Voska luknja
Voska luknja is a cave on the north slope of the Ivanščica massif. It is a diagonal cave, so its horizontal length of is much smaller than its total passage length of. As mapped, it is the second deepest cave on Ivanščica behind Hanžekova jama at, but its total vertical difference is the largest in Zagorje, with potential for further expansion It is difficult to explore because of its narrowness and the entrance is difficult to access, but a tourist path has been planned.
Name
The name Voska luknja is Kajkavian for "Narrow Hole".Description
The cave is located on the slopes of the Dubrava peak. It is an exceptionally narrow cave, partly tectonic in origin, whose widest section is only wide. It is a cascading cave entered from the side with continuations both at the top and at the bottom for a total known vertical difference so far of, but these narrows are impassible without modification. The main chamber leads upwards and goes by the name Veliki kanal. The chamber leading downwards has been nicknamed Banana, ending on a ledge with a narrow continuation. At the far end of the floor of the Veliki kanal there is a narrow downward continuation nicknamed Cerviks, and at the roof there are as many as 4 possible continuations, all very narrow.Speleothems include stalactites, stalagmites, and coralloids, but flowstone dominates, including Cave curtains. A cluster of calcite crystals was found contrasting with brown hematite coloration at a depth of below the entrance.
A map of the cave was drawn in September 2009 by Tomica Matišić.
History
Cavers from the newly founded section Kraševski Zviri discovered both the lower and the upper entrance in August 2009, exploring much of the lower entrance that year. Exploration resumed in June 2010, adding another downward. It was during this exploration that Voska špilja was discovered not far above it. Its regionally unusual depth, proximity to Voska špilja and the potential for a connection to result in a cave with a cumulative depth of around, unusual for the region, made it an attractive target for exploration and garnered significant media attention, and before the discovery of Gliboka jama was sometimes regarded as the deepest cave in Zagorje. In July 2011, the widening of the upper passage with a rock chisel increased its explored length by, with ultimate the aim of connecting it to Voska špilja. Fox bones hinted at a buried intermediary entrance, but they were still far away from Voska špilja.Paleontology
A Cervus elaphus antler was discovered in one of the meanders, possibly brought there during a flooding episode, along with Vulpes vulpes bones in a blind passage of the upper section near a buried upper entrance.Climate
The air temperature of the cave is, and its soil temperature. Its relative humidity is 98%. Its radon concentration was measured in 2012–2013.The cave is not hydrologically active. Seepage dominates in the lower levels.