72 THE ANDES OF SOUTHERN PERU 



at the one place ; they are absent altogether at the other. Torontoy 

 produces corn ; Huadquina produces sugar cane. 



These contrasts are still further emphasized by the sharp topo- 

 graphic break between the two unlike portions of the valley. A 

 few miles below Torontoy the Urubamba plunges into a mile-deep 

 granite canyon. The walls are so close together that it is impos- 

 sible from the canyon floor to get into one photograph the highest 

 and steepest walls. At one place there is over a mile of descent 

 in a horizontal distance of 2,000 feet. Huge granite slabs fall off 

 along joint planes inclined but 15° from the vertical. The effect 

 is stupendous. The canyon floor is littered with coarse waste and 

 the gradient of the river greatly steepened. There is no cultiva- 

 tion. The trees cling with difficulty to patches of rock waste or 

 to the less-inclined slopes. There is a thin crevice vegetation that 

 outlines the joint pattern where seepage supplies the venturesome 

 roots with moisture. Man has no foothold here, save at the top 

 of the country, as at Machu Picchu, a typical fortress location 

 safeguarded by the virtually inaccessible canyon wall and con- 

 nected with the main ridge slopes only by an easily guarded 

 narrow spur. Toward the lower end of the canyon a little 

 finer alluvium appears and settlement begins. Finally, after 

 a tumble of three thousand feet over countless rapids the river 

 emerges at Colpani, where an enormous mass of alluvium has 

 been dumped. The well-intrenched river has already cut a 

 large part of it away. A little farther on is Huadquina in 

 the Salcantay Valley, where a tributary of the Urubamba has 

 built up a sheet of alluvial land, bright green with cane. From 

 the distant peaks of Salcantay and its neighbors well-fed streams 

 descend to fill the irrigation channels. Thus the snow and rock- 

 waste of the distant mountains are turned into corn and sugar on 

 the vallev lowlands. 



the most remarkable cases are the patch of woodland at 14,500 feet (4,420 m.) just 

 under the hanging glacier of Soiroccocha and the other the quenigo scrub on the 

 lava plateau above Chuquibamba at 13.000 feet (3,960 m.). The strong compression 

 of climatic zones iri the Urubamba Valley below Santa Ana brings into sharp contrast 

 the grassy ridge slopes facing the sun and the forested slopes that have a high propor- 

 tion of shade. Fig. 54 represents the general distribution but the details are far 

 more complicated. See also Figs. 53A and 53B. (See Coropuna Quadrangle.) 



