doline

   ; sinkhole

   A basin- or funnel-shaped hollow in limestone, ranging in diameter from a few meters up to a kilometer and in depth from a few to several hundred meters. Some dolines are gentle grassy hollows; others are rocky cliff-bounded basins. A distinction may be made by direct solution of the limestone surface zone, (solution dolines), and those formed by collapse over a cave, (collapse dolines), but it is generally not possible to establish the origin of individual examples [10].

   Solutional enlargement is either circular in plan, if there is one dominant vertical joint, or otherwise irregular if there are several and can achieve dimensions of up to 1,000 meters in diameter and 100 meters deep. Where a karst bedrock is covered by superficial deposits, solutional enlargement permits the latter to subside into vertical fissures, creating subsidence cones or alluvial dolines, whose slopes are unstable because of the unconsolidated nature of the surface material. The bedrock remains covered in the first instance. Dolines are also formed by the large-scale subsidence caused by cave roof-collapse of near-surface caverns; in this instance, the collapse doline, the sides are cliff-like and the floor composed of the irregular blocks from the fragmented roof. Cave roof-collapse is considered a relatively rare phenomenon. Closed depressions receiving a stream are known as swallow holes or stream sinks. A doline which is largely dependent upon snow for solution-enlargement is known as a kotlici or Schneedoline [19].

   In America most dolines are referred to as sinks or sinkholes.

   See also jama; pit; ponor; sink, sinkhole; stream sink; swallet; swallow hole; sumidero.

   Synonyms: (French.) doline; (German.) Dolinen, Karsttrichter; (Greek.) tholene; (Italian.) dolina, pozzo naturale; (Russian.) karstovaja voronka, karstovaja kotlovina; (Spanish.) dolina; (Turkish.) düden, kokurdan, huni; (Yugoslavian.) vrta… a, ponikva, dolac, do, duliba, kotli…, konta.