Why Are Massive Ice Boulders Forming Along Lake Michigan?

Was Mother Nature preparing for a monster snowball fight? Hundreds of massive balls, or boulders, of ice have appeared along Lake Michigan's coastline near Sleeping Bear National Lakeshore. The unusual natural winter phenomenon has attracted the attention of people here and across the nation after photos taken by a local resident went viral across the Internet.

Experts believe that though it's a rare occurrence, there is a simple explanation for the giant ice boulders. Enormous sheets of ice form over Lake Michigan in winter. Chunks of the ice break off, growing layer by layer. As the growing chunks are tossed by waves they eventually form smooth, rounded balls which then wash up along the shores.