Unusual ice disc spotted in Stillwater River

February 14, 2019

While some may not care for the latest blast of winter weather in the Flathead, it did result in a natural oddity that several passersby discovered in Kalispell this week.

Olney resident Ed Clark was the first to alert the Daily Inter Lake of the ice disc. He was driving on Whitefish Stage Road where it crosses over the Stillwater River in Kalispell on Monday when he noticed an ice disc in an eddy of the river as it winds east, not far from the new Glacier Rail Park.

In an email, Clark said he didn’t have a camera with him and he returned Tuesday with a friend to document the disc.

“It was much nicer yesterday (Monday) with the little bit of sun we had in Kalispell. But not too bad today,” Clark wrote.

Clark said he plans to keep an eye on the disc and take some time-lapse video of it when it warms up and it begins to rotate.

Clark described it as about 25 feet in diameter.

A Flathead Valley man named Larry Youmans wrote a guest post about ice discs for the Montana Natural History Center nearly three years ago. It described an ice-disc sighting on the North Fork of the Flathead River near the Glacier Rim boat landing.

Youmans wrote that ice discs are uncommon and sightings have occurred globally in colder climates.

Ice discs, ice circles, ice pans, or ice crepes are a natural phenomenon that occur in slow-moving water in cold climates, according to Wikipedia.

Ice discs form on the outer bends in a river where the accelerating water creates a force called “rotational shear,” which breaks off a chunk of ice and twists it around. As the disc rotates, it grinds against surrounding ice, smoothing into a circle. They have been most frequently been seen in Scandinavia and North America.

One circle that appeared in January 2019 on the Presumpscot River in Westbrook, Maine, in January this year was about 298 feet in diameter.

Montana Fish, Wildlife & Parks Region 4 shared some photographs Jan. 14 on its Facebook page of ice circles on Belt Creek at Sluice Boxes State Park, just southeast of Great Falls.

Ten years ago, some TV news outlets shared a video of an ice disc spinning in the Musselshell River in central Montana.A relatively uncommon phenomenon, one of the earliest recordings was of a slowly revolving disc spotted on the Mianus River near Greenwich, Connecticut. It was reported in an 1895 edition of Scientific American.