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

4. 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 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

7. Glenwood Phase Blue Island Mt. Forest Island Glenwood Island
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

8. 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

9. Glenwood Phase
During Glenwood Phase, glacier continued to advance and retreat
At one point ice retreated past Straits of Mackinac
Happened about 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

10. 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.

12. 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

15. 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

16. 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

18. Algonquin Phase
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

19. Algonquin Phase Lake level rose Algonquin Phase ended by about 10 kya
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

20. 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

22. Chippewa Phase Much of the lake plain dried up
Maybe ? 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

23. Forests grew in what is now deep water.

24. 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 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.

25. 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 feet of water.

27. 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

30. 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.

31. 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

32. 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

33. Lower Tolleston Shorelines
Lower Tolleston Beaches
Originally ranged in height from 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

35. 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

36. 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

37. 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

38. 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.