think the writer of the film 2012 (2010) came out with the idea from thin air? think again. sinkholes happened from natural depression caused by the removal of soil/rock by water under the surface. they can form slowly or instantly. below are 5 of the amazing sinkholes, in alphabetical order:
Bimmah Sinkhole (Oman) - somehow, the residents turned the sinkhole into a tourist park.
Blue Hole (Belize) - it was a perfect circular 305m across, 123m wide deep hole. the hole was once an opening to a cave system during the Ice Age. now, a spot for extreme divers.
Guatemala Sinkhole (Guatemala) - appeared in 2010, it was caused by tropical storm (Agatha), bringing many rains with it.
Neversink Pit (Alabama) - appeared in 1998. 15m deep n housed a large amount of rare ferns. it was bought by a group of cavers later for preservation.
The Devil's Sinkhole (Texas) - appeared in 1867. 122m deep n housed as many as 4 million Mexican Free-tailed Bats. now a registered National Landmark, as well as a well recognized tourism destination.
(taken from Ten Worlds Largest Sinkholes.)