Geologic Hazards of Pennsylvania
Most people would agree that the Latin term terra firma (meaning "solid earth") applies to Pennsylvania.
Yet there are many Pennsylvanians who could point to events that have shaken foundations -- literally.
Earthquakes -- although rarely felt, these occasionally jostle the ground in Pennsylvania, and some have reached magnitudes capable of causing minor damage
Landslides -- whether caused by changes in the weather or land interference by man, houses, and roads are no match for thousands of tons of rock and debris seeking its own equilibrium
Sinkholes -- can impact roadways and buildings, and disrupt utility services in areas underlain by limestone and dolostone bedrock
There are other hazards in Pennsylvania that have a geologic component:
Radon gas -- arguably the deadliest geologic hazard in Pennsylvania -- derived from the weathering of uranium minerals in rocks and soil and thought to be the second leading cause of lung cancer
Subsurface migration of gases like carbon dioxide and methane -- of particular concern in areas where coal and petroleum resources underlie the land surface
Floods -- controlled mainly by precipitation, topography, and surface materials
- Mine subsidence -- collapse of the land surface over an underground mine