Sand Dunes of the Southwest

Cactus Plain, AZ

Cactus Plain

Olsen Family Photo

This area has the impressive appearance of an extensive dune field when you are flying over it in an airplane. In person, however, these western Arizona dunes leave a lot to be desired. Don't expect to see lofty dunes like the ones across the river in California. This is more like an undulating landscape of small sandy hills for as far as the eye can see, the sands varying in type and color as you move from west to east.

Officially called the Cactus Plain Wilderness Study Area but also known as the Bouse Dunes, it is a large open area (59,100 acres) of stabilized and semi-stabilized sand from about 15 miles southeast of Parker to about 3 miles north of Bouse, ranging from 1,250 to 1,650 feet in elevation. This desert wilderness is bordered by the basalt-covered Gibraltar Mountains to the north and the Buckskin Mountains to the northeast.

It's been said that the dunes range in height from 30 to 120 feet, but we've yet to find any that high; so if they're there, they must be far off the beaten track. There are no trails within the wilderness area itself, making access difficult for all but the most intrepid hikers.

At first glance the landscape looks fairly sun-baked and barren, but it does contain a varied combination of desert plants such as paloverde, creosote, ocotillo, cholla cacti, and white bursage. Animal life includes jackrabbits, coyotes, mule deer, and many kinds of rodents. There are even dune grasses and sand-adapted creatures such as Mojave fringe-toed lizards and sidewinder rattlesnakes.

Large areas of the Bouse Dune area have been seriously degraded by an invasion of Sahara Mustard, an exotic weed. They say there used to be spectacular wildflower blooms here, but now the native plants can't compete with the Sahara Mustard, which grows faster and larger.

Not many people venture out onto the Cactus Plain. There isn't any water or shade for miles around, and summer temperatures are extremely hot. The best time to visit is in the winter months from November to April, when daytime temperatures are a comfortable 70-80 degrees and nighttime lows don't go below 50.

There is another sand field called La Posa Plain, which is located directly south of the Cactus Plain and bordered on the east by the Plomosa Mountains. Between the two similarly sandy areas is the Bouse Wash, a sandy wash that runs alongside Highway 72 and separates the two plains.

It used to be thought that the sands of western Arizona must have blown across the Colorado River from the Mojave Desert of California. However, the eastern California dunes are rich in feldspar while the western Arizona dunes are mostly quartz. So the Arizona sands must have come from quartz-rich Colorado River sediments. In the past, when the river's sand supply was greater, the dunes near Parker may have been larger and more active.

Cactus Plain

Google Earth image

References:

http://www.sangres.com/arizona/blm/cactus-plain-wsa.htm
http://thegeozone.com/treasure/arizona/tales/az015b.jsp
http://www.azgfd.gov/w_c/edits/documents/Umascop.d_001.pdf
http://www.blm.gov/ca/pdfs/cdd_pdfs/fringe1.PDF
http://www.desertmuseum.org/programs/flora_bratou-gallery.php
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1170&context=usgsstaffpub - "Eolian Sand Transport Pathways in the Southwestern United States: Importance of the Colorado River and Local Sources," a USGS staff publication. The results presented here demonstrate that a major river system in the southwestern United States is a barrier to the migration of some dune fields, but essential to the origin of others.

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