CHAPTEE XVI 

 GLACIAL FEATURES 



THE SNOWLINE 



South Ameeica is classical ground in the study of tropical 

 snowlines. The African mountains that reach above the snowline 

 in the equatorial belt — Buwenzori, Kibo, and Kenia — have only 

 been studied recently because they are remote from the sea and 

 surrounded by bamboo jungle and heavy tropical forest. On the 

 other hand, many of the tropical mountains of South America lie 

 so near the west coast as to be visible from it and have been 

 studied for over a hundred years. From the days of Humboldt 

 (1800) and Boussingault (1825) down to the present, observations 

 in the Andes have been made by an increasing number of scientific 

 travelers. The result is a large body of data upon which compara- 

 tive studies may now be profitably undertaken. 



Like scattered geographic observations of many other kinds, 

 the earlier studies on the snowline have increased in value with 

 time, because the snowline is a function of climatic elements that 

 are subject to periodic changes in intensity and cannot be under- 

 stood by reference to a single observation. Since the discovery 

 of physical proofs of climatic changes in short cycles, studies 

 have been made to determine the direction and rate of change of 

 the snowline the world over, with some very striking results. 



It has been found 1 that the changes run in cycles of from 

 thirty to thirty-five years in length and that the northern and 

 southern hemispheres appear to be in opposite phase. For ex- 

 ample, since 1885 the snowline in the southern hemisphere has 

 been decreasing in elevation in nine out of twelve cases by the 

 average amount of nine hundred feet. With but a single excep- 



1 Paschinger, Die Sehneegrenze in verschiedenen Klimaten. Peter. Mitt. 

 Erganz'heft, Nr. 173. 1912, pp. 92-93. 



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