With ski & sledge over Arctic glaciers

by Sir William Martin Conway

NEW FRIESLAND FROM HINLOOPEN STRAIT.

The old theory that glaciers not only polish but systematically excavate their beds is practically abandoned. Its supporters naturally considered that the larger the mass of ice the more vigorous would be its excavating action. A great arctic ice-sheet was regarded as an extraordinarily powerful excavator. We now know that moving land-ice does not so operate upon its bed, but, beyond polishing the surface of the rock it covers, has mainly a conservative effect upon it. In the case of a country like the interior of Greenland, wholly buried under ice, the buried land-surface undergoes modelling to a very slight degree, except round the coast. On the other hand, in the case of a glacial region, where mountains rise above the mean level, and where rock-faces are exposed to the rapid denudation that takes place at all snowy elevations, great developments of surface-formation are going forward. In the case of an ice-sheet, the forces acting on the land-surface are conservative; in the case of a glacial region, the acting forces are formative. Hence the immense importance of clearly distinguishing between these two types of ice-bearing country.

Without pausing to describe the particular places or views in Spitsbergen that suggested particular conclusions to my mind, let me rather, for briefness, indicate how it seems to me that one or two well-known mountain groups in Europe have been acted on by glaciers—for instance the Mont Blanc and Bernese Oberland ranges. Both, in their present developed condition, have been carved out of more solid masses which may be described as originally wrinkled plateaus, the original wrinkles having been approximately parallel to their length. Of course the denuding forces, whatever they were, operated simultaneously with the elevating forces; but the two may be considered separately for convenience’ sake, and we may speak of the plateau as first elevated and afterwards denuded. It must, however, be understood that during the earlier stages of the elevating process, water, not snow and frost, was the denuding agent. The culminating point of each plateau was approximately in the position of the highest point of the present ranges. The original main drainage must have run along the lines of the wrinkles; now, in both cases, it runs at right angles to that direction.

In order to indicate my meaning, it is not necessary to reconstruct entirely the original form of the plateau and its lines of drainage; one or two instances will suffice. In the case of the Mont Blanc range,[15] I suggest that originally there was a glacier with its head near the present summit of Mont Blanc, having for its left bank a ridge (or plateau-edge), now represented by the Aiguille du Midi and other aiguilles, the Aiguille Verte, the Aiguille du Chardonnet, and the Aiguilles Dorées; whilst its right bank was approximately coincident with the modern watershed as far as Mont Dolent, except between Mont Blanc de Courmayeur and the Tour Ronde, where it has been denuded away. This ancient drainage system has been broken down, and now the snows of the upper reservoirs are all discharged by such glaciers as the Mer de Glace or the Glacier d’Argentière, which cut across one or other of these old containing ridges or plateau-edges. Similarly with the Bernese Oberland, I suggest that the original crinkled plateau was drained along depressions approximately parallel to its length, whereof one was a high glacier basin with its head near the top of the present Finsteraarhorn and flowing W.S.W. over the Grünhornlücke and the Lötschenlücke and down the Lötschenthal. The old watersheds to right and left of this glacier have been driven back by the general disintegration of the plateau-edge, and broken utterly down in various places, so that its snows are now drained away at right angles to its direction by the Great Aletsch and Walliser Viescher glaciers.

In fact, in these cases it is with the glacial drainage as in the Himalayas it is with the rivers. When the great Asiatic plateau was elevated, whereof Tibet alone retains anything approximating to the original surface condition of the whole, the drainage ran off along the hollows in the line of the crinkling of the surface coinciding with the strike of the strata. Now, however, by the operation of rivers eating their way back into the plateau at right angles to the strike of the strata, all the great rivers flow at right angles to their original direction. The Indus was originally a stream no bigger than the Swat River, flowing down the edge of the elevated region. It ate its way through the Nanga Parbat range into the depression which goes on to Gilgit, and thus it stole all the waters of the upper Indus of to-day, which in the remote past, I believe, discharged themselves (over a high region since excavated into mountain ranges) into the Kunar River, and before that into the Oxus. Similarly the Gilgit River has eaten back through the Rakipushi range and stolen the waters of the Hispar-Hunza valley and the Hunza stream has eaten back through the Boiohaghurdoanas range, and so reached the Kilik Pass. It is noticeable that, in each case, the river has broken its way through a range in the immediate proximity of its highest peak, that is to say, just where the fall and gathering of snow has been greatest and the denudation most energetic.

