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Glaciologists and geographers should not trust any elevation
that is indicated on maps of the Andes Mountains. The sources
of their elevation data are never indicated, and these sources
may differ from one another by several hundred meters. The critical
work of a historian is often necessary to judge accuracy.
Considerable ground geodesy was done at the beginning of the 20th
century by an Argentine-Chilean Comisión de Límites,
which was charged to delimit the international border. The first
edition in 1915 of the Carta Nacional de Chile (CNC), a set of
maps at a scale of 1:500,000, used these data. Its last edition,
with little modification, was published in 1945. Up to recent
times, it was the best source for geographic place-names and for
elevations north of lat 41°30'S. on the Chilean side and near
the border. Near Santiago, Chile, the CNC was improved (more details
and place-names, without modifying the elevations) in 1929 by
W. Klatt and F. Fickenscher (KF). Their map at a scale of 1:250,000
was used by Chilean andinistas (mountaineers) up to 1956. On the
Argentine side, very accurate maps at a scale of 1:25,000 of the
Aconcagua group (lat 32°30'-32°50'S.) and of the glaciers
in the Río del Plomo drainage basin (lat 32°55'-33°20'S.)
were made by terrestrial photogrammetry (Helbling, 1919). Elsewhere,
cartography of the Argentine Andes remained very poor up to recent
times.
In the Andes Mountains near Santiago in normal years, small penitents
about 10 cm high (micropenitents) can be observed as soon as late
winter (Lliboutry, 1961). At 3,500 m, they reach about 50 cm tall
in spring and 1 m in January (summer). The north-south dimension
always remains 2 to 3.5 times smaller than the height of the blades
as the blades melt. But at moderate elevations with the rise of
the mean air temperature, the blades melt and penitents become
mere "sun spikes." It is only at elevations higher than
4,500 m that penitents keep their shape indefinitely.
When the furrows of penitents reach bare soil, the penitents may
be blown down; when the furrows reach glacier ice, the carving
by local melting goes on into this ice (figs. 7, 8). Penitents
on glaciers are, in general, 2-3 m high. Therefore, mountaineers
(in Latin America, andinistas) avoid crossing any glacier, unless
traveling in the east-west direction of the furrows. Nevertheless,
the tallest penitents ever observed (5-8 m high) were not found
on a glacier but on a snowdrift that had become firn. It was at
6,000 m on the north slope of Cerro/Nevado Ojos del Salado (lat
27°S.) in November 1949 (Belastín, verbal commun.,
1952).
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