CAVES
From Encyclopedia Dubuque
CAVES. Naturally occurring caves in the area were sometimes enlarged to allow their use. Miners used caves to access deeper veins of LEAD. Caves offered practical if short-term shelter.
Taking advantage of the cool temperatures of caves, people used them for the preservation of dairy products. ICE, beer and other alcoholic beverages could be stored in them.
Caves and the presence of so many mapped and unmapped MINING tunnels in the bluffs, make the potential for destruction in the event of severe EARTHQUAKES more likely. The danger of caves (natural and man-made) collapsing have caused most to be permanently sealed.

