112 J. G. ANDERSSON 



moving slopes indicates that here the removal of the waste runs 

 on at a rate that may be unsurpassed in other parts of the earth 's 

 surface — except in the deserts. 



But this effective removal of the waste must be balanced on the 

 one hand by a rapid production of new waste, and on the other, 

 by an effective clearing out of valley bottoms by running water. 

 The "subglacial" climate is most favorable for both these processes. 

 In the extra-glacial regions the frost-weathering works with an 

 intensity well known to every student of polar lands and alpine 

 mountains, and the violent summer floods caused by the melting 

 of the winter's snow give to the rivers of these regions an erosive 

 power that is quite surprising. 



When all these conditions are taken into consideration, the 

 "subglacial" chmate must be looked on as an optimum of des- 

 tructive action. In fact, the high mountains, the large folded 

 ranges, where all the agents mentioned work in high intensity, are 

 found to be short-lived features in the earth's surface. In fact, 

 one might be tempted to raise the question whether complete pene- 

 planation is possible in regions where the action of running water 

 is not supported by an effective removal of the waste, such as is 

 produced by solifluction. With this premise, ever}^ peneplain found 

 a climatic token of the same kind as the stone-rivers of the Falk- 

 land Islands and the limestone breccias of Gibraltar. Still I think 

 that such a presumption hides a dangerous exaggeration . It is very 

 possible that in many cases, under other climatic conditions of less 

 erosive power, the process has had time to reach, though at a very 

 slow rate, the end of the cycle of erosion. 



But, on the other hand, it seems certain that solifluction has 

 often been an important agent toward peneplanation. The im- 

 portance of the process, because of its humbleness, has been much 

 undervalued. But I feel sure that it is not until we get a knowl- 

 edge of all the contributive agents that we can reach a full under- 

 standing of all the varied and complicated forms of land-sculpture. 



