THE 



JOURNAL OF GEOLOGY 



JANUARY-FEBRUARY, igos 

 GLACIAL FFATURES IN THE SURFACE OF THE ALPS 1 



ALBRECHT PENCK 

 University of Vienna 



The study of river action has been very much advanced in the 

 Alps, whose torrents give magnificent examples of the destructive 

 and constructive action of running water. But the surface features 

 of this great European mountain chain do not all correspond to those 

 which we might expect after a careful study of river action. Rivers 

 seek to establish a normal curve, which grows continually gentler 

 down-stream. The valleys of the Alps, however, do not show such 

 a regular grade. The floors of the headwaters show many irregu- 

 larities, and gentle grades alternate with steep ones. Instead of a 

 slope curve, there is a succession of descending steps. Farther down 

 we find for several miles a valley floor sloping normally; this floor 

 has been aggraded by the river and often ends in a lake basin, 

 where the normal slope is changed into a reversed one. Most of these 

 features are not produced, but rather are destroyed, by river action. 

 Indeed, we see how the rivers intrench themselves in the steep parts 

 of the stair slope, and how they fill up the lakes, which generally 

 occupy the lower part of "their valleys in the Alps. In short, their 

 action is directed toward removing the irregularities of their courses. 



There is still one other important point in which the slope of Alpine 

 valleys does not obey those rules which control normal valleys; the 

 law of Playfair is not applicable to them. The mouths of the lateral 



1 This paper contains some results to which the author has arrived by researches 

 on the Great Ice Age in the Alps, carried on together with Professor Bruckner, of 

 Halle. A detailed account of this study is given in a book entitled Die Alpen im 

 Eiszeitalter (Leipzig: Tauchnitz). A part of the paper was read at the International 

 Geographical Congress at Washington, September, 1904. 

 Vol. XIII, No. 1 1 



