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Glacial Lake Chicago

Glacial Lake Chicago

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Glacial Lake Chicago

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  1. Glacial Lake Chicago Early Lake Michigan

  2. Ancient Shorelines • This section refers to the phases of Glacial Lake Chicago. • The title “Lake Michigan” refers to stages that occurred after ice had completely left the basin. • 3 Ancient Shorelines • Glenwood • Calumet • Tolleston • Other events • Two-Creeks Stage • Chippewa Stage • Nipissing Stage

  3. Glenwood Phase • 14.5 – 12.2 kya • Lake Michigan began as a pro-glacial lake dammed between the ice front and the moraines that circle the southern end of the Lake Michigan Basin. • The lake overtopped the moraine in what is now southwestern Cook County and rapidly eroded an outlet (the Sag Valley) nearly a mile wide. • Glenwood Phase was 55-60 feet above the present level of the lake. • Total elevation = 640 feet above sea level • Shoreline was uneven with several inlets, peninsulas and offshore islands

  4. Glenwood Phase • Some beaches with dunes • One of these beach-dune complexes was still present near Dyer, IN in 1939 • Sand ridges on the moraines mark the early shoreline. • Best preserved beaches are along Glenwood-Dyer Road, just east of Glenwood, IL • Largest islands were: • Blue Island • Mt. Forest Island • Glenwood Island • Hobart Island in Lake County, IN Cook County

  5. Glenwood Phase • Blue Island • 6 miles long • East side was steep wave-cut cliff • West side had Chicago area’s largest sand deposit • City of Blue Island is at Southern tip • North of Blue Island are Beverly, Morgan Park, Mount Greenwood

  6. Glenwood Phase • During Glenwood Phase, glacier continued to advance and retreat • At one point ice retreated past Straits of Mackinac • Happened about 13-13.5 kya; caused lake level to drop • Straits were lower than the Chicago Outlet and lake water flowed out of Mackinac Outlet. • Ice advanced again and blocked the Straits so water level returned and outlet was south again • Lake level began to drop slowly as Chicago River eroded its valley where lake overtopped the moraine • 12.2 kya lake level dropped as ice retreated past Straits of Mackinac again • End of Glenwood Phase

  7. Two-Creeks Phase • 12.2-11.8 kya • Lake level was low • Determined in 1905 when submerged spruce forest just west of the L. Michigan shore near Two Creeks, WI. • Radiocarbon dating showed that the wood was older than the Calumet shoreline • Water level was lower than Calumet Stage • 1982 – another submerged forest was discovered near the town of Pines (sw of Michigan City, IN) • Partially decayed spruce trees; many still upright • After 200 years, glacier readvanced and blocked the Straits allowing the water level to rise and flood the forest.

  8. Calumet Phase • 11.8 – 11.2 kya • Calumet Phase was 35 feet above the present level of the lake. 20 feet lower than Glenwood level. • Total elevation = 620 feet above sea level • Much smoother coastline • Large number of sand dunes but not as many as before settlement • In some places Calumet Dunes bury part of all of some Glenwood dunes. • Mount Forest Island and Blue Island combined • Washington Heights and Stewart Ridge sand spits formed from the sand that eroded from these islands

  9. Calumet Phase • Ridge Road in Lansing, Munster, and Highland IN is part of Calumet Shoreline • Was an offshore peninsula or spit • Calumet and Glenwood beaches were used as high, flat, dry travel routes by • Native Americans • stagecoaches • Now U.S. Highway 6

  10. Calumet Phase • Calumet Phase lasted 600 years • 11.2 kya when glacier retreated past the Straits of Mackinac for the last time • Lake level dropped about 28 feet to elevation of 592 feet above sea level • Calumet phase was over

  11. Algonquin Phase • 11.2-10.9 kya • Beaches can be found farther north along Lake Michigan few beach deposits of this age at the south end of the lake • 2 possible causes • Short period - only 300 years • Little sand was being transported to southern shores of the lake

  12. Algonquin Phase • Lake level rose • Earth’s crust was rebounding after removal of ice • Lake then eroided the shoreline creating the steep slope north of Ridge Road in County • Algonquin Shoreline is erosional scarp rather than a beach • Algonquin Phase ended by about 10 kya

  13. Chippewa Phase • 10.0 – 5.5 kya • Extreme drop in lake level • Retreating glacier uncovered a very low outlet for the upper Great Lakes to the Atlantic at North Bay, Ontario • Lake level as low as 381 feet above sea level

  14. Chippewa Phase • Much of the lake plain dried up • Maybe 200-350? feet below today’s level • Two deepest parts still had water • Area begins about 30 miles north of today’s southern shore • Also a larger basin farther north had water • Chippewa Phase lasted 4000 years, longest of any of the lake phases • Throughout this phase, earth’s crust kept rebounding • Rebounding slowly raised the level of the North Bay Outlet, and with it the level of Lakes Huron and Michigan

  15. Forests grew in what is now deep water.

  16. Figure 2. (A) Photo of a submerged spruce stump at the Sanilac site from which the cross-section of sample #1 was cut in July 1999. Approximate diameter of this stump at its base is 60 cm. (B) View across an area of dense forest remains located near the study grid. The larger logs to left of center are c. 3.7 m in length. Depth for both photos = 13 m. Photos by Luke Clyburn.

