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Lake Michigan–Huron

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Lake Michigan–Huron

Lake Michigan–Huron
Lake Michigan–Huron lies in the center of the Great Lakes
Location United States, Canada
Group Great Lakes
Lake type Glacial
Primary inflows St. Marys River
Primary outflows St. Clair River
Basin countries United States, Canada
Surface area 45,300 sq mi (117,400 km2)[1]
Max. depth 922 ft (281 m)
Water volume 2,029 cu mi (8,460 km3)
Residence time 100 years
Shore length1 3,250 mi (5,230 km) plus 2,215 mi (3,565 km) for islands[2]
Surface elevation 577 ft (176 m)
Settlements Milwaukee, Chicago, Cheboygan, Port Huron
1 Shore length is not a well-defined measure.

Lake Michigan–Huron (also Huron–Michigan) is the combined waters of Lake Michigan and Lake Huron, which are joined through the 5-mile (8.0 km) wide, 20-fathom (120 ft; 37 m) deep, 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, the water moves in either direction depending on local conditions.

Taken together, the surface waters of Lake Michigan–Huron form the largest fresh water lake (by area) in the world, due to the salinity of the southern parts of the Caspian Sea.

Bathymetry and hydrology

South–facing overhead view of the Straits of Mackinac linking Lakes Michigan (right) and Huron (left)

The connection between Lake Michigan and Lake Huron through the Straits of Mackinac is 5 miles (8 km) wide[3] and 120 feet (37 m) deep.[4] 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 basins, they are still deep and wide enough to allow 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 2011, it was 577 feet (176 m)).[5]

The largest inflow to the system is the St. Mary's River from Lake Superior, and the main outflow is the St. Clair River to Lake Erie; both lie in the Lake Huron basin.[6][7] The combined effects of seiches (resonant standing waves)[8] and of differing weather conditions (atmospheric pressure, wind)[6] 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.[8] 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).[8]

Geologic history

During the last ice age, the sizes and connectivity of the two 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.[9] 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 11,000 years ago, 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.[10] 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.[11] 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.[12][13] 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 reunification of all three basins (Superior, Michigan, and Huron) as the Nipissing Great Lake. 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]

One lake or two?

A [14]

Because of the relatively small depth and width of the Straits of Mackinac compared to the water bodies it connects, the distinct basins which these occupy, and historical naming convention, Lake Michigan and Lake Huron are normally considered 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.[15][16][17][18][19] In the context of hydrology, however, the two are considered one body of water.[14][20][7] Because of the 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.[21]

When Lake Michigan–Huron is treated as a single entity, it is the largest freshwater lake by surface area in the world.[1][21][22]

See also



  1. ^ a b "Great Lakes Map".  
  2. ^ Shorelines of the Great Lakes
  3. ^ Grady, Wayne (2007). The Great Lakes. Vancouver: Greystone Books and  
  4. ^ "Michigan and Huron: One Lake or Two?" Pearson Education, Inc: Information Please Database, 2007.
  5. ^ "Great Lakes Atlas: Factsheet #1". United States Environmental Protection Agency. April 11, 2011. Retrieved 2013-06-06. 
  6. ^ a b Mortimer 2000, p. 59
  7. ^ a b Egan, Dan (April 26, 2013). "International commission wants to look at engineering fix to boost Huron, Michigan levels". JSOnline. Milwaukee Journal Sentinel Inc. Retrieved 2013-04-28. 
  8. ^ a b c 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
  9. ^ a b W.R. Farrand, 1998, The Glacial Lakes around Michigan
  10. ^ "Great Lakes: Physiography". Encyclopedia Britannica. Encyclopedia Britannica, Inc. Retrieved September 17, 2012. 
  11. ^ Larson, Grahame; Schaetzl, R. (2001). "Origin and evolution of the Great Lakes". Journal of Great Lakes Research (Internat. Assoc. Great Lakes Res.) 27 (4): 518–546.  
  12. ^ Schaetzl, Randall. "Mackinac Channel". Geography of Michigan and the Great Lakes Region. Michigan State University. Retrieved 18 September 2012. 
  13. ^ "Ancient Waterfall Discovered Off Mackinac Island's Shoreline".  
  14. ^ a b "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.
  15. ^ Likens, Gene E., ed. (2009). "Historical Estimates of Limnicity". Encyclopedia of inland waters (1st ed.). Amsterdam: Elsevier.   Table 1: The world's lakes >2000 km2 in area, arranged in decreasing order of lake area. See also Lakes (Formation, Diversity, Distribution)
  16. ^ Marsh, William M.; Martin M. Kaufman. Physical geography : great systems and global environments. Table 16.2: Great lakes of the world by lake type. Cambridge: Cambridge University Press. p. 399.  
  17. ^ van der Leeden, Frits; Troise, Fred L.; Todd, David Keith, eds. (1991). The water encyclopedia (2nd ed.). Chelsea, Mich.: Lewis. pp. 198–200.  
  18. ^ "Large Lakes of the World". FactMonster. Pearson Education. Retrieved 14 September 2012. 
  19. ^ Matt Rosenberg. "Largest lakes in the world". The New York Times Company. Retrieved 14 September 2012. 
  20. ^ "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." US Army Corps of Engineers, "Hydrological Components" Record Low Water Levels Expected on Lake Superior. August 2007. p.6
  21. ^ a b 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.
  22. ^ Largest Lake in the World - Largest in the United States - GEOLOGY.COM

Further reading

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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