Authorities fear a woman in western Pennsylvania who disappeared while looking for her cat may have been swallowed by a sinkhole — a phenomenon likely caused by mine subsidence.
Search and rescue crews have not seen or heard anything from 64-year-old Elizabeth Pollard since she disappeared on Monday evening, but a sinkhole appeared around the same time about 20 feet (6 meters) from where she parked her car, raising fears that she had fallen into the void. Her granddaughter was found safely inside the car hours later.
Sinkholes are not always associated with mining. In 2013, a man was killed when a sinkhole opened up beneath his home in central Florida, where the porous limestone base gives rise to thousands of sinkholes every year.
The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania. Fatalities are rare.
What are sinkholes?
A sinkhole is an area of ground that has no natural external surface drainage and can form when the ground below the land surface can no longer support the land above, according to the U.S. Geological Survey.
The land usually stays intact for a period of time until the underground spaces just get too big. If there is not enough support for the land above the spaces, then a sudden, dramatic collapse of the land surface can happen.
How common are sinkholes?