During the period after glaciation the climate was slightly warmer and drier than today. Much of the sand for the Sand Hills probably blew out of river valleys and intermontane basins of Wyoming. 8.2 Sandhills blowout south of highway. The bare sandy area near the top of this hill is called a blowout . The name describes well how the feature forms.
Wind literally picks up and blows the sand away by a process called deflation .
Although the Sand Hills are mostly stabilized by grass and other vegetation, occasionally grazing or other activity disturbs the vegetative cover, exposing bare sand and making the dunes vulnerable to deflation and the formation of blowouts. 10.2 Sand and railroad crossing. Here is evidence of fairly recent movement of sand. 0.0 Junction of highways 385 and 2 at west end of Alliance. Turn south on Highway 385.