Lake Michigan–Huron

Lake Michigan–Huron (also Huron–Michigan) is the body of water combining both Lake Michigan and Lake Huron, which are joined through the , , 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."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."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 However, Lake Superior is larger than either individually, and so is counted as the largest lake when Lake Huron and Lake Michigan 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. 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. 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. 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.Farrand, W. R. (1967, rev 1988
The Glacial Lakes around Michigan
Geological Survey Division Michigan Department of Environmental Quality.

Bathymetry and hydrology

The connection between Lake Michigan and Lake Huron through the Straits of Mackinac is wide and deep. This depth compares with the maximum depths of in Lake Huron and 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 ).

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. The combined effects of seiches (resonant standing waves)Saylor, James H. and Sloss, Peter W. (1976
Water Volume Transport and Oscillatory Current Flow through the Straits of Mackinac
Journal of Physical Oceanography, v. 6, p. 229-237 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 for several hours in either direction. However, the long-term average flow through the Straits is eastwards at , 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.

Entity dispute

Because of the relatively small depth and width of the Straits of Mackinac compared to the water bodies it connects, the distinct basins that these occupy, and historical naming convention, Lake Michigan and Lake Huron are usually 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. Table 1: The world's lakes >2000 km² in area, arranged in decreasing order of lake area. See als
Lakes (Formation, Diversity, Distribution)
In the context of hydrology, however, the two are considered one body of water. 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.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.

When Lake Michigan–Huron is treated as a single entity, it is the largest freshwater lake by surface area in the world.Largest Lake in the World - Largest in the United States - GEOLOGY.COM
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See also

*List of lakes by area
*List of lakes by volume
*Michilimackinac

References

Notes

Further reading

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External links

Lake Iroquois
* ttp://www.glerl.noaa.gov/data/now/wlevels/levels.html Great Lakes water level observations

{{DEFAULTSORT:Michigan-Huron
Great Lakes
*Michigan-Huron
*Michigan-Huron
Lakes of Wisconsin
Lakes of Michigan
Lakes of Ontario
Lakes of Illinois
Lakes of Indiana
International lakes of North America