Environmental Engineering Reference
In-Depth Information
FIGURE 1.18
Photograph of the Atacama Desert, Chile, showing one of many extinct wetlands (diatomaceous badlands in
center) that were active during the late glacial-early Holocene in the now waterless terrain at the base of the
Andes ∼3000 m elevation, where the regional water table intersects the toe of a massive alluvial fan. (From
Quade, J. et al., Quat. Res ., 69, 343, 2008; Courtesy of Julio L. Betancourt. With permission.)
20,000
20,000
Coastal
Cordillera
Longitudinal
Valley
Precordillera
Altiplano
Andes
Cordillera
15,000
15,000
10,000
10,000
5,000
5,000
0
0
0
W
25
50
75
100
125 miles
E
FIGURE 1.19
Topographic profile of the Atacama Desert (22°S) in Chile.
dominated by massive aggradation during the Oligocene and, possibly as a consequence
of the onset of aridity, by subsequent extensive, bedrock-dominated pediment surfaces
developed across a variety of rocks, including granite. 103 Segerstrom 104 referred to the
pediment topography as a “matureland,” although, in reality, it probably consists of
several uplifted and dissected erosional surfaces. There are extensive and probably
complementary piedmont deposits within the Longitudinal Valley, the internal drainage
basins, and along the perennial rivers.
The drainage of the region, especially in Chile, is dominated by enclosed drainage basins
that focus on salars. In addition, snowmelt in the Andes nourishes a few perennial streams
that cross the desert to the Pacific. Only the Rio Loa crosses the driest zone of the Norte
Grande, but to the south, as the precipitation rises and the snowline falls in the Norte Chico,
the rios Copiapó, Huasco, and Elqui all cut across the major zones of longitudinal relief.
Salts, many of which may be of volcanic origin, are widespread. They are found in many
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