Glacières; or, Freezing Caverns

Taluses and Boulder Heaps.—Taluses and broken debris, and in general boulder heaps of all sorts, have interstices and openings between the boulders, and in these it occasionally happens that ice is found. This is most common among the taluses at the base of cliffs, but in some cases ice is found among broken rocks on the sides of gently sloping hills, or even on the plateaus of their summits. Sometimes the ice and snow on the bottom of rock gorges all melts away, while further down, in the hollows of the boulders forming the floor, ice still remains. The rocks of which these ice bearing taluses are formed are generally gneiss, granite, limestone, sandstone, basalt or porphyry. Among such boulder taluses the phenomenon designated as Windröhren or Ventarolen, that is, windholes, is frequently found. Sometimes the air among such boulder formations is quiet, but as a general thing draughts pour out at the lower openings during the hot months, and blow into them during the cold ones.

Freezing Wells, Mines and Tunnels.—Subterranean ice is also found in certain places in connection with man’s handiwork. In a few wells in the United States, the temperature in winter becomes abnormally low, and for four or five months these wells freeze up and become useless. A case of a freezing well was recently observed near la Ferté Milon in Central France.[23] Ice is reported also as forming in various mines in Europe, Asia and America; in fact, it is not an uncommon occurrence. Occasionally, also, ice forms in tunnels.

Cold Caves.—Caves with abnormally low temperatures may be divided into two classes. First, caves where the temperatures are lower than the normal, without becoming low enough for ice to form; and second, caves where the temperatures sink so low, that ice forms.

Caves where the temperatures sink below the normal, but in which ice does not form either in winter or in summer, are found in several places in different parts of the world. They are termed in French cavernes froides and in German kalte höhlen. There are but few data from reliable observers about such cold caves. Some descriptions are given without thermometric measurements, and the statements that the caves are cold, mean nothing beyond the fact that they feel colder than the outside air. It is, however, conclusively proved that cold caves exist, and that while they are not freezing caverns, yet that they have a temperature lower than the mean annual temperature of their district. In fact, the assumption, which had passed into an axiom, that caves always have the same temperatures as the mean annual temperature of the district, must certainly be given up. Cold caves are generally in one of two shapes: 1, in the shape of a sand glass,—two cones above each other meeting at the narrowest point—where the upper cone lets the heavy cold air descend easily, while the lower bell shaped cone prevents its escape; and 2, where two sink holes open into one pit, which is in the shape of a bell.[24]

Glacière Caves or Freezing Caves.—Caves where the temperatures sink so low that ice is able to form, are found in many different rock formations and in various positions, shapes and sizes. The rock formation of freezing caverns is generally limestone, but sometimes it is marble, lava, basalt, gneiss or granite. In all cases, however, the rock is either porous or else it is broken and fissured, as otherwise the water supply necessary to the formation of ice could not find its way in.

Glacière caverns may, for the sake of convenience, be classified into several classes, according to their position or to their form. The lines of transition between them, however, are so indefinite in nature, that it is often difficult to specify a cavern as belonging to any special type. The most important factor in classifying glacière caves is their position. Under this head there are two main divisions: first, pit caves; second, cliff caves.

Pit caves are those where a pit or pits open into the ground, and the ice is found at the bottom. Sometimes there is no roof, when the place may be called a gorge: this occurs at Ellenville, where the roof has fallen. Again, the pit itself is more or less roofed over and the ice is found mainly or wholly under the roof: this is the case at Haut d’Aviernoz, at the Friedrichsteinerhöhle, at Saint-Livres, and at Saint-Georges. Sometimes the pit takes the form of a descending tunnel, leading into a hall or chamber, in which the ice lies under a rock roof: this happens at Chaux-les-Passavant. In all these pit caves the body of the cave is below the entrance, and most of them are fairly well lighted by daylight throughout. Generally there is only one pit, but occasionally there are two connected underground, as is the case at La Genollière.

