How do ice boulders form in lakes?

While it may look like a field of crystal rocks, there's more to those perfectly round boulders than meets the eye. Those are ice balls, or ice boulders, found every winter at places like Lake Michigan.

One recent visitor to the area posted a video of the phenomenon online. It went viral as internet users were entranced by the picturesque wonderland.
The way the boulders form is simpler than one might think. As pieces of ice sheets break off around the lake, the waves make them perfectly round as they roll within the undulating water.

"The water has to get cold enough not to melt the ice chunks, while of course not freezing solid itself," said AccuWeather Meteorologist Faith Eherts.

Ice balls are generally found in the Great Lakes and Antarctica, where there are rolling waves and low temperatures. However, reports of these ice boulders have occurred along coasts in California and Russia as well.

"Some examples are along ocean shores, where the salt water rarely freezes," said Eherts. "It can also occur in large, deep bodies of fresh water, where it takes extended periods of frigid weather for the water to freeze."

For now, the ice balls are immortalized on the internet, until they return for next winter.

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