(A) INTRODUCTION TO THE ALPS
(c) Main Chains of the Alps
In every mountain system geographers are disposed to regard the watershed, or boundary dividing the waters flowing towards opposite sides off the range, as marking the main chain; and this usage is often justified by the fact that the highest peaks lie on, or very near, the boundary so defined. In applying this term in the case of the Alps, there are, however, difficulties arising from their great extent and the number of their branches and ramifications, Many of the loftiest groups lie altogether on one side of that which we call the main chain, and at the eastern extremity, where all the drainage is ultimately borne to the Black Sea, we must be partly guided by geological considerations in deciding which of several ranges deserves to be considered pre-eminent.
Starting form the pass of Altare or Cadibona, west of Savona, the main chain extends first south-west, then nearly due west, to the Col di tenda, but nowhere rising beyond the zone of coniferous trees. Beyond that limit the range is more lofty, and includes four peaks exceeding 10,000 feet in height, till the line dividing the waters flowing to the Adriatic, through the Po, from the short-streams that flow into Gulf of Genoa, reaches the Mont Enchastraye. Beyond that point, although the line of watershed is very sinuous, its general direction for a distance of about 75 miles is nearly due north. On the east side of the waters run to the Po; on the west they flow through the Durance to join the Rhone near Avignon. The most considerable peaks in the range immediately north of the Mont Enchastraye are the Grand Rioyrent and the Aiguille de Chambeyron; but these are much surpassed by the Monte Viso, which is the highest peak in the range dividing Piedmont from dauphine. On the north side of Monte Viso the main chain diminished much in average height, and presents no prominent peaks until we reach the Mont Tabor. That summit forms the apex of a salient angle which the main chain here presents on the side of France. For a distance of about 28 miles this extends eastward to the prominent peak of the Roche Melon, which may be considered as a re-entering angle in the great rampart by which Italy is guarded from her northern neighbours. Here the main chain resumes its northerly direction, and attains a greater average height that it had previously exhibited. Several of the prominent peaks in the range connecting the Roche Melon with Mont Blanc exceed 11,000 english feet in height, though they are much surpassed by the highest group of the Graian Alps, lying on the side of Piedmont, and that of the Tarentaise Alps in Savoy; while there is in this part of the main range but one considerable depression, which is that crossed by the road of the Little St. Bernard. In the range crowned by the summit of Mont Blanc the Alpine chain attains its highest elevation. From thence to the Pass of St. Gotthard its general direction varies between east and north-east. To the east of Mont Blanc a comparatively low tract allows of several comparatively easy passes between Switzerland and Piedmont, one of which has long been famous as the Pass of the Great St. Bernard; but from that to the Simplon Pass, a distance of about 52 miles in a straight line, or about 75 miles if measured along the watershed, the main chain preserves a greater average heights than in any other part. Several peaks lying in the dividing ridge, such as the Grand Combin, Matterhorn, Lyskamm, and Monte Rosa, exceed 14,000 feet in height; and these are rivaled by at least six summits on the north side of the same ridge, which at two points only sinks below the level of 10,000 feet. The Simplon Pass corresponds to what may be called a dislocation of the main chain. From thence to the St Gotthard the dividing ridge runs nearly due north-east, and does not present any dominant summit excepting the Monte Leone. On the east and south-east side of the St Gotthard Pass, as far as that of the Maloya, the line of watershed determined by what may be called accidental conditions. The chief mountain ridges, which culminate in the Cima Camadra, Piz Valrhein, and Tambohorn, instead of being arranged along the parting of the waters, lie in a transverse direction, and hence the natural frontier of Italy is here more broken and irregular than elsewhere; and it is only on the south side of the Maloya Pass that the main chain assumes a tolerable continuous direction from west-south-west to east-north-east, as between Piz Guz and the Bernina Pass it rises into the lofty group whose dominant peaks are Piz Tremoggia, Piz Bernina, and Piz Cambrena. Eastward of the Bernina Pass the same direction is preserved, and in the range including the Corno di Campo, Monte Zembrasca, and Monte Foscagno the level scarcely sinks below 9000 feet; but beyond the last-named summit, in the space lying between the Lower Engadine, the head waters of the Adige, and those of the Adda, the semblance of a continuous ridge forming the watershed between the Inn and the Adriatic altogether disappears. If we adhere to the usage of designating as the main chain the ridges which part the waters flowing in different directions, it must be owned that the disposition of the chief mountain masses has no connection with the direction of that chain. Lying between the great mass of the Orteles Alps to the south and the considerable group of the Silvretta Alps on the north side of the Inn, the greater part of the mass in question is drained by streams that flows into the latter river, but the arrangement of the valleys seems to be largely due to erosive action. Few summits in this part of the main chain exceed 10,000 feet, the highest being Piz Scasvenna, on the east side of Val Scarla.
The break in the continuity of the Alpine chain marked by the deep valley through which the main branch of the Adige descends, first southward and then eastward from its source to Meran and Botzen, is on of the most remarkable features in the orography of the Alps. The little lake which is regarded as the chief source of the river lies within less than five miles of the Inn, where that river enters the Tyrol, and no apparent barrier divides the lake from the Inn valley. Eastward of this limit the Alpine chain exhibits a degree of order in its general arrangement which it is impossible to trace in its western and central portions. For a distance of some 250 miles a broad zone of crystalline rocks extends from west to east, flanked on the north and south sides by parallel zones of sedimentary rocks, chiefly belonging to the older secondary formations. Two great valley systems on the opposite sides of the central zone closely coincide with those geological boundaries, and mark out in the physical aspect of this region the limits between the central and the secondary zones. In the former are situated all the highest peaks of the eastern Alps. For a distance of about 140 miles, from the Schafkogel, south-east of Nauders, to the Markkahrspitz, the average level of the main chain is nearly as high as in any equally long section of the central or western Alps. There is one very considerable depression which is marked by the Brenner Pass, but elsewhere in that long barrier there are but three points where the range is passable by beasts of burden. Between the two main sources of the Adige, at the Reschen scheideck and the Brenner Pass, the considerable groups of the Oetzhal and Stubal Alps attain a great average elevation, though two points only --- the Wildspitz and the Weisskugel --- surpass the level of 12,000 feet. The drainage of these groups is mostly carried to the Inn, and the line of watershed, about 53 miles in length, is much less direct than in the more easterly portion of the chain. This extends nearly due east for about 90 miles from the Brenner Pass, nowhere falling below the level of 8,000 feet, and in two prominent peaks --- the Gross Venediger and the Gross Glockner --- rising considerably above the limit of 12,000 feet. At a point somewhat north of the Markkahrspitz the central chain divided into two parallel ranges, between which lies the upper valley of the Mur. This river flows for a distance of fully 80 miles nearly due east, till at Bruck-an-der-Mur it turns southward to approach the Drave, and ultimately joins that stream. Various reasons combine to induce geographers to regard the more northern of the two ranges above mentioned, which divided the Enns and other minor tributaries of the Danube from those of the Drave, as constituting the eastern extremity of the main chain of the Alps. This extend a little north of due east for more than 110 miles, with a comparatively low mean elevation, from the Arlscharte to the Semmering Pass, which we regard as the eastern limit of the main chain of the Alps.
Measured along the watershed, as above defined, but without taking into account the minor sinuosities, which would considerably increase the total, the length of the main chain is about 790 English miles.
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The Alps - Table of Contents