Clintonville WI booms: Sedimentary rock settling???

Here's another image [link to pubs.usgs.gov] related to aquifers... it's basically the same line... could an aquifer be collapsing as others have mentioned?

And the Mount Simon aquifer: [link to pubs.usgs.gov]

good chance I have heard them where i live
usually followed by eq's

What does it mean? Booms are harmless or precursor to something worse?

the area is not sedementary rock, it is solid granite, according to geologists, but, dont let me get in the way of your compelling theory, what matter are facts when assumption is available?

did anyone notice the bullseye in michigan, looks just like an ancient impact crater, just lovely!

Actually, it's on the boundary between Precambrian igneous rock and ordovician dolomite (the prairie du chien formation). The prairie du chien is riddled with caves and such on both sides of the state and a fair number of sinkholes have appeared in door county, just north and west of clintonville.