Erosion, loss of its bedrock that leads to utter collapse of the (man) cave:
We need to add a picture of the Republican Party national headquarters.
Any comments about the Disney World sinkhole?
Have any of you ever been caught in a sinkhole.
Most Florida lake started out as sinkholes.
Insert insatiable bottom joke here.
Sooo... best to avoid Guatemala City then.
What about me?
Sinkholes are no more real than crop circles or UFOs. The earth is *not* hollow, girls, no matter how many faked photographs you put in your slideshow.
R9, Florida is limestone with water running through it. It is as hollow as hollow can be.
That said Bay Ridge was not a sinkhole but a watermain accident, most likely.
Sinkholes occur anywhere where there is gypsum and limestone/dolostone bedrock, which is susceptible to erosion by groundwater and manmade intrusions (burst pipes, etc).
Look at a map. Much of the USA is built on such surfaces and karst (cave) structures. Florida is a sinkhole paradise. Ultimately made worse by dumping heavy building foundations on these fragile areas.
I would say the space between Sarah Palin's ears is probably the most ravenous sinkhole on record.
Whilst r14 is correct, the best thing to do if moving to a new area (or check your own out) is to look on a geology bedrock site on the internet maybe the US Geological Survey, find out the bedrock for your area.
If you are on sandstone, mudstone or any igneous (volcanic) bedrock you're on pretty solid ground. If you sit on evaporite rocks like limestone, dolomite or gypsum (especially gypsum), I wont say move, but it's more risky. Of course most people never experience a sinkhole in a lifetime spent living in such areas.
Here's a map of the US showing distribution of carbonate/evaporite rock types, all of which cause sinkholes.
Karst = An area of irregular limestone in which erosion has produced fissures, sinkholes, underground streams, and caverns.