Page:1902 Encyclopædia Britannica - Volume 25 - A-AUS.pdf/472

 426

ANDES

to the Cordillera de la Costa on the western side. Silurian, more continuous erosion, this section of the continent Devonian, and Carboniferous rocks contribute to the formation of the region of the maximum rainfall on the western coast to the the pre-Cordillera, between 30° and 33° S. lat. south of the equator. Between the gaps of the river Aysen and Whilst the axis of the Cordillera de los Andes from the south river Cisnes or Frias, which also pierces the chain, is found a as far as 38° S. lat. is crystalline, to the north of this latitude huge mountain mass, in which is situated Mount la Torre, 7 geological features change. At this point the range takes a feet. These form the continental watershed, but in this region the transversal development, dividing itself into three separate erosion is taking place so rapidly that the day is not far distant vast proups, the easternmost being composed of Jurassic-Cretaceous when Lakes La Plata and Fontana, situated to the east at a beds, the central of Mesozoic layers and old eruptive rocks, the height of 3000 feet, and now tributaries of the Atlantic, may western of Tertiary granitic formation, with neo-volcanic lavas become tributaries of the Pacific. Already filtrations_ from the and active volcanoes on its western border. From the volcano of former go to feed western affluents through the granitic masses.^ Copahue (height 9787 feet) the Andes take a great transversal To the north of Mount La Torre flows in the river Cisnes, 44 48 extension ; there are no wide intermediate valleys between the S. lat., across another water gap, continuing the range to the different ridges, but the main ridge is perfectly defined. Volnorth with high peaks, as Alto Nevado, 7350 feet, and Cacique, canic cones continue to predominate, the old crystalline rocks 7000 feet. The glaciers reach almost the western channels, as is almost disappear, while the Mesozoic rocks are most common. the case at river Quelal. The northern glaciers, descending nearly The higher peaks are in the main chain, whilst to sea-level, are situated at 43° 40' S. lat. To the Domuyo (15,317 feet) belongs to a lateral the north of 45° S. lat. a well-defined western eastern ridge. The principal peaks between this longitudinal valley, at some recent time occuand Mount Tupungato at 33° S. lat. are : Mount pied by lakes and rivers, divides the Cordillera Cochico, 8255 feet; Campanario, 13,140 feet; into two chains, the eastern being the main Peteroa, 13,297 feet ; Tinguiririca, Castillo, chain, to which belong Mounts Alto Nevado, 16,535 feet; Volcano Maipu, 17,576 feet; AlvaCacique, Dentista, Maldonado, Serrano, each rado, 14,600 feet; Amarillo, 15,321 feet; Volcano over 7000 feet high ; Torrecillas, 7400 feet; San Jose,19,849 feet; Piuquenes, 17,815 feet; and Ventisquero, 7500 feet; and Tronador, 11,180 Volcano Bravard, 19,619 feet. feet; while the western chain, broken into imNorth of Maipu volcano, ascended by Dr Gussposing blocks, contains several high volcanic feldt in 1883, the Cordillera is composed of two peaks such as Mounts Tanteles, Corcovado, very huge principal ridges which unite and terMinchimahuida, Hornopiren, and Yates. The minate in the neighbourhood of Mount Tupunrivers Palena, with its two branches, Pico and gato. The valley between them is 9000 feet Carrenleufu, Fetaleufu, Puelo, and Manso, cut high ; and in that part of the Cordillera are situthe two chains, while the rivers Renihue, Bodaated the highest passes south of 33° S. lat., one dahue, and Cochamo have their sources in the of which, the Piuquenes Pass, reaches 13,333 main eastern ridge. Mention has been made of feet, whilst the easiest of transit and almost the active volcanoes in 51°, 49°, and 47° S. lat., but lowest is that of Pichachen, 6505 feet, which is these have not been properly located. The active the most frequented during winter. Throughvolcanoes south of 41°, concerning which no out these regions the passes are numerous and doubt exists, are the Huequen, in 43° lat., and of easy access in summer, but in winter they are the Calbuco, both of which have been in erupgenerally dangerous. tion during recent years. To judge by certain features of this section of The surroundings of Mount Tronador, consistthe Andes, it would seem that down to modern ing of Tertiary granite and basalt, form one of times, there existed across these mountains very the most interesting regions in the Patagonian low passes, through which some representatives Andes for the mountaineers of the future. To of the Pampean fauna, such as the Mastodon