Groundwater weakened the strata—once small cracks had started to form, releasing more groundwater and forming a cyclical erosion process—especially if any of it was near enough to the surface to participate in freeze-and-thaw cycles. Either weakening strata with flowing water or wedging into them with ice, it facilitates small cracks to become big fissures. But like you said, the force acting on them is gravity. It’s normal for rock to fault around the edges of mountain ranges as gravity spreads it apart horizontally. It’s unusual, given the scale of geologic time versus human time, to see it fault so suddenly without any significant seismic activity. The groundwater facilitated it opening up in this case.
The main thing is, in the movies, mystical forces have caused the earth to open wide. But that’s not what is happening here. The hole was there the entire time, you just couldn’t see it, and only the very thin layer of unsupported road or concrete slab, etc, is what you are actually standing on. So you didn’t get “swallowed” if you fall into one of these things, you actually just fell through the floor into a hole that was under it.
Amazing I’ve been worried about heart disease and nuclear attacks when it’s the sink holes that are the real killers 
You forgot meteors. Folks *always *forget the meteors. Sneaky devils they are.
Yup. And as soon as they hit you they turn into meteorites to cover their tracks. Bastards.
True dat!
I was there last May, it was filled in. They still have a group of cars pulled out of the hole, some restorable and some beyond repair at this time. the ones that they can save are awaiting funding.
There are non-cavitation causes. One is when the saturation of the soil is very high and there’s actual sizable groundwater movement —you form quicksand.
I blame the Graboids.