Extreme cold caused stacks of ice to form on Lake Superior around Duluth Harbor in Minnesota on Feb. 2. (Radiant Spirit Gallery)

This video of ice stacking on the shore of Lake Superior is both beautiful and mesmerizing. Conditions have to be just right for thin shards of ice pile up like glass. The winds need to be just strong enough to push the ice, but not strong enough to break it — and, of course, the ice needs to be thin and fragile but also in an unbroken sheet.

“The new ice was covered with frost flowers that sparkled in the morning sun,” the husband-wife filming duo wrote on YouTube. “The frost likely gave the wind more surface area to help move the ice.”

Temperatures have dropped below zero in Duluth, where this video was shot, on seven of the nine nights so far this February. Calm nighttime winds allowed the thin ice to develop on the largest of the Great Lakes.

“It is worth wearing our winter layers in frigid, subzero temps to see what Lake Superior offers each day,” the photographers said.