It is normally assumed that the V-shaped cracks forming in a desiccated surface open upward. Such cracks are sometimes filled, preserved, and used to indicate the tops of beds in a sedimentary sequence. In a generally muddy area near Minneapolis, Minnesota, a water puddle had frozen over. The ice had been broken by a passing truck and sediment had been washed into the cracks between the polygonal fragments. When the ice melted the crack fillings slumped into inverted V-shaped ridges, the points upward.