# Cambridge Underground 1982: Expo Cave Development

Cambridge Underground 1982 pp 15-20

## CAVE DEVELOPMENT IN THE TOTES GEBIRGE, AUSTRIA

Webeditor's note: although this article expounds theories somewhat at odds with current thinking, it does have the one great advantage of having been written down and published, something which few of the more qualified club theorists have been able to achieve. It is thus included on the site for completeness, but should probably be taken with a pinch of salt.

### INTRODUCTION

In reading through material related to this discourse I discovered reference to the writings of Cvijic, who had devoted considerable effort to the study of the extensive karst region of Jugoslavia, drawing certain conclusions as to the formation of that area, which I incorporate here as background to the area of Austria we have visited over the last few years considering its apparent similarities.

The basis for Cvijic's cycle of erosion requires three factors to be present: a thick and extensive mass of limestone, accompanied by an underlying impermeable rock for the initiation of a stream pattern.

"A study of the Totes Gebirge region (the Northern Limestone Alps), shows that it is composed mainly of Alpine Triassic and Jurassic (limestone), nonconformably overlain by paralic and largely detrital sediments of late Cretaceous and early Tertiary age (the Gosau Beds found in small scattered concentrations). The main elements of the Northern Limestone Alps are massive carbonate series of the Middle and Upper Triassic which may reach thicknesses of over one kilometre. Below and between the massive carbonate members are found thinly bedded series of shales and evaporites." The requirements seem amply fulfilled.

Cvijic's cycle then has three phases of development; in Youth the upper impermeable layer is removed by streams which then go underground through enlarged joints and fissures, the drainage pattern disintegrates, streams flow down normal valleys only to disappear into solution holes at blind ends. In Late Maturity the underground streams reach the impermeable underlying stratum and cavern roofs collapse, the limestone cover is reduced to a few outliers honeycombed with caves, and is finally removed.

In the area of the Totes Gebirge the Youth phase has been passed with almost no surface drainage now apparent, although Sonnenstrahlhöhle is an example of the result of a previous surface stream pattern which once flowed down a well defined valley into its impressive entrance chamber (partially collapsed). The surface is now generally composed of highly jointed limestone with no soil to prevent water from passing directly underground. How far the area has moved into the Mature stage is the question of greatest interest to the speleologist in the search for a deep system, a question which will be answered by continued exploration.

### DETAILED CONSIDERATION

In the two major systems discovered to date we have encountered the two forms of cave entrance in the shaft-like solution hole of Eislufthöhle, and the funnel-shaped depression of Sonnenstrahlhöhle (considered likely to be a top entrance to the Stellerweg system). In this context their relative positions on the massif are interesting (see map and section). Returning to Cvijic's erosion cycle, the original surface stream pattern formed on an impermeable layer has, in the case of Sonnenstrahlhöhle, followed a well-defined route towards the edge of the massif where it has met a weak point in the limestone structure in the form of a slip fault. The angle of the passage in this cave and Stellerweg is similar (around 60 degrees from the horizontal) and conforms to the notion of water eroding along a line of least resistance, along this fault.

In the case of Eislufthöhle the situation is rather different (refer to map, section and surveys). The cave is situated roughly centrally in a depression surrounded on three sides by steep slopes - a depression of bare, heavily-jointed limestone. During the ice age this high ground would have been covered with a permanent ice field. In this situation the erosional processes would be concentrated under the snow allowing a depression to be formed, itself enlarged into a more circular plan by the action of ablation around its edges. As the depression begins to form its development accelerates as snow becomes more readily captured in it and its permanence becomes enhanced as its bulk reduces the effects of temperature fall. As opposed to the tremendous abrading of the valley glaciers, solution becomes the dominant erosional process as meltwaters flow under the ice searching for the easiest way down to the water table. Over long periods of time a cave system is formed draining the plateau.

The position of the water table then begins to affect the formation of the cave. As long as the water table is beneath the surface, water will percolate down along the easiest route, defined by the structure of the rock itself. The actual form of the water table will itself be dependent on the permeability of the rock - small and irregular joints will form the water table into a dome shape before the pressure of water is sufficient to produce lateral movement; conversely, if the joints have been enlarged by solution (ie. a cave system exists) the water will escape rapidly producing an almost flat water table.

In Sonnenstrahlhöhle there are four levels at which horizontal cave development has occurred. The entrance series results from the direct action of the surface water in its original pre-glacial pattern flowing into the fault and searching for the easiest way down. Down in fact to the second level of horizontal activity at around 1600 metres, at which level a large chamber with side phreatic passages has formed. This is the same level as the horizontal entrance series found in Stellerweg (see surveys).

(It should be noted that the angle of the elevation for the 113 survey does not demonstrate the extent of the horizontal development. For a better picture see plan of 113, Cambridge Underground 1981.)

The series of shafts that dissect the horizontal route from above and continuing below, are the later routes formed by water percolating down from the denuded limestone surface to the much reduced water table below these abandonded upper phreatic sections. By this stage the surface drainage pattern has disappeared and the cave has become a collector of water from numerous sources rather than its original stream route. The horizontal phreatic tube 'entrance' to Stellerweg is a long-abandoned resurgence.

