in the ground
caused by rainwater
eroding sand that was under the ground's surface
. The empty space eventually collapse
s, much to the dismay
of humans who were walking across or building on the surface at that location. Florida
is prone to sinkholes because of the weather
-- lots of rain
for the erosion
and some drought
s which evaporate water from the ground and make the sandy areas take up less volume, weakening the support for anything built on that patch.
They can be sort-of fixed by filling the empty cavern (which may be much bigger than the actual collapsed area) with more sand held together with cement. However, to do so involves knowing where one has formed, which usually isn't discovered before it has collapsed. Sinkholes have "swallowed" whole houses, and one is as I write this forcing the closure of parts of two roads on the University of South Florida campus.