Please Explain: Sink Holes

After a Florida man disappeared into a sinkhole that swallowed his bedroom, many people began wondering how stable the ground beneath our feet really is. On this week's Please Explain, Randall Orndorff, Director of the USGS Eastern Geology and Paleoclimate Science Center, explains what sinkholes are, why they form, where and when they are most likely to occur and how best to prevent them or predict and prepare for them.