. The Andes of southern Peru; geographical reconnaissance along the seventy-third meridian. Yale Peruvian Expedition (1911); Physical geography; Geology. EASTERN ANDES: CORDILLERA VILCAPAMPA 207 Scale of Mile O 1 PANTA (8623 lira, and an unnamed valley farther south at an elevation of 11,500 feet (3,500 m.). A mile below Choquetira a second moraine appears, elevation 12,000 feet (3,658 m.), and immediately above the village a third at 12,800 (3,900 m.). The lowermost moraine is well dissected, the second is ravined and broken but topo- graphically distinct, the third is sharp-crested and
. The Andes of southern Peru; geographical reconnaissance along the seventy-third meridian. Yale Peruvian Expedition (1911); Physical geography; Geology. EASTERN ANDES: CORDILLERA VILCAPAMPA 207 Scale of Mile O 1 PANTA (8623 lira, and an unnamed valley farther south at an elevation of 11,500 feet (3,500 m.). A mile below Choquetira a second moraine appears, elevation 12,000 feet (3,658 m.), and immediately above the village a third at 12,800 (3,900 m.). The lowermost moraine is well dissected, the second is ravined and broken but topo- graphically distinct, the third is sharp-crested and regular. A fourth though minor stage is represented by the moraine at the snout of the living glacier and still less important phases are represented in some valleys—possibly the record of post-glacial changes of climate. Each main moraine is marked by an important amount of outwash, the first and third moraines being associated with the greatest masses. The material in the moraines represents only a part of that removed to form the successive steps in the valley profile. The lowermost one has an enormous volume, since it is the oldest and was built at a time when the valley was full of waste. It is fronted by a deep fill, over the dissected edge of which one may descend 800 feet in half an hour. It is chiefly alluvial in character, whereas the next higher one is composed chiefly of bowlders and is fronted by a pronounced bowlder train, which includes a remarkable perched bowlder of huge size. Once the valley became cleaned out the ice would derive its material chiefly by the slower process of plucking and abrasion, hence would build much smaller moraines during later recessional stages, even though the stages were of equivalent length. There is a marked difference in the degree of dissection of the. 111 m tr * WM ^PfjI^^P'f 16178" vtfc^gS Fig. 136—Glacial sculpture on the south- western flank of the Cordillera Vileapampa. Flat-floored valleys and looped terminal mo- r
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Keywords: ., bookauthorbo, bookcentury1900, bookdecade1910, booksubjectgeology