Cliff caves are those where the entrance is at the base or in the side of a cliff. Frequently the cave is in the shape of a hall or chamber, which begins directly at the entrance, and which may be large or small. This kind always has a down slope directly from the mouth. The Kolowratshöhle, Dóbsina and the Grand Cave de Montarquis may be mentioned as examples. In some cases there is a pit at the base of a cliff and there is a slope leading down to the cave, somewhat in the form of a tunnel: this is the case at Manchester and practically also at Roth. Again there is a more or less long gallery between the entrance and the glacière, which is always below the level of the entrance. The Schafloch, Démenyfálva and Decorah may be cited as examples. As a rule the gallery slopes down from the entrance, but sometimes the floor rises and then sinks to the glacière. The top of the entrance, however, is always higher than the highest point of the floor, as otherwise the cold air could not get in. This is the case at the Frauenmauerhöhle, and, apparently, also at the Posselthöhle. In one case, at Amarnath in Kashmere, the floor is said to rise to the roof at the back; but as the entrance is nearly as big as the floor area, the ice formations must also be below the level of the top of the entrance.

The dimensions of glacière caves vary greatly. Some are large, others are small. Saint Georges, a roofed pit cave, is some twenty-five meters by twelve meters, with a depth of about twelve meters. Chaux-les-Passavant, a cave at the end of a pit tunnel, has a diameter of some twenty-seven meters. The measures of Dóbsina, a cave at the bottom of a cliff, are given as follows: Height of roof above ice floor, 10 to 11 meters; length 120 meters; breadth, 35 to 60 meters, and surface about 4644 meters. The Frauenmauerhöhle is a gallery about one hundred meters long before the ice floor is reached, and this is some fifty meters more in length by about seven meters in width. The glacière cave near Frain, on the contrary, is so small that one can only crawl in some two or three meters. In fact, glacière caves vary in size between great halls and little tunnels where one cannot stand up straight.

The entrances of glacière caves also vary greatly in their dimensions. For instance, the Friedrichsteinerhöhle is on one side of a huge pit and is as large and deep as the pit. Saint Georges, on the contrary, has, near one end of the roof, a couple of holes, some three meters in diameter. The entrance to the Schafloch is four meters wide by four meters seventy centimeters high, while the entrance to Roth is not over one meter each way.

A classification of subterranean ice formations, and one which applies to all the different forms, is into permanent and periodic glacières. When in any underground spot, ice remains throughout the year, the place may be called a permanent glacière; when on the contrary the ice melts away for part of the year, the place may be called a periodic glacière. This classification, which several observers have used already, is convenient and valuable.

Movements of Air.—Another classification of glacières can be made in accordance with the movements of air underground. Glacières may be divided into those where there are no strong draughts in summer and those where there are draughts: or into “apparently static caves”; and “dynamic caves” or “windholes.” The first class includes those caves where there is one or more openings close together and those above the body of the cave. In such hollows the air in summer is nearly still, while in winter there are distinct rotary movements of the air as soon as the temperature outside is lower than that within. Almost all glacière caves belong to this class of caves without strong draughts in summer. Sometimes, however, ice is found in hollows where there are two or more openings, at different altitudes and at different ends of the hollow, and where there are draughts. Occasionally, also, there are fissures in the sides or rear of apparently static caves, which allow something like draughts at times, as is the case at the Grand Cave de Montarquis.

Professor Thury of Geneva coined the terms “static cave” and “dynamic cave” which have come largely into use since, and which practically correspond to the German terms eishöhle and windröhre. I do not think the term “static cave” accurate, and prefer the term “apparently static cave” or “cave without distinct draughts.” For although there are many caves where the air seems stagnant at times, and there are no distinct perceptible draughts, still that the air is really stagnant all summer appears to me doubtful, and it seems as if the movements of air were distinctly apparent only in certain caves and not in others. Air which is apparently stagnant is found in both pit and cliff caves mainly in the summer months, but even in these I have noticed several times in summer slight movements of air, especially near the entrance. I could not exactly feel the air moving, but by lighting a cigar the smoke could be seen borne outwards exceedingly slowly. At the entrance of the Kolowratshöhle I think there was a faint outward current when I was there. The day was hot and windless, and as the cold air met the hot outside air it formed a faint cloud or mist at the mouth of the cavern. At Saint-Georges, although the air seemed tranquil, I found that the smoke of my cigar ascended rapidly just below the hole in the roof, showing an ascending air current. In the double cave of Chapuis, I found one cavern filled by a little lake over which there was a draught.[25]

