Geoscience Reference
In-Depth Information
A
B
Figure 17-8.
Water-supply systems in the Venezuelan Andes Mountains northeast of Mérida. A. Small dam and
water pipe. B. Holding tank and pipelines on valley side. Photos by J.S. Aber.
Figure 17-9.
MODIS image of southern Colorado and northernmost New Mexico, United States. Mountain ranges:
1. San Juan Mountains, 2. Sangre de Cristo Mountains, 3. Wet Mountains and 4. Culebra Range. Acquired 26 October
2001; adapted from visible-color image of NASA
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http://visibleearth.nasa.gov/
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.
at least one mile (1.6 km) during the past
few million years (Sahagian, Proussevitch and
Carlson 2002; McMillan, Heller and Wing 2006;
Pelletier, 2009). Mountains were deeply eroded
as a consequence (see Fig. 16-1), and valleys
were ini lled with thick sediment accumulation.
Erosion was further enhanced during the Pleis-
tocene by a combination of increased precipita-
tion, runoff, and glaciation (Dethier 2001).
As with the Andes Mountains, climatic condi-
tions and vegetation cover vary greatly over
short distances, according to elevation and pre-
vailing wind, from sagebrush desert, to sub-
alpine conifer forest, and, at higher elevations,
to alpine tundra (Fig. 17-10). The following case
studies focus on the Culebra Range, which
forms the front range of the southern Rocky
Mountains, and the San Luis Valley, which is part
of the Rio Grande rift system.
17.3.1 Culebra Range
The Culebra Range is the southern segment of
the Sangre de Cristo Mountains, which extend
from south-central Colorado into northern New
Mexico (Fig. 17-11). The Culebra Range com-
prises mainly sandstone, siltstone and shale of
the Sangre de Cristo Formation (see Color Plate
