Heavy rains followed by a sudden freeze can produce icy puddles like this one. Because the pool was shallow to begin with, it likely froze rapidly. As the temperature continued dropping, the newly-formed ice contracted; the ring pattern of the cracks tells us the stress in the ice was primarily radial. Once formed, the cracks provided a path for any unfrozen water still in the puddle to get squeezed up onto the surface through capillary action and any further expansion or contraction of the ice. (Image credit: D. Stith; via EPOD; submitted by Kam-Yung Soh)
Rings of Ice
