mirror of
https://expo.survex.com/repositories/expoweb/.git/
synced 2024-11-23 07:41:56 +00:00
267 lines
15 KiB
HTML
Executable File
267 lines
15 KiB
HTML
Executable File
<!DOCTYPE html>
|
|
<html>
|
|
<!-- NB the report was all one CTS ref. but has had to be split to
|
|
accommodate the graphics... -->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>Cambridge Underground 1982: Expo Cave Development</title>
|
|
<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
|
|
</head>
|
|
<body>
|
|
<center><font size=-1>Cambridge Underground 1982 pp 15-20</font>
|
|
<h1>Loser Plateau: Geology and Speleogenesis</h1>
|
|
|
|
<h2>CAVE DEVELOPMENT IN THE TOTES GEBIRGE, AUSTRIA</h2></center>
|
|
|
|
<p><font size=-1>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.</font>
|
|
<hr>
|
|
<p>Locally-hosted copies of extensive archive of geology and cave formation papers:
|
|
<ul>
|
|
<li><a href="/expofiles/documents/cave_science_articles/structural-geology/">
|
|
Structural geology</a>
|
|
<li><a href="/expofiles/documents/cave_science_articles/speleogenesis/">
|
|
Speleogenesis</a>
|
|
<li><a href="/expofiles/documents/cave_science_articles/landscape-evolution-paleoclimate/">
|
|
Paleoclimate and landscape</a>
|
|
<li><a href="/expofiles/documents/cave_science_articles/">
|
|
Other cave science articles</a>
|
|
<li><a href="/expofiles/documents/cave_science_articles/german-stuff/">
|
|
(papers in German)</a>
|
|
</ul>
|
|
<h3>INTRODUCTION</h3>
|
|
|
|
<p>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.
|
|
|
|
<p>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.
|
|
|
|
<p>"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.
|
|
|
|
<p>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.
|
|
|
|
<p>In the area of the Totes Gebirge the Youth phase has been passed with
|
|
almost no surface drainage now apparent, although
|
|
<b lang=de>Sonnenstrahlhöhle</b> 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.
|
|
|
|
<h3>DETAILED CONSIDERATION</h3>
|
|
|
|
<p>In the two major systems discovered to date we have encountered the two
|
|
forms of cave entrance in the shaft-like solution hole of
|
|
<b lang=de>Eislufthöhle,</b> and the funnel-shaped depression of
|
|
<b lang=de>Sonnenstrahlhöhle</b> (considered likely to be a top entrance
|
|
to the <b lang=de>Stellerweg</b> system). In this context their relative
|
|
positions on the massif are interesting (see <a href="tmmap.htm">map and
|
|
section</a>). Returning to Cvijic's erosion cycle, the
|
|
original surface stream pattern formed on an impermeable layer has, in the
|
|
case of <b lang=de>Sonnenstrahlhöhle</b>, 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 <b lang=de>Stellerweg</b> 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.
|
|
|
|
<p>In the case of <b lang=de>Eislufthöhle</b> the situation is rather
|
|
different (refer to <a href="tmmap.htm">map, section</a> and
|
|
<a href="tmelev.htm">surveys</a>). 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.
|
|
|
|
<p>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.
|
|
|
|
<p>In <b lang=de>Sonnenstrahlhöhle</b> 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
|
|
<b lang=de>Stellerweg</b> (see <a href="tmelev.htm">surveys</a>).
|
|
|
|
<p>(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.)
|
|
|
|
<p>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.
|
|
|
|
<p>At 1600 metres, therefore, <b lang=de>Sonnenstrahlhöhle</b> 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
|
|
<b lang=de>Stellerweg</b> (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 <b lang=de>Stellerweg</b> at 1400 metres.
|
|
There is considerable horizontal development in <b lang=de>Stellerweg</b> at
|
|
this level which has not been explored as yet, but suggests the possibility
|
|
of a link with <b lang=de>Sonnenstrahlhöhle</b> 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.
|
|
|
|
<p>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
|
|
<b lang=de>Eislufthöhle</b> to the features of the caves at the edge of
|
|
the massif some two kilometres away to the north. It is clear that
|
|
<b lang=de>Eislufthöhle</b> has a level of horizontal, if not distinctly
|
|
phreatic, development at around 1400 metres - the same as in
|
|
<b lang=de>Stellerweg</b> and <b lang=de>Sonnenstrahlhöhle</b>. 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 <b lang=de>Eislufthöhle</b> compares with the phreatic level
|
|
around 1200 metres in <b lang=de>Stellerweg</b>.
|
|
|
|
<h3>CONCLUSIONS</h3>
|
|
|
|
<p>The indications are that, considering its close proximity and similarity
|
|
of development to <b lang=de>Stellerweg, Sonnenstrahlhöhle</b> should
|
|
continue to a depth approaching that of <b lang=de>Stellerweg</b> 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 <b lang=de>Stellerweg</b>. 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.
|
|
|
|
<p>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 <b lang=de>Stellerweg</b> 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
|
|
<b lang=de>Sonnenstrahlhöhle</b>). Other routes in
|
|
<b lang=de>Eislufthöhle</b> have never been pushed to a conclusion, but
|
|
will anyone ever go back?
|
|
|
|
<p>Any comment on the state of <b lang=de>Stellerweg</b> 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.
|
|
|
|
<p>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;
|
|
<b lang=de>Sonnenstrahlhöhle</b>, 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 <b lang=de>Sonnenstrahlhöhle</b>
|
|
is the top entrance to the whole system. If this is the case and
|
|
<b lang=de>Sonnenstrahlhöhle</b> can be connected to the
|
|
<b lang=de>Stellerweg</b> system, there is the possibility of
|
|
achieving a 1000 metre cave - unless fears of the cave joining
|
|
<b lang=de>Nagelsteghöhle</b> prove justified.
|
|
|
|
<h4>REFERENCES</h4>
|
|
|
|
<p>Studies in Physical Geography, ed. K.J. Gregory, Dawson Publishing<br />
|
|
Periglacial Processes and Environments, A.L. Washburn, Arnold<br />
|
|
The Geology of Western Europe, M.G. Rutten, Elsevier<br />
|
|
Jurassic Environments, A. Hallam, Cambridge Earth Science Series<br />
|
|
Geomorphology and Climate, ed. E. Derbyshire, John Wiley and Sons<br />
|
|
Weathering, Geomorphology, Text 2, C.D. Ollier<br />
|
|
Structural Geomorphology, J. Tricart<br />
|
|
Geomorphology, B.W. Sparks, Longman
|
|
|
|
<p>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.
|
|
|
|
<p align=right>Tony Malcolm
|
|
|
|
<hr />
|
|
Link to <a href="https://en.wikipedia.org/wiki/Eastern_Alps">Wikipedia: Eastern Alps Geology</a>.
|
|
<br />
|
|
Link to <a href="geolog2.htm">Anonymous Geological Outline (2015?)</a>.
|
|
<br />
|
|
Link to <a href="years/1987/geolog.htm">Jared's Geological Guide (1988)</a>.
|
|
<br />
|
|
Link to <a href="years/1981/cavdev.htm">Tony Malcolm's Geological Guide (1982)</a>.
|
|
<br />
|
|
Link to <a href="https://onrappel.blogspot.com/2018/05/dachstein-massif-geology-intro.html">Excellent long article on Dachsteinkalk</a>
|
|
<hr />
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|