The New International Encyclopædia/Andes

ANDES, ăn'dēz (Deriv. uncertain, usually explained as Copper Mountains, from the Peruvian word anti, copper; cf. in Germany Erzgebirge, Ore-Mountains, and Bleiberg, Lead-Mountain). The great mountain chain of South America, extending closely parallel with the Pacific coast, and nowhere far from it, from Cape Horn to the northwest coast of the South American continent. Its length is about 4500 miles, extending in latitude from 56° 30' S. to 11° N. In a way, it may be regarded as continuous with the Cordilleras of North America, the two forming a well-nigh continuous mountain system 9000 miles in length, stretching from Cape Horn to the Aleutian Islands. The average breadth may be set at 150 miles, although this differs greatly in different parts of the system. Its average height of 12,000 feet is subject to the same qualification. Following the coast, the system trends a little west of south through Colombia and Ecuador, but on entering Peru it turns to the southeast, in which direction it extends through that country and part of Bolivia. Through south Bolivia, Chile, and Argentina, its trend is nearly south, but it swings in a broad curve to the eastward near Magellan Strait. The mountain system rises abruptly on both sides throughout its course. Everywhere it presents a steep wall to the Pacific, and on the east it drops abruptly to the Amazon Valley; farther south, in Argentina, the land rises somewhat to meet it, and there are outlying ridges, but the main ascent is everywhere steep. The southern part of the system consists of a single range, with here and there outliers of comparatively little height, but from northern Chile and Argentina to Colombia, it consists of a high, broad plateau, capped by two or three ranges, with hundreds of high volcanic peaks, some active, others dormant or extinct.

Geologically, the system is of recent origin, although its age has not been closely determined. The material of which it is composed is in the main granites, with schists, slates, and other metamorphic rocks and the oldest of stratified rocks; here and there upturned beds of more recent formation, up to the Jurassic, lie upon the flanks of the ranges, while in Peru, the eastern range is composed largely of Silurian beds. Over all, in the neighborhood of the volcanic peaks, which are very numerous in all parts of the range, are spread lava, pumice, scoria, and ashes, in many places burying deeply the metamorphic rocks. Near the northern end, in Colombia and Venezuela, the eastern branches are composed of recent stratified rocks. For detailed description it will be convenient to refer to the countries traversed by this mountain system, and this order will be followed, commencing at the north.

Colombia and Venezuela. The Andes originate on the north in Colombia and Venezuela in several distinct ranges, which, trending south to southwest, meet and coalesce in the Pasto Knot in southwest Colombia. The westernmost range of magnitude is the Cordillera Occidental, which rises just east of the mouth of the Atrato, and trends southward, parallel to the coast, throughout Colombia. In this are summits 10,000 and 11,000 feet in height, the highest peaks being in the southern part. Near the boundary line with Ecuador it is cut through by the Rio Patia, which flows south and west into the Pacific. East of the Cordillera Occidental, and separated from it by the narrow valley of the Cauca, a branch of the Magdalena, is the Cordillera Central. This range rises from the lowlands between the Cauca and the Magdalena, and attains a great height, with Cumbal, 15,715 feet; Guacau, 16,683 feet; Guican, 15,748 feet; Santa Marta, 19,029 feet; Santa Isabel, 16,732 feet; Herveo, 18,045 feet; Ruiz, 17,388 feet; Sugarloaf, 16,000 feet; Tolima, 18,425 feet, and many others of equal height. The range is composed mainly of crystalline schists, while the higher peaks are volcanoes, which have spread lava and ashes over many parts of the range. East of the Cordillera Occidental and across the valley of the Magdalena, is the Cordillera de Bogota, originating in several ranges in the north of Venezuela, which trend in a general southwest direction and come together at various points; the principal ones are the Parija and Merida ranges, which unite near Bogota, beyond which point the range is single. Its highest peak is Cocui, 16,680 feet high. The range is in the main composed of strongly folded Cretaceous and Tertiary beds, and contains no volcanoes.

