The Patagonian Cordillera and Its Main Rivers, between 41° and 48° South Latitude (Continued) Author(s): Hans Steffen Source: The Geographical Journal, Vol. 16, No. 2 (Aug., 1900), pp. 185-209 Published by: geographicalj Stable URL: http://www.jstor.org/stable/1774557 Accessed: 27-06-2016 04:52 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The Royal Geographical Society (with the Institute of British Geographers), Wiley are collaborating with JSTOR to digitize, preserve and extend access to The Geographical Journal This content downloaded from 131.247.112.3 on Mon, 27 Jun 2016 04:52:42 UTC All use subject to http://about.jstor.org/terms ( 185 ) THE PATAGONIAN CORDILLERA AND ITS MAIN RIVERS, BETWEEN 41? AND 48? SOUTH LATITUDE.* By Dr. HANS STEFFEN. To return to the lacustrine basin of the Puelo valley, we see that it is confined on its northern side by the snow-clad mountain mass already mentioned, and as yet unexplored; while on its southern side runs, in a decidedly south-easterly direction, the lofty and steep barrier of the " Cordon de las Hualas," the precipitous flanks of which, towards the valley depression, offer a truly impressive sight. They fall hardly short of the perpendicular, and afford a most precarious hold for a scanty vegetation. Enormous masses of rocks detached from its upper parts have been heaped chaotically in spots near the shores of those lakes, where they lie now half hidden amongst the outgrowth of vegetation. The Cordon de las Hualas, crowned by a high crest and snow-fields, keeps on its parallelism with the following part of the Puelo valley, that is characterized by an alternate succession of extensive widenings and narrow defiles between minor chains, this being another typical feature in all the large rivers of Chilean Patagonia. Within the con- tinuous depression of the main valley the river meanders for long stretches between low banks formed by alluvial river deposits, covered with exuberant vegetation. The river-bed is bounded by extensive gravel or sand beaches, and the cliffs of the hills bordering the valley are far enough from the river channel to allow the construction of roads on both sides. There are frequently found amidst those white plains swampy grounds, bare of trees, or partly covered with bushes of scanty cipres and slim bamboos; those swamps are called in Chile, " nadis " or " trapenes," and their origin is explained by the deficient sloping of long stretches of ground, underneath which there is an impermeable layer of subsoil, this preventing the drainage of the water accumulated by the incessant rainfalls. The alluvial fields at the river-sides often show evident indications of their being covered by the great floods which, we have evidence of it, sometimes rise as much as 15 to 20 feet above the regular summer level of the river. This is obviously a great drawback to the agricultural use of such lands; but there are also extensive plains of gentle slope, and sufficient altitude over the river, to be out of the range of floods. These plains, called " llanadas" by the Chilotes, are frequently, as in the Puelo valley, of such an extent that inexperienced people getting sight of them from a low point of the valley have been led to * Read at the Royal Geographical Society, March 19, 1900. Map, p. 140. It is hoped to publish a more detailed map in a future number. Continued from p. 38. This content downloaded from 131.247.112.3 on Mon, 27 Jun 2016 04:52:42 UTC All use subject to http://about.jstor.org/terms 186 THE PATAGONIAN CORDILLERA AND ITS MAIN RIVERS, believe that they were nearing the borders of the Cordillera, the eastern ranges of which are sometimes barely seen on the distant horizon of these plains. They are covered by extensive forests of high trees, among which are to be found, besides those growing near the coast, as the groups of Myrtacese and Cupuliferse, certain species that do not grow on the coast, as the Libocedrus chilensis, commonly called " Cedro " or " Cipres de la montaia," and the timber of which is particularly valuable for the construction of buildings, ships, etc. Under the lofty trees grows the dense underbrush, mainly composed of " colihuales," so thickly pressed sometimes that they do not allow any other vegetation, the fallen leaves being then the only clothing of the ground. Some of these colihue-bamboos are 25 to 27 feet high, and 4 inches round their base. Beautiful creepers (Mitraria, Boquila, Luzuriaga, etc.), with white or red flowers, are entangled between the trees, rendering the march very troublesome. When the colihuales are not so