Index map
The low, arc-shaped ridges just west of the "thumb" region
of northeast Michigan are recessional moraines composed
of glacial rubble that overlie the Pennsylvanian-age bedrock shown
on the map. They mark the northeastward retreat of the Huron Lobe
of the last Pleistocene
ice sheet from Saginaw Bay about 10,000 years ago (Lake Huron
is not shown). Similar moraines south of Lake Michigan, west of
Lake Ontario, and in eastern Wisconsin (Green Bay) are not well
represented by the rather coarse terrain data available to make
the shaded relief map.
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