Nyereg-hegyi Cave

The Nyereg-hegyi-eresz is a cavity located on the Tihany Peninsula, within the Balaton Uplands National Park.

Description

The 60 m long, 8–10 m high geyser strip that forms the ridged spine of Nyereg Hill is situated on the Ny side at an elevation of 221 m above sea level. It is 1.5 km east of the Abbey church ruin.

Its significance is primarily due to its geological formation and scenic beauty. The rock fissure facing Ny, 22.6 m long, deepens variably, the greatest depth on the D side being 3 m with an average of 1.5 m. Its height is also variable, the highest on the D side 3.6 m, but there are places where it is only 1.5 m. The cavity volume is about 65 m³. The floor of the fissure rests on a basaltic rock slab that is 0.8–1 m higher than the road leading to it, covered thinly by breccia debris from various rocks. The geyser wall that forms the fissure leans over this stepped, locally water‑filled basaltic floor. In the É side of the fissure, at a height of 1–1.5 m, there are several dissolved cavities 1–2 m deep and varied, lace‑like prepared side forms.

The fissure formed at a rock‑type boundary, thus illustratively exposing several layers of basaltic rock as well as the geyser variations that settled on them. The general dip of the Nyereg-hegyi-eresz, affecting all rock layers, is 25–30°/105°. From bottom to top the following rock strata can be observed:

1. The fissure floor consists of layered brecciated, microlithic‑containing sandy basaltic rock. 2. In the fissure’s overhanging wall, at the bottom, there is a 30–40 cm thick layer of yellow‑gray, silty ash tuff, layered with small pebbles. 3. Above this, a 10–20 cm thick microlithic calcareous‑clay‑bound tuff. 4. A 1.5 m thick finely laminar, wavy‑layered, less clay‑rich spring limestone. 5. At the top, a 3–5 m thick cellular, porous, almost clay‑free hydroquartzite, with yellowish and violet‑reddish opal nodules.

The possibility of the rock fissure being formed by deflation was proposed by Jenő Cholnoky in 1940, but István Eszterhás's opinion is that it is not that simple, it cannot be attributed to a single genetic factor. The problem of the fissure's formation must start with the fact that every rock layer of Nyereg-hegy is inclined. This inclination is not autochthonous; originally the rocks were deposited almost horizontally, both the basalt tuffs and the geyserites. This is most illustratively demonstrated by the clayey, fine-gravel tuff layer, which could not have been deposited at an angle. In the geyserite, primarily in the upper, more porous parts, hydrometric dissolutions developed. The tilting of the rocks is probably attributable to the riss orogenic movements, when the detachment of the northern part of Nyereg-hegy may also have begun. The wind then attacked the thus exposed hollow rock fissure, eroding the less resistant clay tuff and the calcareous, laminated spring limestone. This deflation activity is further supported by freezing and thawing processes, which again exert their influence most strongly in the middle layers.

In 1983 the cavity was first called Nyereg-hegyi-eresz in the literature. The cavity appears in the literature under the names 6/1 and 6/2 caves (Eszterhás 1984), Apátgerinci stone niche (Bertalan 1958), Apáti-gerinc stone niche (Eszterhás 1984), Apáti-hegyi stone niche (Kordos 1984), Apátihegyi stone niche (Bertalan 1976), Apáti-hegy stone niche (Eszterhás 1984), Nagy-Nyereg stone niche (Eszterhás 1987), Nagy-nyereg stone niche (Eszterhás 1984), Nyereg-hegyi stone niche (Eszterhás 1984), Nyereg-hegyi rock fissure (Eszterhás 1983) and Nyereghegyi rock fissure (Bertalan 1976).

Research History

The undoubtedly very early known Nyereg-hegyi-eresz was first mentioned in 1931 by Károly Kaán according to István Eszterhás. However, a review of Károly Kaán's work finds no mention of the cavity. András Hoffer wrote a short, concise description of the cavity in 1934. In his 1940 book Jenő Cholnoky regarded the Nyereg-hegyi-eresz as a deflation cavity and this theory was adopted by several others (Károly Bertalan 1958, Ferenc Zákonyi 1958, János Örvös 1965, Károly Bertalan 1972, 1932–1974). Károly Bertalan provided its essential data. According to the description, the deflation stone niche is located at the foot of a hydroquartz rock wall on the steep northern slope of the Apáti-gerinc, on the northern part of the Tihany Peninsula.

In 1967, Árpád Halász separated two cavities from the fissure and treated them as separate cavities. In the manuscript titled *Caves of Hungary*, completed in 1976, it is written that in Tihany, on the steep southern slope of the Apáti ridge (Nyereg Hill), at an altitude of about 220 m above sea level, it is located at the foot of a rock wall of a geyser. Directly beside it runs a branch of the tourist trail. At the border of the basaltic rock and the geyser, a deflation rock cavity about 2 m long, 20 m wide and 3 m deep was formed. The part of the manuscript describing the cavity was written based on four literary works. Some guidebooks also mention it, for example the guidebook written by András Uzsoki and published in 1980.

In 1983, István Eszterhás investigated the cavity from a speleological perspective. In 1984, the book *Caves of Hungary* listed the cavity in the national cave list under the name Apáti‑hegyi‑kőfülke with the variant name Nyereghegyi sziklaeresz. Associated with the list is a 1:500 000 scale map showing the geographical location of the caves of Southern Bakony, the Balaton Highlands and the Keszthely Mountains, indicating the geographical position of the cavity. In the 1984 compilation *List of the Bakony Caves*, Nyereg‑hegyi‑eresz is the name of the cavity in the cadastral area 4463, on the Tihany Peninsula, in Tihany, which also has the names Nyereg‑hegyi‑sziklaeresz, Nyereg‑hegyi‑kőfülke, Apáti‑gerinc kőfülkéje, Apáti‑hegy kőfülkéje, Nagy‑nyereg kőfülkéje, caves 6/1 and 6/2. The post‑volcanic cavity is 22 × 3 m and 3 m high. In the 1989 special issue of *Karst and Cave*, an English‑language study (*The caves of Hungary*) reported that deflation can create rock‑fissure‑like caves. Such a cave is the Nyereg‑hegyi‑eresz located on the Tihany Peninsula. The cavity formed at the border of basaltic rock and geyser.