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It has been suggested that this article be merged into Great Lakes. (Discuss) Proposed since September 2012.

Lake Michigan–Huron (also Huron–Michigan) is the combined waters of Lake Michigan and Lake Huron, which are joined through the narrow, open-water Straits of Mackinac. They are sometimes considered a single lake because the flow of water through the straits keeps their water levels in near-equilibrium. Although the flow is generally eastward, it can be in either direction depending on local conditions.

Although Lake Michigan and Lake Huron are geographically distinct, some sources count Michigan-Huron as a single lake, or a single lake in certain contexts such as level data and hydrology, making it the largest fresh water lake by area in the world.

Bathymetry and hydrology

The connection between Lake Michigan and Lake Huron is the Straits of Mackinac, which are 5 miles (8 km) wide and 120 feet (37 m) deep. 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 local bathymetry, defining two distinct topographic basins, they are still deep enough and wide enough to allow free exchange of water between the basins on either side without requiring a significant excess hydraulic head on one lake compared to the other. Thus, because of the link through the Straits, both Lakes Michigan and Huron have a mean water level of 577 feet (176 m).

The combined effects of seiches (resonant standing waves) and of differing weather conditions (atmospheric pressure, wind) over each basin act to drive flow either way through the Straits on a variety of characteristic timescales, with discharges sometimes exceeding 75,000 m/s for several hours in either direction. However, long term average flow through the Straits is eastwards at around 1,500–2,000 m/s, in keeping with the main inflow to the system from Lake Superior through St. Mary's River in the west, and the main outflow through the St. Clair River in the east.

History

During the last ice age, the sizes and connectivity of the two basins varied dramatically through 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. At various times what is now Michigan–Huron was clearly separated into two lakes, and at other times was part of a single, deeper lake. At its peak, around 11,000 years ago and dammed by the ice sheet to the northeast, what is known to geologists as Lake Algonquin incorporated both modern lakes Huron and Michigan, as well as much of modern lake Superior. Before that Lake Chicago occupied the southern tip of the Lake Michigan basin, at the southern extent of the glaciers. Around 9,500 years ago, new pathways draining the system to the east were opened by the retreat of the ice, and what is now Lake Huron (known to geologists as Lake Stanley) was separate from what is now Lake Michigan (Lake Chippewa), with Lake Michigan at a slightly higher level. They were connected by the now submerged Mackinac Channel, which discharged into post–glacial Lake Huron over Mackinac Falls. Ongoing warping of the surface by isostatic uplift due to the removal of the glacial ice continued to perturb the drainage structure of the region, allowing re-integration 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 postglacial evolution.

One lake or two?

Because of the relatively small size in both depth and width of the Straits of Mackinac compared to the water bodies on either side, the distinct topographic basins which these occupy, and historical naming convention, Lake Michigan and Lake Huron are considered to be geographically distinct. For instance, these two lakes are typically recorded as separate entries in lists of the largest lakes in the world by area and volume. In the context of hydrology, however, the two can be considered as one body of water. Because of the strong hydrologic connectivity through the Straits, some sources have considered the total area and volume of Lake Michigan-Huron when placing this system in a global or regional context. When Lake Michigan–Huron is treated as a single entity, it is the largest freshwater lake by surface area in the world.

