So, apparently a “600 foot long and 50 feet wide” sinkhole just opened up in Mississippi. It obviously didn’t take long to form - minutes? Seconds?
How is this possible? I can see a big crack forming in the earth. Totally plausible. But happening explosively and suddenly instead of gradually over time? What makes this possible?
The hole forms gradually underground, but eventually it gets so big that there isn’t enough support for the ground above it (plus, in this case, several cars).
Yes - it’s a big cavern - you’re standing on top of the roof. Over time, bits of the ceiling of the cavern fall away until the roof is no longer strong enough, and it collapses. Surface soil flows into the hole and creates the classic sinkhole funnel.
That makes a ton more sense. So it did form over time. If you had acoustic sensors you could actually detect the sinkholes as they form over a period of months to years. Maybe fill em in with mud or concrete instead of letting them wreck property like in the OP.
Yeah, or just evacuate. Some of these things are part of quite extensive limestone cave systems though - way too big to fill in.
Two years ago one opened up in Florida under a sleeping man’s house. His body was never found. It reopened this past August…
. . . and bottomless!
The one referred to in Florida was natural.
The recent one in Mississippi is man-caused - an underground pipe collapsed, the water washed out the ground around it causing a long, tube-like void, and the roof of it collapsed.
Don’t forget the sinkhole in Bowling Green, KY. It formed right underneath the Corvette Museum and swallowed just under a dozen, IIRC, cars on display.
This actually looks more like some sort of drainage tunnel has collapsed. If you look at the video on the BBC News website, at 6 seconds in, you can see the brickwork of the remaining tunnel. The people are standing on it, probably not the safest place to stand if you ask me.
Similar effect, different mechanism:Queensland’s Inskip Point at Rainbow Beach which occurred in in September this year.
This example isn’t a “sinkhole” i.e. with the collapse of the roof of a cavern, rather it’s an underwater landslide and the collapsed material has moved out into the channel.
There’s also this giant crack in the earth in Wyoming. Another picture here. You can see how a hill has split in the middle, the weight of the sides pulling it apart. Whole hillsides may slide down in an avalanche when the ground loses tension and can’t continue to hold itself together.
Folks have brought up some interesting & cool examples.
Here’s a place for the OP to begin to learn about the mechanism in general: Karst - Wikipedia
Not really.
The actual collapse may be , at least in part, due to many things including
a. corrosion of steel components - eg brackets,ties, internal reinforcing corroded away.
b. Settling of the ground… ground movement … clay soil swelling or shrinking ?
c. fluid pressure, eg burst pipe…
d. erosion, leakage carried away soil making a hole, into which the culvert aka tunnel fell ?
e. The flow of water created cavitation, which is where the negative pressure “sucks” (that is, it lets the outside world push… ) the structure apart.
I saw one appear overnight on our farm once.
In a space of about 30 feet wide between the dog kennels and the back of a horse barn. Just came out one morning and there was suddenly a hole there, about 10 feet wide and 15 long, and 6-10 feet deep. Took several dump truck loads to fill it in.
In front of the kennels was an outdoor water faucet, the freeze-proof kind where the actual valve is located 6-8 feet underground. Apparently this valve had sprung a leak, and for months (or years) water had been leaking underground. There was about 1-2 feet of clay & gravel on top, that had been hard-packed by tractors, haywagons, etc. passing over it, and then just plain dirt underneath. The water leak had washed away the dirt underground over time, until eventually the top level just fell into the hole one rainy night.
We were lucky that it happened then: a couple days later we were going to be baling hay and driving a tractor pulling a loaded haywagon right over that spot!
For the specific case in the OP of a wholly man-made sinkhole I agree you’re on the right track.
Karst terrain is the driver for the much more common natural sinkholes. Or at least nature is the source for most of the big ones. Many of us have had spade-sized sinkholes created by leaking lawn sprinklers. But they hardly count IMO.
And from that article one can follow links to details on sinkholes as a mechanical phenomenon, etc. Fighting Ignorance and all that. 
It’s become so popular that the museum has decided to preserve it as a permanent exhibit rather than fill it in.
A few years ago, a 50’ wide and maybe 20’ deep sinkhole opened in Montreal a few seconds after a bus passed over it. Fortunately, no one was there at the time. It was on Sherbrooke St, just outside the McGill campus.
The cause was determined to be a leaky water pipe that had gradually scoured the dirt that underlay the street.
I hope people don’t start throwing stones in it.
/Cue Movie trailer horror music
/Cue deep-voiced movie trailer narrator
"And now, it’s hungry again!
