Sun cups are hollows or depressions in the snow made as the snow is melting on clear, sunny days. The snow is not melting at a precise, uniform rate--the areas that melt faster become the hollowed area of the cups, while the snow still frozen is the cup itself. There are a multitude of factors that can affect snowmelt and lead to the creation of sun cups. These include: slope; "shade, wind exposure, air and water drainage, ... the presence or absence of vegetation, the juxtaposition of snow, soil, and vegetation surfaces, the albedo of snow, and the specific heat capacity and thermal conductivity of soils." These variables affect the rate of snowmelt even between very small, neighboring patches of snow, which leads to the formation of geological features like sun cups.