Bolha-hegyi Cave

The Bolha-hegyi Gorge Cave is one of the caves in the Danube–Ipoly National Park, located in Biatorbágy.

Description

The Bolha-hegyi Gorge Cave is situated on the edge of Biatorbágy, on the north side of the Benta stream, on the side of Bolha Hill that faces east. The cave entrance can only be noticed from up close, because it is a narrow fissure opening at the bottom of an oval (maximum 2 m diameter) depression in the soil of the grassy, sparsely shrub‑covered hill slope. Near the cave entrance, about 50° away and 50 m up the hill, there is a small stone quarry, which can already be seen from the Biatorbágy–Sóskút road.

Approaching the cave is recommended from the direction of the fishing pond next to the aforementioned road. At the fishing pond, after crossing the Benta stream, turn east at the first opportunity, then proceed (by car) through the holiday plots as far as possible. From the end of the drivable road, one can continue on foot along an old quarry road, relatively densely overgrown with vegetation, further north. After covering almost 350 m, the small stone quarry mentioned earlier becomes visible (more precisely, can be inferred) on the right‑hand (west) side.

The cavity is located in middle Miocene limestone (Tinnyei Formation). The cave entrance is a fissure that opens to the surface. After the narrow descent, one can reach the inner parts of the cave by passing through an extremely tight section. The whole cave is very fissure‑like. Towards the end there is a relatively wider (about 1.2 m) chamber with a floor composed of large stone blocks. After the chamber, the fissure flattens significantly within a few metres. The cave floor is mostly powdery, due to the relative softness of the limestone. The easily accessible cave can be explored without permission using basic caving equipment, but some passages are impassable.

In 2004 the cave was first called Bolha-hegyi-hasadékbarlang in the literature. In the literature Bolha-hegyi-hasadékbarlang also occurs under the names Bolha-hegyi-barlang (Kárpát 1990) and Bolha-hegyi-sziklahasadék (Szabó, Szabó 1989).

Research history

In a manuscript written by the Budapest Barit Caving Group in 1989 it is mentioned that the group members on April 1, 1989 discovered a tectonic, blocked small cave on the northern slope of Bolha Hill. The east‑west oriented cave is about 3 m long, about 2.5 m deep and about 40–50 cm wide. The filling in the cavity consists of sand and debris. The fissure narrows in both directions, downward as if it splits. No traces of water origin were found in the cavity. The report includes a site plan illustrating the geographical location of the Bolha-hegyi-sziklahasadék. The manuscript shows a photograph depicting the entrance of the cave. In 1990 Bolha-hegyi-hasadékbarlang was surveyed by Zoltán Szabó and Zsolt Visnyei (two members of the Acheron Caving Research Section), and using the survey the floor plan map, longitudinal section map and five cross‑section maps of Bolha-hegyi-barlang were produced. On the floor plan map, for which the east direction is indicated on the map sheet, the locations of the five cross‑sections in the cave can be seen.

In the 1990 report of the Acheron Cave Exploration Department it is mentioned that the department found a small fissure cave on Bolha Hill in Biatorbágy in 1989, which most certainly opened due to a collapse. The cave (Bolha-hegyi-barlang) has its entrance on the K side of the hill. Its funnel‑shaped entrance connects to a fissure that was only 2 m deep at the time of the cave’s discovery. In the small fissure it was initially almost impossible to move, because in one direction the wall consisted of earth fill, while in the other direction the fissure narrowed. The department members lowered the floor level by about 2 m, so the fissure became 4 m deep and its walls were spaced 1 m apart. They named this part a “luck‑mine”. In one half of the mine they found a small hole, while in the opposite direction the fissure was about 15 cm wide for about 1 m length and then suddenly widened. They tried to chisel through it, but the space proved too narrow. They did not advance far with the chiseling, but noticed that the fissure widened downward, so they deepened the floor level further.

They crawled through the narrow passage and thus found a small chamber, which they named the Secret Chamber. The chamber narrowing upward comes very close to the outer surface. It ends in a 1 m deep pit at the bottom. Its floor is filled with stone blocks and rubble. By throwing a rope into a small hole they measured a great depth, so they continued work at the hole, but the deposition of the excavated material was slow because of the narrowness. Upon a more detailed examination of the chamber, the outline of a dark opening emerged among the debris. This was unusual, because it was the first passage that was perpendicular to the previously known section. On 2 June 1990, after a short excavation they entered a 4 m long passage. The walls here were everywhere yellow, smooth and dissolved, while the ceiling was closed in slate, which had not been encountered elsewhere in the cave. They named this part of the cave Dissolved‑Stone. Since similar passages were found here, work was continued at this location.

On June 15 the floor level was lowered by half a meter. The end of the passage is very narrow and is closed by a single stone wall. To the right a narrow fissure begins, in which the stone rolls lengthwise, but its carving was found to be impossible. The possibilities for further progress in the cave were examined and it was decided that, because of the sudden widening of the Luck‑pit and the possibilities of deposition, the work would continue in the pit. Between July 29 and 31 they camped on Bolha Hill and then began to lower the floor level, but soon huge blocks of stone emerged. Lacking suitable tools, they spent the rest of the day in the cave cooling down, because outside on the barren mountain slope the thermometer rose up to 40 °C several times. During the investigation they thought that the terminal fissure could be broken through if the fissure widened in the same way as experienced in the Luck‑pit. At the individual workplace the work continued diligently, and the fissure widened.