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Glacial Lake Chicago
Early Lake Michigan
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
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Glenwood
Calumet
Tolleston
 Other events
 Two-Creeks Stage
 Chippewa Stage
 Nipissing Stage
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.
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Total elevation = 640 feet above sea level
Shoreline was uneven with several inlets, peninsulas
and offshore islands
Glenwood Phase
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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
Cook County
 Glenwood Island
 Hobart Island in Lake County, IN
Glenwood Phase
 Blue Island
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6 miles long
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East side was steep wave-cut cliff
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West side had Chicago area’s largest sand deposit
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City of Blue Island is at Southern tip
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North of Blue Island are Beverly, Morgan Park, Mount
Greenwood
Glenwood Phase
 During Glenwood Phase, glacier continued to advance
and retreat
 At one point ice retreated past Straits of Mackinac
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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
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.
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.
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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
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
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Native Americans
stagecoaches
Now U.S. Highway 6
Calumet Phase
 Calumet Phase lasted 600 years
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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
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
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Short period - only 300 years
Little sand was being transported to southern
shores of the lake
Algonquin Phase
 Lake level rose
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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
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
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
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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
Forests grew in what is now deep water.
Figure 2. (A) Photo of a
submerged spruce stump at the
Sanilac site from which the crosssection 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.
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 4050 feet of water.
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
High Tolleston Shoreline
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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.
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
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
Lower Tolleston Shorelines
 Lower Tolleston Beaches
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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
Current Conditions
 Current level of Lake Michigan was reached 1500
years ago
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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
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
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Mt. Tom,
Mt. Holden
Mt. Jackson
Mt. Baldy is a migrating dune moves se about 4-6 feet
per year
Reversing the Chicago River

Chicago River flowed into Lake Michigan
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Carried sewage into the lake which was the
source of Chicago’s drinking water
Reversed when canal was dug 1900
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.