of the Cuzco Valley, Peru. 9 



reaching upward to heights exceeding 14,500 feet. This bor- 

 dering wall is breached by passes between 12,000 and 11,000 

 feet high, through which access is afforded to the valley floor, 

 lying below 11,100 feet. The extremes of elevation are the 

 summit of Cerro Pachatucsa (15,915 feet) and the mouth 

 of the Huatanay (10,100 feet). 



The floor of the Cuzco Valley, 19 miles in length, is divided 

 by the Angostura and Oropesa narrows into three oval areas 

 of flat-lying land, displayed like links in a chain. From these 

 valley flats thinly coated rock slopes rise with a gradient of 

 1,000 to 2,000 feet to the mile, in places becoming precipitous. 

 The steeply inclined slopes continue upward from the central 



Fig. 



d. 



MOLLENDO VITOR 



LIVIJACA aAPyRIMAC LARELS 



H-URUBAM^A R.PAUCARTAMBO 



jcuz.coi 



s.ooo - 

 5E.A LEVEL 



R. ALTO 

 R.MISHAGUA 



r s, ooo 



5,0 "> 



a. 



4.000 jJ 

 3,000 UJ 

 ■ 2,000 



ooo 



Fig. 3. Surface profile of Southern Peru, drawn across the mountainous 

 area from the Pacific Ocean to the Amazon Plains on the 72° W. longitude. 



valley until areas of slight relief (the pampas) are reached. 

 Huaca-Cancha, Bambanusa, and Huanca-Huanca pampas 

 spread out at elevations of 13,500 feet; Pampa de Kkallackaca 

 and adjoining plateaus, developed on the limestone north of 

 Cuzco, stand at about 12,000 feet — 1,000 feet above the valley 

 floor. The outer wall inclosing the Cuzco Valley is trenched 

 in many places by streams leading away from the valley and 

 toward the Apurimac and the Urubamba ; the serrate rim of 

 the valley therefore does not correspond to the divide between 

 drainage basins. In general the southward facing slopes of 

 the valley are cut by deep canyons and exhibit great local relief ; 

 the northward-facing slopes are gentler and less abrupt and in 

 places above Angostura 1ST arrows are traversed by flat-floored, 

 terraced valleys. 



Extrusive volcanic rocks have modified the topography of 

 Bambanusa Pampa and have interfered with the normal develop- 

 ment of relief at Oropesa and Pumiccolca ; elsewhere the 

 surface is elaborately dissected in response to the influence 

 of the variable composition and complicated structure of the 

 underlying sedimentary rocks. 



