A sinkhole is a natural depression or hole in the Earth’s surface caused by:
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karst processes or the chemical dissolution of carbonated rocks or salt beds.
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suffosion processes for example in sandstone.
Carbonated rocks such as limestone can be dissolved by water, especially acidic water.
When the carbonated rocks dissolved, there will be empty space or hole under the ground.
When there is nothing more to support the surface land, the gravity caused the surface land to suddenly collapse into the underground hole.
And that causes a sinkhole.
Suffosion processes can also cause sinkholes.
This picture will explain the suffosion processes.

Sinkholes are very dangerous especially when it happens in the city under big buildings or busy highways.
In 2010, a giant sinkhole in Guatemala City caused by heavy rain from Tropical Storm Agatha swallowed at least one three-story building!
This is a disaster.
Here are photos of some sinkholes:




