A cave, or cavern is an opening of some size in the solid crust of the earth beneath the surface. Caves are principally met with in limestone rocks, sometimes in sandstone and in volcanic rocks. Some of them have a very grand or picturesque appearance, such as Fingal's Cave in Staffordshire, others, such as the Mammoth Cave of Kentucky, which incloses an extent of about 40 miles of subterranean windings, are celebrated for their great size and subterranean waters, others for their gorgeous stalactites and stalagmites; others are of interest to the geologist and archaeologist from the occurrence in them of osseous remains of animals no longer found in the same region, perhaps altogether extinct, or for the evidence their clay floors and rudely-sculptured walls, and the prehistoric implements and human bones found in them, offer of the presence of early man.
Caves in which the bones of extinct animals are found owe their origin, for the most part, to the action of rain-water on limestone rocks. The deposit contained in them usually consists of clay, sand, and gravel combined. In this are embedded the animal remains, and stones either angular or rounded. Some of the remains found in European caverns belong to animals now found only in the tropical or subtropical regions, and others are the remains of animals now living in more northerly areas; others, again, are the relics of extinct animals. Among the latter class of animals are the cave bear and lion, the mammoth and mastodon, species of rhinoceros, etc. Of others that have only migrated may be mentioned the reindeer, which is no longer found in Southern Europe; and the Hyoena crocuta, found in the Gibraltar caves, which now lives in South Africa. The ibex, the chamois, and a species of ground squirrel, are shown to have once lived in the Dordogne, but are now found only on the heights of the Alps and Pyrenees.
Thus it is evident that the geographical conditions of the country must have been very different from what they are now. Man's relation to these extinct animals, and his existence at the time these changes took place, are demonstrated by such discoveries as those of human bones and worked flints beneath layers of hyena droppings, as in Wokey's Hole, near Wells, England; mixed up indiscriminately, as in Kent's Hole, near Torquay, with bones of elephant, rhinoceros, hyena, etc; and by the fact that many bones of the extinct animals are split up, evidently for the sake of the marrow.
In the Dordogne and Savigne caves fragments of horn have been found bearing carved, or rather deeply scratched, outline figures of ibex, reindeer, and mammoth. Among the most remarkable bone-caves are those of Kirkdale, in Yorkshire; Kent's Hole, Wokey's Hole; of Franconia, in Bavaria; the banks of the Meuse, near Liege; and the south of France. Research Cave
A Fohn wind is a warm, dry wind blowing down the sides of mountains facing away from the prevailing wind. It is best known in the valleys of the northern Alps. Other fohn winds are the Chinook (the eastern side of the Rocky Mountains, Canada and the USA); the Nor'Wester (New Zealand) and the Samoon (Iran). Research Fohn Wind
Glaciers are icy masses of great bulk, harder than snow, yet not exactly like common ice, which cover the summits and sides of mountains above the snow-line. They are found in Switzerland, Scandinavia, the Andes, etc.
They extend down into the valleys often far below the snow-line, and bear a considerable resemblance to a frozen torrent. They take their origin in the higher valleys, where they are formed by the congelation and compression of masses of snow in that condition called by French writers neve, by German authors, firn.
The ice of glaciers differs from that produced by the freezing of still water, and is composed of thin layers filled with air-bubbles. It is likewise more brittle and less transparent. The glaciers are continually moving downwards, and not unfrequently reach the borders of cultivation. The rate at which a glacier moves generally varies from 45 to 60 cm in twenty-four hours.
At its lower end it is generally very steep and inaccessible. In its middle course it resembles a frozen stream
with an undulating surface, broken up by fissures or crevasses. As it descends it experiences a gradualdiminution from the action of the sun and rain, and from the heat of the earth. Hence a phenomenon universally attendant on glaciers - the issue of a stream of ice-cold turbid water from their lower extremity. The descent of glaciers is shown by changes in the position of masses of rock at their sides and on their surface. A remarkable glacier phenomenon is that of moraines, as they are called, consisting of accumulations of stones and detritus piled up on the sides of the glacier, or scattered along the surface. They are composed of fragments of rock detached by the action of frost and other causes.
The fissures or crevasses by which glaciers are traversed are sometimes more than 30 meters in depth, and from being often covered with snow are exceedingly dangerous to travellers. One of the most famous glaciers of the Alps is the Mer de Glace, belonging to Mont Blanc, in the valley of Chamouni, about 1740 meters above sea level. It is more especially, however, in the chain of Monte Rosa that the phenomena of glaciers are exhibited in their greatest sublimity, as also in their most interesting phases from a scientific point of view.
Glaciers exist in all zones in which mountains rise above the snow-line. Those of Norway are well known, and they abound in Iceland and Spitzbergen. Hooker and other travellers gave accounts of those of the Himalaya. They are conspicuous on the Andes, while the Southern Alps of New Zealandrival in this respect the Alpine regions of Switzerland.
The problem of the descent of the glaciers is of extraordinary interest, and various theories have been put forward to account for it. It was shown by Professor Forbes, of Edinburgh, that a glacier moves very much like a river; the middle and upper parts faster than the sides and the bottom; and he showed that glacier motion was analogous to the way in which a mass of thick mortar or a quantity of pitch flows down in an inclined trough. His theory is known as the viscous theory of glaciers, which presupposes that ice is a plastic body, and this plasticity has been satisfactorily explained by Professor James Thomson of Glasgow by the phenomenon of the melting and refreezing of ice.
Water, he discovered, when subjected to pressure, freezes at a lower temperature than when the pressure is removed. Consequently when ice is subjected to pressure it melts; if it is relieved of pressure the water again solidifies. Therefore if two pieces of ice are pressed together, they tend to relieve themselves by melting at their points of contact, and the water thus produced immediately solidifies on its escape. If ice is strained in any way it similarly relieves itself at the strained parts, and a similar regelation follows. This, when applied to the glaciers, gives a complete explanation of their plasticity. Pressed downwards by the vast superincumbent mass, the ice gradually yields. Melting and re-freezing takes place at some parts, at others the gradual yielding at strained points goes on. In the latter process there is no visible melting, but there is the gradual yielding from point to point to the pressure above, and there is the transference relatively to each other of the molecules that constitute the, at first sight, solid mass. If, however, at certain points the strain is intense, the ice becomes extremely brittle. The latter fact disposes of Tyndall's objection to Forbes' theory, which was based on the fact that crevasses proved the brittleness, and not the viscosity of ice. Research Glacier
Mountains are often classified according to their mode of formation: Fold
mountains; Block mountains; Residual mountains; Volcanic mountains.
High mountain chains such as the Himalayas, Andes, Alps, and Rockies are known as new fold mountain systems. The term 'fold' is a reference to the way in which such mountains have been formed. Throughout millions of years slow movements of the earth's crust have caused these
mountains to be raised. The movements which have resulted in mountain buildings were not, however, vertical uplifts. They were primarily horizontal movements, the effect of which was to cause the crust of the earth to 'wrinkle', in a similar way to which a tablecloth wrinkles if it is pushed along the table. The arched or upraised parts of the folds are known as anticlines and the troughs as synclines. These folds can vary greatly in size. Mountain building is undoubtedly due to some deep-seated cause. For a long period the most simple explanation was that folding was entirely due to the cooling and contraction of the earth, so that the crust, already cold and shrunken, had to wrinkle to fit itself to the still cooling and contracting 'core'. One of the objections advanced against this theory is that the amount of shrinking necessary to account for the Himalayas, Alps, etc., seems to be greater than the mere contraction of the earth would allow. While the theory of contraction cannot be completely rejected, serious consideration must be given to the more recent explanations of mountain building. For instance, Wegener suggests that mountain building may be due to the 'wrinkles' produced by the drifting of a continental mass, e.g. that the Alps were formed by the northward drift of the African continent towards the more stable blocks of Central Europe. As the African mass drifted slowly northward the zone between it and the European mass became narrower, and the land was raised into high ridges or folds. The raising of the Alps was accompanied by the formation of the deep trough which contains the Mediterranean Sea. The same hypothesis would account for the building of the Himalayas and the depression of the Indo-Gangetic trough by the northward drift of the Deccan mass.
