I was amazed at the familiarity many Naturally Curious readers have with “ice pancakes!” For those of you who, like myself, may not be familiar with these creations, these formations are essentially frozen foam.
Ice pancakes usually form on ocean water or lakes around the Arctic Circle where the movement of water keeps the ice from forming a flat sheet. Small needle-like crystals called frazil crystals rise to the surface of very cold water and accumulate together. In calm water these typically form a greasy film that freezes into a flat surface ice. However, in rough or choppy water, these crystals congeal together into slushy circular disks. As these disks bump into each other and are buffed by the water, they develop ridges and raised edges, giving them a distinctive dinner plate appearance. In the polar seas these can sometime have a thickness of close to 4 inches and diameter of between 12 inches and 9 feet. Eventually the plates fuse together to form consolidated sea ice that can have ridges that are up to 60 feet thick. In northern freshwater rivers, pancakes can accumulate downstream of faster water that is thought to have created foam, that then froze. (Thanks to Jim Moul for the use of his photograph of New Hampshire ice pancakes.)