Velebitaška jama, also known as Batinova jama or Jama na Jazbinjaku, is a karst pit cave situated on the Medvednica massif near Zagreb, Croatia. At a depth of 45 metres (148 ft) it is the deepest pit cave and the second‑deepest cave on the Medvednica massif, after the nearby Veternica system. The cave’s total surveyed length is approximately 95 metres (311 ft).
Location and Access
The entrance lies at an elevation of 417 metres (1,368 ft) above sea level on the western slope of Medvednica, about 2½ km west of the Automatizirana streljana Vrapčanski potok shooting range. The entrance opening is narrow (≈1 × 1 m) and descends through a series of chambers and vertical drops before reaching the deepest point at 372 metres (1,220 ft) above sea level. The cave is under special protection and is closed to the general public.
Physical Description
The cave’s morphology combines vertical and horizontal passages. After the initial 4 m of entrance passage the floor drops 12 m to a ledge, then a further 30 m to the bottom of the entrance chamber. From there, several narrow vertical shafts lead to a horizontal canal containing a small stream that flows southwest. The explored horizontal section extends about 51 m; beyond this, the canal narrows to 10 cm, precluding further passage without modification. Speleothems such as stalactites and stalagmites are present, though the cave is less decorated than some neighboring systems.
Discovery and Exploration
The entrance was first noted in 1971, but the small opening and blockage by rocks and soil delayed exploration. The cave was cleared and entered on 5 March 1973, with subsequent mapping by the Speleološki klub “Željezničar” and later by a team from the University of Zagreb (2019–2020) using 3‑D point‑cloud techniques. The cave has also been used for rescue‑training exercises by the Croatian Mountain Rescue Service and for caving practice by local speleological clubs.
Geology
Velebitaška jama developed in Upper Tortonian (Late Miocene) deposits comprising organogenic and bioclastic limestone, sandstone, and lime‑clay marlstone. The cave formed away from major fault lines and exhibits typical karst features, including speleothems and mud‑filled hydrologically active sections.
Climatology
The internal temperature averages 10.1 °C (50.2 °F) with relative humidity around 95 %. Airflow is minimal. Radon concentrations have been measured up to roughly 4,000 Bq m⁻³, exceeding recommended exposure limits for prolonged stays.
Protection Status
The cave is listed in the Croatian speleological register (cadastral code HR01426) and falls within the protected area of Park prirode Medvednica. Access is restricted to authorized scientific and rescue activities.
See also
- List of caves on Zagrebačka gora (Zagreb Hill)
- Veternica (cave)
- Speleology in Croatia
References derived from the Wikipedia article “Velebitaška jama” (accessed 2024).