J. Ryan Macy took this photo of rare blue ice in the waters off Michigan's Mackinac Island.
CNN  — 

Folks in northern Michigan are getting to enjoy a phenomenon normally only seen in glaciers: blue ice, piled up in the Straits of Mackinac.

Photographer Kim Mettler has lived in the area for about two years and had never seen blue ice there before. She drove about an hour on Tuesday to take pictures near the Mackinac Bridge.

“We had a warm-up here in Northern Michigan, which is why I went out that day,” she said. “It was about 40 degrees with partly cloudy skies.”

She saw a lot of people clamber dangerously far into the frozen straits, which separate Lake Michigan and Lake Huron, to explore.