and the east extends the large and picturesque lake Equus, reached Chile, the remains of which have of Nahuel-Huapi, to the west is Lake Todos Los been discovered in the central valley of that Santos (50 square miles), to which the access is country. The Andean glaciers at that time easy and of which the scenery is of surpassing spread themselves down to the plain at the foot beauty. Between 41° and 38° S. lat., among other of the two slopes which then contained vast smaller lakes, are Lakes Traful (45 square miles), lakes, and where now exist extensive moraines Lacar (32 square miles), which, properly belongand large erratic boulders. Mount Tupungato ing to the system of Atlantic lakes, empties reaches 22,329 feet, according to Argentine itself by the only water gap that occurs in this measurement. To the north ot this mountain, zone of the Cordillera into the river Valdivia, a situated at the watershed of the Andes, extends tributary of the Pacific, Lake Lolog (15 square a lofty region comprising peaks such as Chimbote, miles), Huechu-lafquen (45 square miles), and 18,645 feet, and Mount Polleras, 20,266 feet. Lake Alumine (21 square miles). The volcanoes The Pircas Pass is situated at a height of 16,962 of Lanin, 12,140 feet; Quetropillan, 9180 feet; feet. The gaps of Bermejo and Iglesia, in the Villarica, 10,400 feet; Yaimas and Tolhuaca are Uspallata road, the best known of all the passes all more or less active ; the first is in the main between Argentina and Chile, are at 13,025 feet chain, while the others are on the western slope. and 13,412 feet altitude respectively, while the The scenery in the neighbourhood is magnificent, nearest peaks, those of Juncal and Tolorsa, are the snowy cones rising from amidst woods of 19,358 and 20,140 feet high. Mounts Tupunaraucaria, and being surrounded by blue lakes. Aconcagua, 23,393 feet, ascended lately by While the scenery of the western slope of the 8 V.Darhtikir*owart& Qxfad rgof gato, Mr Fitzgerald, Mr Vines,and Sir Martin Conway, Andes is exceedingly grand, with its deep fiords, Scheme of the Andes Eange. and Mercedario, 21,982 feet, are the highest peaks glaciers, and woods, yet the severity of its of the central Argentine-Chilian Andes. These climate detracts considerably from its charm. The climate of the eastern slope, however, is milder, the land- three peaks are formed of eruptive rocks, surrounded by Jurassic scapes are magnificent, with wooded valleys and beautiful lakes. beds which have undergone a thorough metamorphosis. While The valleys are already partly settled by colonists. Between 52° in the west of the Andes, from the latitude of Aconcagua, the and 40° S. lat. the erosion (fractures of the earth’s crust) has central valley of Chile runs without any notable interruption to carried the watershed of the continent from the summit of the the south end of the continent, a valley which almost disappears to the north, leaving only some rare inflexions which are conCordillera to the eastern plains of Patagonia. Between 38° and 33° S. lat. the Andes have been somewhat sidered by the Chilian geographers and geologists to be a conextensively explored during the last ten years by the Argentine tinuation of the same valley ; to the east in Argentine there and Chilian Boundary Commissions. The highest peaks are vol- commenced a longitudinal valley perfectly characterized, which canic, and their eruptions have sensibly modified the character runs along the eastern foot of the Cordillera separating this from of the primitive ridges. Outflows of lava and tufa cover the the pre-Cordillera, which is parallel to the Cordillera de la Costa mountain sides and fill up the valleys. The Jurassic and Creta- of Chile. Between Aconcagua and Mercedario are the passes of ceous formations, which, in the Southern Cordillera are situated Espinacito, 14,803 feet, and Los Patos or Valle Hermoso, 11,736 outside of the range to the east, form to a considerable extent feet, chosen by the Argentine General San Martin, when he made the mass of the great range, together with porphyric quartz, the his memorable passage across the chain during the War of IndeTertiary, granite, and other eruptive rocks, which have been pendence. North of Valle Hermoso the Andean ridges, while observed along all the chain in South America up to Alaska in the very high, are not abrupt, and the passes are more numerous north. Gneiss is seldom met with, but there are crystalline than in the south ; some of them descending 10,000 feet, but rocks, belonging chiefly to the pre-Cordillera of the eastern, and most of them carrying between 13,000 and 14,000 feet. Pass