From the few winter observations we have, there can be no doubt that in winter the movements of the atmosphere are lively, the break in the air column occurring as soon as the outside temperature is lower than that within, when the outer air immediately begins to sink into the cave.[26]

If I have doubts as to the existence of absolutely static caves, it is different about dynamic caves. When a subterranean hollow goes through rocks, with one opening higher than the other, there will surely be distinct draughts. These dynamic caves exist in many parts of the world under such names as cold current caves or blowing caves or windholes. Sometimes they are fissures in broken limestone. Often they are the cracks between piles of boulders. A cool air generally pours from the lower opening in summer while the cold air pours into it in winter, the draught being then reversed. At the upper opening the operation takes place in the opposite way, the hot air being sucked in in summer, and given out in winter. Sometimes, however, changes take place, according to the differences in the outside temperature, in the direction of the air current in the course of a single day.

The causes of the movements of air in these windholes are exceedingly simple. The movements of air depend on the fact that in summer the air in the tube becomes colder from contact with the rocks and, therefore, heavier than the air outside, and by gravity the heavy inside air displaces the lighter outside air and comes rushing out at the lower opening. This leaves a vacuum, which is filled by the warmer air dropping into the tube from above. In winter on the contrary, the air within the tube is warmed by contact with the rocks and becomes lighter than the air outside. It, therefore, rises and streams out from the upper opening, and the vacuum is filled by the heavy cold air pushing in at the lower opening.

G. F. Parrot’s[27] explanation is so satisfactory that I give it with one or two changes. He considers the air movements an ordinary statical phenomenon of the air, in caves which have two openings at different altitudes. Let E G D represent the section of such a cave with the openings A and B. Let us think that there are over C and B two vertical air columns and from B to C a horizontal air column B C; then the two air columns over B and C are at all times of the year equal in weight. Not so the air columns A C and A E G D B, because their temperatures are different. Assume the temperature in the cave G is +12° the whole year round. If in summer the air column A C is at a temperature of +25°, then the heavy air in the cave G pours out through A and is replaced by air flowing in through B. If in winter the air column A C is at a temperature of -1°, then the air pours with equal inverse velocity at A into the cave, and out at B. The velocity of the current in both cases depends on the difference of temperature within and without.

The foregoing explanation makes it evident that the movements of air in these windholes do not depend on the presence of ice. In many of those I have examined myself there was no ice visible, and from the temperature of the air current, there could not have been any ice within the mountain. Still, there are numerous cases where ice is found in windholes among boulders, and a few cases where windholes exist in connection with apparently static glacière caves. Undoubtedly the great majority of windholes do not contain ice in summer, or, indeed, at any time of the year, and, as far as I can see, windholes, according to their temperatures, belong rather to the class of normal caves than to that of glacières.

Forms of Ice.—Almost all the forms assumed by underground ice are different from those assumed by overground ice. This is not surprising, as the conditions, under which the ice is formed, are so different. Almost all the lines of underground ice are rounded. The sharp angles and fractures visible on glacier or iceberg are absent. Instead of seracs and crevasses, broken ice falls, or piled up ice floes, we have hanging stalactites and rising stalagmites, smooth ice floors and curved ice slopes. This difference is of course due to the fact that most subterranean ice is formed from the drip from the roof or the sides of caves, and because the factor of motion—which plays so large a part in the shaping by fracture of overground ice—is practically wanting.

The most striking forms of subterranean ice are the ice stalactites and stalagmites. They descend from the roof as icicles or rise from it as rough cones or pyramids. The icicles are of all sorts of shapes and sizes: sometimes they are tiny; sometimes they grow downward till they reach the floor and form regular columns, in some cases no less than eleven meters in height.

