Lake Michigan–Huron Explained

Lake Michigan–Huron
Location:United States, Canada
Group:Great Lakes
Lake Type:Glacial
Inflow:St. Marys River
Outflow:St. Clair River
Basin Countries:United States, Canada
Area:45300sqmi
Max-Depth:925feet
Volume:2029cumi
Residence Time:100 years
Shore:3250miles plus 2215miles for islands[1]
Elevation:577feet
Islands Category:Islands in the Great Lakes
Cities:Milwaukee, Chicago, Sarnia, Owen Sound, Cheboygan, Sheboygan, Port Huron, Traverse City
Pushpin Map:North America
Pushpin Map Alt:Location of Lake Michigan–Huron in North America.

Lake Michigan–Huron (also Huron–Michigan) is the body of water combining Lake Michigan and Lake Huron, which are joined through the 5adj=midNaNadj=mid, 295feet, open-water Straits of Mackinac. Huron and Michigan are hydrologically a single lake because the flow of water through the straits keeps their water levels in overall equilibrium. Although the flow is generally eastward, the water moves in either direction depending on local conditions. Combined, Lake Michigan–Huron is the largest freshwater lake by area in the world.[2] [3] [4] Lake Superior is larger than either individually, so it is counted as the largest of the Great Lakes when Lake Michigan and Lake Huron are considered separately.

Geologic history

During the last ice age, the sizes and connectivity of the two lake basins varied dramatically over time. Sequential advances and retreats of the Laurentian ice sheet repeatedly opened and dammed various possible outlets from the area, as well as providing dramatically varying amounts of meltwater to the system. Numerous proglacial lakes formed in various places and configurations as the ice sheet advanced and retreated. At various times, what is now Michigan–Huron was clearly separated into two or more lakes, and at other times was part of a single, deeper lake.

Around 9,000 years BC, as the ice sheet retreated, the modern Lakes Huron, Michigan, and much of Superior, were a single lake known to geologists as Lake Algonquin. Ice sheets dammed Lake Algonquin to the northeast.[5] Before that, Lake Chicago occupied the southern tip of the Lake Michigan basin, at the southern end of the ice sheet. Lake Algonquin and Lake Chicago both drained south into the Mississippi River watershed.[6] Around 9,500 years ago, new pathways draining the system to the east were opened by the retreat of the ice, and proglacial Lake Stanley (precursor of Lake Huron) was separated from proglacial Lake Chippewa (precursor of Lake Michigan), with Lake Chippewa at a slightly higher level. They were connected by the now-submerged Mackinac Channel, which discharged into Lake Stanley over Mackinac Falls.[7] [8] Ongoing warping of the land by post-glacial rebound due to the retreat of the glacial ice continued to modify the drainage structure of the region, allowing the reunification of all three basins (Superior, Michigan, and Huron) as the Nipissing Great Lakes. This arrangement was probably stable for more than 1,000 years, ending only when lake outlets other than the St. Clair River were cut off around 4,000 years ago. The current configuration of the lakes reflects the latest step in a long history of their post-glacial evolution.[9]

Bathymetry and hydrology

The connection between Lake Michigan and Lake Huron through the Straits of Mackinac is 5miles wide[10] and 120feet deep.[11] This depth compares with the maximum depths of 750feet in Lake Huron and 923feet in Lake Michigan. Although the Straits create a pronounced bottleneck in the contours of the shoreline and a major constriction in the local bathymetry, defining two distinct basins, they are still deep and wide enough to allow the free exchange of water between the two sides. Because of the link through the Straits, Lakes Michigan and Huron have the same mean water level (in June 2015 it was 580feet).[12]

The largest inflow to the system is the St. Mary's River from Lake Superior, and the main outflow is the St. Clair River toward Lake Erie; both lie in the Lake Huron basin.[13] The combined effects of seiches (resonant standing waves)[14] and of differing weather conditions (atmospheric pressure, wind) over each basin act to drive water either way through the Straits on a variety of characteristic timescales, at amounts sometimes exceeding 75000m3/s for several hours in either direction. However, the long-term average flow through the Straits is eastwards at 1500-, toward the outlet of the St. Clair River. Flows into the system from Lake Superior are controlled by the bi-national Lake Superior Board of Control through the operation of locks and canals.[15]

Constituent lakes

Compared to the water basins it connects, the wide and deep Straits of Mackinac appear relatively small. Thus by historical naming convention, Lake Michigan and Lake Huron are usually considered distinct, e.g. in lists of the largest lakes in the world by area and volume.[16] [17] [18] [19] [20] In the context of hydrology, however, the two are one body of water.[13] [3] [21] Because of the hydrologic connectivity through the Straits, some sources consider the total area and volume of Lake Michigan–Huron when placing this system in a global or regional context.[22]

When Lake Michigan–Huron is treated as a single entity, it is the largest freshwater lake by surface area in the world.[2] [23] [24]

