The cakes can be rounded, oblong or irregularly shaped aggregations, ranging from several inches to several feet in diameter but typically less than about four inches (10 cm) in thickness. They’re formed from accumulations of frazil ice in relatively fast flowing water. Note the slightly upturned edges, which are the result of repeated impacts with other cakes. The raised rims on small ice chunks amid otherwise unconsolidated icings is often a clue that the formation of pancake ice is underway. Click here to see a time-lapse animation of pancake ice formation. Photo taken near Leland, Michigan on March 25, 2011.