During the physical history of the earth, mountain building appears to have proceeded more actively at some periods than others. Fold mountains are, therefore, not all of the same age. The newest group of fold mountains include the Himalayas, Alps, Rockies, and Andes. During an earlier period of folding (the Carboniferous) the Pennines, Appalachians, the Cape Ranges of South Africa, and the Dividing Range of Australia were uplifted. A still earlier period of folding accounted for the original mountains of Scotland and Norway, of which the present mountains are merely the worn down stumps. The older fold mountains, which have been subjected to the forces of denudation (such as the weather, rivers, glaciers, etc.) for long geological periods, are much lower and less rugged than the newer fold mountains. The term 'new fold' is applied to the mountain ranges which have been folded most recently, but they seem very old when their age in actual years is considered because they were uplifted many millions of years before historic time. Mountain building is a very long and slow process; and in the case of certain mountain chains, such as the Andes and the mountains of Japan, is probably still proceeding.
The new fold mountain systems of the world, except in such instances as the simple low folds of the Weald (South-east England), usually consist of high parallel ranges, the average height being well over 3000 metres. In the Himalayas' the highest peak rises to 8840 metres; in the Andes 7000 metres; in the Rockies 6000 metres; in the Alps to 4600 metres. Vast though these heights appear, the wrinkles of the earth's crust are only slight. The highest mountain in the world (MountEverest) is about five miles high, so that on a globe of 40 cm, diameter it would protrude only 2.5 mm. Most of the active volcanoes are found in the neighbourhood of fold mountains, where the crust of the earth has been fractured during the process of folding. All around the PacificOcean there are many active and extinct volcanoes, as in New Zealand, the East Indies, Japan, and North, Central, and South America. Another belt of active volcanoes is associated with the fold mountains of the West Indies. The mountains of this type are characterised by ruggedness of relief in contrast to the smooth and rounded contours of mountain areas which have been subjected to weathering agents for long periods of time. This is obvious if pictures of the Alps and the Scottish Highlands are compared.
Mountains are effective climatic barriers, and the climates of regions on either side of a high mountain range are very different. For example, the coast lands of British Columbia have an equable climate and a heavy rainfall, while the lands to the east of the Rockies have an extreme climate and light rainfall. Again, the climate of the mountainous areas differs from that of the adjacent lowlands. The great mountain systems of the world are mainly important for their minerals, and, in the temperate zone, for their lumber. In the plateau regions of some mountain systems agriculture has been made possible by irrigation, and above the forests in temperate areas there are valuable alpine pastures. The swift streams of mountains are frequently sources of hydro-electric power, especially in countries which have no coal, such as Switzerland and Norway. In North America, the Western Cordillera provides gold, copper, lead, and silver, especially in the states of Nevada and Montana. The Andes provide tin and copper (Bolivia), gold and platinum
(Colombia), and silver (Peru). The Highlands of East Australia are important for copper and gold. The lumbering industry is specially important in British Columbia, Washington, and Oregon (soft woods), the Central American mountainous lands (hard woods), the Himalayan slopes (teak and sal), and the Scandinavian mountains (soft woods).
To provide food for the mining communities in inaccessible mountain areas, agriculture has been developed. There are numerous irrigation schemes in operation in most of the mountain states of the USA, e.g. at SaltLake City in Utah. Similarly, the Andean states, e.g. Bolivia, grow small quantities of cereals in the plateau areas. Mountain pastures have been utilised most extensively for cattle rearing in Switzerland and Scandinavia. The vast central plateau of Asia is, owing to difficulty of access and climatic extremes, so isolated from other regions that very little development of any kind, on modern lines, has taken place. High mountain ranges are also barriers to communication, and so tend to separate peoples. Traffic across mountains is limited to the passes, which are often so high as to be snowbound in winter. Such ranges as the Alps, Andes, etc. can only be crossed with great difficulty or by expensive tunnelling.
