9— SOLIFLUCTION. 



By Prof, E. H. L. Schwarz, A.R.C.S., F.G.S., 



[Abstract.] 



Prof. J. G. Andersson, of Upsala, in a recent paper, (') pro- 

 posed to call the movement of rock waste saturated with moisture, 

 down the slopes of hills, " solifluction," from solum, soil, and -fluere, 

 to flow. Andersson took most of his examples of this movement 

 from high latitudes, and from lofty mountains, where the disinte- 

 gration of rocks is rapid, and the amount of water, resulting from 

 the thawing of the covering of snow and ice, was very great. Thus 

 the stone rivers of the Falkland Islands are explained on this 

 assumption of flowing soils, and similar occurrences are noted in 

 Spitzbergen, Scandinavia, Tibet, the Urals, etc. Prof. W. M. Davis 

 had already noticed the slow movement of the waste-sheet down 

 slopes in temperate climates, (^) and Andersson's term is now gener- 

 ally applied to this movement, whether rapid or slow, according to 

 the climatic conditions of the locality. 



In South Africa, both the rapid and slow varieties of solifluction 

 occur. Of the former, an excellent example occurred at Clifton, 

 near Sea Point, Cape Peninsula, which was fully described in the 

 loth Annual Report of the Geological Commission; (') here the soil 

 was scorched by a bush fire, and the loose grains absorbed moisture 

 till a quicksand was formed on the surface, which gathered into a 

 stream that tore down the hill-side, carrying huge boulders along 

 with it. It is to be noted, that the specific gravity of the viscous 

 mud or quick-sand is very little less than that of the boulders which 

 it carries along with it, hence its ability to move huge blocks, which 

 practically float in it. 



Mr. Schlinnberger, in a similar mud-rush in the Alps, estimated 

 that the amount of water entangled in the sand was in the proportion 

 of one to three. {*) 



Along the faces of the steep hill-sides in the Karroo, and in 

 the coastal ranges of the South West of Cape Colony, there are often 

 seen lanes of bare stones, usually bordered by green strips of luxuri- 

 ant bush. These have formed in the same way through transport by 

 solifluction. On examining the fresh falls, the stones are seen im- 

 bedded in sand, but subsequently the sand is washed from between 

 the blocks on the surface, and a stone river is exposed. 



A more general example of solifluction occurs in hills like those 

 round Grahamstown. On the north of the town there are steep 

 slopes, capped with hardened gravels, belonging to an ancient pene- 

 plain. The latter occurs almost like a horizontal covering of lava, 



(1) Solifluction, a component of subaerial denundation ; Journal of Geology 

 Chicago, 1906, p. 91. 



(2) W. M. Davis, Physical Geography, p.p. 263, 267. 



(3) The term "solifluction" was applied to this independently by S. 

 Passurge, Petermann's Geogr., Mitteilungen, 1907, xii. p. 229. 



(4) P. Demontzey, Reboisement des Montagnes, Paris, 1889, Note A. 



