The morphological features of the Patagonian Andes begin at 36° S. lat.[53] The edge of the Cordillera, in the Malargüe depression, below 35° S. lat., still presents the typical scenery of the central Andes. The dejection-cone of the Atuel resembles that of the Mendoza. The fringe of torrential deposits, distributed in cones over which the waters spread, is due to the rapidity of the disintegration of the rocks in a desert climate. Keidel has pointed out the part played by the summer rains in transporting mobile elements, which the water drops as soon as the slope diminishes; the amount of precipitation being too slight to permit the formation and spread over the plain of a regular network of streams. From the Rio Grande onward the dejection cones disappear. The streams tend to become permanent, and sink into narrow valleys. The summer rains cease, and the water produced by the melting of the snows has only a feeble capacity for transporting stuff. The soil of the Cordillera is protected by a denser vegetation. The first thickets of molle appear in the valleys, the first scattered cypresses on the slopes, at the Rio Agrio, a tributary of the Neuquen. Then the forest invades the mountain: at first, from 38° S. lat. to 39° 30′ S. lat., a resinous forest of araucarias. At length, at Lake Nahuel Huapi, the forest assumes the general appearance which it has as far as the Magellan region. It is chiefly made up of different kinds of beeches. The coihue (Notofagus dombeyi) is the most conspicuous for about three quarters of a mile, rising above an impenetrable undergrowth of bamboo. Higher up the domain of the lenga (Notofagus pumilio) extends as far as the fringe of the Alpine forests. The forest does not reach the eastern limit of the lakes. In the sub-Andean depression it is reduced to thickets of ñirre (Notofagus antarctica) and mayten and clumps of calafate (something like myrtles).

It is on the Alumine, about 39° S. lat., that we find traces of glacial erosion, as they spread over the landscape. At present there is no ice on the mountain except on the peaks of Lanin and Tronador, but from the Rio Puelo onward (42° S. lat.), glaciers clothe all the summits which rise above 6,500 feet. North of the Aisen they form a narrow, but almost continuous, line. From the Aisen to the Calen fiord, and beyond the gap of the fiord as far as 52° S. lat., the ice spreads in a considerable sheet which in some places attains a breadth of eighty miles. The tongues of the glaciers reach the Pacific below 46° S. lat., and Lake San Martin on the Argentine slope below 49° S. lat. In Tierra del Fuego the snow-line is at 2,300 feet, and the glaciers which the snows feed, reach as far as the fiords and Lake Fagnano.

Lake Carri Lauquen, on the Barrancas (36° 20′ S. lat.), which was almost entirely drained in 1914 through the breaking down of the natural dam of soft earth which confined its waters, is not a glacial lake.[54] The chain of glacial lakes stretches from the Alumine to the Seno de la Ultima Esperanza, and is continued southward by Skyring Water, Otway Water, and Useless Bay—genuine lakes in communication with the Pacific by means of narrow channels. The lakes sometimes lie in a narrow and deep glacial valley, the bottom of which they fill; sometimes they branch out into the neighbouring valleys; at other times they advance eastward beyond the zone of the mountains and spread into round basins surrounded by circles of moraines. The largest of them include groups of ramified fiords, which represent their western half, while the eastern half spreads between lower banks.[55]

YOKE OF CREOLE OXEN USED FOR THE TRANSPORT OF TIMBER ON THE EASTERN CHACO, OR CHACO OF SANTA FÉ.

On the Central (or Santiago) Chaco mules are used for transport.

Photograph by the Author.

[Click to view larger image.]