The Two Rivers end moraine, marking the outer limits of a significant readvance of retreating Wisconsin ice, extends across the lake between Manitowoc and Ludington. Morphology of the Mid-Lake Plateau, a cuesta defended by eastward-dipping, presumed Devonian limestones, is more accurately revealed. This delta and channel are evidence of overflow, possibly catastrophic, of Lake Superior into Lake Michigan via the Au Train-Whitefish Channel during the Lake Chippewa low stand. A large drowned river channel leads upstream from this delta, across the floor of Green Bay and into Little Bay De Noc.
A drowned delta lying at depths of 50 to 60m dominates the lake floor east of Washington Island. The Mackinac Channel, a subaerial river channel which drained Lake Chippewa, has a sill depth of about 30m and extends from north of Garden Island eastward through the Straits of Mackinac. This bathymetry resolves physiography of the lake floor to an extent that known features are revealed more accurately and features never before seen are revealed for the first time. Bathymetric contours were scanned and vectorized to geographic coordinates from scale 1:250000 compilation sheets. Was compiled utilizing the entire historic sounding data base. Ridges and Valleys in the Islands Area (area 6).Bathymetry of Lake Michigan Great Lakes Data Rescue Project - Lake Michigan Bathymetry
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