MARSTERS, PHYSIOGRAPHY OF THE PERUVIAN ANDES 2'd>7 



Arequipa. Arequipa is some miles within the interior of the "West Range 

 Of the Andes. It stands on the slope and near the edge of the lava flow, 

 or flows, playing so important a role in the lithological content of the 

 coastal plain to the southwest. To the rear of the city, and forming a 

 most picturesque background, the majestic cones of Misti, Pichu-pichu 

 and other volcanic ridges rear their heads to 19,000 feet or more above 

 sea level, and 9,000 to 10,000 feet above the light-colored lava plains of 

 the Arequipa campo. The Chile River coming from the high plateau to 

 the interior passes between two of these cones, where it has cut a most 

 picturesque camion, pushing its way across a part of the mud flow until 

 it reaches the contact with pre-Tertiary formations of the foothills. The 

 important fact to note here is that where the Chile succeeded in making 

 a valley-floor, namely, at the moment it reached the contact referred to 

 above, there was located the city of Arequipa. Here we find agricultural 

 pursuits well developed. In all of the southern part of Peru there is no 

 prettier bit of landscape to be found than the campo of Arequipa. It is 

 the Switzerland of Peru. That is to say, physiographic features were the 

 determinative factors in the location of this important trade center. 



In the Valhry of Majas, we again find that a valley-floor has been 

 developed near the contact of : the inner edge of the coastal plain with the 

 edge of the foothills of the West Eange. Here has developed a large grape 

 culture and the manufacture of wine ; but from this locality across tbe 

 plain Ave find little chance for the fanner. Not until the Majas passes 

 through a deep, narrow gorge cut in the coastal ridge, or cadena de la 

 costa, do we find an additional opportunity for the development of agri- 

 culture. As soon as the Majas passes beyond the west slope of the ridge, 

 it has greatly widened its valley, having cleaned away the sediments on 

 the west flank and built for itself a broad, semi-triangular fluviatile 

 plain, which has pushed seaward sufficiently to be a menace to the mari- 

 ner. On this plain, we find the agricultural town of Camana located 

 and a campo alive with agricultural activities. 



The plain on which stands the city of Lima and its suburban towns is 

 but a repetition of the same physiographic sequences, the difference being 

 that the Lima plain was built at the edge of the cordillera or foothills 

 proper of the West Range of the Andes, while the latter developed on tbe 

 seaward edge of an outlier of the same physiographic province. 



In the Valley of Pacasmayo, we find that the river cut its way to the 

 sea and at the same time widened its floor throughout its entire course ; 

 as a consequence, no inconsiderable part of the entire floor from the edge 

 of the foothills to the present coast line is under cultivation, or has been 

 at various periods. The amount of cultivation is, in some cases, de- 