Ecuador. The Andes of Ecuador form two ranges, the Cordillera Occidental, the continuation of the range of the same name in Colombia, and the Cordillera Oriental, or Real; the two are separated by a high plateau, from 70 to 100 miles wide, with an average elevation of 8000 feet; connecting cross ranges divide this plateau into ten basins or high mountain valleys. The western range is composed of porphyries, diorites, and greenstone, and the eastern and higher range is composed of gneiss, schist, and granite. Above them tower many high volcanic cones, which have spread lava and ashes over great areas. The great peak of the western range is Chimborazo, 20,498 feet; with Cotocachi, 16,300 feet; and Pichincha, 15,918 feet, the last named near the city of Quito, while in the eastern range are Cotopaxi, 19,613 feet; Antisana, 19,335 feet; Cayambe, 19,186 feet; Altar, 17,736 feet; Illiniza, 17,023 feet; and Carahuairazo, 16,515 feet, with the active volcanoes Tunguragua, 16,690 feet, and Sangai, 17,464 feet. The cross ranges also contain many volcanic peaks, indicating that the whole region must once have been the centre of tremendous volcanic activity.

Peru. In Peru, Bolivia, and the northern part of Chile, the system is much broader and more complex. The Andes of Peru consist of three ranges, the two westernmost being the Maritime or Black, and the Central Cordillera, trending parallel to one another and to the coast, and in the north separated only by a narrow, high plateau, known as the Puna, with an average height of 12,500 feet, and in the south by the narrow valley of the Rio Huay. The Eastern Cordillera, though otherwise continuous, is cut through by no less than six of the head tributaries of the Amazon. The broad, elevated region lying between this and the Cordillera Central, known as the Sierra, is broken by mountain spurs, with broad valleys and plateaus. East of the Eastern Cordillera, or the Andes, as it is locally known, are several lower ranges, trending parallel with the system, and separating tributaries of the Amazon. The Maritime and Central Cordillera are composed of crystalline and volcanic rocks, with stratified beds of Jurassic age resting upon their outer flanks. The Eastern Cordillera is composed mainly of stratified beds of Silurian age, with some intrusions of granite. These ranges are connected at the mountain knot of Cerro de Pasco, 14,293 feet high, and again further to the southeast, at the Knot of Vilcanota, 17,390 feet. South of this latter peak the Central and Eastern Cordillera enclose the lofty plateau on which is Lake Titicaca, situated partly in Peru and partly in Bolivia, and 12,545 feet above the sea. North of the Cerro de Pasco, the Sierra comprises the upper valley of the Marañon, the largest and longest of the head branches of the Amazon, which cuts through the Eastern Cordillera just south of the Ecuador frontier. Between the Cerro de Pasco and the Knot of Vilcanota, the Sierra is drained by the head streams of the Ucayali, a large tributary to the Amazon. These streams also cut gorges through the eastern range. This region was the site of the ancient Inca civilization, and is still thickly settled. Among the high peaks of this part of the Andes are Huascan, 22,051 feet; Huandoy, 21,089 feet; Misti, 20,013; Chacani, 19,820 feet; and Tutupaca, 18,960 feet.

Bolivia. In Bolivia the system comprises two main ranges, one of which is formed by the coalescing of the two westernmost of the Ecuador ranges. These ranges are widely separated and enclose a broad, greatly elevated plateau, 125 miles in breadth in the northern part, and nearly 300 miles in the south, with an altitude of almost 13,000 feet. The plateau of the Andes has here the greatest lateral extent and altitude in the entire system. The western range has an average altitude of 15,000 feet, while the Eastern, or Cordillera Real, is still higher, having peaks exceeding 20,000 feet; among them are Illampu, 21,490 feet; Illimani. 21,030 feet; Ancohuma, 21,490 feet; Haina, 20,171 feet; Paniri, 20,735 feet: Licancaur, 19,521 feet; Sajama, 21,047 feet; Isluga, 17,000 feet: and Cacaca, 20,250 feet, all of them near Lake Titicaca. East of this range are several lower subsidiary ranges, which form a complicated system. Lake Titicaca drains southeastward into Lake Poopo, a sink which collects the waters from a large area of the plateau. In the Cordillera Real and the lesser ranges to the east, rise tributaries of the Madeira, one of the main branches of the Amazon, and of the Pilcomayo, tributary to the Plata.

