Michigan in Indiana. Lake bed deposits Lake Chicago covered only a narrow strip of land on the south and east side of modern Lake Michigan. From Holland northward across the Lake Chicago, the lake bed extends 10 to 25 miles (16 to 40 km) inland. The widest expanse is almost entirely fine sand. There is more sand than clay in a narrow strip along the shore. The clayey portions have till at only a few inches depth. The offshore winds along the east shore of Lake Michigan have created sand dunes, burying the older glacial beaches and lake beds. Today Vast amounts of sand in spits, dunes and beach lines—particularly at the southern tip of Lake Michigan—were left behind by each of the three stages of lake level drop. Today, evidence of these vast sand deposits is still clearly visible. Northern Indiana, for example, contains the Indiana Dunes, and many of the Chicago area's trails and roads follow some of these ancient beach lines or ridges in the sand spits. For example, Ridge Road from Homewood, Illinois, through Thornton and Lansing, Illinois, and then crossing the state border into Munster and Highland, Indiana, is one; Michigan City Road through Riverdale, Dolton, and Calumet City, Illinois, is another; LaGrange Road is another; Riverside Drive in Riverside; Ridgeland Avenue in Oak Park, or Grosse Point Road, Carpenter Road, and Ridge Avenue (The Rosehill Spit) in the Rogers Park/West Ridge neighborhood of Chicago, north of Devon Avenue and continuing north through Evanston, Illinois, are some others. Blue Island, Illinois, and Stony Island were, literally, islands left behind as Lake Chicago's water level fell. See also References External links Bretz, J.H. 1939. Geology of the Chicago Region, Part 1 - General. Illinois State Geological Survey, Bulletin 65. 118 pages. Killey, Myrna M. 1998. Illinois' Ice Age Legacy. Illinois State Geological Survey GeoScience Education Series 14. 66 pages. Willman, W.B. 1971. Summary of the Geology of the Chicago Area. Illinois State Geological Survey, Urbana, IL. Circular 460. 77 pages. Oak Park - Ancient Lake Chicago & Continental Divide Former lakes of the United States Geology of Illinois Geology of Indiana Geological history of the Great Lakes Proglacial lakes Lake Michigan Glacial lakes of the United States Geography of Chicago