Subsidence
After coal has been extracted from the earth, large voids are left underground. Usually wooden beam supports have been put in place to secure the roof above, but overtime are rotted. The result is a threat to roads and buildings. Sometimes the damage may be a minor hairline cracking in a building, but other times a complete building can collapse.
http://www.dep.state.pa.us/dep/deputate/minres/Districts/abandone.htm