A
hole in the
ground caused by
rainwater eroding sand that was under the ground's
surface. The empty space eventually
collapses, 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
droughts 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.