The Andes of southern Peru, geographical reconnaissance along the seventy-third meridian . aste-cloaked slopes of the higher levels are in-terpreted as the result of prolonged denudation in an erosioncycle which persisted through the greater part of the Tertiaryperiod, and which was closed by uplifts aggregating at least sev-eral thousands of feet. Above the level of the mature slopes risethe ragged profiles and steep, naked declivities of the snow-cappedmountains which bear residual relations to the softer forms attheir bases. They are formed upon rock masses of greateroriginal elevation and
The Andes of southern Peru, geographical reconnaissance along the seventy-third meridian . aste-cloaked slopes of the higher levels are in-terpreted as the result of prolonged denudation in an erosioncycle which persisted through the greater part of the Tertiaryperiod, and which was closed by uplifts aggregating at least sev-eral thousands of feet. Above the level of the mature slopes risethe ragged profiles and steep, naked declivities of the snow-cappedmountains which bear residual relations to the softer forms attheir bases. They are formed upon rock masses of greateroriginal elevation and of higher resistance to denudation. Thoughthey 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 featuresof equal prominence: gorges and canyons up to 7,000 feet deeply intrenched streams are broken by waterfalls and al-most continuous rapids, the valley walls are so abrupt that onemay, in places, roll stones down a 4,000-foot incline to the river. Fig. 121.
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Keywords: ., bookauthorbo, bookcentury1900, bookdecade1910, booksubjectgeology