  17. Chippewa Stage • Great Lakes Huron and Michigan, as they probably looked during the "Stanley Low" period some 8,000 years ago.  • The drowned forest site is now about two miles offshore in 40-50 feet of water.

  18. High Tolleston Shoreline • The Nipissing Phases • Began 6- kya • Lake Michigan water rose slowly past today’s level • About 4.7 kya (603 feet) third major shoreline began forming at Southern tip of Lake. • Shoreline runs through Chicago, calumet City, Hammond, Gary, Ogden Dunes, Dune Acres, Beverly Shores, and Michigan City • Beach began as a long spt/barrier beach that separated Calumet lagoon from the lake. • 3.8 kya lake level began to drop and Calumet Lagoon drained and became the floodplain of what is now the Little Calumet River

  19. High Tolleston Shoreline • Tolleston Shoreline Dunes were generally taller than the older and higher shorelines. • Most were removed years ago and the sand was used to raise ground levels elsewhere • High Tolleston Shoreline at 605 feet above sea level • 15 feet lower than the Calumet Shoreline • 25 feet higher than today’s level • Can be seen today east of Michigan Avenue near Roseland in Chicago (between 100th and 127th Streets). • Much of the area is now protected as part of the National Lakeshore or State Park • Cowles Bog, Great Marsh and Dunes Creek • This phase left several prominent landmarks, including the beach ridge that provided the route for Clark Street in Chicago.

  20. Lower Tolleston Shorelines • Outlets of the Great Lakes • When the Tolleston Shoreline first formed, the Upper Great Lakes had three outlets • North Bay Outlet near Georgian Bay • Port Huron Outlet past Detroit • Chicago Outlet • Crustal rebound continued up north, so northernmost North Bay Outlet was raised higher than the two southern outlets – couldn’t carry water out of lakes • Erosion lowered Port Huron Outlet slightly – levels of Lakes Huron and Michigan go down also • Chicago Outlet dried up

  21. Lower Tolleston Shorelines • 3.8 kya – Algoma Phase • Lake level dropped to current level • This happened in a pulsating manner • Lowered water levels resulted from a combination of erosion at Port Huron and dry weather conditions • Higher water levels were caused by periods of greater rainfall • Pulsating pattern produced a series of more than 150 small beach ridges all roughly parallel to the lake and all located north or east of the High Tolleston beach. • Between the ridges were long, low swales that often contained standing water. • These ridges are called the Lower Tolleston Beaches

  22. Lower Tolleston Shorelines • Lower Tolleston Beaches • Originally ranged in height from 5 -12 feet and 150 feet in width • Most were leveled as SE Chicago, Gary, Hammond, and East Chicago were developed • Can see some in Miller and Tolleston/Brunswick areas of Gary • Gibson Woods has the longest ridges still remaining

  23. Current Conditions • Current level of Lake Michigan was reached 1500 years ago • Currents of the lake bring sand soutward and deposit it at the southern end of the lake • 1500 years ago a sand spit grew south of Stony Island (a bedrock island in the lakde) • Sand spit enclosed a bay creating Lake Calumet • 400 years later Wolf Lake formed in a similar manner • Weather patterns cause lake level to fluctuate seasonally • May rise more than a foot from late winter low level to a summer high and then back down again • Concerns about global warming and lake levels

  24. The Future • Lake level will most likely drop again • Level of Lakes Michigan and Huron is determined by the level of Lake Eried iinto which they flow • Depends on the erosion of Niagara Falls, Lake Erie’s elevation will remain the same, but as the falls erode away, Lake Erie will drop and so will Lakes Michigan and Huron. • Largest southern sand dunes are in Porter County Indiana • Mt. Tom, • Mt. Holden • Mt. Jackson • Mt. Baldy is a migrating dune moves se about 4-6 feet per year

  25. Reversing the Chicago River • Chicago River flowed into Lake Michigan • Carried sewage into the lake which was the source of Chicago’s drinking water • Reversed when canal was dug 1900

  26. Reversing the Chicago River • A solution proposed in 1889 recommended that the Chicago River be reversed. • Instead of flowing into Lake Michigan it would, in effect, flow into the Gulf of Mexico. • The project involved the construction of a 28-mile channel through a glacial moraine and bedrock ridge. • The Sanitary and Ship Canal would connect Lake Michigan at Chicago with the Des Plaines River at Lockport. • It would also be connected to the Chicago River and would be deep enough to permanently reverse the flow of the river.