282 THE ANDES OF SOUTHERN PERU 



attempt to determine the snowline of the glacial period in the belt 

 of country along the route of the Expedition. 



In the group of peaks shown in Fig. 188 between Lambrama 

 and Antabamba, the elevation of the snowline varies from 16,000 

 to 17,000 feet (4,880-5,180 m.), depending on the topography and 

 the exposure. The determination of the limit of perpetual snow 

 was here, as elsewhere along the seventy-third meridian, based 

 upon evidences of nivation. It will be observed in Fig. 191 that 

 just under the snow banks to the left of the center are streams of 

 rock waste which head in the snow. Their size is roughly propor- 

 tional to the size of the snow banks, and, furthermore, they are not 

 found on snow-free slopes. From these facts it is concluded that 

 they represent the waste products of snow erosion or nivation, 

 just as the hollows in which the snow lies represent the topo- 

 graphic products of nivation. On account of the seasonal and an- 

 nual variation in precipitation and temperature — hence in the ele- 

 vation of the snowline — it is often difficult to make a correct snow- 

 line observation based upon depth and apparent permanence. 

 Different observers report great changes in the snowline in short 

 intervals, changes not explained by instrumental variations, since 

 they are referred to topographic features. It appears to be im- 

 possible to rely upon present records for small changes possibly 

 related to minor climatic cycles because of a lack of standardiza- 

 tion of observations. 



Nothing in the world seems simpler at first sight than an ob- 

 servation on the elevation of the snowline. Yet it can be demon- 

 strated that large numbers of observers have merely noted the 

 position of temporary snow. It is strongly urged that evidences 

 of nivation serve henceforth as proof of permanent snow and that 

 photographic records be kept for comparison. In this way meas- 

 urements of changes in the level of the snowline may be accurately 

 made and the snow cover used as a climatic gauge. 



Farther west in the Maritime Cordillera, the snowline rises to 

 18,000 feet on the northern slopes of the mountains and to 17,000 

 feet on the southern slopes. The top of the pass above Cotahuasi, 

 17,600 feet (5,360 m.), was snow-free in October, 1911, but the 



