GLACIAL FEATURES 281 



a lower mountain, but also loses it faster on account of the 

 smaller extent of surface upon which it is disposed and the pro- 

 portionally larger extent of counteractive, snow-free surface 

 about it. Among the volcanoes of Ecuador are many that show 

 differences of 500 feet in snowline elevation on windward and lee- 

 ward (east)- slopes and some, as for example Chimborazo, that 

 exhibit differences of 1,000 feet. The latter figure also expresses 



iooo'-^-<r-X go Gradient 



Fig. 190 — To illustrate the difference in the degree of canting of the snowline on 

 large and on small mountain masses. 



the differences in the broad Cordillera Vilcapampa and in the 

 Maritime Cordillera, though the rate of canting as expressed in 

 degrees is much greater in the case of the western mountains. 



The advantages of the proposed method of indicating the de- 

 gree of canting of the snowline lie in the possibility thus afforded 

 of ultimately separating and expressing quantitatively the vari- 

 ous factors that affect the position of the line. In the Cordillera 

 Vilcapampa, for example, the dominant canting force is the dif- 

 ference between sun and shade temperatures, while in the vol- 

 canoes of Ecuador, where symmetrical volcanoes, almost on the 

 equator, have equal insolation on all aspects and the temperature 

 contrasts are reduced to a minimum — the differences are owing 

 chiefly to varying exposure to the winds. The elusive factors in 

 the comparison are related to the differences in area and in ele- 

 vation. 



The value of arriving finally at close snowline analyses grows 

 out of (1) the possibility of snowline changes in short cycles and 

 (2) uncertainty of arriving by existing methods at the snowline 

 of the glacial period, whose importance is fundamental in refined 

 physiographic studies in glaciated regions with a complex topog- 

 raphy. To show the application of the latter point we shall now 



