Things are looking blue this week in Michigan.
On Sunday, people near The Mackinac Bridge – which straddles Lake Michigan to the West and Lake Huron to the East – noticed huge blue hunks of frozen lake water coming ashore.
It’s a rare sight to see this kind of brightly colored ice in the state. Blue ice is usually seen in permanently chilly spots like Antarctica and the North Pole, as well as on other slippery glaciers around the world.
As a result, some photographers were downright giddy to share their photos with Business Insider.
Take a look.
It’s been a cold winter in Michigan, with sub-freezing temperatures and lots of snow. On Monday, the view from Mackinaw City, up at the top of Michigan’s lower peninsula, was quite a sight.
Blue-hued ice came towards the shores in jagged piles, inundating a local park where people trotted out to see the oddly colorful ice.
“The ice looks even better than photos can do justice,” Photographer Jeff Caverly told Business Insider in an email.
Blue ice isn’t any colder than normal ice. But it does have less air inside.
This ice is really dense.
Ice is typically white because of the tiny air bubbles that form inside the water as its freezing. You might be familiar with this if you’ve ever watched someone pour a beer into a glass.
“The white color of bubbles at the top of a dark beer work the same way,” Photographer Benjamin Drummond explains on his “Blue Ice” website. When ice is white, it’s because “small pockets of air reflect and scatter visible light,” he says.
Ice only turns blue when it’s so tightly packed that those air bubbles inside aren’t big enough to reflect and scatter light anymore. The bubbles are so crammed together, they don’t have as much room to let the light shine through.
As the scientists at the Alaska Satellite Facility (who see a lot of glacial blue ice) point out, the air bubbles are so consolidated in blue ice that if you put a hunk of blue ice into a glass of water, the pressurized chunk might blow up your glass.
At the north and south poles, where glacier ice slowly slides down towards the oceans, air often gets squeezed out of the ice, making it really dense like this.
Most blue ice shows up at the poles, but this year some compact glacier-style ice is showing up in the waters of The Great Lakes, which are the largest freshwater source on the Earth.
“Only the polar ice caps contain more water,” the Environmental Protection Agency (EPA) says.
This isn’t the first time that people in Michigan have seen blue ice, but it is pretty rare to get so much.
Blue ice does “show up from time to time,” in Michigan, photographer Tori Burley told Business Insider in an email. “But the last time I saw them this big and gorgeous was in 2011.”