Glacial Ohio

It's Ohio as you may never have seen it: a map from the state geologic agency showing not bedrock, but the surface formations of sand and mud and gravel laid down over the last million years by the great glaciers. Some 20 American states, and of course every province of Canada, need two separate maps to keep track of the glacial blanket and the true bedrock beneath. In Ohio's case, I've just added it to the Geologic Maps of the 50 States.