SOLIFLUCTION, A COMPONENT OF SUBAERIAL 

 DENUDATION 



J. G. ANDERSSON 

 Upsala University, Sweden 



According to the theory of river development, as it has been 

 worked out in its full modern form by a number of eminent Ameri- 

 can morphologists, the occurrence of narrow v-shaped valleys in 

 a region indicates that the region in question has passed only the 

 very first stages of the cycle of erosion. This type of valleys, con- 

 sidered by older European geologists as the most important feature 

 of river-action, is, according to the modern American school, only 

 an immature stage in the development of river valleys. 



In the course of time the blocks of land left between the prin- 

 cipal valleys will be dissected by secondary streamlets, the valleys 

 will be broadened, and their slopes will get more and more gentle. 

 At last, if the subaerial denudation has time enough to fulfil its work 

 under unaltered conditions, the hills are wholly consumed, the 

 region is base-leveled, and the land once deeply dissected is turned 

 into a slightly undulating plain with broad and shallow, faintly 

 insected river valleys. . Not till then has the process reached the 

 final stage of its cycle, the "peneplain." 



This theory of subaerial denudation is based upon the premise 

 that river-erosion works all over the areas, and not only linearly, 

 as was supposed by an older school of geologists. This assumption 

 looks at first somewhat startling. Evidently the main stream and 

 the principal tributaries of a river form only a branching system 

 of erosive lines. Only when the innumerable rivulets and feeders, 

 all the transient small waters washing hillsides and slopes at 

 rainfalls and snow-meltings, are taken into consideration, does 

 the erosive system present a network so close that it can be said 

 to cover all the area. 



In its finest embranchments, in the region of the primal feeders, 



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