Sand Dunes of the Southwest

Great Sand Dunes, CO

Great Sand Dunes

Olsen Family Photo

The Great Sand Dunes of Colorado are the tallest in North America. The highest, Star Dune, stands at 750 feet and an elevation of over 8,000 feet. Besides having high dunes, the dune field itself is large. The Great Sand Dunes National Park covers 39 square miles in the San Luis Valley of Colorado.

These dunes are truly magnificent, not just because of their impressive size, but also due to their scenic location on a grassy high plain set against a dramatic mountain backdrop. The 14,000-ft. Sangre de Cristo Mountains were formed by rifting and uplifting of a geologic plate. The San Juan Mountains, on the opposite side of the valley, were formed by volcanic activity.

Another special feature of these dunes is the presence of a year-round stream at their base, coming out of the mountains. Sediments and water from both mountain ranges once flowed down into the San Luis Valley, into what geologists have named Lake Alamosa. Most of the ancient lake disappeared due to climate change, leaving behind an enormous sand sheet.

This sand is constantly pushed back and forth by the predominant winds. Prevailing winds blow the sand to the east, and storm winds blow the sand toward the west. It is these opposing forces that cause the dunes to grow vertically, creating the huge star-shaped dunes. In addition, barchan dunes can be found at various locations throughout the park. Some barchan dunes connect with others forming barchaniod ridges. If the ridges become fairly straight, geologists call them transverse dunes. Along the southern boundary of the Great Sand Dunes, a series of transverse dunes are fed by recycled sand transported by Medano Creek. Parabolic dunes are also common in the sand sheet southwest of the main dunefield.

Experience the panoramic view from the top of the highest sand dune in North America, the Great Sand Dunes "Star Dune," in this video: http://www.youtube.com/watch?v=1TQTjDv5wqU

Great Sand Dunes

Google Earth image

References:

http://www.nps.gov/grsa/naturescience/sanddunes.htm - Animation showing how the Great Sand Dunes formed.
http://www.nps.gov/archive/grsa/resources/overview.htm - Explore the wonders of the Great Sand Dunes with this extensive collection of natural history resources from the National Park Service.
http://www.nps.gov/archive/grsa/resources/curriculum/intro.htm - An online curriculum for K-12th grade teachers and students with lessons, activities, and animations for learning about the natural and cultural history of the Great Sand Dunes, made possible by "Parks as Classrooms."
http://www.nps.gov/grsa/ - the official National Park Service website for Great Sand Dunes National Park and Preserve.
http://www.nps.gov/archive/grsa/resources/maps/GRSA_Sand_Deposits.jpg
http://esp.cr.usgs.gov/info/dunes/

Website design and content (c)2010 by Peter Olsen. This educational unit study was my PVCC honors project for GPH 211 Landform Processes.