Geologic Hazards in Pennsylvania
Most people would agree that the latin term terra firma (meaning "solid earth") applies to Pennsylvania. Yet there are enough Pennsylvanians who would point to events that have shaken foundations – literally. Although rare, earthquakes occasionally jostle the ground in Pennsylvania. More commonly, sinkholes cause damage and trouble in areas underlain by carbonate rocks like limestone and dolomite. Large sinkholes have been known to destroy roads and buildings and are a particular nuisance in many areas of the state. Landslides are a serious geologic hazard across the Commonwealth. Houses and roads are no match for thousands of tons of rock and debris seeking its own equilibrium. Although these three types of geologic hazards get most of the attention, other hazards can be just as intrusive. Radon gas, arguably the deadliest geologic hazard in Pennsylvania, is thought to be the second leading cause of lung cancer. The subsurface migration of other gases like carbon dioxide and methane also can have adverse consequences. Floods and mine subsidence are other hazards in Pennsylvania that have a geologic component.