Chile and Argentina. The broad, high plateau, with its bordering ranges and subsidiary eastern ranges of Bolivia, extends southward into these countries, gradually narrowing and decreasing in altitude, until in latitude 32° the Andes become reduced to a single range, except for spurs and outliers, most of which are of comparatively little importance. In the northern part the altitude of the ranges decreases greatly, Juncal, in latitude 26°, having a height of 17,530 feet, and Copaipó volcano, 19,700 feet. Farther south, in the neighborhood of Santiago. the mountains again become loftier. Here are Mercedario, 22,315 feet; Tupungato, 20,286 feet; San Jose, 20,020 feet; and Aconcagua, 22,860 feet; this latter peak is the highest summit of the entire system, and of the whole continent, so far as known. Still further south, the range again diminishes in height. In latitude 34° is Maipo volcano, 17,670 feet: in latitude 36° is Descabezado, 12,760 feet; in latitude 42° is Tronador volcano, 9790 feet. Here begins the remarkable fiord coast, which extends south to Cape Horn. The heavy precipitation on the west side of the range here produced in past times extensive glaciers, which chiseled the mountains far down below sea level, producing many islands, and an intricate system of mountain-walled channels. These glaciers have been able, by reason of their rapid descent, to cut back their heads across the range in many places, so that now, after their recession, many of the streams which have succeeded them rise far to the east of the Andes, upon the plains of Argentina, and flow through the range to the Pacific. In this region the mountains become still lower, their height ranging from 4000 to 8000 feet, until they finally disappear at Cape Horn.

The lower limit of perpetual snow, although an extremely indefinite line, varying from year to year with exposure and precipitation, has in general, in equatorial regions, an altitude of about 15,500 feet, but ranges a thousand feet on each side of this figure, being higher on the east and lower on the west side of the range. In other words, it is higher where the precipitation is abundant, and lower where it is scanty. It diminishes as the latitude increases, being about 13,000 feet in the latitude of Santiago, and falling to 3000 feet near the southern point of the continent. Glaciers are found on all the high peaks, even those in equatorial regions, which exceed 13,000 feet in height. Here, however, they are small, descending the mountain slope only a few thousand feet. In southern Chile, on the west side of the range, are many of considerable size, originating upon mountains of inferior height, and descending to sea level, even entering the sea, at the heads of fiords.

Volcanoes. One of the striking features of the Andes is its great number of active and extinct volcanoes. Probably not over sixty are now known to be active, but the extinct ones are numbered by hundreds, and have played a very important part, though a secondary one, in creating the present conformation of the mountain system. Three principal centres of volcanic activity are recognized: one in the Andes of the north, in Colombia and Ecuador, extending in latitude from 5° N. to 3° S.; a second in Peru, Bolivia, and northern Chile, extending in latitude from 15° to 28° S.; and a third in central Chile, extending from 32° to 40° S. The highest peaks of the Andes are of volcanic formation, and their peculiar conical forms are distinctive features of the Andean landscape. Many of the most prominent and highest ones have been mentioned; it remains to speak of those which are now active, or which have been active within historic times, and briefly describe their eruptions.

The northern group, mainly comprised in Ecuador, is the most imposing collection of active and extinct volcanoes on earth. Of these, Cotopaxi, Tunguragua, Sangai, and Pichincha have repeatedly been in eruption in historic times, but most, if not all, of the others have for a long time been quiescent. The Altar, a truncated mountain, 17,736 feet in height, is said to have once been the highest in the region, but after a long period of eruption it collapsed within itself. Ruiz, in Colombia, is still smoking, and Tolima is not quite extinct, but as late as 1829 was in eruption. In 1849 Purace, in southern Colombia, suddenly exploded, flooding the neighboring country, and covering it with ashes. A similar eruption took place in 1869. Imbabura, in Ecuador, is said to have discharged a deluge of mud and water at the time of the great earthquake in 1868. Antisana is reported as having been in eruption in 1590, and even now sulphurous fumes arise from it. Cotopaxi, always smoking, has been repeatedly in eruption, although its great eruptions have occurred at intervals of centuries. The last one was in 1877. Tunguragua also is active at irregular intervals, the latest eruption being in 1886. Sangai sends off steam constantly with tremendous force and noise. Pichincha has, since its eruption in 1660, given off nothing but steam and a little ashes.