At 1600 metres, therefore, Sonnenstrahlhöhle has become a collector for waters searching for the water table which, following the advance of the neighbouring valley glacier, has been greatly lowered. The cave enters a vertical phase, a large shaft enlarged by spray action, until it reaches 1500 metres at a very jagged broken floor with an immature stream outlet and a small meandering phreatic tube opening once more onto an enormous shaft section - this has no apparent equivalent in Stellerweg (perhaps it can be attributed to a localised change in the character of the rock). The termination of the next vertical section is, however, directly reflected in Stellerweg at 1400 metres. There is considerable horizontal development in Stellerweg at this level which has not been explored as yet, but suggests the possibility of a link with Sonnenstrahlhöhle because of the abandoned phreatic development evident there also and an apparent continuation of that section, unfortunately blocked by boulders at present. The complex phreatic entrance series to 115 is also located at this level. This is obviously the level of the water table following the first major invasion of ice in this area. The large, now abandoned, phreatic cave passages developed during a period of stability during and after the retreat of the ice, emerging as tubes of varying sizes from the valley sides. These holes are, however, now perched several hundred metres up the sheer slopes. Following a further advance of the ice which brought about a further severe reduction of the valley floor and thus the water table, in Stellerweg and 115 we find a further phreatic level developed extensively at 1200 metres, at which a tortuous streamway meanders at a gentle incline before descending in a further series of pitches.

It is interesting to make a comparison between these closely related caves, and it is also interesting to note (see map, section and surveys) the apparent direct relationship of the development of Eislufthöhle to the features of the caves at the edge of the massif some two kilometres away to the north. It is clear that Eislufthöhle has a level of horizontal, if not distinctly phreatic, development at around 1400 metres - the same as in Stellerweg and Sonnenstrahlhöhle. If these levels defining stages of development of the caves correspond directly, the resultant very flat water table suggests a veritable network of caves sending water rushing away to the edges of the limestone. Further the level of the sump in Eislufthöhle compares with the phreatic level around 1200 metres in Stellerweg.

### CONCLUSIONS

The indications are that, considering its close proximity and similarity of development to Stellerweg, Sonnenstrahlhöhle should continue to a depth approaching that of Stellerweg and may well join it. The doubts raised are whether the next section, the first in fact in the cave, of wet and awkward streamway will lead to the head of a shaft, as has already happened in Stellerweg. Clearly the streamway does not end immediately as it did not back up in its constricted passage in flood conditions, and there was still a strong draught at this level. With progress down to this point being relatively straightforward, a further visit seems imperative.

The question of Eislufthöhle is an interesting one. Depending on the point of view, two different conclusions may be drawn: if the cave ends at 1150 metres, the water table is domed and there will be no hope of deeper caves in that area. If the development of the cave is directly related to the falls in the water-table as seen in Stellerweg then the water table is very flat and further depth should be possible, the sump therefore being a perched one. Reference to the other major discoveries in the area and the levels at which they terminate (see surveys) suggests, tantalisingly, that it is only a question of finding a way through an apparent end, no matter how obscure (as demonstrated on two occasions in Sonnenstrahlhöhle). Other routes in Eislufthöhle have never been pushed to a conclusion, but will anyone ever go back?

Any comment on the state of Stellerweg may seem obvious, however it would seem likely that a further 200 metres should be added to its depth (down to the neighbouring lake level of 712 metres). The extent of the phreatic development threatens to be vast, the hillside quite honeycombed with cave passage (as predicted in Cvijic's erosion cycle). If the water table is flat, there should be passages heading away into the mountain, carrying the waters from the plateau.

Finally, the intriguing question of cave draughts often raised its head in discussion in Austria. Almost all the caves that we have explored in the area have had powerful draughts emanating from the entrance; Sonnenstrahlhöhle, however, had a distinct inward draught at the entrance, reverting to outward at around the 1600 metre level. In winter, the cave apparently sends clouds of snow billowing up from the entrance as the relatively warm cave air rises (as substantiated by our local contact on a ski trip). It would be expected that the other entrances draught inwards in winter as the air is drawn up through the cave system. The obvious conclusion is that Sonnenstrahlhöhle is the top entrance to the whole system. If this is the case and Sonnenstrahlhöhle can be connected to the Stellerweg system, there is the possibility of achieving a 1000 metre cave - unless fears of the cave joining Nagelsteghöhle prove justified.

#### REFERENCES

Studies in Physical Geography, ed. K.J. Gregory, Dawson Publishing
Periglacial Processes and Environments, A.L. Washburn, Arnold
The Geology of Western Europe, M.G. Rutten, Elsevier
Jurassic Environments, A. Hallam, Cambridge Earth Science Series
Geomorphology and Climate, ed. E. Derbyshire, John Wiley and Sons
Weathering, Geomorphology, Text 2, C.D. Ollier
Structural Geomorphology, J. Tricart
Geomorphology, B.W. Sparks, Longman

For detailed surveys see Cambridge Underground from 1978 onwards, which will give more details of the caves mentioned above as well as other smaller discoveries.

Tony Malcolm

- Cambridge Underground 1982 Table of Contents
- 1981 Expedition info:
  - Expo report, Cambridge Underground 1982
  - Logbook
  - BCRA Caves & Caving Report
- Index to all publications
- Back to Expeditions intro page
- CUCC Home Page