Due to a warm climate and evapotranspiration rates surpassing precipitation rates, the southern Interior Plains are highly susceptible to droughts and soil erosion. A significant feature of aeolian erosion in the Interior Plains is the ubiquitous loess deposits. The deposits were placed by winds during the Pleistocene epoch. The Nebraska Sand Dunes are an example of the sand and loess during the epoch. These dunes were formed during the Pleistocene by Northwesterly winds depositing alluvial silt and sand. That loess is so prevalent in the Interior Plains is evidence of significant aeolian erosion, as deposits are generally accumulations of wind-blown dust.