See also

• List of lakes by area
• List of lakes by volume
• Michilimackinac

References

Notes

1. ^ Likens, Gene E., ed. (2009). "Historical Estimates of Limnicity". Encyclopedia of inland waters (1st ed.). Amsterdam: Elsevier. ISBN 0120884623. Table 1: The world's lakes >2000 km in area, arranged in decreasing order of lake area. See also Lakes (Formation, Diversity, Distribution)
2. ^ Marsh, William M. Physical geography : great systems and global environments. Table 16.2: Great lakes of the world by lake type. Cambridge: Cambridge University Press. p. 399. ISBN 0521764289. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
3. ^ van der Leeden, Frits; Troise, Fred L.; Todd, David Keith, eds. (1991). The water encyclopedia (2nd ed.). Chelsea, Mich.: Lewis. pp. 198–200. ISBN 9780873711203.
4. ^ "Large Lakes of the World". FactMonster. Pearson Eduction. Retrieved 14 September 2012.
5. ^ Matt Rosenberg. "Largest lakes in the world". About.com. The New York Times Company. Retrieved 14 September 2012.
6. ^ David Lees in Canadian Geographic writes, "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."Lees, David. "High and Dry" Canadian Geographic (May/June 2004) pp.94-108.
7. ^ "Great Lakes Map". Michigan Department of Environmental Quality. Retrieved 20 September 2012.
8. ^ "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." NOAA, 2006.
9. ^ "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." U.S. Army Corps of Engineers, "Hydrological Components" Record Low Water Levels Expected on Lake Superior. August 2007. p.6
10. ^ Largest Lake in the World - Largest in the United States - GEOLOGY.COM
11. Grady, Wayne (2007). The Great Lakes. Vancouver: Greystone Books and David Suzuki Foundation. pp. 42–43. ISBN 978-1-55365-197-0.
12. "Michigan and Huron: One Lake or Two?" Pearson Education, Inc: Information Please Database, 2007.
13. Wright, John W. (ed.) (2006). The New York Times Almanac (2007 ed.). New York, New York: Penguin Books. p. 64. ISBN 0-14-303820-6. {{cite book}}: |first= has generic name (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
14. ^ James H. Saylor & Peter W. Sloss, 1976, Water Volume Transport and Oscillatory Current Flow through the Straits of Mackinac, Journal of Physical Oceanography, v. 6, p. 229-237
15. ^ Mortimer 2000, p. 59 harvnb error: no target: CITEREFMortimer2000 (help)
16. "Great Lakes: Physiography". Encyclopedia Britannica. Encyclopedia Britannica, Inc. Retrieved September 17, 2012.
17. Schaetzl, Randall. "Mackinac Channel". Geography of Michigan and the Great Lakes Region. Michigan State University. Retrieved 18 September 2012.
18. "Ancient Waterfall Discovered Off Mackinac Island's Shoreline". Mackinac Island Town Crier. Retrieved 18 September 2012.
19. W.R. Farrand, 1998, The Glacial Lakes around Michigan

Further reading

• Burg, J. P. (1959). "Precipitation and the levels of Lake Michigan-Huron". Journal Geophysical Research. 64: 1591–1595.
• De Geer, Sten (1928). The American manufacturing belt. Volume 4 of Geografiska annaler. Svenska Sällskapet för Antropologi och Geografi.
• Mortimer, Clifford H. (2004). Lake Michigan in motion : responses of an inland sea to weather, earth-spin, and human activities. Madison, Wis.: University of Wisconsin Press. pp. 59–78, 190–192, 300–309. ISBN 9780299178345. {{cite book}}: Invalid |ref=harv (help)
• Schaetzl, Randall J. (2000). "Postglacial Landscape Evolution of Northeastern Lower Michigan, Interpreted from Soils and Sediments". Annals of the Association of American Geographers. 90 (3): 443–466. doi:10.1111/0004-5608.00204. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Schaetzl, Randall J. (2002). "Measurement, Correlation, and Mapping of Glacial Lake Algonquin Shorelines in Northern Michigan". Annals of the Association of American Geographers. 92 (3): 399–415. doi:10.1111/1467-8306.00296. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Sellinger, Cynthia E. (2008). "Recent water level declines in the Lake Michigan–Huron system". Environ. Sci. Technol (42): 367–373. doi:10.1021/es070664+. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Shelton, William A. (1912). "The Lakes-to-the-Gulf Deep Waterway: I". Journal of Political Economy. 20 (6): 541–573.

External links

• Lake Iroquois
• Drifting Buoys Track Water Currents in the Great Lakes Straits of Mackinac
• Great Lakes water level observations

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