Sinkholes can form anywhere there is soluble rock present underground. This is known as "karst terrain," according to Randall Orndorf the director at the Eastern Geology and Paleoclimate Science Center of the United States Geological Survey. Rock solubles that could potentially lead to sinkhole formation include, limestone, gypsum and salt.
Significant rainfall is a key ingredient as to whether a sinkhole will open, because the water becomes acidic once it is underground and without proper drainage can pool in sinkholes. Florida is a prevalent state when it comes to sinkholes, but more than 20 percent of the country is above "karst terrain," according to the U.S. Geological Survey (USGS). Other states where sinkholes are prevalent are Texas, Alabama, Missouri, Tennessee, Kentucky and Pennsylvania.
Sinkholes can also be man made even if rock solubles are not present underground. According to the USGS, a leaky faucet, old mine shafts and sewage malfunctions are three examples of how man made sinkholes can form.
Sinkholes are dangerous because as the water and rock dissolve, spaces and caverns form underground until they are too big and a collapse occurs.
Three cars were the victim of an opening sinkhole in Chicago this past week, after heavy rainfall inundated the city. One man was injured and taken to the hospital. The two other cars were parked and did not have anyone inside.
The USGS maps the nation and monitors sinkholes. By monitoring a property, it is possible to see it the land if susceptible to sinkholes. To do this, survey the land for holes or cracks in the soil, and check with local government, or the USGS to see if the property is above a "karst terrain."