The Andes of southern Peru . arriedaway from the glacier ends were stre^\^l along the valley floors,forming a deep alluvial fill. Thereby the canyon floors were ren-dered habitable. In the chapters on human geography we have already calledattention to the importance of the U-shaped valleys carved by theglaciers. Their floors are broad and relatively smooth. Theirwalls restrain the live stock. They are sheltered though all the human benefits conferred by ice action are insig-nificant beside those due to the general shedding of waste fromthe cold upper surfaces to the warm levels of th
The Andes of southern Peru . arriedaway from the glacier ends were stre^\^l along the valley floors,forming a deep alluvial fill. Thereby the canyon floors were ren-dered habitable. In the chapters on human geography we have already calledattention to the importance of the U-shaped valleys carved by theglaciers. Their floors are broad and relatively smooth. Theirwalls restrain the live stock. They are sheltered though all the human benefits conferred by ice action are insig-nificant beside those due to the general shedding of waste fromthe cold upper surfaces to the warm levels of the valley alluvium-filled valleys are the seats of dense populations. Inthe lowest of them tropical and sub-tropical products are raised,like sugar-cane and cotton, in a soil that once lay on the smoothupper slopes of mountain spurs or that was ground fine on the bedof an Alpine glacier. The Pleistocene deposits fall into three well-defined groups:(1) glacial accumulations at the valley heads, (2) alluvial deposits. Fig. 179—Snow fields on the summit of the Cordillera Vilcapampa near Ollantay-tambo. A huge glacier once lay in the steep canyon in the background and descendedto the notched terminal moraine at the canyon mouth. In places the glacier wasover a thousand feet thick. From the terminal moraine an enormous alluvial fan extendsforward to the camera and to the opposite wall of the Urubamba Valley. It isconfluent with other fans of the same origin. See Fig. 180. In the foreground areflowers, shrubs, and cacti. A few miles below Urubamba at 11,500 feet.
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Keywords: ., bookcentury1900, bookdecade1910, bookidandeso, booksubjectgeology
