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/
Michigan has sleeping Bear Dunes....state park...I climbed those things with my 5 kids. They got to the top fast and the older one’s came down and dragged their poor mother up to the top as a couple disappeared over the top of the dunes and I was afraid I’d lose them....they were the younger 3...climbing dunes sucks......GG that was about 44 years ago..