Lake Chicago
Lake Chicago | |
---|---|
Laurentide Ice Sheet | |
Primary outflows | Chicago River |
Basin countries | United States |
First flooded | 18,000 years before present |
Max. length | 241 mi (388 km) |
Max. width | 57 mi (92 km) |
Average depth | 160 ft (49 m) [1] |
Residence time | 4000 years in existence |
Surface elevation | 160 ft (49 m) |
References | The Pleistocene of Indiana and Michigan and the History of the Great Lakes; Frank Leverett and Frank B. Taylor; Monographs of the United States Geological Survey; Volume LIII; Washington; 1915 |
Lake Chicago was a prehistoric proglacial lake that is the ancestor of what is now known as Lake Michigan, one of North America's five Great Lakes. Formed about 13,000 years ago and fed by retreating glaciers, it drained southwest through the Chicago Outlet River.
Origin
The city of
Much later, the
Chronology
13,000 to 11,000 years before present
The earliest formation of Lake Chicago occurred when the Michigan Lobe of the glacier retreated northward into the basin of modern
The ice continued northward forming the next phase of Lake Chicago. The lake level remained at 640' above sea level,
When the ice retreated northward enough to open the Mohawk River valley, the waters in the Lake Huron and Lake Erie basin diverted from the Michigan outlet, leaving Lake Chicago as a headwaters lake. Continued northward migration of the glacier set the stage for the next major proglacial lakes in the Lake Michigan basin as Lake Algonquin and then Nipissing Great Lakes.[4]
Size
Extending somewhat further south, west and east than Lake Michigan, Lake Chicago extended west to present day La Grange, Illinois and south beyond Homewood and Lansing, Illinois, completely covering what is now Northwest Indiana, including the cities of Hammond and Gary, Indiana.
As the
Outlet and beaches
As the Michigan Lobe of the
The outlet channel is more than 1 mile (1.6 km) wide and cuts through glacial deposits. Near the head of the channel, rock layers have been cut through. It is probable that the distinct beaches from Lake Chicago are the result of these rock layers giving way rapidly, dropping the lake level from higher to lower levels. After each stage, the next barrier remained solid, holding the lake stable and creating distinct beaches. If the outlet were formed by a steady erosion of the barrier, it would have been less likely that the well-defined beaches would have been created.[5]
Along the eastern shore of Lake Michigan, the beaches of Lake Chicago have been destroyed by erosion, except the highest beach, much of which has also been destroyed.[5] The best remaining segments are along the southern tip of Lake Michigan in Indiana.
Lake bed deposits
Lake Chicago covered only a narrow strip of land on the south and east side of modern Lake Michigan. From Holland northward across the Lake Chicago, the lake bed extends 10 to 25 miles (16 to 40 km) inland. The widest expanse is almost entirely fine sand. There is more sand than clay in a narrow strip along the shore. The clayey portions have till at only a few inches depth. The offshore winds along the east shore of Lake Michigan have created sand dunes, burying the older glacial beaches and lake beds.[5]
Today
Vast amounts of sand in
For example, Ridge Road from Homewood, Illinois, through Thornton and Lansing, Illinois, and then crossing the state border into Munster and Highland, Indiana, is one; Michigan City Road through Riverdale, Dolton, and Calumet City, Illinois, is another; LaGrange Road is another; Riverside Drive in Riverside; Ridgeland Avenue in Oak Park, or Grosse Point Road, Carpenter Road, and Ridge Avenue (The Rosehill Spit) in the Rogers Park/West Ridge neighborhood of Chicago, north of Devon Avenue and continuing north through Evanston, Illinois, are some others. Blue Island, Illinois, and Stony Island were, literally, islands left behind as Lake Chicago's water level fell.
See also
|
References
- ^ "Geologic History" (http://lwr.state.wi.us/subcategory.asp?linksubcatid=440&linkcatid=481&li nkid=). Lower Wisconsin State Riverway Board. Retrieved 2012-05-20.
- ^ a b "Lake Chicago". Forest Preserve District of Cook County. March 16, 1946. Archived from the original on April 26, 2006. Retrieved 2022-02-10. This article incorporates text from this source, which is in the public domain.
- ^ a b Bulletin 4, The GLACIAL LAKES around Michigan; William R. Farrand, University of Michigan, Ann Arbor, Michigan; 1988
- ^ a b c The Illinois Ice Lobe; Frank Leverett; U.S. Geological Survey, Monograph, #38; Government Printing Office; Washington, D.C.; 1899, Plates 14, 16, 53
- ^ a b c d e Publication 9. Geological Series 7; Surface Geology and Agricultural Conditions of the Southern Peninsula of Michigan; Frank Leverett with a Chapter on Climate by C. F. Schneider; Michigan Geological and Biological Survey Lansing Michigan; 1911
External links
- Bretz, J.H. 1939. Geology of the Chicago Region, Part 1 - General. Illinois State Geological Survey, Bulletin 65. 118 pages.
- Killey, Myrna M. 1998. Illinois' Ice Age Legacy. Illinois State Geological Survey GeoScience Education Series 14. 66 pages.
- Willman, W.B. 1971. Summary of the Geology of the Chicago Area. Illinois State Geological Survey, Urbana, IL. Circular 460. 77 pages.
- Oak Park - Ancient Lake Chicago & Continental Divide