Kettle lakes are a landscape feature characteristic of glacial terrain. When glaciers that covered the Northern Great Plains melted, the rock materials that were incorporated in and on top of the glaciers remained on the land surface. These materials commonly enclosed blocks of glacial ice that took many years to melt because they were insulated from solar radiation by the surrounding rock materials. When the buried ice blocks finally melted, they left a depression in the landscape. If the area was wet enough to have a high water table, the depressions filled with water to form kettle lakes. These lakes commonly are isolated from one another with respect to surface drainage. They accumulate water from precipitation, overland runoff, and groundwater, and they lose water to evaporation and seepage to groundwater.
The region of the Great Plains most recently covered by continental glaciers lies within the southern parts of Alberta, Saskatchewan, and Manitoba in Canada, and north and east of the Missouri River in Montana, North Dakota, and South Dakota in the United States. Kettle lakes, commonly called prairie sloughs in Canada and prairie potholes in the United States, are a defining landscape feature in this region because of their abundance. The great majority of kettle lakes are very shallow (less than ten feet deep), but a few are nearly as deep as the thickness of the glacial deposits that surround them (as much as 100 feet deep).
See also PHYSICAL ENVIRONMENT: Glaciation.
Thomas C. Winter U.S. Geological Survey, Denver