Sand Dunes of the Southwest

Navajo Dunes, AZ

Navajo Dunes

Public Domain Photo

The photo above shows sand ripples in Monument Valley, with the "Totem Pole" in the background. Monument Valley Tribal Park straddles the northeast corner of Arizona and southeast corner of Utah. The park is accessible from Highway 163, about halfway between Kayenta, AZ and Mexican Hat, UT.

Sand dunes are surprisingly rare in Arizona, but they can be found in certain wind-swept regions of the high desert in the northeastern corner part of the state. Sand supplies here are abundant from both sandstone rock and dry riverbeds. On the Navajo Reservation, for example, sand dunes are a predominant surface feature, covering approximately one-third of the huge Navajo reservation, which is equivalent to thousands of square miles (see map below).

Navajo Dunes

The Navajo Indians have lived in this land of Sei Nahogishii, or “tumbling sands,” for centuries; so sand is an important part of their culture. Making the best use of everything at their disposal, talented Navajo artists actually take colored sand and make beautifully designed paintings out of it. They learned early on that sand dunes, while dry on the surface, are surprisingly good retainers of water below a certain depth; so corn planted there has a good chance for survival. Even in dry years, seepage from sandstone aquifers provides a water source.

In recent years, the Navajo Nation has been experiencing prolonged drought conditions, which is changing the face of the sands. Due to a lack of precipitation, the reactivation of stabilized sand is occurring in many areas on the reservation. This is because the vegetation that stabilizes the sand cannot acquire the needed water to maintain its growth on the dunes. This leads to a loss of plant cover, which results in more erosion and more loose sand blowing around.

In addition, it is difficult for plants to grow on mobile dune fields. Only a few types of plants can keep pace with moving sand and tolerate abrasion from the sand. As a dune progresses, plants on the leeward face of the dune gradually get completely covered by the approaching dune. Ironically, the Navajo creation legend features a sand monster, named “Seit'aad,” that buried its victims in dunes.

As a result of the increasing aridity, the dunes themselves are losing their inner moisture which exacerbates the problem. During 2009, an unusually windy and dry year, researchers measured dune migration rates as high as 34 to 48 m/yr. Dune mobility is threatening homes and property, as well as causing transportation problems. Roads in the area can become impassable due to active sand dunes.

One of the biggest impacts of dune mobility is on agricultural fields and rangeland, which consequently affects many Navajo people who raise crops and livestock. Shifting sands may also contribute to a loss of rare and endangered plants. Moreover, once the growing conditions become altered, invasive plants like Russian Thistle (tumbleweeds) have an opportunity to move in. Even when wetter periods return, the native plants will have permanently lost their niche in the ecosystem.

Navajo Dunes

Google Earth image

References:

http://geochange.er.usgs.gov/sw/impacts/geology/sand/ - Reactivation of Stabilized Dunes on the Colorado Plateau
http://www.indiancountrytoday.com/national/76233607.html
http://www.usgs.gov/corecast/details.asp?ep=94
http://www.lpi.usra.edu/meetings/dunes2010/pdf/2039.pdf
http://esp.cr.usgs.gov/info/sw/swdunes/navajo_dunes.html
http://www4.nau.edu/tribalclimatechange/tribes/southwest.asp
http://www.ucar.edu/tools/newvoices/thornbrugh/ - "Between Grazing Land and Barren Sand: Investigating a Tipping Point," by Casey Thornbrugh. (Thornbrugh's main research tool is a widely used index of sand dune mobility, developed by Nicholas Lancaster of the Desert Research Institute.)

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