The ice stalagmites likewise are of all sorts of shapes and sizes, some of them growing to a height of seven or eight meters. Occasionally they have hollow bases, but this is rare. How these hollow cones are formed is a still uncertain matter; but it is in some way by the action of the drip. At the Kolowratshöhle I saw the drip from the roof cutting out in July the basin, whose tall remaining sides suggested that early in the spring it was probably a hollow cone. The cone at the Schafloch of which I saw one half remaining, could only be accounted for by some action from the drip.[28] The warmth of the rock floor may help perhaps also, in melting away some of the base of the hollow columns.

The frozen waterfalls which issue from fissures in the rock walls of caves are another form of ice seen only below ground. For lack of a better name, I call them fissure columns. A peculiarity of these is that, while the rock fissure is more or less rectangular or at least sharp angled, the ice column issues in a rounded stream. Sometimes these fissure columns stream over the rock; sometimes they spring out far enough from the rock to be quite away from it. They vary from about one to five meters in height, and at the base they almost always spread out in a shape resembling that of a fan.

The ice on the bottom of caverns of course takes its shape from the form and angles of the floor of the caves. If the bottom is level or nearly so, the ice lies on it as a sheet or floor. If the bottom of the cave is sloping, the ice follows the angles of the slope, forming an ice slope or ice wall, and sometimes becoming nearly or quite vertical. These ice slopes distantly resemble the portions of glaciers called an ice fall, with the great difference, however, that there are no crevasses, not even tiny ones.

Occasionally, slabs of ice are found reposing in a fractured sheet over a solid ice floor. This means that a lake has formed on this spot in the spring, frozen over, and then run off, leaving its frozen surface in broken pieces on top of the under ice.

Another kind of frozen water is the hoar frost which forms on the rock roofs and walls. This is not at all rare. It is an open question whether this is not the same thing as that which has been described as subterranean snow.[29] I found myself in Dóbsina a small sheet of what to look and touch was snow. I wrote of this as snow in my first paper about glacières[30], but I am of the opinion now that it was the hoar frost detached from the roof and not genuine snow.

At Dóbsina, also, I noticed that the ice of the ice wall of the Korridor assumed a stratified or laminated form. Mr. John F. Lewis of Philadelphia suggested to me that this was probably due to a precipitation of the hoar frost from the roof, and I think his explanation is correct. The hoar frost forming at a certain degree of cold, would doubtless be precipitated at a rise of temperature, and would then act much as do the different layers of snow in the upper portion of glaciers.[31] It would consolidate gradually, layer over layer, and form strata, producing the banded or laminated structure visible in the vertical ice of the Dóbsina Korridor.

The ice in caverns is sometimes found with a structure which is, I believe, of rare occurrence above ground. This is when it takes the shape known as prismatic ice, which means that if a lump is broken from a column or icicle, the fracture will show regular prisms. This phenomenon is not as yet satisfactorily accounted for; the only thing certain about it is, that it does not occur in ice of recent formation. From my own observations, I should say that ice became prismatic at the end of summer; at least I have always found it in August or September rather than in June or July.[32]

Besides building up ice heaps, the drip, also, has the function of destroying its own creations. If there are no crevasses, there are holes and runnels. These are generally found at or leading to the lowest point of the ice floor. Occasionally the holes are deep, sometimes many meters in depth. They are certainly cut out by the melting water, to which they offer an exit; in fact they are a part of the drainage system present in all glacière caves, where there must be some outlet for surplus water at or near the lowest point: and as the caves are always in porous or broken rock, the drainage takes place through the cracks and fissures.

The drip produces also the exact opposite of pyramids in the shape of ice basins. These are cut in the floor by an extra strong drip from the roof at those spots. Basins exactly like these are not seen on glaciers. Not infrequently they are full of water of considerable depth.

Lakes and pools are found in glacière caves. Sometimes they are on the ice floor, and in this case they are due either to rain-water collecting faster than it can flow off, or else because the cave is in a state of thaw. Sometimes these pools are among the rocks in one part of a cave, while the ice is in another part.

