The glaciers advanced into the Great Lakes region as a series of ice lobes, each lobe seeking out the lowest preexisting spots on the landscape. To the various glacial lobes we have given the names of the Great Lakes and bays which eventually occupied the enlarged depressions after the ice had disappeared. Thus we had the Superior Lobe, with the Keweenaw lobe as an offshoot; the Lake Michigan lobe, with its Grand Traverse and Green Bay appendages; the Huron Lobe, with its subordinate Saginaw Lobe which played as important a part as its parent; and the Erie and Ontario Lobes. Slowly the lobes made their way southward out of the old widened river valleys and during the climax of the last, or Wisconsin stage of glaciation, all the lobes were welded together south of the Great Lakes region, and advanced southward as one broad sheet of ice or glacier with slightly lobate front. Not until the ice melted back into southern Michigan did the ice front again become separated into distinct lobes.
gr-lakes-reg-maj-lobes-wis-advance.jpg (141779 bytes)

The ice lobes became, perhaps, more apparent during retreat than they may have during the advancing phase of the glacier.  The image below shows the ice lobes as they would have looked about 14,000 years ago.

ice-bdy-14k.GIF (63944 bytes)

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