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Glacier Recession and Periglacial Phenomena in the Ruwenzori Range (Belgian Congo)

Published online by Cambridge University Press:  30 January 2017

Jean de Heinzelin
Jean de Heinzelin*
Affiliation:
Institut Royal des Sciences Naturelles de Belgique, and Institut des Parcs Nationaux du Congo Belge
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Abstract

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Type
Research Article
Information
Journal of Glaciology , Volume 2 , Issue 12 , 1952 , pp. 137 - 140
Copyright
Copyright © International Glaciological Society 1952

Introduction

The Ruwenzori Range is composed of Precambrian (granitic and metamorphic) rocks, whereas the other glaciated central African mountains are the result of volcanic processes. Their morphologies are also different, Ruwenzori being decidedly more alpine. Mount Stanley is the most western ridge and, with the highest peaks of the range, forms the boundary of the Belgian Congo.

Explorations and Cartography

The summits of Mount Stanley were reached for the first time in 1906 from Uganda by the Duke of Abruzzi’s expedition.Reference Filippi 1 Stuhlmann had previously approached them in 1891Reference Stuhlmann 2 from the Semliki valley but a track to the glaciers was not open on this side before 1932 and the advent of the Mission Scientifique Belge au Ruwenzori.Reference Grunne 3a , Reference Jeannel b About the same time N. HumphreysReference Humphreys 4 carried out numerous explorations and reconnaissance flights. Many travellers followed later but the published accounts are very scarce and concern Uganda only.Reference Hicks 5a , Reference Menzies b The cartography of Mount Stanley’s glaciers is practically restricted to the rough contour maps of the 1906 and 1932 expeditions. The sketch map on p. 139 is based on Colonel Hoier’s survey made for the Institut des Parcs Nationaux du Congo Belge.

Comparison of Records

In July 1950 the writer was able to travel on the western slope of Mount Stanley and the evidences of glacial retreat appeared so fresh and extensive that a close comparison with the previous observations promised interesting results. Considerable help was given by the Directors of the Institut des Parcs Nationaux du Congo Belge, who kindly permitted the use of its copious and well classified records. Among them the photographs taken by De Grunne’s expedition (July 1932), J. H. Bredo (July 1935) and A. Gilliard (July 1939) require special notice. In the last sixty years the snow capping the highest peaks has been slightly reduced. This may be due to purely local causes. The larger ice mass of the Stanley Plateau and Stanley Pass has not apparently altered its outline. On the other hand, its margins have receded in places and every tongue nourished by this accumulation of ice has been considerably shortened. From north to south, one can observe:

  • (i) Alexandra Glacier: no records for comparison.

  • (ii) Western Stanley Glacier: this is the best known glacier and its retreat has been established by numerous observations since 1932. In that year the tongue was stationary near Lac Gris, almost damming the transverse trough and enclosing therein the greatest part of a rocky threshold. In 1935, the tip of the tongue sloped downwards and began to clear the rocky threshold. It was still in contact with the rock in 1939 but crevasses opened in the glacier margin. The recession greatly increased until 1950. Lac Gris is now surrounded up-stream only by bare rocks and stony debris. The glacier vanishes halfway down the slope, its front is carved up by melting processes and looks almost like dead ice. The profile from Stanley Plateau down to the front was smooth and steady in 1932 but it is now broken and truncated at the base. These facts show a recent raising of the snow line, estimated at 4450 m. in 1932. A small new lake appeared above Lac Gris between 1935 and 1939: it is called Lac Blanc. During the last fifteen years, vegetation has become rapidly established. The region between Lac Gris and Lac Blanc was practically barren in 1935 but now senecios and everlasting flowers are to be found there. Above Lac Blanc only lichens flourish.

  • (iii) Southern margin of Stanley Glacier; this already appears on Stuhlmann’s photograph of 1891. It looked rather thick at that time; in 1932 it had not yet greatly altered but now large patches of bare bedrock have appeared.

  • (iv) Moebius Glacier: on Stuhlmann’s photograph of 1891 it has a long tongue descending low into the trough. By 1932 this tongue had evolved into a hanging glacier and it is still thinner to-day. Outcrops of bedrock have appeared recently.

  • (v) Western Elena Glacier: no records for comparison. In 1933, P. MichotReference Michot 6a , Reference Michot b had noted: “… régression certainement récente puisque les appareils édifiés, particulièrement fragiles, sont parfaitment conservés.”

Older Features

The conditions described above constitute the last and shortest phase of a longer evolution. Lac Gris is dammed by a moraine which still looks fresh and is only moderately colonized by plants. Up-stream, traces of the corresponding basin can be seen with abrasion and discolouration of bedrock, roches moutonnées, erratics and little patches of ground moraine not completely dispersed. The age of this glacial extension is certainly not in the remote past; it has probably been completed, say, in historic times.

On its whole length, the Ruwenzori Range bears the traces of Pleistocene glaciations of a much greater extent, and of which many lakes are still now the most spectacular remnants. It would be more than conjectural to try a correlation between those stages and the general chronology of Pleistocene deposits without accurate morphological mapping, and careful investigation of the torrential fans deposited lower in the plains.

General Evolution

To summarize, the glacier tongues of Mount Stanley have undergone the following evolution:—very old Pleistocene stages; historic basin and terminal moraines; retreat; possible advance slightly before 1890; retreat, accelerated since 1939.

Those dates correspond with details reported from other central African glaciers, Kilimanjaro and Kenya,Reference Geilinger 7a – Reference Klebelsberg i which have been more fully investigated than Ruwenzori.

Periglacial Phenomena

C. TrollReference Troll 8a , Reference Troll b has written a very full and detailed paper about the comparison of various soil structures and periglacial phenomena in every kind of cold climate. From Kenya and Kilimanjaro he brought illustrations of features that looked typical for high mountains of low latitudes. Nevertheless these facts were never quoted in connection with the Ruwenzori Range where they appear with remarkable diversity and intensity. Here we find polygonal networks of ‘floating type,” more or less deformed on sloping ground, stone stripes, solifluxion flows and several vegetation patterns such as hummocks, thurfur, tundra ponds and “coussins.” The terrain in the neighbourhood of Lac Gris and Lac Blanc are quite representative in their aspects and, as a whole, one can point to a surprising similarity with the periglacial areas of the Icelandic glaciers, especially along the south coast of the island in summer. The soil structures they both show are quite different from those caused by frost action on the perenially frozen subsoil existing in periarctic countries.Reference Rutten 9

References

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