I have said above that motion in subterranean ice is practically wanting. This is proved by the lack of crevasses on the ice slopes or ice walls, and also by the fact that basins and cones appear year after year in the same spots, where they remain whether they are increasing or diminishing. But this statement cannot be held to cover the entrance snow and ice slopes of some of the open pit caves such as the Gottscheer cave, or Saint-Livres or Haut d’Aviernoz. Here the snow, which falls on the entrance slope, must gradually gravitate to the bottom. The question is whether it only descends in the shape of water after melting or as snow before solidifying; or whether it ever slides down at all after becoming somewhat solidified. Probably, however, the ice of these slopes, judging from the fact that crevasses are entirely lacking, remains stationary.

Color Effects.—The color effect of every glacière cavern has a certain individuality, according to the color of the rocks, the quantity of ice, and the amount of daylight admitted through the entrance. In my opinion, the white note given by the ice, makes a fine glacière cave the most beautiful of all subterranean hollows. In this respect it seems to me that they are similar to high Alps, which are certainly most impressive with coverings of snow and glacier.

There are, however, two distinct notes in the color effects of glacière caves and these may be described as the partly subterranean, or as the wholly subterranean. In the former case the local tints stand out more clearly. For instance, at the Kolowratshöhle the ice is beautifully transparent and of a pale ochre-greenish hue: the limestone rocks are streaked with iron, and thus have a reddish hue, while, owing to the entrance admitting plenty of daylight, the effect is only semi-subterranean. Again, at Chaux-les-Passavant plenty of daylight is admitted: the rocks are a yellowish brown, and the ice is white and blue. At the Schafloch or the Frauenmauer, on the contrary, the effect is wholly subterranean: daylight is so completely absent that black is the predominating note, the ice itself looking gray. Dóbsina is an exception, as, thanks to the electric light, white is the conspicuous tone, even though rocks and shadows dull many places and corners into a sombre gray.

More than once, on returning to daylight from the intense blackness of a cave, I have seen the rocks near the entrance appear a dark blue color, exactly simulating moonlight. This effect is common to both glacière caves and ordinary caverns. It is a striking but rare phenomenon, and depends apparently on the shape of the cave. This moonlight effect only seems to occur when a cave makes an elbow directly after the mouth and then goes straight for some distance. When the daylight is actually in sight, the moonlight impression vanishes.

Carbonic Acid Gas.—Carbonic acid gas, judging from the most recent explorations, is more of a rarity in rock caves with normal temperatures than is generally supposed. There appears to be only one case on record where this gas was observed in a cold cave. This was in the Creux-de-Souci,[33] which is rather a cold than a freezing cavern, but which on one occasion was found to contain snow, and whose temperature is always extremely low. From the present state of knowledge, therefore, it may be assumed that if carbonic acid gas does form in glacière caves, it does so only seldom.

Fauna.—No attention whatever has been paid, practically as yet, as to whether any distinctive animal life exists in glacières. So far, I have seen none myself. The Rev. G. F. Browne, in four instances, found a large red-brown fly nearly an inch long, which is supposed to be Stenophylax Hieroglyphicus of Stephens; and at Chapuis, he obtained an ichneumon of the genus Paniscus. At Font d’Urle, Monsieur Villard captured a blind specimen of a coleoptera, Cytodromus dapsoïdes. A variety of rotifer, Notholca longispina, is now living in the Creux-de-Souci. In Skerisora, remains of bats have been found, not very different from those now living in the neighborhood.[34] It is, in any case, certainly remarkable that the same kind of fly should have been discovered in several glacières in different localities; and it may some day be shown that there is a special insect fauna. Certainly the subject is worth investigating.[35]

Flora.—The flora of glacières has been as little observed as the fauna. There are scarcely any references to such a thing as glacière plant life in literature. Whether there is a special flora in any glacière cave is still an open question. In the cases of several boulder taluses, there is no doubt that, even if there is not a special flora, at least that the plants near the ice beds are greatly retarded every year in their development. Probably the flora among the boulders blooms a month or six weeks later than the flora in the immediate vicinity. In the cases of the Cave of Paradana and of the Kuntschner Eishöhle it is reported that the plant life becomes more and more arctic in character towards the bottom of the pit.[36]

Paleontology.—No paleontological remains have as yet been reported from glacière caves. No bones of animals have been found, except those of bats in Skerisora[37] and a few of the common genus bos.[38] No relics of the handiwork of man have been discovered; nor, indeed, with the exception of the skeletons found in the cave of Yeermallik in Kondooz,[39] anything which reveals the presence of man in glacières or that they were ever used for habitation. The reason that there are so few remains in glacière caves is undoubtedly because their temperatures are too low for their occupation by animal or man; but, from the evidence afforded by their non-occupation, may be drawn the valuable inference that the glacière caves of to-day were glacière caves long ago.

