountain front where the wind regime becomes complex and vertically growing dune forms develop. Fluvial processes also shape Great Sand Dunes. Water transports sand into the system and within the system it moves sand in the direction opposite to the wind. Equilibrium between the two transport mediums causes the deflection of streams flowing around the dunefield where erosion creates large dune forms as the streams truncate the dunefield. Once the streams get past the dunefield, the sand they deposit can be blown back into the dunefield creating other large dune forms. Water also supports the biological diversity in the park and provides recreational value. Water use in the San Luis Valley has historically been greater than water supply, so current management efforts are trying to attain sustainable water use levels. Increased knowledge of the aeolian system has improved the story that the National Park Service passes on to the visiting public. The variety of dune types present in the park, the elevation of the park, the large volume of sand that accumulates there, and the proximity of the dunes to the adjacent mountains all serve as valuable analogs to aeolian deposits on Mars.