GLACIAL FEATURES 279 



the first pass) because they are to leeward of the border range, 

 hence receive less precipitation. The depressive effect of increased 

 precipitation on the snowline is represented by A-B, Fig. 184; in 

 an individual range the effect of heavier precipitation may be off- 

 set by temperature contrasts between shady and sunny slopes, as 

 shown by the line a-b in the same figure. 



The degree of canting of the snowline on opposite slopes of 

 the Cordillera Vilcapampa varies between 5° and 12°, the higher 

 value being represented four hours southwest of Arma on the 

 Choquetira trail, looking ^^_^^ 

 northeast. A general view i j o o - ^ *^~~ ----- ^r^v. r ? n n o ' 

 of the Cordillera looking ^^__^— -^ \. 

 east at this point (Fig. 186), ' — - 1 



Fig. 184 — To illustrate the canting of the 



Shows the appearance Of the snowline . A-B is the snowline depressed 



Snowline as One looks along toward the north (right) in response to heavier 



„ , _ precipitation. The line a-b represents a de- 



the flanks Of the range. In pression in the opposite direction due to the 



detail the Snowline is fur- different degree of insolation on the northern 



., Tjii i (sunny) and southern (shady) slopes. 



ther complicated by topog- 

 raphy and varying insolation, each spur having a snow- clad and 

 snow-free aspect as shown in the last figure. The degree of dif- 

 ference on these minor slopes may even exceed the difference 

 between opposite aspects of the range in which they occur. 



To these diversifying influences must be added the effect of 

 warm up-valley winds that precede the regular afternoon snow 

 squalls and that melt the latest fall of snow to exceptionally high 

 elevations on both the valley floor and the spurs against which 

 they impinge. The influence of the warmer air current is notably 

 confined to the heads of those master valleys that run down the 

 wind, as in the valley heading at the first pass, Cordillera Vilca- 

 pampa, and at the heads of the many valleys terminating at the 

 passes of the Maritime Cordillera. Elsewhere the winds are dis- 

 sipated in complex systems of minor valleys and their effect is 

 too well distributed to be recognized. 



It is clear from the conditions of the problem as outlined on 

 preceding pages that the amount of canting may be expressed in 

 feet of difference of the snowline on opposite sides of a range or 



