Lake Mille Lacs EarthCache

Almost all the lakes in Minnesota were formed by glacial action. Many small lakes formed after the glaciers receded and blocks of ice buried in the sediment melted, leaving holes called kettles, that filled with water. Other lakes occupy basins that were scraped out of solid rock by glacial ice. Lake Superior is a prominent example of a lake bottom scoured by glacial ice. Lake Mille Lacs, by contrast, is not a kettle lake or a basin lake. It is considered a Moraine Lake. It was formed as a result of two separate glacial lobes.

End moraines, or terminal moraines, are ridges of unconsolidated debris deposited at the snout or end of the glacier. They usually reflect the shape of the glacier's terminus. Glaciers act much like a conveyor belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape is determined by whether the glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place the more debris will accumulate in the moraine. There are two types of end moraines; terminal and recessional. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats the end moraine may be destroyed by post-glacial erosion.