Predominantly circular pieces of ice from 30cm–3m in diameter, and up to 10cm in thickness (unrafted), with raised rims due to the pieces striking against one another. It may be formed on a slight swell from grease ice, shuga or slush or as the result of the breaking of ice rind, nilas or, under severe conditions of swell or waves, of grey ice.
A common process of sea ice development in the Antarctic is "the pancake cycle". The pancakes start with a diameter of tens of centimetres, but through wind and wave action they aggregate with loose frazil crystals to increase in diameter, and raft with other pancakes to increase in thickness. In this manner the pancakes can rapidly grow to a few metres in diameter and up to 1 m thick. Eventually the pancakes can freeze together into larger floes or a consolidated ice cover.