A Demonstration of Earth-based Heating

I took these two photos a few days apart:

IMG 1467

The interesting point is the ridge of snow in the left photo that lies directly over the crack in the asphalt in the right photo. Why would a crack in the asphalt have a ridge of snow over it? The answer lies in the process by which the snow melted. 

The diagram on the left shows what the snow on the road looked like immediately after the snowfall. The earth remains at a temperature of around 52ºF a few feet below the surface; the surface is warmed by that heat, and the temperature under the blanket of snow rises above freezing. This causes the snow to melt from below, and the snow sinks down. However, the snow in the crack melts and leaves an air gap that acts as an insulator. Therefore, the snow directly over that air gap does not melt as quickly as the other snow, leaving a ridge of snow along the line of the crack. 

Pretty cute, huh?