Sinkholes

Do you ever get that sinking feeling?  If so, pay attention because you could actually be sinking.  Roughly 35 to 40% of the ground in the United States is susceptible to developing sinkholes.  The page below from the U.S. Geological Survey explains how sinkholes form and includes a map showing which areas of the country are more prone to sinkhole formation: 

http://ga.water.usgs.gov/edu/sinkholes.html 

All things considered, it's somewhat surprising that no one has written "Chicken Little II:  The Ground is Falling!  The Ground is Falling!"