The middle volcanic group is found in both the eastern and western Cordilleras; in Peru it includes Sarasara, Atchatayhua, Corupuna, Ampato, Chachani, and Misti, all now quiescent. Omate and Tutupaca have been in eruption in historic times; indeed, the former was one of the most active in Peru. In Bolivia are Mount Sorata, or Illampu, Sajama, Aucaquilcha, Chachaconiani, Huiana, Cacaca, Mesada, and Illimani, while in northern Chile are many volcanic cones, some of great height; among them are Tacora, 19,750 feet, Chipicani, Pomerape, Pariuacota, Iquima, 20,275 feet, and Toroni, 21,340 feet, all in the western range. In the eastern range are Tuachela, Olca, Mino, and Ollagua, all smoking or emitting lava. South of Ollagua are at least thirty extinct volcanoes, exceeding 16,500 feet in height; among them are Autopalla, 20,920 feet, Socompa, 19,620 feet, and Llullaillaco, 21,670 feet.

In the central Chilean region are Tupungato, San Jose, Maipo, Tinguiririca, all supposed to be extinct. Las Damas and Peteroa are said to have been in eruption in the last century. The volcanoes grouped about Descabezado are quiescent, though appearances indicate recent eruption. Chilean ranges contain several vents, from which lava and ashes have been ejected in recent years. Autuco also has had eruptions within historic times. Farther south, Villarica volcano has frequently been seen in eruption, in all probability, other active volcanoes exist in the fiord region of South Chile, although none has yet been reported.

Hydrography. The Andes system is the source of most of the larger streams of South America. Through nearly its whole extent, wherever the system comprises more than a single main range, the westernmost of these ranges separates the drainage to the Atlantic from that to the Pacific. In Ecuador, however, no fewer than seven of the ten high valleys between the ranges are drained westward, and in southern Chile, as has been seen, glaciers have eroded their sources back across the whole range to the Argentina plains. The western streams are short, and owing to the light rainfall on most of the western slope, have small volume. Hence their cutting power is slight. On the other hand, the streams to the east are long, with great drainage basins, and, except in Argentina, are supplied with abundant precipitation by the trade winds. Hence they are powerful streams of large volume, and have eroded their courses far up into the mountains.

The Andes of Colombia are drained northward to the Caribbean Sea by the Magdalena, Cauca, and Atrato rivers, and eastward to the same body of water by the Orinoco, and to the Atlantic by the Negro and Yapurá great branches of the Amazon. The system in Ecuador, Peru, and most of Bolivia is drained eastward by countless tributaries of the Amazon, among which are the Napo, Marañon, Ucayali, Beni, and Mamore. Of these, the Marañon heads between the ranges far to the south, near the Knot of Cerro de Pasco, flowing northwest within the mountain system for 400 miles before breaking through the eastern range into the Amazon basin. The Huallaga, Mantaro, Apurimac, and Urubamba, tributaries of the Marañon, also head between the ranges, cutting gorges through the eastern range. In Bolivia and northwest Argentina is a great region, 800 miles in length, lying between the ranges, with an average altitude of 13,000 feet, which has no drainage to either ocean. In this region is the great Lake Titicaca, which drains by the Pio Desaguadero to Lake Poopo, where the drainage of this semi-desert region is collected. This lake in earlier times drained to the Amazon, but by shrinkage in volume its outlet has been closed, and now it discharges only by evaporation. The eastern slope of the Andes in southern Bolivia and northern Argentina is drained to the Plata, while farther south shorter streams, the Rio Colorado, the Negro, Chubut, and the Deseado, and the Arroyos Bayo and Salado, and other smaller streams, carry the drainage directly to the Atlantic.

