Karst Hydrology and Physical Speleology

The formation of karst landscapes and karst hydrography is related to the occurrence of specific rocks. These must be soluble and may leave but little residue, so that the interstices widened by the processes of solution remain open, which is a prerequisite for the characteristic underground drainage.

Corrosion, used in the geomorphological sense, is the dissolution of rocks. The term chemical erosion, which used to be applied to this phenomenon, is too narrow and causes confusion because it inadequately expresses the basic processes. Today it is rarely used any more.

Superficial karst phenomena, exokarst, are created by the dissolving effects of precipitations. They are often related to karst hydrology. For this reason the reader will be given a review of such surface forms. The manifestations of exokarst are by definition corrosion forms on soluble rocks at the earth’s surface. Also belonging to this category are forms which are only indirectly the result of corrosion, e.g., collapsed dolines, dry valleys, stepped pavement karst, and poljes. The forms are classed in the following categories:

Endokarst is underground karst. It is not a primary phenomenon because sedimentation takes place without forming syngenetic cavities. Simultaneously, however, the disposition for bedding interstices (banking) is created. Reef limestones are an exception to this rule because primary cavities are formed in them during the growth of the biological reef components(bryozoa, sponges, corals). Such cavities do not belong to karst because they are not created by processes of karstification, e.g., corrosion. They can, however, be incorporated into the process of karstification and promote it (Bretz, 1960).

Hydrostatics and Hydrodynamics determine the flpw-behavior of subterranean water. Since the shape of caves and of rock surfaces defies quanrtitave description in physical or geometrical terms, hydrodynamics may only be summarily considered (for more detail see Prandtl, 1969).

Underground cavities with karst-hydrological activity percade the karstified region in a three-dimensional network. The movements of the water, especially the slow ones, are hindered only slightly so that there is a division in space, the accumulations of water below, the water-impoverishes areas above. The very dense network of interstices and narrow open joints shows a behavior of its own and will only be included in this division to a limited degree.

In the previous chapters there has again and again been a noticeable contrast between karst water and groundwater. This is a peculiarity of the German language but is nevertheless of general significance. It is a consequence of Grund’s theory of karst groundwater (1903) (see Chap. 6.2.3). Hence an investigation will be made to see whether this is really a question of contrasts. It is characteristic that many karst hydrogeologists in Germany who are concerned with useful water reserves in karst (Weidenbach, 1960; Eissele 1963; Groschopf, 1963) speak of groundwater, but that karst researchers reject this expression. Wagner (1960) writes: “Karst water is a special kind of groundwater” (p. 66).

In Europe underground karst levels were a subject of controversy for a long time. Today their existence is assured although in a few single cases it is still disputed. Swinnerton’s conception (1932) of the predominance of underground water-flow through the shallow phreatic zone supplies one of the causes of the formation of karst levels (see Chap. 6.3). It is this which explains the horizontal passages which stretch for kilometers in the Flint Mammoth Cave System in Kentucky (Gardner, 1935). Deike (1967), Miotke and Palmer (1972) have proved the relationship between this cave system and the surface morphology. The chronological identification of the underground karst level with systems of terraces on the surface in the Alps did not meet with approval from all sides. Krieg (1954, 1955) was in support of such levels and used Bock’s cave-river theory (1913) as evidence for them. This aroused intense debate in which Arnberger (1955) and Trimmel (1955) rejected both the cave-river theory and the levels as Krieg meant them, as well. Schauberger (1955) compiled the heights of all cave entrances of the greater limestone massives east of the Salzach and thereby confirmed a storeyed structure which was, however, attributed by others to petrographic causes. On the other hand Roglić (1960), who illuminated the relationship of river erosion to the karst process, failed to make any reference to a relationship between the phases of valley formation and underground karst levels. Droppa (1957) has convincingly proved that the storeyed structure is a result of phases in which the valley was deepened in the case of the Demänovské Jaskyne (Demänova Caves) in Slovakia.

Karst springs are water outlets from karst-hydrologically active cavities in water-soluble rocks, whether they are on the surface or within the earth (cave springs). There are scarcely any other characteristics which apply to them alone. The same lime contents, the same amounts of discharge and the same temperatures can be found in other springs as well. Springs emerging from rocks which are permeable, but practically insoluble and therefore nonkarstifiable (volcanic tuffs, lava, etc.) are exempted from this definition.

