Physics Photo of the Week - Feb. 27, 2004

Warren Wilson College

Ice Spike

Ann Otterness and her brother Phil sent us this unusual photograph of an ice spike that formed in her ice-cube tray.  I am somewhat at a loss to explain it fully.  Usually ice cubes bulge gently in the middle due to the expansion of ice when freezing, but the expansion showing this dramatic ice spike is highly unusual.  My guess is that the ice skimmed-over by rapid freezing, that the water under the skin was supercooled - below freezing, but still liquid.  Somehow a pinhole formed on the top skin (due to internal pressure, or due to a disturbance) and the supercooled water rapidly rose through the pinhole and froze upon leaving the chamber of the ice cube.  Why this process would form a narrow spike (presumably hollow) and not a broad hump is a mystery.  Donald F. Colllins