It sometimes happens that movement of the earth's crust occurs along cracks or faults. Where such movement leaves a block of higher land standing between two areas of lower land, the highland is known as a 'Block Mountain' or horst. The Vosges and Black Forest Mountains are examples of such formations These mountains are usually very steep-sided, and often the summit levels are roughly the same.
When an area of highland remains standing above the general level after rivers and other natural agents have lowered the surface of the surrounding area, the name residual mountain is used. Sometimes such highlands are called 'mountains of denudation'. This term can usually be applied to the mountain ridges associated with 'dissected plateaux'. Included in this class are the mountain ridges of the Highlands of Scotland, the Sierras of Central Spain, and the Mesas and Buttes of the western plateaulands of the United States.
Mountains may be formed by volcanic material piled up around a crater, such mountains are popularly known as volcanoes. Research Mountains
Alpine Plants is the name given to those plants whose habitat is in the neighbourhood of the snow, on mountains partly covered with it all the year round. As the height of the snow-line varies according to the latitude and local conditions, so also does the height at which these plants grow. The mean height for the alpine plants of Central Europe is about 6000 feet; but it rises in parts of the Alps and in the Pyrenees to 9000, or even more. The high grounds clear of snow among these mountainspresent a very well marked flora, the general characters of the plants being a low dwarfish habit, a tendency to form thick turfs, stems partly or wholly woody, and large brilliantly-coloured and often very sweet-smelling flowers. They are also often closely covered with woolly hairs. In the Alps of Middle Europe the eye is at once attracted by gentians, saxifrages, rhododendrons, primroses of different kinds, etc. Ferns and mosses of many kinds also characterize these regions. Some alpine plants are found only in one locality. Considerable success has attended the attempt to grow alpine plants in gardens. Research Alpine Plants
Auricula is a garden flower derived from the yellow Primula Auricula, found native in the Swiss Alps, and sometimes called bear's-ear from the shape of its leaves. It has for centuries been an object of cultivation by florists, who have succeeded in raising from seed a great number of beautiful varieties. Its leaves are obovate, entire or serrated, and fleshy, varying, however, in form in the numerous varieties. The flowers are borne on an erect umbel and central scape with involucre. The original colours of the corolla are yellow, purple, and variegated, and there is a mealy covering on the surface. Research Auricula
Bembidion is a genus of over 100 species of small (three to six millimetres in length) beetles of the ground beetle family, Carabidae. Most of the species live beside water, either stagnant or running, and most species hibernate. Colouration varies between species, Bembidion lampros which is common in Britain is a uniform bronze-black colour; Bembidion tricolour, common in the Alps, has a bicoloured elytra - the anterior half reddish yellow, the posterior metallic black or blue;
Bembidion genei has a metallic green coloured body and four yellow spots on the elytra. Research Bembidion
The blind mole (Talpa caeca) is a smaller mole, with a longer, slender nose, and whitish hair on the lips, legs, tail and particularly the forelegs found in the Iberian peninsula, northern Italy, the Adriatic coast and Greece. The eyes are permanently closed by a thin membrane which cannot be opened without damage. The upper incisor teeth form a V-shape with the largest, central (first) incisors being more than twice the size of the smallest, peripheral (third) ones. The blind mole is confined to mountainous areas, in contrast to the Roman and Common Moles which are both found in various habitats from the Appenine Mountains and Alps through to coastal areas. In contrast to the Roman Mole (which does not overlap with the Common Mole), the Blind Mole is generally thought to overlap in distribution the Common Mole. Like the common mole, the blind mole eats primarily earthworms, plus beetles and fly larvae, slugs, centipedes and millipedes. Research Blind Mole
Collembola is the springtail sub-order of Apterygota. They are small, wingless insects which have a forked organ turned forwards under the abdomen. When this organ is suddenly released, it strikes the surface on which the insect is standing and throws the insect up into the air. Springtails are commonly found under stones, bark and flowerpots. Some of the species are aquatic, and one, the glacier flea, is found on the ice in the Alps. Research Collembola
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Cave
