There are two main types of sinkholes: those that form slowly over time (cover-subsidence sinkholes) and those that appear suddenly (cover-collapse sinkholes). While it is usually the latter type ...

In many Iranian cities, the ground is sinking due to land subsidence caused by the excessive extraction of water resources, ...

Sinkholes can range in size from just a few feet wide to ones that cover a vast area spanning ... s southwestern region is at risk for soil subsidence, where underground materials shift or fall ...

The opening of the sinkhole, originally about the size of a utility access hole cover, had grown to about ... occur in the area because of subsidence from coal mining activity.