11.1.1. Sink Holes, Swallow Holes, Dolines and Uvalas/valley sink

A sinkhole is a surface depression or hole in a region of limestone terrain. Sinkholes can range in size from a few feet or meters to over 100 meters (300 feet) deep. A sinkhole can even collapse through the roof of an underground cavern and form what's known as a collapse sinkhole

Gradual enlargement of sink holes due to continuous dissolution of limestones result in the coalescence of closely spaced sink holes into one large hole which is called Swallow hole.

Further enlargement of swallow holes due to continuous solution result into a larger depression which are called dolines in karst erosion.

Uvalas are extensive depression. Larger uvalas have been seen to cover several square kilometers, with a depth of up to 200 metres. They are formed due to coalescence of several dolines due to continuous solution and enlargement of dolines, or due to collapse of upper roof of large cavities formed underground or due to coalescence of various sink holes.