Salt: A World History by Mark Kurlansky
While this this sounds pedantic (who besides me would get excited about a good explanation the origins of "the Hanseatic League"?) but Kurlansky really makes it fascinatingly rich reading.
I once believed that salt mines were a perfect storage place for environmental/nuclear crap. That is, until I read
"Salt: A World History" by Mark Kurlansky
British towns in the 19th century collapsed when salt miners removed subterranean salt by pumping water in and brine out:
Here's a nice picture(scroll down to see the leaning houses):
Turns out that if you pour water into a salt deposit, dissolve the salt and pump out the brine, the terrain above may collapse (salt columns were supporting it). Any remaining brine not pumped to the surface may travel who-knows-where underground to dissolve other salt deposits.
England went through decades of lawsuits and legislation wherein landowners cried for recompense of their collapsed lands from salt producers. The salt producers claimed it wasn't their mining that caused the collapses and the landowners usually lost.
Fast forward to oil/gas fracking in Texas, Oklahoma and other states:
most gas/oil deposits are under salt domes. Fracking injects water (and other chemicals) into the subterranean structures, the salt dissolves and the oil/gas is freed to rise. As in England, the brine that is not removed is free to travel miles underground, removing structure that has lain dormant for eons and collapsing the land above. But fracking also uses chemicals, not merely brine, and so the chance of pollution (esp. of water wells) is increased. The frackers say it does no harm. But funny sounds are coming from below and fracking chemicals are showing up in places (e.g., water wells) where they are not wanted: