184 THE ANDES OF SOUTHERN PERU 



from depths of over 20,000 feet beneath sea level to snowy sum- 

 mits, a total altitude of 40,000 feet (12,200 m.), their excessive 

 boldness would be more apparent. No other mountains in the 

 world are at once so continuously lofty and so near a coast which 

 drops off to abyssal depths. 



The view from the shore is, however, but one of many which 

 the Andes exhibit. Seen from the base the towering ranges dis- 

 play a stern aspect, but, like all mountains, their highest slopes 

 and spurs must be crossed and re-crossed before the student is 

 aware of other aspects of a quite different nature. The Andes 

 must be observed from at least three situations : from the floors 

 of the deep intermontane valleys, from the intermediate slopes 

 and summits, and from the uppermost levels as along the range 

 crests and the highest passes. Strangely enough it is in the sum- 

 mit views that one sees the softest forms. At elevations of 14,000 

 to 16,000 feet (4,270 to 4,880 m.), where one would expect rugged 

 spurs, serrate chains, and sharp needles and horns, one comes fre- 

 quently upon slopes as well graded as those of a city park — grass- 

 covered, waste-cloaked, and with gentle declivity (Figs. 121-124). 



The graded, waste-cloaked slopes of the higher levels are in- 

 terpreted as the result of prolonged denudation in an erosion 

 cycle which persisted through the greater part of the Tertiary 

 period, and which was closed by uplifts aggregating at least sev- 

 eral thousands of feet. Above the level of the mature slopes rise 

 the ragged profiles and steep, naked declivities of the snow-capped 

 mountains which bear residual relations to the softer forms at 

 their bases. They are formed upon rock masses of greater 

 original elevation and of higher resistance to denudation. Though 

 they are dominating topographic features, they are much less ex- 

 tensive and significant than the tame landscape which they sur- 

 mount. 



Below the level of the mature slopes are topographic features 

 of equal prominence : gorges and canyons up to 7,000 feet deep. 

 The deeply intrenched streams are broken by waterfalls and al- 

 most continuous rapids, the valley walls are so abrupt that one 

 may, in places, roll stones down a 4,000-foot incline to the river 



