Lake Michigan–Huron (alsoHuron–Michigan) is the body of water combiningLake Michigan andLake Huron, which are joined through the 5-mile-wide (8.0 km), 295-foot-deep (90 m), open-waterStraits of Mackinac. Huron and Michigan arehydrologically a singlelake 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 largestfreshwater lake by area in the world.[1][3][4][5]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.
During the lastice age, the sizes and connectivity of the two lake basins varied dramatically over time. Sequential advances and retreats of theLaurentian ice sheet repeatedly opened and dammed various possible outlets from the area, as well as providing dramatically varying amounts of meltwater to the system. Numerousproglacial lakes formed in various places and configurations as the ice sheet advanced and retreated.[6] 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.
Glacial Lake Algonquin and its Correlatives, approximately 11,000 years ago
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 asLake Algonquin. Ice sheets dammed Lake Algonquin to the northeast.[7] 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 theMississippi River watershed.[8] Around 9,500 years ago, new pathways draining the system to the east were opened by the retreat of the ice, and proglacialLake Stanley (precursor of Lake Huron) was separated from proglacialLake 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.[9][10] Ongoing warping of the land bypost-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 theNipissing Great Lakes. This arrangement was probably stable for more than 1,000 years, ending only when lake outlets other than theSt. 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.[6]
ANOAA schematic of the hydrology of the Great Lakes depicts Lake Michigan–Huron as a single lake with three basins: Lake Michigan, Lake Huron, andGeorgian Bay.[4]
The connection betweenLake Michigan andLake Huron through theStraits of Mackinac is 5 miles (8 km) wide[11] and 120 feet (37 m) deep.[12] This depth compares with the maximum depths of 750 feet (229 m) in Lake Huron and 923 feet (281 m) in Lake Michigan. Although the Straits create a pronounced bottleneck in the contours of the shoreline and a major constriction in the localbathymetry, 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 580 feet (177 m)).[13]
The largest inflow to the system is theSt. Mary's River fromLake Superior, and the main outflow is theSt. Clair River towardLake Erie; both lie in the Lake Huron basin.[14][3] The combined effects ofseiches (some being resonant standing waves)[15] and of differing weather conditions (atmospheric pressure, wind)[14] over each basin act to drive water either way through the Straits on a variety of characteristic timescales, at amounts sometimes exceeding 75,000 m3/s (2,600,000 cu ft/s) for several hours in either direction.[15] However, the long-term average flow through the Straits is eastwards at 1,500–2,000 m3/s (53,000–71,000 cu ft/s), toward the outlet of the St. Clair River.[15] Flows into the system from Lake Superior are controlled by the bi-nationalLake Superior Board of Control through the operation of locks and canals.[16]
The overhead view of the Straits of Mackinac, which are 4 miles (6.4 kilometers) wide, and 295 feet (90 meters) deep. It links Lakes Michigan (left) and Huron (right).
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 byarea andvolume.[17][18][19][20][21] In the context of hydrology, however, the two are one body of water.[3][4][22] 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.[23]
^"Hydrological Components".Record Low Water Levels Expected on Lake Superior(PDF). United States Army Corps of Engineers. August 2007. p. 6. Archived fromthe original(PDF) on October 15, 2008.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
^abFarrand, W. R. (1988) [1967].The Glacial Lakes around Michigan(PDF). Michigan Department of Environmental Quality Geological Survey Division. Archived fromthe original(PDF) on May 22, 2013. RetrievedSeptember 30, 2018.
^Marsh, William M.; Kaufman, Martin M. (April 30, 2012).Physical geography: great systems and global environments. Cambridge: Cambridge University Press. p. 399, Table 16.2: Great lakes of the world by lake type.ISBN978-0-521-76428-5.
^abLees, David (May–June 2004). "High and Dry".Canadian Geographic. pp. 94–108.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
Polderman, Nathan J.; Pryor, Sara C. (2004). "Linking Synoptic-scale Climate Phenomena to Lake-Level Variability in the Lake Michigan-Huron Basin".Journal of Great Lakes Research. Vol. 30, no. 3. pp. 419–434.doi:10.1016/S0380-1330(04)70359-7.
Schaetzl, Randall J.; Krist, Frank J.; Rindfleisch, Paul R.; Liebens, Johan; Williams, Thomas E. (2000). "Postglacial Landscape Evolution of Northeastern Lower Michigan, Interpreted from Soils and Sediments".Annals of the Association of American Geographers. Vol. 90, no. 3. pp. 443–466.doi:10.1111/0004-5608.00204.S2CID55689261.
Schaetzl, Randall J.; Drzyzga, Scott A.; Weisenborn, Beth N.; Kincare, Kevin A.; Lepczyk, Xiomara C.; Shein, Karsten; Dowd, Cathryn M.; Linker, John (2002). "Measurement, Correlation, and Mapping of Glacial Lake Algonquin Shorelines in Northern Michigan".Annals of the Association of American Geographers. Vol. 92, no. 3. pp. 399–415.doi:10.1111/1467-8306.00296.S2CID56412226.
Sellinger, Cynthia E.; Craig A. Two; E. Conrad Lamon; Song S. Qian (2008). "Recent water level declines in the Lake Michigan–Huron system".Environ. Sci. Technol. Vol. 42, no. 42. pp. 367–373.doi:10.1021/es070664.PMID18284132.
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