"It looks like a picture from space", wrote Tiffany Nelson on the city's Facebook page.
Ice disks occur at bends in rivers where faster water creates a force that chips away edges as the ice spins.
Rob Mitchell, who owns a nearby office building, spotted the alien-looking disk on Monday morning and immediately notified the city of Westbrook, just outside Portland. "However, as it slowly froze into a solid plate, and since pieces of ice are probably being added from upstream, it slowly grew into a perfectly circular disk". "I think it will continue to gain in thickness as long as it keeps spinning", said Mitchell, adding that the massive saucer acted as a giant Lazy Susan for ducks that made a decision to investigate it.
The City of Westbrook, Maine, is inviting fans of unusual natural phenomena to come check out a massive ice disc rotating in the Presumpscot River - and perhaps you could patronize some local restaurants while you're at it.
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More than 13,000 people have seen the clip since it was posted to the Australian Open's YouTube channel today. Defending champions Caroline Wozniacki and Roger Federer were scheduled to play night matches later Monday.
Westbrook City's marketing and communications director Tina Radel captured the drone footage of the disk and posted it online. "It was a big duck-go-round".
According to published reports, the largest ice disk recorded was a 160-foot diameter circle in Sweden's Pite River in 1987.
Paul Nakroshis, an associate professor of physics at the University of Southern Maine, tells Maine Public Radio that the formation of the ice disks is not totally understood.
The city, located about seven miles west of Portland with a population of fewer than 20,000, is basking in the sudden media glare.