Great Sand Dunes NP, CO

For Fall Break of 2011, Becky (my wife) and I took a vacation from Utah to Durango, Colorado. While there, we drove over to the South-central part of the state to explore the Great Sand Dunes National Park.

The Southern Colorado area map

To encounter the giant, golden sand dunes of southern Colorado is as surprising as it is uplifting.

General Map of the Great Sand Dunes National Park and Preserve, (image provide by the National Park Service).

These wind-sculpted hills rise up suddenly, over 210 m high from the floor of the San Luis Valley, between the Rio Grande and the Sangre de Cristo mountains.

I’m standing a few kilometers from the Great Sand Dunes National Park in Colorado.

The great dunes are the tallest dunes in the United States, and cover over 90 square kilometers. They are particularly breathtaking to see in the early evening when sunlight highlights their sinewy outline and their rich golden color from the west.

October of 2011 at the Great Sand Dunes National Park

Dune formation began in the Pleistocene era when glaciers formed in mountain valleys, pouring ice and rock far into the San Luis Valley.

Becky standing in the cold October wind at the Great Sand Dune National Park in 2011.

About 12,000 years ago, a warming climate melted the Pleistocene glaciers, creating rivers and streams. This carried large quantities of silt, gravel, and sand into the San Luis Valley. Prevailing winds from the southwest, carried sand to the eastern edge of the valley. Pictured above behind Becky, the Sangre de Cristo Mountains on the eastern side acted as a barrier, forcing the winds to lose energy and release their clutch of the sand. As a result, the dunes were gradually enlarged by the wind.

A National Park Service Map of the Great Sand Dune National Park.
Looking north at the Great Sand Dunes of Colorado, near the Sangre de Cristo Mountains.

Even though they look dry, these sand dunes kept their shape because they are quite moist and dense under their surface. By wicking water from the high water table and nearby creeks, the dunes act like a sponge. Pictured above, notice the abundant vegetation on the level field and the line of trees, showing a river beneath the surface.

A look at the eastern edge of the Great Sand Dunes of the San Luis Valley.

Medono Creek is a small snow-fed stream from the Sangre de Cristo mountains that flows along the eastern edge of the dunes during the spring. [Unfortunately, Becky and I were there in October]. For several hundreds of feet the creek babbles over a stretch of sand, a foot deep and then suddenly disappear into the sand, only to pop up again several feet away.

Ring Muhly at the Great Sand Dunes National Park

The picture above shows the famous “Ring Muhly”. It is a grass that grows in a circle. This grass grows outward, releasing a chemical inside the circle that prevents other grass from growing there. In this way, a “bucket” is formed that captures rainfall in the desert climate.

I’m standing in the Great Sand Dunes National Park, Colorado in October 2011.

Although the predominant wind direction is from the southwest, winds from the east occur during storms, and together, these opposite-direction wind patterns cause the dunes to grow vertically as their sand material gets blown back and forth, piling up on itself. Though generally quite stable, some dunes are migratory, and many change shape seasonally.

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