Ice Boulders Form Under Lake Michigan's Rolling Waves

Boulders of ice formed and shaped into spheres by the rolling waves of Lake Michigan were washing up along the shore of Indiana Dunes State Park near Chesterton, Indiana, on the morning of January 31.

Park officials shared this footage of the boulders, which they said was taken at 8:30 am local time (CST).

“Similar to building a snowman, Lake Michigan’s waves did all this work this weekend to make these boulders from ice sheets and the slushy snow we had,” park officials wrote on Facebook. “As the waves break off pieces of the ice sheets along the shore, the chunks fall off into the water. The waves then roll these ice chunks over and over again, smoothing and shaping them into spheres.”

Officials noted that the “beautiful ice phenomenon might not last long,” as the “temperature and the size of the waves determine whether ice balls can grow, and the results can range from pingpong ball-sized to these large boulders.” Credit: Indiana Dunes State Park via Storyful