Climate. The climate of the Andes differs widely in different parts, with latitude, altitude, and exposure. The eastern slope of the system from the northern end southward to latitude 25°, comprising the portions drained by the Orinoco and Amazon, and lying almost entirely within the tropics, has a heavy, and, in many localities, a profuse, rainfall. Farther southward in the temperate zone, in the region of prevailing westerly winds, the rainfall on this side of the range diminishes, becoming very light in Argentina, with only eight inches or less in the driest parts. On the west side of the system, the rainfall conditions are very nearly reversed, though in the north, in Colombia, the tropical rainfall passes around the end of the range and extends down the western side for some distance, giving to the valleys of the Magdalena, Cauca, and Atrato abundant moisture, and extending southward along the coast as far as Guayaquil, Ecuador. Thence southward, the western coast is an arid and desert region, as far as latitude 30° S. Below this point the precipitation increases, as the westerly winds bring moisture, and the southern coast is well watered.

From Guayaquil a cooler climate is reached either by going south or by going directly up the mountains. The base of the mountains, within the tropics, has a mean annual temperature of 80° F. or more, while in southern Argentina it is not more than 25°. Within the tropics the temperature ranges from 80° at the base of the mountains to 20° or less at their summits, a range due to altitude alone. Upon the Titicaca plateau Arctic conditions prevail, with frost every month of the year. Where the rainfall is copious, as it is on the eastern side within the tropics, the range of temperature between summer and winter is slight, while upon the west coast, in the same latitudes, where desert conditions prevail, the range is very great. In general, as the mountains are ascended, the contrasts of temperature become greater, owing to the rarefaction of the air. At great altitudes, even, the contrast between day and night is great. South of the latitude of Coquimbo, 30° S., these temperature conditions are reversed, the west slopes having the smallest annual and diurnal range.

Means of Communication. Routes of travel across the Andes are few in number, the passes are very high, and the roads traversing them are, as a rule, very bad. Communication between the peoples on the two sides of the mountains is slight. The high land between the ranges is the best settled part of these sparsely settled countries, and the inhabitants of these elevated regions have some intercourse with the western seaboard, but very little with the low country to the east. But with the development of the mining industry in the mountains and the exploitation of the rubber resources of the upper waters of the Amazon, it may be expected that means of communication across the range will be improved in the near future. In Colombia the main routes of travel follow the valleys of the Cauca and the Magdalena, while the chief route across the Cordillera Central is via Quindio Pass, connecting Cartago, on the Cauca, with the valley of the Magdalena, and ultimately with the capital, Bogota. In Ecuador the main routes pass north and south through the succession of mountain valleys, connecting with the coast at Guayaquil, by railroad from Chimbo, or northward down the Cauca and Magdalena. The most frequented eastward route crosses the Eastern Cordillera between Saraurcu and Antisana, and reaches navigable water in the Napo at Puerto Napo. In Peru the plateau within the ranges is connected with the coast by two railways, which are marvels of engineering. The Oroya Railway connects Lima and Callao with Oroya and Concepcion, crossing the Western Cor- dillera at an altitude of 15,665 feet, in a distance of 106 miles from Lima. The second railway connects Mollendo on the coast with Lake Titicaca. It crosses the Western Cordillera at an altitude of 14,666 feet, and terminates at the little town of Puno, on the shore of Lake Titicaca, 12,540 feet high. Several other short lines run from the coast to the foot of the mountains and even some distance into them, following the stream valleys; among them is the line up the Rio Santa to Huaraz.

The somewhat broken character of the ranges in Peru and Bolivia has made the plateau easier of access than it is farther north, and there are many roads and trails from the coast to the summit; but routes of communication to the east, to the country about the upper waters of the Madeira and Plata, are almost entirely lacking. From Antofagasta in northern Chile, on the coast, a railway has been constructed to Oruro, on the plateau, north of Lake Poopo. This road has a total length of 560 miles, making it much the longest of the Andean lines. In central Chile and Argentina a transcontinental railway has long been in course of construction, which is to cross the Andes at Uspallata or Cumbre Pass, not far from Santiago, at an altitude of 12,340 feet. This is the most frequented pass in Chile, as almost all the transcontinental travel goes over it.

