Natural and induced sinkholes of the Obruk Plateau and Karapınar-Hotamış Plain, Turkey

The number of sinkholes (locally known as obruks) has increased rapidly in recent years near Karapınar, located in the semi-arid Konya Closed Basin in Central Anatolia. Nineteen sinkholes have formed in the last 33 years (1977–2009) as a result of the collapse of cavity roofs in the Neogene lacustrine limestone in the Obruk Plateau and beneath Quaternary lake sediments in the Karapınar-Hotamış Plain. Of these, 13 have formed within the past 4 years (2006–2009). The Obruk Plateau takes its name from the presence of several hundred paleo-sinkholes which formed as a result of natural processes during the Quaternary period. More recently, human activity has induced the formation of new sinkholes, which presents a hazard to life and property. Changing agricultural patterns have led to the opening of thousands of deep wells in recent years, and increased water pumping currently exceeds the sustainable yield of the aquifer. Thus the formation of sinkholes has been triggered by a combination of natural and human causes. The groundwater level has dropped almost 24 m in the vicinity of Karapınar during the last 26 years (1983–2008). Approximately 8 m of this drop occurred within the 4 years prior to the study (2005–2008). Legally-binding precautions must be taken to prevent further water table decline, in order to decrease sinkhole formation within the basin in the years to come.

Research highlights
► Sinkholes are among the most significant natural hazards.
► The number of sinkholes has increased rapidly in recent years near Karapınar.
► Nineteen sinkholes have formed in the last 32 years.
► Natural processes and human activities have induced the formation of sinkholes.
► Increasing aridity and excessive pumping has induced the sinkhole formation.