186 



THE ANDES OF SOUTHERN PERU 



5. At the valley heads are a full complement of glacial features, such as cirques, 

 hanging valleys, reversed slopes, terminal moraines, and valley trains. 



6. Finally there is in all the valley bottoms a deep alluvial fill formed during 

 the glacial period and now in process of dissection. 



Though there are in many places special features either re- 

 motely related or quite unrelated to the principal enumerated 

 types, they belong to the class of minor forms to which relatively 

 small attention will be paid, since they are in general of small ex- 

 tent and of purely local interest. 



The block diagram represents all of these features, though of 



Fig. 126 — Block diagram of the typical physiographic features of the Peruvian 

 Andes. 



necessity somewhat more closely associated than they occur in 

 nature. Eeference to the photographs, Figs. 121-124, will make it 

 clear that the diagram is somewhat ideal : on the other hand the 

 photographs together include all the features which the diagram 

 displays. In descending from any of the higher passes to the val- 

 ley floor one passes in succession down a steep, well-like cirque at 

 a glaciated valley head, across a rocky terminal moraine, then 

 down a stair-like trail cut into the steep scarps which everywhere 

 mark the descent to the main valley floors, over one after another 

 of the confluent alluvial fans that together constitute a large part 

 of the valley fill, and finally down the steep sides of the inner val- 

 ley to the boulder-strewn bed of the ungraded river. 



