Frost in Action
January 20, 2007
The slow but sure work of freezing water is evident on the above photo showing a sidewalk crack. It was taken in front of the building where the Northeast Section of the Geological Society of America met in Saratoga, New York (March, 2005). Meltwater from a light snowfall that had fallen a few days earlier seeped into this fissure and froze solid overnight. Since water expands in all directions as it freezes, it exerts tremendous pressure on the walls of the crack, widening it a little more during each freeze/thaw cycle. I've not been back to Saratoga since then, but it's a good bet that the crack is wider today than it was in 2005. Roadway "pothole season" in New York begins in late winter when daytime temperatures are warm enough to melt snow, and nighttime temperatures are still cold enough to freeze any meltwater that finds its way beneath the pavement.