Mark Battle, an associate professor of physics at Bowdoin College in Brunswick, told the Press Herald the disk's movement could be attributed to the river current, the thickness of the ice, and to the friction caused by the ice grinding against the shoreline.
As if a seemingly-alien ice disc wasn't enough reason for locals to be a bit anxious about their place in the universe, the Portland Press Herald notes that a "giant snake eating a beaver", dubbed locally as "Wessie", was spotted nearby in 2016. "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".
Its appearance has been likened to a moon, an alien creation, a crop circle and a giant Lazy Susan; regardless, a sprawling disk of ice spinning in the Presumpscot River in Westbrook, Maine, has people talking. "It was a big duck-go-round".
Drone footage taken by Tina Radel, the marketing and communications manager for the city, shows an nearly 100-metre circle spinning in a counter-clockwise direction.
Locals say they've seen smaller ice disks before, but nothing like this one, Radel said.
A strange-looking disk of ice is creating a stir in a ME city.
A resident uploaded videos of the ice circle to the internet and tourists came to the river to watch.
Westbrook is a city of 17,500 just to the west of Portland.