It may be of scientific as well as of economic interest to know the origin of a springs’s water, or where losses of water in the underground flow to. Problems arising from such questions can often not be solved directly, even though, with the help of geology, an underground catchment area is roughly comprehensible. It is not unusual that watersheds at the surface are not identical with underground watersheds. The showpiece is the Danube’s loss of water, in which case the water runs under the European watershed to flow into the Untersee near Constance and into the Rhine.

Incasion, breakdown, comprises all processes which cause the walls and ceilings of an underground cavity to break down naturally, and also as an exception the passage floor (bumps). In French the terms effondrement, éboulement, affaissement, décollement are used, in German Deckenbruch, Versturz, Einsturz, Höhlenverfall, Ablösung, Bergschlag, etc. The term incasion is derived from the Latin incadere, which means to crash into or to break into; the prefix in points out that the crashing rock falls into a cavity. Incasion is equal to the two other cave forming factors: corrosion and erosion.

Speleomorphology is cave-oriented geomorphology, the description and interpretation of the forms in the underground which are due to corrosion, erosion, and breakdown. The wealth of forms which are the result of sedimentation (see Chap. 13) are not included in it, in contrast to surface morphology which also embraces all forms due to sedimentation.

The term cave sediments embraces all clastic, organic, and chemical deposits occurring in subterranean cavities and cave entrances. They are the same three main groups as on the earth’s surface. The clastic deposits hardly differ from those on the surface. Organic and chemical sediments differ less chemically than morphographically from the corresponding ones on the surface. For cave ice refer to Chapter 16.

Speleogenetics are defined as the totality of all processes which effect the creation and development of natural underground cavities. These comprise corrosion, erosion, and incasion as have already been discussed. They are influenced by lithology, tectonics, and climate from which springs the morphological and karst-hydrological diversity of karst regions. The result is that speleogenetic theories are heavily dependent on the region studied by the author in question. Yet it can be generally stated that in karst interstices and joints are widened to form caves by the dissolution of rocks. D.C. Ford (1970) rightly questions the validity of this statement as a definition of speleogenetics, considering it to be much too general and to express too little. Other authors, mostly American, have also expressed negative opinions of general speleogenetic theories, such as White and Longyear (1962) who observed: “… the multitudinous theories are neither correct nor incorrect in the general case, they are irrelevant” (quoted by Ewers, 1972). Howard (1963) said: “… an universally applicable origin of caves is impossible unless one speaks in the vaguest and most inconsequential terms,” (p. 54). Halliday (1960) expresses it a little more mildly: “Only in the broadest terms can it be said that all limestone caves develop in the same way, and terminology which suggests that this is true should be replaced by the description of individual speleogenetic sequences,” (p. 23, Abstract).

Speleometeorology is concerned with instantaneous processes in the atmosphere of caves, speleoclimatology with their average states. However, with the exception of wind, variations in the parameters are so small that there is only a slight difference between instantaneous and average values. Therefore speleometeorology and speleoclimatology are usually used with the same meaning, apart from their differing points of view. The former is preferred in English and in German usuage (Kyrle, 1923; Myers, 1962; Wigley and Brown, 1976), the latter in French (Gèze, 1965). In Germany and Austria mining terms such as Höhlenwetter, Bewetterung and Wetterwechsel (change in wind direction) are frequently used, thus in Kyrle who defines Höhlenwetter as “the total contents of the cave in gas-form”. He supports the use of these expressions with the argument that “cave meteorology is very similar to that in mines” (p. 203).

According to definition ice caves are caves with permanent ice, even when the ice remaining in autumn is not larger than a felt hat. Caves in ice are called glacier caves. Although it may seem inconsistent, the distinction is made in this way. The primary factor is the formation of ice within the cave yet only its preservation is decisive in making an ice cave out of an ordinary cave. For the former cold winters are required, for the latter, however, cool summers in humid climates. That limits their occurrence in Central and Western Europe to the high mountains and highlands over 700 m above sea level.

The classification of underground cavities can be made on one hand according to their genesis or according to their size, or on the other hand according to striking characteristics, which is, however, quite arbitrary.