What causes sinkholes

POSTED: 1:48 PM Aug 12 2013   UPDATED: 3:46 PM Mar 26 2015
brazil sinkhole bus

In March 2015, a sinkhole swallowed a tour bus in northern Brazil. The incident happened near a flooded river. Everyone aboard escaped safely. Take a look at what causes a sinkhole and some other notable sinkholes that have made headlines.