See also

Further reading

External links

Notes and References

  1. Web site: Shorelines of the Great Lakes . https://web.archive.org/web/20150405211915/https://www.michigan.gov/deq/0%2C4561%2C7-135-3313_3677-15959--%2C00.html . April 5, 2015 . Michigan Department of Environmental Quality .
  2. Web site: Great Lakes Map . . September 20, 2012 .
  3. Web site: Lakes Michigan and Huron are considered to be one lake hydraulically because of their connection through the deep Straits of Mackinac." Great Lakes Environmental Research Laboratory, part of the National Oceanic and Atmospheric Administration. . Great Lakes Sensitivity to Climatic Forcing: Hydrological Models . https://web.archive.org/web/20100808074846/http://www.glerl.noaa.gov/res/Programs/glscf/hydrology.html . August 8, 2010 . National Oceanic and Atmospheric Administration . 2006 .
  4. Book: Lakes Michigan and Huron are considered to be one lake, as they rise and fall together due to their union at the Straits of Mackinac . United States Army Corps of Engineers . Hydrological Components . Record Low Water Levels Expected on Lake Superior . https://web.archive.org/web/20081015125647/http://www.edisonsault.com/CustServ/USACOE%20LS%20WATER%208%2007.pdf . October 15, 2008 . August 2007 . 6 .
  5. Encyclopedia: Great Lakes: Physiography . Encyclopædia Britannica . September 17, 2012 .
  6. Larson . Grahame . Schaetzl . R. . Origin and evolution of the Great Lakes . Journal of Great Lakes Research . 27 . 4 . 518–546 . 2001 . 10.1016/S0380-1330(01)70665-X . September 21, 2012 . dead . https://web.archive.org/web/20081031073825/http://www.geo.msu.edu/schaetzl/PDFs/Larson-Great_lakes.pdf . October 31, 2008 .
  7. Web site: Schaetzl . Randall . Mackinac Channel . Geography of Michigan and the Great Lakes Region . Michigan State University . September 18, 2012 .
  8. Web site: Ancient Waterfall Discovered Off Mackinac Island's Shoreline . . September 18, 2012 . https://web.archive.org/web/20080719181426/http://www.mackinacislandnews.com/news/2007/0825/front_page/003.html . July 19, 2008 . dead .
  9. Book: Farrand, W. R. . 1967 . 1988 . The Glacial Lakes around Michigan . Michigan Department of Environmental Quality Geological Survey Division . September 30, 2018 . May 22, 2013 . https://web.archive.org/web/20130522052835/http://macd.org/ME/Resource%20Material/Soils%20and%20Geology/The%20Glacial%20Lakes%20Around%20Michigan.pdf . dead .
  10. Book: Grady, Wayne . The Great Lakes . . Vancouver . 2007 . 978-1-55365-197-0 . 42–43 .
  11. Web site: Michigan and Huron: One Lake or Two? . Pearson Education . Information Please Database . 2007 .
  12. Web site: Weekly Great Lakes Water Levels . June 22, 2015 . June 15, 2015 . United States Army Corps of Engineers .
  13. Web site: International commission wants to look at engineering fix to boost Huron, Michigan levels . Milwaukee Journal Sentinel . April 26, 2013 . April 28, 2013 . Egan . Dan .
  14. Saylor . James H. . Sloss . Peter W. . 1976 . Water Volume Transport and Oscillatory Current Flow through the Straits of Mackinac . Journal of Physical Oceanography . 6 . 229–237 .
  15. News: What happens when Lake Superior has too much water? . Briscoe . Tony . July 13, 2018 . Chicago Tribune . July 15, 2018 . en-US .
  16. Encyclopedia: Historical Estimates of Limnicity . Likens . Gene E. . Encyclopedia of inland waters . 2009 . Elsevier . Amsterdam . 978-0-12-088462-9 . 1st . Table 1: The world's lakes >2000 km2 in area, arranged in decreasing order of lake area. See also Lakes (Formation, Diversity, Distribution)
  17. Book: Marsh . William M. . Martin M. . Kaufman . Physical geography: great systems and global environments . Cambridge University Press . Cambridge . 978-0-521-76428-5 . p. 399, Table 16.2: Great lakes of the world by lake type . April 30, 2012 .
  18. Book: van der Leeden . Frits . Fred L. . Troise . David Keith . Todd . The water encyclopedia . 1991 . Lewis . Chelsea, Mich. . 978-0-87371-120-3 . 198–200 . 2nd .
  19. Web site: Large Lakes of the World . FactMonster . Pearson Education . September 14, 2012 .
  20. Web site: Largest lakes in the world . Rosenberg. Matt . About.com . The New York Times Company . September 13, 2012 . February 17, 2017 . https://web.archive.org/web/20170217040540/http://geography.about.com/od/lists/a/largestlakes.htm . dead .
  21. Web site: Lake Huron Wisconsin Sea Grant . Wisconsin Sea Grant . University of Wisconsin . 26 June 2023 . 14 August 2018.
  22. David . Lees . . Contrary to popular belief, the largest lake in the world is not Lake Superior but mighty Lake Michigan–Huron, which is a single hydrological unit linked at the Straits of Mackinac . High and Dry . May–June 2004 . 94–108 .
  23. Web site: Largest Lake in the World - Largest in the United States . Geology.com .
  24. Web site: Predicting Currents in the Straits of Mackinac . September 24, 2022 . Great Lakes Environmental Research Laboratory . National Oceanic and Atmospheric Administration . EN-US .

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