Here's what causes giant spinning ice discs like the one in Maine

People are flocking to the tiny town of Westbrook, Maine, to see a huge spinning circle of ice.

The ice is estimated to be about 100 yards across and is slowly spinning on the Presumpscot River.

But while residents and visitors alike are amazed by the sight, ice discs do occur, albeit rarely.

These huge, spinning disc usually form in a slow-moving, rotating part of the river, like an eddy.

As this moving water freezes faster than the water around it, it can cluster, creating a circle or pan-shaped ice formation.

So how does it spin? We know that ice breaks apart and melts. When this happens, the cold water that comes from the melting ice disc sinks down underneath it.

This colder water below the disc generates a “vertical vortex” that actually causes the disc to spin at a constant rate.