One day, everything looks normal. The next, there's a giant hole in the ground.
When these holes suddenly form where what looked like solid ground used to be, it's called a sinkhole.
These occur when earth beneath the surface erodes away and causes the surface to collapse within itself.
Some rocks and minerals can easily be dissolved in water. If those rocks and minerals dissolve below the surface, then the water level drops, the surface falls through from lack of any support underneath.
According to the United States Geological Survey, about 20 percent of the country is susceptible to naturally-occurring sinkholes. Most of those places are in the South, especially Florida.
Since water plays such a big part in dissolving the rocks and minerals beneath the surface, many sinkholes appear a day or two after a big rain event.
Most sinkholes occur naturally, but they can also be man-made. Sometimes mines, sewers, or other underground city infrastructures fail, and when that happens, the surface above collapses.
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