Karolina Trench Lower Shamcave

The lower subcave of Karolina Trench is one of the subcaves located in the Karolina Trench in the Visegrád Mountains of the Danube–Ipoly National Park, at Pomáz. It is also mentioned in tourist guidebooks.

Description

It is located 200 metres above the point where the Karolina Trenches merge into the Holdvilág Trench. The cavity is on the valley floor, its entrance faces south from the rock gorge. A narrow gorge segment forms the subcave.

Its rock material consists of agglomerate and tufaceous layers of various grain sizes. At the subcave the rock ledge of the valley’s intermittent stream is only 160 centimetres wide but 4–5 metres high, into which a 5‑metre‑high waterfall occasionally pours from the western side. The work of this occasional waterfall creates the subcave. Erosion has deepened its walls, and water has also rolled the rock blocks onto the top and carried away soil. Its height is 4.8 metres and its width 1.6 metres.

The entrance is lined with stone boulders, has a nearly vertical wall, and is followed by a 4.6‑metre‑long rock fissure that tapers slightly inward. On the side walls the stratification, mostly of agglomerate with less tufaceous material, is clearly observable. The rear wall is shaped by slumped detachments, making it irregular. Its average height is 4.5 metres. The floor consists of stone boulders and debris wood.

In 1984 the subcave was mentioned for the first time in literature as the lower subcave of Karolina Trench. In literature it also appears under the names Karolina Trench lower subcave (Ozoray 1963) and Karolina Trench lower cave (Eszterhás 1993).

Research History

According to the study published in 1963 in *Karst and Cave* by György Ozoray, there are a few insignificant‑sized but morphologically and origin‑wise interesting non‑karst cavities in Karolina Trench. A valley stair about 5 metres high is located a few hundred metres from the mouth of Karolina Trench. Here the upward‑narrowing, overhanging fissure is only 2–3 metres wide. The agglomerate material of the two walls is not exactly the same, but downward the tufaceous material becomes dominant and the grain size refines on both sides. The incision is almost vertically oriented. Erosion may have formed this section along a sloping rock slab.

The lower part of the upper valley stair is formed by a coarse-grained, resistant agglomerate pad. This intermittent water flow cut across the rock layer, reaching the softer layers beneath. The end of the lower level of the gorge is covered, forming a stone niche with agglomerate blocks that fell from the former waterfall wall. Genetically this shape is a semi‑cave formed by covering an erosional gorge with a scree. It is open at the front, its two sides are rock walls, also furrowed with erosional grooves. A mass of scree covers its base. Its top consists of toppled rock blocks, among which there are several cubic‑meter ones. The rear wall was created by erosion and has been altered by collapses.

Probably most of the water did not fall straight down but from the right side. Currently the semi‑cave is completely dry. The blocks, filled with soil‑clay brought in by the scree, form a small hill at the bottom of the upper valley stair. This diverts the water’s path. Instead, the water has cut a shallow rock trench only a few decimetres deep, which bypasses the semi‑cave from the west above and from the right. The semi‑cave narrows inward. We can easily walk through it inside. By walking back a little, on the right side one can slip through a narrow opening between the debris blocks and the rock.

The upper valley staircase can be reached in this way. A cross‑section map has been attached to the publication, which depicts the lower subcave of the Karolina trench and its surroundings. The map was made by Fodor Tamásné and Ozoray György. In the book Pilis guidebook published in 1967 it is written that in the foot of the vertically descending steps of the Karolina trench there are small cavities, which are filled with collapse material in a cave‑like manner. In the Pilis guidebook published in 1974, in the list of caves of the Pilis Mountains and the Visegrád Mountains (pages 19–20), it is mentioned that the cavities of the Karolina trench are located between the caves of the Pilis Mountains and the Visegrád Mountains. In the section describing the caves of the Visegrád Mountains the description mentioned in the 1967 guidebook is repeated.

In the manuscript Hungary’s Cave Register, completed in 1976 and written by Bertalan Károly, it is written that the lower subcave of the Karolina trench is in the Pilis Mountains, the Visegrád Mountains, in Pomáz, about 2.5 km east of Csobánka, in the right‑hand side subsidiary cone of the Holdvilág trench. Its entrance is a few hundred metres above the throat, at a 5 m high valley staircase. The cavity is 7 m long and 5 m high. The erosional gorge of a waterfall cut into andesite conglomerate is covered by fallen blocks. The part of the manuscript concerning the subcave was written based on three literary works.

In the national cave list of the book *Caves of Hungary* published in 1984, the phantom cave is listed as the Lower phantom cave of Karolina Trench among the caves of the Szentendre–Visegrád Mountains. Related to the list, the geographic location of the phantom cave is shown on a 1:500 000 scale map presenting the geographic positions of the caves of the Danube‑Foot Hills. In the regional bibliography section of the bibliography published in 1986 in *Karst and Cave*, the phantom cave is listed under the name Lower phantom cave of Karolina Trench. According to the compilation, one of the writings published in *Karst and Cave* deals with the phantom cave.

In István Eszterhás's manuscript *List of Hungary's Non‑Karst Caves*, prepared in 1989, it is stated that the Lower phantom cave of Karolina Trench in Pomáz, in the Visegrád Mountains, on the 4900 cave‑survey area, formed in an andesite conglomerate. The cave is 7 m long and 5 m deep. The list mentions the 220 objects (203 caves and 17 artificial cavities) created in Hungary in non‑karst rock that became known by the end of 1989. In Hungary, 14 caves have formed in andesite conglomerate. According to the compilation, László Kordos's cave list published in 1984 also includes 119 such caves that originated in non‑karst rock.