Penck — Climatic Features in the Land Surface. 165 



Art. X. — Climatic Features in the Land Surface ; 

 by Albkecht Penck. 



The surface of the land is composed of slopes which are 

 for the most part gentle. Steep cliffs and overhanging forms 

 are exceptional and insignificant features ; where they occur, 

 they are soon destroyed. Their fragments fall and slide and 

 finally creep down ; thus all cliffs and overhanging forms are 

 transformed in the course of time into slopes and finally into 

 long grades. It is important to see that this process can be 

 accomplished simply by the force of gravity, helped by the 

 action of weathering, but without the interference of water. 

 The grading of the land surface is therefore a planetary process 

 which will occur on every planet whose surface is liable to 

 weathering as a result of changes of the surface temperature. 

 The slopes formed by weathering are normal to the direction 

 of those cliffs from which they originated, and if there was no 

 stream or wave action, no glacial or wind action on the earth, 

 the direction of slopes would be determined chiefly by the 

 direction of the cliffs formed by earth movements, and we 

 should observe in all slopes of the surface of the earth the 

 directions of crustal and volcanic movements. 



But the direction of the slopes on the land surface reveal 

 other features, and a study of the processes going on on the 

 rland surface shows us that the origin of its slopes is above all 

 connected with atmospheric action. Running water produces 

 long and extensive slopes by its erosive and constructive force; 

 it is enabled to transform slopes caused by crustal movements 

 into others which show a perfect adjustment to the material of 

 the earth's crust ; and finally it wears the land down to gently 

 sloping surfaces of the highest resistance. Running water also 

 deposits material in the form of gently sloping plains, which 

 extend very far. The action of running water is therefore 

 both a degrading and an aggrading one, and $he grades which 

 it forms show a systematic arrangement ; they slope down in 

 the direction in w^hich the water moves, mostly towards the 

 sea ; on one quarter of the land surface, however, towards 

 the interior of the continent, where the running water is evap- 

 orated ; and exceptionally in several regions composed of soluble 

 rocks, to those points where water enters the rock to follow 

 there a subterranean course. The latter case is a rather 

 unusual one ; it is connected with the very remarkable forms 

 of the Karst phenomenon, which, however, are only of limited 

 extent. 



Glacial action also produces slopes, either due to erosion or 

 to accumulation, but these slopes do not show such a systematic 



