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 10,0 ...

that formed during the late

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

epoch along the Redwater River in eastern Montana. After the Laurentide Ice Sheet 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 Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...

. The bottom is poorly drained and about in width. It lies above the sea level and above the

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 List of cities and towns in Montana, third most populous city in the U.S. state of Montana and the county seat of Cascade County, Montana, Cascade County. The population was 60,442 according to the 2020 United States census, 2 ...

, 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 a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

, southeastward into

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and southwestern

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

. 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, 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 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 Mo ...

in the region of the Musselshell River.

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 point (geometry), points in a plane (mathematics), plane that are at a given distance from a given point, the Centre (geometry), centre. The distance between any point of the circle and the centre is cal ...

Geology of Montana

Natural history of Montana

Glacial Event

See also

References

Bibliography

Bibliography