We live on the edge of the where the Des Moines Lobe of the Wisconsin Glacier reached its farthest southern extent. You can see it in the landscape–a number of small hills show where the glacier stopped and dropped its load of rocks and gravel.
This rock along the fencerow came from that glacier. At least I think so.
This is the north side of the rock. I am not sure how long it has been in this location, but I know it has been here for at least a dozen years. This side is smooth, but does have some lichens growing on it.
The south side of the rock is rougher.
If you look closely, it has lichens as well. But it also has sort of a lime, aggregrate crust with small stones set into it. At some point in the rock’s history, I assume this part was in contact with water and the calcium and magnesium salts deposited themselves on the rock.
Or so it would seem.