In the case of rivers the eating back process is well recognised and understood. It is not really the work of the river, but it is accomplished by the various forces of atmospheric denudation, by frost and thaw, by avalanches and so forth, all taking place about the head-waters of the stream. I suggest that, under the action of similar forces, glaciers likewise creep back, and that the modelling of snow-mountains out of high plateaus is largely due to this process. According to this theory, though glaciers do not excavate their beds to any great extent, they widen them by carrying away the results of atmospheric and other denudation, and similarly they eat back at their heads. The most striking examples of this process I have seen are in Garwood Land. There, far in the interior, are a series of cliffs, several hundred feet in height. What the origin of these cliffs may have been is immaterial to the question under consideration. They form the front of the remains of the old plateau, which is being and has been eaten away. At the foot of the cliffs are the snowfields of the great glaciers which flow thence in a south-east direction to the head of Wybe Jans Water. By the melting of the snows above the cliffs and on their ledges, and by the action of frost and thaw, the rocks are rapidly broken up. The débris fall upon the glaciers below, and are carried away. If there were no glaciers in this position, the débris would pile up, a slope would be formed, and would presently reach up to the top of the cliff, and protect it from further denudation. The presence of the glaciers below prevents the débris from collecting. The cliff thus continues its existence, and merely moves backward by a steady progress, just as the cliff retreats over which Niagara falls. Where weaker rocks are encountered, or denudation is locally more energetic, the cliff eats backward more rapidly. An embayment is formed, which tends both to widen and to creep backwards, becoming in time a tributary valley. Of such valley heads which have crept back into the plateau we saw several examples; one in particular I remember in the midst of King James Land, which had annihilated a portion of a mountain range dividing two great glaciers, and had thereby caused what had originally been the chief névé basin of one of these glaciers to drain into the other instead of down its own tongue. When two neighbouring embayments, reaching back from the lower level into a plateau, send arms to join one another, or meet obliquely, a nunatak is formed. The nunatak near our farthest point in Garwood Land was produced in this manner.

BLUFFS OF THE SASSENDAL.

Keenly possessed by the memory of these phenomena, I went recently to Grindelwald, and was immediately struck by the resemblance in character between the great bluffs of the Bernese Oberland—the Eiger, Mettenberg, and Wetterhorn—and the bluffs of Spitsbergen’s Sassendal. The latter, as we know, were formed, and are still in process of development, by means of the torrents draining the snowfields above, which eat away the plateau and cut back into it, thus carving out a row of flat-topped steep-fronted hills that jut forward into the ever-widening main valley. It seemed evident that the ancient Oberland plateau had been similarly cut down, the excavation not having been accomplished by the grinding action of glaciers pushing forward and filing down their beds, but by the action, first, of torrents, before the plateau was elevated above the snowline, afterwards of glaciers; both torrents and glaciers creeping backwards at their heads, where faces of rock are exposed to rapid atmospheric denudation, and the débris that fall are transported to low levels by the movement of the flowing ice.

It was thus, I suggest, that the Upper and Lower Grindelwald glaciers and the Rosenlaui Glacier invaded the plateau and crept back into the heart of the mountain mass, isolating as high individual peaks the Wetterhorn and Schreckhorn. Originally they were “corrie glaciers,” plastered on to the north face of the plateau—just such glaciers, in fact, as is the Guggi Glacier, which lies in the hollow between the Jungfrau and the Mönch. They have crept farther back than it, because they had the better start, but the Guggi Glacier now emulates their former vigorous initiative. The cliffs at its head are being continually broken and worn away by the action of frost. The rocks that fall from them either tumble on to the névé and are carried down or roll into the bergschrund, and so get under the ice, where no doubt they are ground to dust, and may do some excavating in the process. That, however, can only be in the upper regions; lower down, the waters below the glacier are the excavating agent, rather than the glacier itself, except, perhaps, at the edge of some sub-glacial cliff beneath an icefall. In this way the rocks of the north face of the ridge between the Jungfrau and Mönch are being eaten away, and the ridge itself is not merely being lowered, but its crest is being pushed backward towards the south. Every yard of its movement is made at the expense of the Jungfrau Glacier. Let the process go forward for a sufficiently long time, and the area now occupied by the upper basin of the Jungfrau Glacier will be occupied by a snow-basin lying at a lower level, and draining northward down the Guggi Glacier.