Dust in the Wind: A Quick Overview of the Sand Fields of the Great Plains
This is an overlay of Arbogast 1996 on a slightly broader, annotated US map of the region to include a few more reference points. The map itself is adapted after Muhs and Holliday 1991. It is interesting to note that few cities developed in the sand fields. Cheyenne, Denver, and the other cities of Front Range are to the west of the sand fields while Albuquerque and El Paso are even further westward. Likewise, Omaha, Wichita, Oklahoma City, Fort Worth and Dallas are all to the east. Amarillo and Lubbock are the exceptions to the rule. Below is a similar, more recent view from Busacca 2003.
The fact that there are sand dunes lying across much of the Great Plains is not common knowledge for many Americans nor is it obvious to the casual traveler. When we see the grass growing on the plains, our mind’s eye first sees these as grass covered hills of dirt. It takes a moment before we realize that the hills in the background are of the same sand as that in the exposed cut.
It is easier to recognize the nature of sand dunes from space. This is the Nebraska Sand Hills.
Even most of those familiar with the Nebraska Sand Hills, probably aren’t familiar with the full distribution of sand fields across the plains – from Wyoming and Nebraska, down through Colorado and into Kansas, through Texas and New Mexico and on into Mexico. If you pay attention to the road cuts, however, you can see sand dunes right along the Colorado front range, such as with this road cut on the north side of Colorado Springs, just a few miles from the Air Force Academy.
The are eye-witness reports of open dunes in the great plains in the late eighteenth century and mid-nineteenth century. Paleo-climate studies also show that some of these fields have been active during the Holocene. Holocene sand mobility over the last few thousand years has been linked to both solar variability and Pacific ocean variability. There are two key climate factors that play into the activation/stabilization of the sand fields: (1) the amount of time that the winds are of sufficient strength to move local sand (W%) and (2) the ratio P/PE of precipitation (P) to potential evapotranspiration (PE). The diagram below (developed from Lancaster 1988) shows how sand mobility (M) is related to increasing W% and/or decreasing P/PE.
Muhs and Holliday 1995 sketched a process flow showing how increased temperatures and decreased precipitation lead to increased sand mobility.
But there are also modern factors that work against increased sand mobility: widespread irrigation, decreased vegetative damage from bison herds, and water-managed rivers that result in deepening river beds, less loss of vegetation from river banks and sand islands, and fewer sand beds exposed by very low flows.