Recent sinkholes in an area of intensive karst development in northern Lithuania

The karst of northern Lithuaniais developed in gypsiferous layers of the Pasvalys andNemunelis beds of the Tatula Formation of the Upper Devonian (Frasnian) stage. The new sinkholcs formed during the last ten years in around Biriai and Pasvalys indicatc recent karst activity. 84 rcccnt sinkholcs appeared around the villages of Karajimilkis, Mantagaililkis in the Biriai district from 1995 to 1999. The thrcc biggest sinkholes occur in Pasvalys. Karst proccsscs and phenomena are particularly dangerous in urban areas. The suddcn appearance of sinkholes and ground subsidence have oftcn caused building damage. New sinkholes indicate a vcry scnsitive engineering geological environment.