408 SOUTH AMERICA— THE ANDES REGIONS. 



In this region the Andes ramifies into two distiuct ranges enclosing shallow 

 basins probably of lacustrine origin, which generally bear the name of i^ampas. 

 The Huasco and Chacarilla pampas stand at the respective altitudes of 12,6-35 and 

 12,670 feet. Above the east side of the encircling heights rise the snowy Iquima 

 (20,275 feet) and Toroni (21,340). 



The western chain culminating in the Tata Yachura and Yabricoya, both about 

 17,000 feet, falls east of Iquique, developing an extremely regular plateau at a 

 mean elevation of 13,650 feet, which from its resemblance to a " table" bears the 

 name of ^nesa. It serves as an outer terrace to the eastern chain, that is, the 

 true Cordillera, which here takes the name of Sierra de Sililica, and where occur 

 the highest peaks, as well as still active craters. Tua, Chalo (Chela), Olca, Mino, 

 ranging from 16,400 to 17,400 feet, and Ollagua (19,330), all emit vapours or dis- 

 charge lavas, and are flanked on the west side by the San Pedro volcano rising 

 above a lateral ridge. 



All these cones are disposed in irregular order to the right and left of the 

 normal axis of the system, while Aucasquilucha (Aucaquilcha), the loftiest summit 

 in this section of the Andes (20,260 feet) stands quite apart, raising its isolated dome 

 above the saline wastes in Bolivian territory. None have been ascended, or even 

 seen near enough to permit of accurate measurements, except Ollagua, whose crater 

 was reached in 1880 by the engineer, Hans Berger, engaged in the construction 

 of the Antofagasta-Huanchaca railwa3^ The present crater, which lies 1,150 

 feet below the highest peaks, is not of the normal circular form, but comprises a 

 number of fissures and cavities, from which escape white wreaths of aqueous and 

 sulphurous vapours accompanied by hissing and rumbling sounds. Clear yellow 

 crystals are deposited round all the apertures. Hound the cone are seen traces of 

 glaciers with their semi-circular moraines, showing that the climate was formerly 

 more humid, as in the Cordillera generally. 



South of Ollagua the main range, in which are comprised all the igneous vents, 

 at first trends regularly north and south, then bends round south-westwards to its 

 junction with the West Andean chain under the latitude of Copiapo. Above the 

 pedestal of the chief cordillera rise the domes or pyramids of at least thirty extinct 

 volcanoes, all exceeding 16,400 feet in altitude. Atacama, Licancaur, Toconado, 

 Hlascar, Tumisa, Socaira, follow at short distances, and are flanked on the right by 

 the Antopalla group (20,920), and on the west by Socompoz (19,620), Guanaquero, 

 and Llullaillaco (21,670). These, also, despite their great altitude and easy access, 

 are little known, and Licancaur alone has been ascended to within 1,300 feet of 

 the summit by Steinmann, who found traces of habitations up to the point reached 

 by him. 



The whole of the Atacama region is occupied by parallel ranges disposed mostly 

 north and south, but also throwing off irregular spurs and foothills of considerable 

 elevation. Even in the vicinity of the coast heights occur exceeding 6,500 feet, 

 and here Trigo rises to 8,780 feet, while the Cerro Negro farther inland east of 

 Antofagasta attains 10,970 feet. The Caracoles or " Shell " Mountains, so called 

 from their fossil ammonites, also exceed 10,000. 



