Giant ice boulders are appearing all over Lake Michigan.

The boulders, which weigh up to 75 pounds, began appearing on the lake about one week ago. It's something that's happened before, but it doesn't happen often.

"It's not that it never happens and this is a once in a decade thing," Deputy Superintendent from the Sleeping Bear Dunes National Lakeshore Tom Ulrich said. "It happens more often than that, but these are very large and got bigger than they normally get."

Word of the boulders began to spread after Michigan resident Leda Olmstead posted pictures of them on Facebook. After the posting, the images went viral. Olmstead was walking her dogs when she noticed the boulders. She said that hundreds of the objects on went for about 100 feet near the lake.

"I thought it was the coolest thing ever especially since I've never seen anything like it," Olmstead said. "I have a small English bulldog, and they were as tall as her. They were pretty massive."

Though certainly an odd presence, there is an explanation for the ice boulders' formation. According to Sleeping Bear National Lakeshore's chief of interpretation and visitor services Lisa Myers, the ice balls form much the way that smooth stones do, starting in chunks that break off from the lake's larger sheets of ice. Waves then smooth the ice and wash them ashore.

"The Great Lakes create their own weather," Myers says. Other interesting ice attractions at the lake include large icicles and ice caves.

While the presence of the giant ice balls is certainly unusual, it may serve to boost the appeal of the Great Lakes area, especially now that the image of the objects is so popular.

"People think it's so boring and gross up here in the winter," Olmstead says. "But I think it's beautiful."