BTW, I've got a huge version of this map on my computer for the whole of North America; all 54Meg of it that I can't locate on the web any more...
This is windblown sand ~ the City of Chicago is built on top of massive dunes pushed over into the lake. Indiana's dunes are still mostly there, and there are some large ones in Michigan too.
South of the dunes it's REALLY FLAT ~ and I mean flat ~ like lake bottom.
I took a look on Google.earth to see what it was your pictures showed, and that's THE DUNES.
Try this: http://www.msue.msu.edu/objects/content_revision/download.cfm/item_id.211898/workspace_id.26697/How%20The%20Great%20Lakes%20Were%20Formed%20(Video).swf/
Because the glaciers are so devastatingly huge little is left behind from earlier glacial periods ~ most of what we see is pretty recent. The Great Lakes are, so far, believed to be of recent origin. HOWEVER, there are all sorts of volcanic vents throughout the Midwest that are buried with dirt pushed in by the glaciers. Most people don't know they are there unless they happen to tap in for free heat and hot water. One large vent is actually at the East End of Lake Superior!
Beneath all of that is a mountain range entombed in vast shale and limestone deposits ~ and compounding that are a couple of major faults ~ one 17 miles deep under the route of the Mississippi, and other less deep called the Carmel Fault which runs through Southern Indiana to roughly Indianapolis/Carmel.
These features are left over from a time when the proto-North American continent was splitting in two ~ like the Afars region and the Great Rift Valley in Africa.
In between there are oil bearing shales, and even a range of shale running about 150 miles North to South bisecting Indiana, and underlying the region about 20 miles wide ~ and it has vast but currently untapped uranium deposits.
This region could eventually be put to use providing America all the energy it will ever need.