Modern Geography

by Marion I. Newbigin

There is still one other feature of glaciated regions to which reference must be made. This is the occurrence of peculiarly open passes in considerable numbers across mountain regions which have been recently glaciated. In the geography books and in some maps, the Alps, for example, are represented as a great barrier, shutting off the fertile plains of Italy from the countries of Central Europe. But history shows that they have never been such a barrier, and the phrase of “splendid traitor” has been applied to the whole mountain range, in order to emphasise its total inadequacy as a barrier, either to armed or to peaceful invasion.

Since the time of Napoleon I public attention has been focussed upon a few great Alpine passes, notably the Mont Cenis, the Simplon and the St. Gothard, which are crossed by great carriage roads, now functionally replaced by railway tunnels beneath. But we must not forget that in addition to these and the other great passes there are almost innumerable ways of crossing the Alps on foot, and the presence either of Hospices or of small inns on many of the smaller passes shows that they are constantly used at the present time, in spite of railway tunnels and carriage roads elsewhere. Even a pass relatively so difficult as the Théodule, was used by very large numbers of Italian peasants during the time when work on the Simplon railway made great demands on Italian labour.

Any one of the passes, great or small, shows in outline the same characters. There is a steep ascent, often steeper on the Italian than on the other side, then a broad, windswept, open summit, sometimes almost level, below which the rapid descent begins. Not infrequently a lake, or lakes, may be found near the summit.

On a smaller scale the same phenomenon occurs in such glaciated regions as Scotland, the relatively low connections between one valley system and another greatly facilitating communication, and usually carrying both road and railway, where the latter exists. Such connections between two drainage systems (that is, the existence of a very low divide between the two) only exist on a small scale outside glaciated regions, so that they, with all their effects upon communications, must be largely ascribed to ice-action. We shall describe one case in a little detail, with the proviso that while no one denies the frequency of such passes in glaciated regions, some authorities believe that their production was due more to glacial torrents than to the erosive action of ice itself.

A very pretty example is the picturesque pass known as the Gemmi, which is traversed only by a mule path, and connects Kandersteg, and thus the lake of Thun and the town of Berne, with the Rhone valley, which the path enters at the village of Leuk. The walk proper is, however, over at the Baths of Leuk, a small health resort lying at the foot of the great Gemmiwand, a wall of rock over 1,600 feet in height on the summit of which is the Gemmi pass. Readers of Mark Twain’s A Tramp Abroad will remember his interesting description of the crossing of the pass, which is part of the regulation tour in Switzerland.

The excursion may be very briefly described. The traveller starts from the village of Kandersteg, and almost immediately begins a steep climb, which after a rise of over 2,000 feet leads him over a ridge to a pasture, once swept by an avalanche. Another short but steep rise (note the staircase arrangement) leads him to the lonely Daubensee, a little lake which is frozen for more than half the year and has no outlet. It is itself fed by a glacier lying to the traveller’s right, the Laemmern glacier, which is shrinking and exposing more and more of its old bed. Even to the most inexperienced traveller it is obvious that this present day shrinkage is, as it were, the last remnant of a shrinkage which has been going on for a prolonged period, so that the route by which the traveller ascended from Kandersteg is but a remnant of the bed of the old glacier. The point of special interest, however, is that at the end of the Daubensee the traveller leaves the glacial valley by which he has ascended, and passing through a great notch or gateway in a wall of rock, begins the almost precipitous descent to Leukerbad, which lies at his feet, 1,600 feet below. It is this notch which makes the pass, and it is fundamentally a breach in the mountain wall which separates the drainage of the Rhine from that of the Rhone. Comparing small things with great we may note that this gateway presents some resemblance to the Tyne and Aire Gaps in the Pennines, already mentioned, which may also have been modified by ice-action.

The explanation given is as follows:—At the time when the glaciation reached its maximum height the mass of ice in what is now the Laemmern glacier was so great that it could not be contained within its own valley. The ice was piled up so high that it over-rode the watershed, rose up beyond the containing wall of its own valley, and pushed a long arm over the valley wall, down into the Rhone valley. This tongue of ice, either by its own erosive power, or because of the glacial and sub-glacial streams which it produced, wore out a notch in the wall as it crossed, and it is this notch which makes the pass. As the glacier gradually shrank, it could no longer send this tributary over the wall into the valley below, and was constrained to send all its drainage into its own valley, that is ultimately into the Rhine. But the Gemmi pass persists as a proof of its former magnitude, of the fact that once part of the Laemmern drainage reached the Mediterranean instead of the North Sea, that there was once a communication between the Rhine and the Rhone drainage systems.

Many at least of the great Alpine passes are believed to have been produced in this way, and therefore we must add to the peculiarities of recently-glaciated countries, the fact that passes are likely to be frequent across their hills and valleys, owing to the power which ice possesses, when enormously developed, of rising above valley walls, and streaming down into another valley system. Some of the great Alpine passes, perhaps, arose in other ways, but this brief description may be of interest as suggesting one, probably common, mode of origin.

If we sum up what has been said as to the special features of glaciated regions, we may note that their valleys tend to be U-shaped, and to be discontinuous with their tributary valleys, which “hang” over them. On the top of the cliff from which these tributary streams leap is a shelf, which is clearly a portion of the floor of the pre-glacial valley and is covered by glacial débris. At the heads of the valleys there are often cirques or plateaux, which again are markedly discordant, hanging high above the valley below. In the main valley itself there are similar discordances, giving rise to a staircase arrangement. Finally, different valley systems often communicate with each other by passes, natural highways which hang high above both valley systems alike.

Obviously, however, we might replace this detailed summary by the simple statement that whereas in a region subjected only to the action of running water, there is a marked tendency to continuity of slopes throughout, a tendency more and more marked the longer the water acts, in glaciated regions there is an equally obvious discordance, a discontinuity of slope, most marked where water has not had time to begin its smoothing action. As every glaciated valley which we can study in detail has been subjected to the action both of ice and of water, it is a simple deduction that the discontinuity is due to the differential action of the two. This is the point of geographical importance, and to the geographer it is of minor importance to know whether it is the passive resistance of the ice which has caused the discontinuity, or whether it is the water which has been unable to keep pace with the activity of the ice.