Formation of Landscape
About a million years ago, during what was known as the Great Ice Age, four great glaciers advanced and retreated across what is today the state of Minnesota, shaping the land into what it is today. These glaciers were created during a time in which the snow did not melt, gradually accumulating into thousands of feet. The snow at the bottom became compacted into ice under the weight of further snow, and was spread out in all directions by the snow.
Lakes were formed as these advancing glaciers scraped rock and soil off the Earth’s surface. As they advanced, these glaciers carried along with them everything from dust to boulders, and scouring and striating the rocks that they passed. The boulders being carried by the ice gouged large grooves into the bedrock, creating lake basins. As part of the Mississippi River basin, Mille Lacs natural drainage direction is to the south and west, but the water is blocked there by a glacial deposit known as a moraine, which rises as high as 130 feet at one location. The water is blocked by and ponded behind this moraine, which acts as a dam.
Lake Mille Lacs is the second largest inland lake in the state of Minnesota, spreading over an area of 132,516 acres, or 207 square miles. The maximum depth of the lake is 43 feet, and the average depth is 21 feet. Twenty percent of the Lake’s surface lies over a water depth of 15 feet or less.
