|Image: shallow bowl-shaped solutional doline in the area called Schwäbische Alb (Swabian Jura), Germany.|
A doline, sink or sinkhole is a closed depression draining underground in karst areas. It can be cylindrical, conical, bowl- or dish-shaped. The diametre ranges from a few to many hundreds of meters.
The name doline comes from dolina, the Slovenian word meaning valley. So this was originally a colloquial Slovenian word which was used by the geologists to describe a geologic feature.
There are two different mechanisms for the forming of dolines:
|Image: Cylindrical doline, the entrance to Dunmore Cave, Ireland. Image by Mathias Duckeck.|