Huge ice disc makes rare appearance on South Thompson River 

A strange, swirling circle of ice that appeared at a bend in the South Thompson River has attracted plenty of attention in the Kamloops, B.C., area. 

The 40-metre ice disc is an example of an uncommon and fascinating natural phenomenon, said Laval University chemistry professor Normand Voyer.  

 “The one you’re seeing right now in Kamloops is really cool but it’s not unique,” Voyer told Daybreak Kamloops host Shelley Joyce. “It has been observed last year in Gaspé, and two years ago there [was] one observed in Maine, which was twice as big as this one, almost 100 metres in diameter.”

“These ice discs have mesmerized people for years and there have been a lot of claims, especially about alien stuff,” he said. They’ve also been compared to crop circles. 

“But scientists have been studying the phenomena for years and you know what? They came up with a very simple explanation.”

‘Magnificent chemical’ explains oddity

The simple explanation involves “a magnificent chemical called H2O: water,” Voyer said.

Water is one of the few chemicals with a lower density in its crystallized form, he said. Meanwhile warm water is less dense than cold water, so it rises to the surface.

A giant spinning disc of ice formed in the Presumpscot River in Westbrook, Maine, around this time last year. (Tina Radel/City of Westbrook)

Nature’s recipe for a rotating ice disc is “a little open water, a little water current and an ice patch,” Voyer said.

When the temperature warms a bit, water molecules begin to warm up and migrate to the top. If the water surface is covered with an ice patch, those warm water molecules begin to move laterally with the current, creating a vortex like water down a bathtub drain.

Perfect conditions needed

“So the warm water vortex will push up the ice cover,” Voyer said. “Eventually the ice cover will crack along the edge of the vortex. And the reason for that is because the forces are stronger along the edge and the water is warmer.”

The result is a very rough ice disc, which then grinds itself into a perfect circle as it rotates, he said.

Ice discs rarely form, because conditions must be perfect: warming temperatures, not too much current and not too much wind. 

A strange, swirling 40-metre wide circle of ice that appeared at a bend in the South Thompson River in mid January has attracted the attention of area residents, and explanation from a Laval University chemistry professor 0:23

The phenomenon is often fleeting, lasting a couple of days or a couple of weeks before wind or strong current causes the fragile disc to break apart.

“Also, there is the possibility that during the night there’s aliens that will come and throw rocks at it or something like that,” Voyer joked. 

With files from Daybreak Kamloops