The ever-changing dune field is nestled up against a kink in the Sangre de Cristo Mountain range just east of the dunes and covers over 30 square miles.
It is also home to the pulsing or surging Medano Creek which flows in the spring. The surge feature is a unique hydrologic phenomenon seen in this two-minute video. The National Park Service describes the connection between water, sand, and slope causing the surging flow as being akin to ocean waves. This excellent link on surge features describes Medano Creek and other surface creeks and the underlying water table as similar to the circulatory system of the human body.
The 150,000 acre dune field is also home to the Tiger beetle, found only at the Great Sand Dunes.
The San Luis Valley graben that contains the park (and the adjacent horst that includes Mt. Zwischen) is one of the northernmost reaches of extensional Basin and Range that dominates the state of Nevada. The San Juan mountains border the graben to the west.
In 1807, Zebulon Pike described the dunes, "Their appearance was exactly that of a sea in a storm (except as to color), not the least sign of vegetation existing thereon."
Streams and creeks flowing out of the San Juan Mountains to the west over millennia carried gravel and sand into shallow lakes or sabkhas (salt flats) in the San Luis Valley.
During drought periods, these lakes dried, releasing the sand particles to the action of the wind. Strong prevailing southwesterly winds carry the tiny grains toward the Sangre de Cristos, piling them up against the foothills.
Yes, in the name of science and PEOTS, Maizie and I will be traveling southward this week to report on the state of the dunes. (Yes, we sacrifice for this blog!)
Have you been to the Great Sand Dunes? Before or after 2004 when it was elevated from National Monument to National Park status?
From the sand dunes ocean state,
Steph
Cattle guard sign just south of the Great Sand dunes (Everything is pristine and quiet at the dunes. . .)
