28 



SOUTH AMERICA— THE ANDES REGIONS. 



On the other hand, the southern section of South America may be regarded as 

 lying within a cold zone, where the thermometer falls to 41° or even 39° Fahr. 

 on the plains, standing at a slight elevation above sea-level. On the coast ranges 

 the temperature, falling with the altitude, soon reaches freezing point. In this 



Fig. 9. — Main Geological Divisions of Sottth America. 

 Scale 1 : 55,000,000. 



Crystalline, volcanic, 

 and paleozoic rocks. 



Mesozoie 

 formation. 



Recent 

 formations. 



. 1,240 Miles. 



southern region the natural limit between the temperate and frigid zones is clearly 

 indicated on the west side by the fjords indenting the Chilian seaboard. The 

 sudden break in the uniformity of the coastline occurs a little north of 42° south 

 latitude, at the Chacao passage separating the island of Chiloe from the mainland. 



