Wisconsin isn't known for volcanoes, but they're nevertheless appearing along the shores of the Great Lakes.

Every year, a combination of heavy waves and ice creates “ice volcanoes.” When strong waves splash up between ice shoves, or cracks in the ice near shore, the resulting spouts create volcano-lake cones.

Even longtime residents of Wisconsin haven't heard of ice volcanoes. But according to Carolyn Rock, a naturalist at Whitefish Dunes State Park in Door County, once they witness them they're often captivated.

“Those that've been here and have seen them come back and are looking for them,” said Rock.

She added: “It's not like the ice caves on the Apostle Islands — it’s not that way yet.”

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The volcanoes or, “blowholes,” are early this year because of the November cold snap. Rock said they’re an ephemeral phenomenon.

“They can appear in a day and they can disappear in a day,” said Rock.

Rock invites people to look at the volcanoes from a distance. She cautions them not to get too close because of the risk of falling through the ice.

For a glimpse of an ice volcano, watch this video of a Green Bay one, courtesy of the state Department of Natural Resources: