Lake Great Falls
Lake Great Falls was a prehistoric proglacial lake which existed in what is now central Montana in the United States between 15,000 BCE and 11,000 BCE. Centered on the modern city of Great Falls, Montana, Glacial Lake Great Falls extended as far north as Cut Bank, Montana, and as far south as Holter Lake. At present-day Great Falls, the Glacial Lake Great Falls reached a depth of 600 feet (183 metres).
Approximately 1.5 million years ago, the Missouri River, the Yellowstone River and Musselshell River all flowed northward into a terminal lake. During the last glacial period, the Laurentide and Cordilleran ice sheets pushed these lakes and rivers southward. Between 15,000 BCE and 11,000 BCE, the Laurentide ice sheet blocked the Missouri River and created Glacial Lake Great Falls.
About 13,000 BCE, as the glacier retreated, Glacial Lake Great Falls emptied catastrophically in a glacial lake outburst flood. The meltwater poured through the Highwood Mountains and eroded the hundred mile-long, 500-foot-deep (150 m) Shonkin Sag—one of the most famous prehistoric meltwater channels in the world.
- Montagne J.L. "Quaternary System, Wisconsin Glaciation." Geologic Atlas of the Rocky Mountain Region. Denver: Rocky Mountain Association of Geologists, 1972.
- Hill, Christopher L. and Valppu, Seppo H. "Geomorphic Relationships and Paleoenvironmental Context of Glaciers, Fluvial Deposits, and Glacial Lake Great Falls, Montana." Current Research in the Pleistocene. 14 (1997); Hill, Christopher L. "Pleistocene Lakes Along the Southwest Margin of the Laurentide Ice Sheet." Current Research in the Pleistocene. 17 (2000); Hill, Christopher L. and Feathers, James K. "Glacial Lake Great Falls and the Late-Wisconsin-Episode Laurentide Ice Margin." Current Research in the Pleistocene. 19 (2002); Reynolds, Mitchell W. and Brandt, Theodore R. Geologic Map of the Canyon Ferry Dam 30' x 60' Quadrangle, West-Central Montana: U.S. Geological Survey Scientific Investigations Map 2860, scale 1:100,000. Scientific Investigations Map 2860. Washington, D.C.: U.S. Geologic Survey, 2005.
- Feathers, James K. and Hill, Christopher L. "Luminescence Dating of Glacial Lake Great Falls, Montana, U.S.A." XVI International Quaternary Association Congress. Stratigraphy and Geochronology Session. International Quaternary Association, Reno, 2003.
- Kidston, Martin J. "Prehistoric Find." Helena Independent Record. June 20, 2004.
- Alt, David and Hyndman, Donald W. Roadside Geology of Montana. Missoula, Mont.: Mountain Press Publishing, 1986. ISBN 0-87842-202-1; Stickney, Michael C. "Quaternary Geology and Faulting in the Helena Valley." In 1987 Guidebook for the Helena Area, West-Central Montana: Guidebook for the 12th Annual Field Conference. Richard B. Berg and Ray H. Breuninger, eds. Montana Bureau of Mines and Geology Special Publication 95. Helena, Mont.: Montana Bureau of Mines and Geology, 1987.
- Clawson, Roger and Shandera, Katherine A. Billings: The City and the People. Helena, Mont.: Farcountry Press, 1998. ISBN 1-56037-037-8
- McRae, W.C. and Jewell, Judy. Moon Montana. 7th ed. Cambridge, Mass.: PublicAffairs, 2009. ISBN 1-59880-014-0
- Axline, Jon and Bradshaw, Glenda Clay. Montana's Historical Highway Markers. Rev. ed. Helena, Mont.: Montana Historical Society, 2008. ISBN 0-9759196-4-4; Bowman, Isaiah. "Forest Physiography: Physiography of the United States and Principles of Soils in Relation to Forestry." American Environmental Studies. Reprint ed. Charles Gregg, ed. New York: Arno Press, 1970. ISBN 0-405-02659-5