"I have seen this for years, and many times thought that I would try to get it on film," Trond Stordal, a local from nearby Otta told Norway's NRK broadcaster. "I spent some time one morning and got myself some good pictures."
Adi Bertoli, who lives close to the site, says that the phenomenon is known locally as "kværna" is and usually arises in November before the ice is properly frozen.
"I've never actually seen it before in January. But there has been open water for a lot of this winter, so that's maybe the reason," she said.
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Ånund Sigurd Kvambekk, an engineer with the Norwegian Water Resources and Energy Directorate, said that the phenomenon sometimes happened in the backwaters of rivers, where there's a calm flow of water and it normally triggered by a sudden change of temperature.