Flora. In plant life the Andes is the richest of any mountain system in the world. Not only do these mountains sustain at their bases the flora of all climates, from the equatorial zone at the north to the cold zone at the south, but they possess these zones in altitude as well; and moreover, certain species of plant life are peculiar to this special region. Plant life is especially prolific in the rainy regions of Venezuela, Colombia, Chile, and Bolivia. In Colombia the palms and their associated tropical flora extend upward on the Andean slopes to an altitude of about 4500 feet, while above this is a mixed sub-tropical belt, extending to an altitude of nearly 10,000 feet, in which grow the cinchona, tree fern, and wax palm, and still higher up, at an altitude of 10,000 to 12,000 feet, the higher Andean bush growth, including the Andean rose; a species of bamboo also grows at these high altitudes.

Farther to the south, in the region of less rainfall, the flora on the east and west sides of the Andes is quite different. On the west side, in lower Ecuador and Peru, the plant life is poor, and is that peculiar to a semi-desert region; but it extends up to high altitudes, lichens being found at 18,500 feet altitude; while on the moister Bolivian and Brazilian side the various altitudinal zones occur, beginning with the rich flora of western tropical Brazil and extending up to the true Andean flora. In northern Chile and western Argentina, where there is a rather light rainfall on both sides of the Andes, there is a continuation of the sparser vegetation of the relatively dry region, and the flora of the two sides of the Andes differs less than elsewhere. In the Chile-Argentina region there is a great contrast between the rich vegetation on the moist Chilean side and the thin vegetation on the dry slopes of Argentina. In the southern part of this Andean region great forests of stunted beech and firs occur in the lowlands and extend part way up the mountain slopes. Southward along the Andean chain the altitudinal zones diminish in width in about the same ratio as the decrease in altitude of the snow-line, so that in the south, by making an ascent of less than a vertical mile, one can pass through as many vegetation zones as would be encountered in an ascent of three miles under the equator. The upper limit of tree growth, or the timber line, is a far more definite line than the snow line, yet in many places it is not easy to define. It ranges in the Andes from an average of 11,500 feet under the equator, down to about 3000 feet near Cape Horn. It is higher, for apparent reasons, on the moist, than on the dry, side of the range; thus, in Ecuador it ranges nearly 1000 feet higher upon the east side than upon the west.

Fauna. In the northern Andes of Venezuela and Colombia, where the tropical and sub-tropical forests extend up to an altitude of 10,000 feet, we find the fauna of tropical America existing up to similar high altitudes. The jaguar, puma, bear, ocelot, monkey, tapir, ant-eater, and capibara are found in these forests. Bird life is abundant, and the bat family is well represented. Snakes, saurians, and turtles are met in great numbers at lower altitudes. Above 6000 feet in altitude there is a great diminution of animal life. In Ecuador there occur certain representative species of the southern Andes, such as the llama and the condor. Insect life also continues very abundant, and fish are found up to an altitude of 14,500 feet. In the Peruvian and Bolivian Andes on the Pacific side, the fauna, like the flora, is limited, but on the eastern or Brazilian slope is exceedingly rich. The vicuña, guanaco, and alpaca are still found in the wild state, and with them are found the chinchilla and viscacha. On the Bolivian slopes the fauna is much more abundant than in Peru. Further south on the Andean chain the fauna is less rich, and especially there is to be noticed the disappearance of the larger animals of the northern Andes. Herds of guanacos are numerous, and birds are present in great variety and large numbers, but the reptiles show a decided change of form. At the extreme south the land fauna is but poorly represented.

Bibliography. Orton, The Andes and the Amazon (New York, 1870); Crawford, Across the Pampas and Andes (London, 1884); Güssfeldt, Reise in den Andes (Berlin, 1888); Whymper, Travels Among the Great Andes of the Equator (London, 1892); Fitzgerald, The Hiqhest Andes (New York, 1899); Conway, The Bolivian Andes (New York, 1901); Reclus, Physical Geography, translated and edited by Keane and Ravenstein (London, 1890-95).