Sinkholes

Sinkholes are among the most distinctive features in karst lands and represent the most direct connection in karst between the ground surface and the subterranean world (Fig. 1). An alternative word is doline, derived from the Slav term which indicates generically a depression but is actually used to designate a variety of surface landforms in karst, such as blind or dry valleys and even polje. As pointed out by Williams (2005), sinkhole and doline are not strictly synonymous so that adding a further qualification is required in order to better specify the origin of each single feature. ThetermdolinewasusedbyCvijicinhisclassicalworkin1893,toindicateanycircular,closeddepressioninkarst.Overtime,the useofthistermhasbeenmostlypreferredbyEuropeanscholars,typicallyfromageomorphologicalandmainlydescriptiveviewpoint (Sauro,2003).Ontheotherhand,sinkholehasbecomeprogressivelymorepopularinNorthAmerica,fromanengineeringapproach, with the word accompanied by adjectives to better specify the processes acting at the origin of the observed surface feature.