Sinkholes

A sinkhole is a surface karst form, common in karst terrains. It is a closed hole, shaped like a circle or oval funnel. The diameter can be 100 meters or more, the depth can be more than 10 meters. It always applies that the width of the sinkhole is greater than the depth. In Slovenia, 14 different types of sinkholes are known. They are divided based on their formation and shape.

Two main formation methods are surface collapse and erosion.
Cover-collapsed sinkholes form when the surface collapses into the cavern below, steep slopes, and vertical stone walls are typically associated with them. A cover-collapsed sinkhole occurs through long-term thinning of the surface ground and walls above caverns and underground rivers. Necessary for the formation are: appropriate rocks, that start to crumble when the cavern or the tunnel reaches a large gap, and when the underground water dissolves the limestone and carries the stones away. If the underground river did not carry the rocks at regular intervals, the cavern or tunnel below the sinkhole would fill and stop the process. A permanent water source is located at the bottom of the sinkhole. Such a sinkhole is located near Semič.

Vodenica Sinkhole is the biggest and deepest sinkhole along the Lebica-Krupa Karst Educational Trail. The sinkhole is located in the forest by the Brsovec Village. It is 46 meters deep. At the bottom, a smaller walled spring is located. In the past locals used it for drinking and livestock drinking water. Even during droughts, the sinkhole has water.

Cover-subsidence sinkholes form where the dissolution of limestone and sediments into empty caverns is the strongest. Rainwater penetrates the surface through cracks and collects in larger crevices, where it more aggressively dissolves the rock. As water drains away from the area, the surface gradually forms into a funnel shape.

Vrhovci Sinkholes

The Vrhovci Sinkholes, located on a karst field south and west of Vrhovci Village, on the gravel road Preloka - Adlešiči, represent the typical karst terrain full of sinkholes. The area, almost 55 hectares, has around 100 sinkholes. Despite the difficult cultivation conditions, sinkholes are still meticulously cultivated. The average bottom diameter of the Vrhovci Sinkholes is only 20 meters, the depth ranges from 5 to 10 meters. The sinkholes slopes are steep, yet flat enough to access it with agricultural equipment. The space between the sinkholes is mown, only in some places do shrubs and groups of trees occur.
Vrhovci Sinkholes represent an exceptional cultural landscape of the shallow karst terrain. Because of its geomorphological importance and uniqueness, the sinkholes were declared a natural monument.