Lake Circle was a

glacial lake A glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land and then melts, filling the depression created by the glacier. Formation Near the end of the last glacial period, roughly 10, ...

that formed during the late

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

epoch along the Redwater River in eastern Montana. After the

Laurentide Ice Sheet The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glacial epochs, from 2.58 million year ...

retreated, glacial ice melt accumulated in the basin surrounded by the ridges of the preglacial valley and the retreating glacier. Southwest of Nickwall are the remnants of a broad abandoned valley with long side slopes. The valley runs north from Redwater Creek to the Missouri River. The bottom is poorly drained and about in width. It lies above the sea level and above the Missouri River bottomland. The upland slopes are extensive, clear and flat. The valleys surrounding it are dissected with V-shaped coulees. The difference between the Redwater valley and those around it reflect stream erosion vs. lake sedimentation. The drift in the valleys, appears to be as left by the glacier in the previously created valleys. Using the dating of lake deposits near

Great Falls, Montana Great Falls is the third most populous city in the U.S. state of Montana and the county seat of Cascade County. The population was 60,442 according to the 2020 census. The city covers an area of and is the principal city of the Great Falls, M ...

, the Havre lobe of the Laurentide Ice Sheet dammed the ancestral Missouri River during the late Wisconsin Glacial Period.Geologic Framework and Glaciation of the Central Area, 1-1-2006; Christopher L. Hill; Boise State University, Boise, Idaho; 2006

Glacial Event

A lobe of the late Wisconsin Laurentide Ice Sheet advanced from central

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

, southeastward into

Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...

and southwestern

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North ...

. It left the Cypress Hills and Boundary Plateau undisturbed. As the glacier crossed the present day Milk River valley in southern Alberta, it was split into two lobes by the

Sweetgrass Hills The Sweet Grass Hills (Blackfoot: ''kátoyissiksi'', Cheyenne: ''vé'ho'ôhtsévóse'', Salish: ''ččaɫalqn '', "three peaks") are a small group of low mountains rising more than 3,000 feet above the surrounding plains southwest of Whitlash, Mo ...

, which became an island in the glacier. The western lobe or Shelby lobe, moved southward to the Missouri River, near Great Falls, Montana. The Havre lobe, east of the Sweetgrass Hills, moved in two directions. The Lorna sublobe, advanced over the Missouri River to north of the

Highwood Mountains The Highwood Mountains are an island range (sub-range of the Rockies entirely surrounded by prairie) which cover approximately 4,659 km² (1,799 sq mi) of the Central Montana Alkalic Province in north central Montana in the U.S. They are in ...

. The Malta sublobe expanded southeastward along the present-day Milk River, between the Boundary Plateau and the

Little Rocky Mountains The Little Rocky Mountains, also known as the Little Rockies, are a group of buttes, roughly 765 km2 in area, located towards the southern end of the Fort Belknap Indian Reservation in Blaine County and Phillips County in north-central M ...

in the region of the

Musselshell River The Musselshell River is a tributary of the Missouri River, long from its origins at the confluence of its North and South Forks near Martinsdale, Montana to its mouth on the Missouri River. It is located east of the Continental divide entirel ...

References

Bibliography

*Alden, W. C., 1958, Physiography And Glacial Geology Of Eastern Montana And Adjacent Areas, U. S. Geological Survey Professional Paper 174. *Colton, R. B., Lemke, R. W., and Lindvall, R. M., 1961, Glacial map of Montana East of the Rocky Mountains, U. S. Geological Survey Miscellaneous Geological Investigations Map I-327. *Howard, A. D., 1958, Drainage Evolution In Northeastern Montana and Northwestern North Dakota, Bulletin of the Geological Society of America, v69, 575-588. *Lemke, R. W., Laird, W. M., Tipton, M. J., and Lindvall, R. M., 1965, Quaternary Geology Of Northern Great Plains, in Wright, H. E., Jr., and Frey, D. G., Eds, The Quaternary of the United States, Princeton University Press, Princeton, NJ. *Lindvall, R. M., 1962, Geology Of The Eagle Buttes Quadrangle, Chouteau County, Montana, U. S. Geological Survey Miscellaneous Geological Investigations Map I-349. *Thornbury, W. D., 1965, Regional Geomorphology Of The United States, John Wiley & Sons, Inc., New York. *Trimble, D. E., 1980, The Geologic Story Of The Great Plains, Geological Survey Bulletin 1493. *Wayne, W. J., Aber, J. S., Agard, S. S., Bergantino, R. N., Bluemle, J. P., Coates, D. A., Cooley, M. E., Madole, R. F., Martin, J. E., Mears, B., Jr., Morrison, R. B., and Sutherland, W. M., 1991, Quaternary Geology Of The Northern Great Plains, in The Geology of North America, Vol K-2, Quaternary Nonglacial Geology: Conterminous U. S., The Geological Society of America.

Bibliography

Circle A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is const ...

Geology of North Dakota

Natural history of North Dakota

Glacial Event

See also

References

Bibliography

Bibliography