Vértessomlói Cave

Vértessomlói Cave is one of the specially protected caves of Hungary. It is the longest and third deepest cave of the Vértes Mountains. (The deepest is the Hamar Cave, the second deepest is the Dűlt-kúti water-well cave.) It is one of the two specially protected caves of the mountain range (the other is the Csákvári Cave).

Description

In the former limestone mine on the Nagy-Somlyó ÉNy side, located in the outskirts of Vértessomló within the Danube–Ipoly National Park, at the junction of the mine wall and the rubble dump, at an altitude of 235 m above sea level, the cave opens with a vertical, fissure-like entrance. The hydrothermal-origin cave was formed not in the dolomite bedrock typical of the Vértes Mountains, but in Upper Triassic Dachstein limestone, probably due to phreatic dissolution below the karst water level.

The cave’s mineralogical peculiarity is that the sheet-like barite crystals, which in Hungarian caves are observed only as speleothems or in cavity sections barely reaching cave size, in Vértessomlói Cave adorn the walls of a spacious chamber. Some of the sheet-like barite crystals reach a length of 2 cm. This outcrop layer decorates the floor and the non‑overhanging parts of the side walls over an area of several 10 m². Because the large barite crystals formed deep below the karst water level, associated with hydrothermal processes, have a cavity‑filling character, it is assumed that the cavitation is very old and that the cavitation occurred under special conditions. Future studies may shed light on the details of the crystals’ formation. The stepwise deepening cave consists of two large chambers, the narrow vertical parallel fissure passages of the entrance section, and a spacious shaft at its end. The horizontal extent of the cavity is about 30 m.

The entire cave shows a fracture system that indicates the main direction of dissolution, and in the upper parts (including the high-reaching stalagmite at the end of the lower large chamber) the fractures also determine the shape of the passages. Along this preforming fracture system the host rock is highly fractured‑brecciated, its crystalline matrix being altered, and on the walls there are locally characteristic cell‑casket boxwork structures. The cave’s morphological diversity in the upper parts has been partly modified by later dissolution‑reprecipitation processes, but the lower part clearly indicates a sub‑karst‑water‑level, phreatic origin due to its cupola‑type solution forms, spherical‑cavity fillings and small side passages ending in chambers. Here, in the lower large chamber, are the barite deposits that constitute the cave’s curiosities.

In addition to the barite crystals, the cave’s mineral deposits include a thin brown‑black coating of still unidentified composition on the surfaces of the barite crystals, small spots or pearl‑like clusters of pea‑sized stones, as well as a few small stalactites, a stalagmite flag and stalactite curtains. Near the latter, sparse water dripping can be observed, although the cave is dry. The air in the lower part of the cave contains noticeably high carbon dioxide. The fill of the floor consists of rock debris in the upper parts, clay in the lower large chamber, and several massive rock blocks spanning the deepest pit. The underside of these blocks is also filled with clay.

Summer roost for bats and an important permanent winter roost of the mountain range. The average air temperature is 10.5 °C, which is typical for Hungary, and the air carbon‑dioxide content sometimes exceeds 1.5 % in the deep section. The cave with a closed entrance can be visited only for research purposes, using electric lamps, with the permission of the Danube–Ipoly National Park Directorate. For the visit (except for the deep pit requiring rope‑technical equipment) only basic caving gear is needed. Because of the need to preserve the calm of the hibernating bats, entry into the cave is prohibited during the hibernation period (from 1 October to 30 April).

In 2001 the cave was called Vértessomlói Cave for the first time in the literature. The cave also appears in the literature under the name Slagos cat cave (Polacsek 2001), a name it received based on the suggestion of Ákos Kocsis.

Research history

The first printed news about the cave appeared in the MKBT Information Bulletin in 2001. According to the notice, during a field survey carried out by the Tatabánya Cave Research Association on 2 January 2001, the association, following the guidance of Ákos Kocsis, found a vent. The vent was discovered in the Vértes Mountains, about 800 m east‑north‑east of Vértessomló. The association members, after inspecting it, determined that they had discovered a minimally blocked cave entrance. Since Ákos Kocsis had already done some digging at the entrance and squeezed into a passage about 6–8 m long, the association members only had to widen a very narrow section, after which they could crawl through an opening into the top of a cave chamber. This chamber is about 18 m long, up to 4 m wide in places and 8 m high. Through another narrow gap, after a short digging, another chamber was revealed, whose dimensions exceed those of the previous one. According to their estimates this chamber is 20 m long and 7 m wide.

From the floor of the hall begins a shaft with a 6×2 m cross‑section. They were able to descend to the bottom of this shaft on 5 January 2001. Here debris blocks further passages. The shaft is 9 m deep, and the dome rising from the hall’s ceiling is 13 m high. The cave bears signs of karst formation, its walls are massively covered with aragonite—and even tabular overgrown barite crystals. In some places there are stalactite draperies, straw stalactites and stalactite flags. Upper Triassic Dachstein limestone is the host rock of the cave. The cave is at least 110 m long and 27 m deep, therefore it is currently the deepest cave in the Vértes Mountains, and possibly also the longest. The chamber near the entrance was named the Stalin Chamber, and the inner chamber was named the Zsófika Chamber. The cave received the name Slagos cat‑cave on the suggestion of Ákos Kocsis.