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II.—Moraines and Mud-streams in the Alps

Published online by Cambridge University Press:  01 May 2009

Canon T. G. Bonney
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Extract

It has often occurred to me during my Alpine wanderings that masses of earthy material containing boulders are too readily identified as moraines. That the latter exist, both here and in other mountain regions, no one would for a moment dispute, but deposits, sometimes very closely resembling till, may be produced in other ways. One is by a bergfall. The result of this in some cases, as at Goldau, Plurs, near San Vito (Ampezzo road), or the Col de Cheville, can be easily recognized; but when the fallen material consists largely of shale and friable rock, when there is a certain admixture of boulders from a distance (formerly perched blocks), its origin is not so readily determined. The enormous mass of débris on the north bank of the Rheinthal, between Chur and Ilanz—a mass which extends from Digg, through Flims, to rather beyond Laax, consisting of earthy stuff, probably mainly smashed shale or slate, and of boulders, apparently limestone—is regarded as bergfall by the Swiss geologists, and yet any section in it might readily be taken for moraine. Even more moraine-like in general aspect are the singular mounds of débris in the valley of the Rhone near Sierre.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 1 , January 1902 , pp. 8 - 16
Copyright
Copyright © Cambridge University Press 1902

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References

page 9 note 1 I was informed that the stream, some two or three thousand feet above Zinal, had been dammed by a slight landslip till the ponded-back water burst the barrier.

page 10 note 1 A summary of the facts will be found in Joanne, “Itinéraire de la Suisse,” Route 25 (between St. Maurice and E'vionnaz).

page 10 note 2 See also Dr.Irving, A., Quart. Journ. Geol. Soc., vol. xliv (1888), p. 158Google Scholar.

page 10 note 3 “In the Ice World of Himalaya,” p. 156.Google Scholar

page 10 note 4 “Climbing in the Himalayas,” p. 323.Google Scholar

page 11 note 1 See also “The Making of a Frontier,” by Durand, Colonel A., pp. 33, 34Google Scholar. (As I have explained in a paper now in the hands of the Geological Society, I think Sir M. Conway's description includes with the mud avalanches a breccia which has a rather different history.)

page 11 note 2 I had examined this during the previous Summer (1892).

page 11 note 3 In my diary I have given the facts which make for the one or the other conclusion, but as there is no impossibility that both may occur in this valley I deem it needless to enter into particulars.

page 11 note 4 It is shown clearly on the Geological Map, where it is marked as “Terrain Glaciaire.” The material, from which the actual pillars are carved, is perhaps more directly in the line of the Val d'Hérémence.

page 12 note 1 Note written on the spot in 1900, when I saw them again after an interval of twenty-four years.

page 13 note 1 I have little doubt that the Zwerglithurm near the path from Viesch to Eggischorn, figured by Sir C. Lyell (“Principles of Geology,” ch. xv), which I examined in 1881, has been carved out of similar material.

page 14 note 1 As is the case with the trass which still remains in places in the Brohlthal (Eifel).

page 15 note 1 So far as I can judge from the excellent illustrations to the papers mentioned above, the débris can hardly amount to one-fifth of the whole mass, so that the former is seldom likely to exceed 20 feet, and would generally be much less.

page 15 note 2 This, if I mistake not, is included by Continental writers in the term ‘Glacial Schotter.’