Pond Stars
April 09, 2018
Photographer: John A. Adam
Summary Author: John A. Adam
During a sustained sub-zero spell in mid-January this year I noticed some remarkable star-like patterns on a small pond next to my building at Old Dominion University. There were about a dozen scattered across the snow-covered frozen surface, the largest being several meters across (from a radial finger-tip to the opposite finger-tip). While convection may be a mechanism in some instances, it's perhaps more likely that a crack in the ice layer or a protruding stick was the means by which the slightly warmer water from below the ice flowed through and melted the layer of snow, producing a striking dark, almost fractal-like star pattern. Interestingly, in 1847, H. D. Thoreau observed: "spider web or rosette figures in the ice" on his beloved winter Walden Pond.
Photo Details: Top - Camera: Motorola Moto G (5) Plus; Exposure Time: 0.0007s (1/1344); Aperture: ƒ/1.7; ISO equivalent: 64; Bottom - same except: Exposure Time: 0.0013s (1/797).