Photo: Massive Ice Balls Along Lake Michigan

Lake Michigan ice balls — Enormous ice balls line the shores of Lake Michigan in this Feb. 21 photo by Cedar, Mich., resident Leda Olmsted.

(Image credit: Leda Olmsted)

Floating boulders of ice the size of basketballs lined the shores of Lake Michigan last month, and were captured in a photo.

Weighing in at up to 50 pounds (22 kilograms) each, the ice spheres are a winter weather phenomenon resulting from wind and wave action along the shore, according to reporting by NASA's Earth Science Picture of the Day. Small fragments of floating ice act like seeds, with layers upon layers of supercooled lake water freezing around them as the balls churn in the waves. Wind then pushes the ice concretions onshore.

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Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.