This is really interesting...
There are (at least) two salt mines under Lake Erie (1700 to 2000 feet down), the one at Cleveland shut down in August because of "closure". Not sure if it ever reopened. Lots of salt being used around here this winter...
Note that the article quotes a guy who said:
The problem is called "convergence," Klein said. "Either the floor is coming up a little or the ceiling is coming down a little."
Klein said Cargill monitors measurements of the shaft and the room at the bottom of the mine on a regular basis.
"We're looking for movements of like one one-hundredths of an inch," he said.
The lake is only 35 minutes from where I live. I remember what happened very well. Many old timers thought the world was comming to an end.
Other Weird Disasters--Molasses & Beer Floods
A search on Wikipedia about the Lake Peigneur disaster provided a link to the Great Boston Molasses Flood. In turn, that led to a link to the London Beer Flood. What a way to die!
Other Weird Disasters--Molasses & Beer Floods
Did you note the season of the Boston Molasses Flood/disaster? Stuff flows pretty fast in the winter time!
Other Weird Disasters--Molasses & Beer Floods
I was talking to a geotech engineer here in Boston a few years back and they were talking about how they often run into a molasses layer in soil borings they do in the area of the "flood".