Sinkholes are formed by the actions of

Sometimes, heavy weight on soft soil can result in collapse of ground, resulting in asinkhole. Sinkholes can also form when the land surface is changed. Areas that have a bedrock made of limestone, salt deposits or carbonate rock are most susceptible to erosion and the formation of such holes.

Sinkholes mainly occur in what is known as 'karst terrain'; areas of land where soluble bedrock (such as limestone or gypsum) can be dissolved by water. With cover-subsidence sinkholes the bedrock becomes exposed and is gradually worn down over time, with the holes often becoming ponds as the water fills them in.