Frank Cave

Frank Cave is one of the specially protected caves of Hungary. It is located in the area of the Aggtelek National Park. Together with the other caves of the Aggtelek Karst and the Slovak Karst, the cave has been part of the World Heritage since 1995. It is one of the eight specially protected caves of Bódvaszilas. On the Lower Hill it is the only cave in which a stream flows.

Description

In Bódvaszilas, northwest of the settlement, above the Acskó spring, about 50 metres higher, on the side of a dry valley, the protected, developed and locked entrance opens with a ramp. It is located in a small quarry. No marked tourist trail leads to it, but it is not far from the tourist trail marked with a red band. This is the only Lower Hill cave whose passages formed in middle Triassic Gutenstein limestone. The entrance modestly but continuously expands into a 60‑metre‑long slope, later a stair‑like passage, which ends in a large chamber 16 metres deep.

The chamber leads to the largest chamber of the 75‑metre‑long active stream main branch. Going opposite to the stream flow, heading northwest, after a short winding passage 35 metres long, the Source siphon is reached. Initially one must walk in the main branch, then traverse above the stream. In the sandy, two‑ to four‑metre‑wide main branch heading southeast, in the direction of the stream flow, after 25 metres a suddenly descending, 12‑metre‑long and gradually lowering passage ends at the Sink siphon. From the descent, continuing in the main branch, the passage reaches a high fissure that probably comes very close to the surface, because the top of the fissure is 25 metres above the floor of the passage.

Beautiful meanders can be seen in the entrance section. A few stalactites are observable at the collapse of the main branch. Overall, little mineral deposition has formed in it. The dissolved wall surfaces and the red‑sandy fill on the floor of the passages, which hinders entry, are characteristic of the cave. Its horizontal extent is 79 metres. Bats occur in the passages. The presence of the greater horseshoe bat, the lesser horseshoe bat, the water bat and the common bat has been established in it. It is visitable by speleologists experienced in cave walking, with the permission of the Aggtelek National Park Directorate and the use of rope‑technical equipment.

Regarding its hydrology, it has a periodically active and an active part. The southern siphon is very narrow and muddy. Water enters the passages before the cave siphon through the northern siphon. In the permanently water‑bearing stream at its bottom, waters come from the Hangyás water sink opening at a line‑of‑sight distance of 450 metres and from the Bába Valley water sink No. 3 opening at a line‑of‑sight distance of 650 metres. The water sinks ensure the constant inflow of water. After 16 hours, the water flowing through the cave was detected in the Acskó spring, which emerges at less than 200 metres, by a test performed with fluorescence diluted with salicylate. In addition to the Acskó spring, it is also hydrologically connected with the Acskóréti sink and the Csörgő spring cave. Water reaches the Csörgő spring cave from the Acskóréti sink in 44 hours.

One of the eight specially protected caves of Bódvaszilas, the other seven are the Almási sink, the 2nd water‑sink cave on the Kopaszgally side, the Kopasz‑vigasz cave, the Meteor cave, the Szabó‑pallagi sink, the Széki sink and the Vecsembük sink.

The cave occurs in literature under the names Acskó-source cave (Plózer 1974), Acskói-cave (Bertalan, Kordos, Országh 1976) and Frank cave (Vlk 2019). In 1972 the cave was first called Frank-cave in the literature (Csernavölgyi 1972).

Research history

According to the 1964 Karst and Cave Research Bulletin, the Lower Acskói water collector belongs to the southern ridge line of Lower Mountain, whose water probably emerges at the Lower Acskó spring. The existence of the cave has been known since 1971. Contemporary written documents do not mention the exact date of the discovery or the circumstances of the exploration. In 1972 the Red Meteor Tectonics Cave Research Group participated in the autumn cave‑research camp led by István Szenthe, and in the subsequent weekend field trips on which the group also explored the cave. On 11 June 1973 Péter Mozsáry, Gábor Mozsáry and János Nagy tried to pass through the southern, clayey and very narrow siphon at the end point of the Main branch, but without success.

The 1973 Karst and Cave Research Bulletin published that on the plateau of Lower Mountain there is a single cave that is a stream cave. This cave is the Frank-cave. The cave’s large cross‑sectional dihexagonal quartz‑crystal deposits support the exhausted water‑collector theory. The 1974 Karst and Cave Research Bulletin states that in 1973 the Tectonics Cave Research Group, with the participation of one of its members, took part in a siphon‑swimming experiment in the explored cave. According to the publication appearing in the 1974 Karst and Cave, the active, water‑filled cave was formed in Gutenstein limestone along the E–D fault line. The water temperature is 10 °C. The water flow is small and it is close to the debris zone of the spring delta.

In 1976 Lajos Böszörményi tried, under the supervision of insurance magnates László Czakó and Géza Fodor, to swim through the cave's evening siphon. At that time, swimming against the water, he found after a muddy, very narrow 15 m long passage an air-filled chamber. After the chamber, at a water depth of 5 m, the clay on the bottom prevented further passage. In the same year Zoltán Szabó also swam through the siphon. According to the 1976 MKBT Report, light divers managed to reach 8–10 m in the siphon within the cave. This part of the cave becomes narrow and muddy at a depth of 4 m, and the ceiling collapses.