Why Are Ice Volcanoes Erupting on the Shores of Lake Michigan?

They’re not really volcanoes. But they do spew freezing cold water, and that’s very cool

On Sunday, a National Weather Service employee snapped a photo of two ice volcanoes erupting on the shores of Lake Michigan. National Weather Service, Twitter

Something very cool is happening on the shores of Lake Michigan. After spitting thousands of variably-sized ice balls into Holland State Park in Michigan state last Friday, its wintry waters have served up a second scoop of frigid fun: ice volcanoes, spewing slushy water out of cone-shaped mounds of ice.

Captured in photographic form by National Weather Service meteorologist Ernie Ostuno at Michigan’s Oval Beach on Sunday, the ice volcanoes aren’t really volcanoes, per se, and have occasionally appeared around the Great Lakes before.

While true volcanoes belch up magma from Earth’s upper mantle, ice volcanoes are a temporary product of partially-frozen lakes. When local temperatures drop, large lakes sometimes end up rimmed by a thin halo of ice, blocking water en route to land. As large, strong waves, buoyed by powerful winds, continue to course toward shore, they build up pressure beneath the ice, and can eventually burst through cracks at the surface. If spray that emerges then freezes and settles back down to the surface, it may accumulate in a hump with a hole, jetting plumes of water out its top each time a new wave rolls in.

In other words, a lot of climatic factors must conspire for this chilly blowhole-like structure to arise. “It’s almost a Goldilocks situation where you need just the right conditions over a period of time,” explains meteorologist Matt Benz to Adriana Navarro at AccuWeather.

Similarly strict requirements seem to govern the formation of last Friday’s ice balls—lumps of frozen slush that get sculpted into spheres by the lake’s roiling waves before tumbling ashore, reports Frank Witsil for the Detroit Free Press. The orbs only appear when frigid temperatures hit shallow beaches.

Sadly, these strict requirements also mean most types of icy architecture aren’t long for this world, as Cort Spholten, a meteorologist with the National Weather Service of Grand Rapids, tells Bisma Parvez at the Detroit Free Press. But they’ve been glimpsed before on the shores of Lake Erie—another Great Lake that’s seen some wild weather-related phenomena, including ice tsunamis, in years past.

With their miles-long shorelines and frequent, hefty waves, the freshwater Great Lakes seem to be pretty good at providing all the necessary ingredients for these chilly events. And should a similar cocktail of conditions appear again, both ice balls and ice volcanoes may be back for yet another encore act.

Cheekily dubbed “cold as balls” by Holland State Park representatives on Facebook, the icy spheres are mostly harmless, as long as beachgoers remain mindful of debris. But should you be lucky to come across an ice volcano, experts recommend the frigid mounts be enjoyed only from afar. As with true volcanoes, the consequences of attempting to summit an ice volcano can be dire.

As Tom Niziol, a contributor for Weather Underground's Category 6 blog, explains in a Facebook post, the structures “are hollow and built over that hole in the ice. Don't ever go venturing out onto them!!”

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