Legend has it that some of Minnesota's 10,000 lakes formed in the footprints of Paul Bunyan's blue ox, Babe. Actually, there are over 15,000 lakes in the state, and many of them formed during the last Ice Age--when glaciers moved back and forth across most of Minnesota. In places, particularly those near ice margins where a lot of sediment was being deposited, large fragments of ice could become buried under layers of dirt. The buried ice would eventually melt and the dirt collapse leaving holes, called kettles, in the ground. The kettles filled with water to become lakes. Areas of Minnesota where a lot of lakes occur may mark the edge of an ice sheet.