Principal-component analysis of Landsat Thematic Mapper images from eastern Colorado reveals stabilized dune fields that are composed of single and compound parabolic dunes, some longer than 10 km. These dunes have been reactivated at least four times in the past 10000 yr, at ca. 9500 to 5500 yr B.P., 5500 to >4800 yr B.P., 4800 to >1000 yr B.P., and <1000 yr B.P., during droughts that probably exceeded the dry conditions during the 1930s. Dune orientations indicate that these landforms were molded by winds from the northwest, which now dominate during the winter and spring with the passage of Pacific air masses. This study underscores the sensitivity of the landscape of the High Plains to drought conditions, which may become more prevalent because of the anticipated effects of greenhouse warming.

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