thick, the ground is carpeted by a deep moss covering, saturated like sponges with rain- water, and a profusion of ferns, amongst which the Alsophila pruinata is conspicuous by its colossal dimensions, break the monotony of the forest. Day after day we marched on level ground, the sombre cover of the evergreen foliage of the trees allowing but little of the daylight to pass, and where the abundance of moisture prevents the evaporation and permeates the air with an intense smell of damp- ness proceeding from the numberless fallen tree-trunks in course of decomposition, and from the dense layer of decayed leaves and mould covering the soil. The transition between the orographical characters of the broad parts of the valley and the narrow is usually rapid, and this happens at the intermediate course of the Puelo valley. The traveller finds himself of a sudden at the entrance of a darksome defile with per- pendicular walls, the minor windings of which correspond to the rocky spurs encroaching on the river-bed from each side. The advance by land in such defiles would meet with insuperable obstacles, as there are such tight places that even the most skilful mountaineer would not be able to find his way by the steep sides that confine the river. These narrow parts would form insurmountable obstruction if the borders or cliffs reached a considerable height; but as a general rule their upper part does not rise more than 200 to 300 feet above the river, being formed by plains, as an extension of the " llanadas " of the wider valley. The path must be looked for then, making a detour by these upper parts, and to arrive there it will sometimes be necessary to go up and down secondary spurs, and to cross over ditches and torrents on their way down from the upper terrace to the level of the river, which is frequently reached by the waters in the shape of a cascade over the cliff border. An interesting feature to be observed in the forms of this inter- This content downloaded from 131.247.112.3 on Mon, 27 Jun 2016 04:52:42 UTC All use subject to http://about.jstor.org/terms BETWEEN 41? AND 48? SOUTH LATITUDE. 187 mediary part of the valley are the gravel and pebble-stone terraces that lie with some interruptions, forming successive steps; these terraces are evidently the remains of deposits corresponding to the various levels of the river course at former periods. At some places where the Puelo valley is remarkably wide, as at that called " Cor- rales " by us, the successive terraces are outlined with surprising regu- larity along the slopes confining the circus-like enclosure of the valley. Four different levels may be detected from afar, their perfectly horizontal upper lines contrasting visibly with the rugged outline of the surround- ing mountains. In some other valleys, as in that of the Cisnes river, which will be described further on, and in the Corintos valley, tributary RIVEP AISEN NEAR ITS MOUTH (LOOKING WEST). to the Futaleufi-Yelcho, the successive terraces are so regularly heaped up that they look like a railway embankment in course of construction. The Patagonian Cordilleran valleys offer thus many instances of a phenomenon that has been the object of much study in the Alps, Pyrenees, and other mountains of the Old World; in both cases the explanation is to be found in the periodical accumulation of increased deposits at the time of greater glacial activity and their subsequent wearing out by the streams. We have observed in this respect an interesting fact in the Puelo country; it is that the remains of those terraces are precisely found in such places of the main valley as lie directly down stream of the mouths of the tributary torrents into those Cordilleran depressions, where the bordering mountains show actual glaciers which still contribute to swell the volume of waters of the main river. We must make here some remarks about the orographical forms of This content downloaded from 131.247.112.3 on Mon, 27 Jun 2016 04:52:42 UTC All use subject to http://about.jstor.org/terms 188 THE PATAGONIAN CORDILLERA AND ITS MAIN RIVERS, the part of the Cordillera that we have reached through the course of the Puelo valley. We have mentioned the high barrier of the Hualas range, which lies along the southern side of that valley, and extends without a perceptible break over 50 miles in a south-easterly direction, until it is knit to- gether with the powerful mass of andine mountains, 6000 to 8000 feet high, that surround on the southern side the Lake Superior basin, which must be considered as the main receptacle of water feeding river Puelo.