Great Sands Dune National Monument

Basic Information - Camping - Activities - Geology

Nestled in southern Colorado, North America's tallest dunes rise over 700 feet high against the rugged Sangre de Cristo Mountains. The wind shaped dunes glow beneath the rugged backdrop of the mountains. This geologic wonderland, containing 39 square miles of dunes, became a national monument in 1932. With the passage of the Great Sand Dunes National Park and Preserve Act of 2000, resources now also include alpine lakes and tundra, six peaks over 13,000', ancient spruce and pine forests, large stands of aspen and cottonwood, grasslands, and wetlands--all habitat for diverse wildlife and Rocky Mountain plant species.

Basic Information

Operating Hours, Seasons
The monument is open 24 hours a day, 365 days a year. Visitor center open daily, closed on winter holidays.

Getting There
PLANE - Limited air service is available to Alamosa, Colorado. Airports in Colorado Springs, Denver, and Albuquerque are all within 4 hours drive.

CAR - Great Sand Dunes National Monument is located 35 miles northeast of Alamosa,Colorado, reached by US Highway 160 and Colorado Highway 150 from the south. or from Colorado Highway 17 and County Six Mile Lane from the west.

Weather & Climate
In fall, winter, and spring, expect moderate daytime temperatures and freezing to sub-zero temperatures at night. Summer temperatures during the day average 70 to 80 degrees, lows may drop to 40 degrees. Sand temperatures can reach 140 degrees in summer; shoes are highly recommended for hiking the dunes.

Accessibility
The Visitor Center and restrooms are fully accessible. There is an accessible trail at the visitor center, two accessible campsites and one backcountry accessible campsite.

Getting Around
By foot, bicycle, or personal vehicle. Please note: bicycles are not permitted on trails.

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Camping

Pinyon Flats
Open All Year
Pinyon Flats campground is open year-round, and has 88 campsites available on a first-come, first-served basis. Fire grates, picnic tables, flush toilets and drinking water available. The campground is located in pinon/juniper forest and has excellent views of the dunes and the Sangre de Christo mountains. Winter low temperatures average between 0 and 13 degrees F. Fire wood can be purchased in the visitor center, open daily 8:30 am to 4:340 pm.

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Activities

If possible, spend at least a few minutes hiking on the dunes. If you have more time, there are nature trails and longer trails and routes. You may observe flora and fauna, picnic, and camp in the campground or backcountry. Medano Creek, which flows at the base of the dunes during spring and early summer, allows for sand castle building and pleasant, refreshing hikes. In winter, its icy stillness is lovely!

Photographing the dunes, especially in late afternoon when the shadows deepen, is rewarding.

Wildlife sightings are common. Recent observations include mule deer, elk, coyotes, golden and bald eagles, ravens, magpies, and, just outside park boundaries, bison. Keep wildlife wild! Never feed wild animals--it's dangerous for you and unhealthy for them!

Allow about two hours to hike the dunes. 'Friends of the Dunes, Inc.' host several summer events: castle building and kite flying contest, summer concerts, seminars, and photography workshops.

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Geology

While the exact age of the dunes is unknown, they probably began to form about 12,000 years ago as glaciers from the last Ice Age began to melt. The Rio Grande, swollen with glacial melt-water and debris, spread sand and gravel across a large portion of the San Luis Valley. Today, as yesterday, the wind sweeps across the valley and carries the sand toward a natural barrier, the Sangre de Cristo Mountain range. Here, at the foot of the mountains, the sand is deposited as the wind loses velocity and funnels through three low passes.

Both the San Juan Mountains and the Sangre de Cristo Mountains are responsible for the mass of sand found in the area. Most of the sand comes from the volcanic San Juan Mountains, where the fine-grained sand contains pumice, ash, and lava. Sangre de Cristo sand is comprised of many rock types and is more coarse-grained than San Juan sand because it does not have to travel as far. Sand grains from both sources range in size from 0.2 mm to 2 mm.

The dune shapes you see today would likely be what you would see if you visited next year, in 10 years, and even 100 years from now. There is a great deal of sand movement with each wind storm, but moisture in the dunes seems to have a stabilizing effect, maintaining the height, contours and shape of the sand in the main dune mass. If you were to dig down into the sand, generally within 8-10 inches, you would find moist sand.

The prevailing southwest wind carries sand from ancient river beds and moves it across the valley floor toward the dunes in three ways; saltation, surface creep, and suspension.

Saltation is a process where the sand grains bounce as they are transported by wind. This leaping movement accounts for about 95% of sand grain movement.

A sand grain "creeps" when it collides with other grains, causing it to roll or make small jumps. Surface creep may account for about 4% of sand movement.

Suspension involves movement of sand grains when sand is blown high into the air. Suspension accounts for about 1% or less of sand grain movement.

Southwest winds funnel through three low mountain passes in the Sangre de Cristo Mountain range. The northern most pass and highest pass is Music Pass. It is located out of view behind Mount Herard, the flat-topped mountain to the north of the dunes. Because of its height and location, Music Pass probably has the least effect on the dunes.

Medano Pass is the middle pass, visible in front and to the right of Mt. Herard. Of the three passes, it is the lowest (under 9,700 feet), the widest, and likely has the most effect on the Great Sand Dunes. Medano is a Spanish word meaning "sandy or sand dune".

Dunes have two slopes or "faces". The windward face has a gradual slope. Sand blown from the windward face is deposited on the steeply sloping leeward side. Sand on the leeward side or slipface is subject to constant change, avalanching when the sand reaches its maximum angle of repose, at 34 degrees. Impossible as it may seem, no slipface can exceed a 34° angle.

Although the wind typically blows from the southwest, occasional violent storms also blow in from the northeast. These winds can blow the sand on the crests and ridges of the sand dunes in a reverse direction, looking as if the ridge tops had folded back on themselves. These reversing dunes are called "Chinese Walls".

Magnetite, a volcanic mineral originating from the San Juan Mountains, shows itself as black streaks in the sand is readily attracted to a magnet. Because magnetite is heavier than most minerals, it remains on the surface of the sand while the lighter materials are carried away by the wind. The presence of magnetite indicated the presence of gold. The sand contains pieces of gold, called "flour gold". Enterprising prospectors in the early 1900's tried to extract gold from the sand, but gained little profit.

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