Eolian processes have substantially modified the landscape on the Southern High Plains within historic times. The maximum inferred rate of deflation was 18.9 mm/year at a site in Bailey County, Texas, a region of loose, sandy soils and frequent, seasonal dust storms. At least locally, agricultural practices have accelerated natural rates of erosion and deposition by winds. An extensive cover of windblown sand and silt mantles the gently sloping surface of the Southern High Plains. Eolian deflation and deposition are among the dominant geomorphic processes affecting this region throughout most of the Holocene and Pleistocene time. Historically, human activities have heightened the importance of wind action by disrupting the natural vegetative cover, thereby exposing the unconsolidated sediments.
Agriculture, particularly dry-land cultivation, has been the principal form of land use in the area since the early 1900s or before (Webb, 1931). The effects of tilling practices on deflation are shown in Figure 1. The cultivated field on the right (east) is approximately 0.8 m lower than the range site on the left (west). This long, narrow field was cleared and probably brought into cultivation in the 1920s (C. D. Tunnell, personal communication, 1983). Its furrows run from north to south, along the field's long axis. The orientation of these furrows tends to maximize local deflation, as the furrows are parallel to the dominant winds. During the winter and early spring, some of the strongest winds are from the north, whereas the prevailing wind direction is southerly at other times of the year (Bomar, 1983). Other factors that enhance the erosional impact of the wind include antecedent dry conditions and frost heaving. Both are seasonal effects that increase the soil's susceptibility to removal during the frequent spring dust storms. After becoming entrained, soil aggregates from this field and others like it are transported from their source and redeposited as a broad sheet of eolian sediment.Bureau of Economic Geolog