Legends and Religion.—There are scarcely any legends connected with glacières. I know only of one about one of the caves of the Mont Parmelan.[40] Nor does there seem to be any reference to glacière caves in works of fiction. Dante makes his last hell full of an ice lake, but an attentive perusal fails to reveal a single line which in any way describes or suggests a glacière. In at least two cases,[41] however, the ice in caves is connected with religion, as in Kashmere, the Hindoos, and in Arizona, the Zuni Indians, either worship or pray at glacière caves, overawed, from some mystical feeling, by the permanence of the ice formations which they connect with their deities.

II.

The cause of the formation of subterranean ice is undoubtedly one of the most intricate problems in connection with caverns. Various theories have been advanced why ice is found in certain caves and not in others. Some writers have held that it is a remnant of a glacial period; others that it is owing to the presence of salts in the rocks; some have said that it is due to the rocks retarding waves of heat and cold; and still others think that it is formed by pressure on the percolating waters. Many of these theories were formulated in explanation of the belief of peasants living near the caves, who almost always say that the ice is formed in summer and melts in winter. Most scientific observers on the other hand claim that the ice is due to the cold of winter, and a few think that it is formed or helped by draughts and by evaporation and expansion of the air. The variety of opinions put forth, show at any rate the intricacy of the problem.

All my own observations have tended more and more to make me believe that the cold of winter is the cause of the ice. Before elaborating my own views, however, I wish to take up seriatim the theories which have been formulated, principally in explanation of the belief that the ice was a summer product, and to give my reasons for my disbelief in them.

Glacial Period.—The first theory, perhaps, to touch on, is the one that the ice is a remnant of a glacial period. This seems to occur to many persons as a solution of the question when they first hear of glacières, and it has been several times propounded to me, and naturally enough, always by scientific men.[42] Still I do not think it has ever been held by anyone who had made a study of glacières.

The theory is, indeed, untenable in regard to freezing caves, as it does not accord with the observed facts of the yearly disappearance of the ice in many caves and taluses. At Szilize every year the ice has disappeared pretty completely by November, and the cave is free; but in April or May the floor is again covered with ice, and columns and icicles have formed on the roof and sides. At La Genollière the cave is used by the people of the neighboring châlets, through the spring and early summer, to help in the operation of butter making; by the middle or the end of August it has entirely disappeared, but is found formed afresh the following spring. At the Rumney Talus, at the Cave of Decorah, at the Gorge of Ellenville, and at the Williamstown Snow Hole, I found no snow or ice.[43] Yet it is abundant in all these localities in the spring. Too many examples of the complete melting away of the ice every year can be cited, to permit any doubt: glacière caves are not connected with a glacial period.

Though it may be stated positively that the ice in caves is not a remnant of a glacial period, yet this cannot be done so authoritatively about subsoil ice sheets and freezing wells. At Brandon, Owego and Decorah the gravel was found frozen at the time the wells were dug, and it is of course impossible to determine for how long a time this was the case previous to the digging. The proofs, however, are so strong that the ice re-forms every winter at such freezing wells, that they may be considered as in every respect following the same general laws as glacière caves. That the ice in these wells is not the remains of a glacial period, seems proved moreover by the work of the Boston Natural History Society, which sank two wells at Brandon near to the Freezing well. One of these was only twenty-one meters distant and went through the same gravel drift. Yet it did not strike ice.[44] A somewhat similar state of things appears to be the case with the Centennial Lode and other lodes on Mount McClellan,[45] where the causes also seem to be local, as there is no ice in mines on neighboring mountains.