Geoscience Reference
In-Depth Information
Oregon
N
Idaho
Nevada
Utah
Figure 18.2 Uluru in central Australia.
Uluru is the best ex-
ample of an inselberg, or island mountain, in the world. This iconic
landform is composed of hard sandstone that was once buried
by other rocks that have been removed by erosion. The beauty
of Uluru is magnified in the arid environment of central Australia.
California
Arizona
0
100
200 300 km
0
100
200 mi
(a)
great places because you can see landforms very clearly and
the important elements such as rock structure and differential
weathering that influence their evolution. A superb example
of this visual effect can be seen at
Uluru
(formerly known as
Ayer's Rock) in central Australia (Figure 18.2). Uluru is the
best example of an
inselberg
(island mountain) in the world.
Composed of hard sandstone, this prominent landform towers
over the surrounding landscape because differential weathering
over millions of years removed the rocks that once covered it. In
this desert environment, it is possible to visualize this process.
Although landforms in humid regions may have similar histo-
ries, it can be more difficult to visualize because thick stands of
vegetation often mar the view.
Wasatch
Range
Sierra Nevada
The Southwestern United States
An excellent place to
see desert geomorphology where you may one day visit is the
southwestern United States. This region lies in the rain shadow
of the Sierra Nevada (Figure 13.23) and encompasses a number
of previously discussed arid places such as the Sonoran Desert
(Figure 10.l6) and the Grand Canyon (Figure 12.20a). Perhaps
the most obvious variable, other than climate, that strongly in-
fluences landforms in the West is rock structure. A spectacular
example of the effects of normal faulting (Figure 13.22), for
example, is the geologically famous Basin and Range Province
in the southwestern United States. This region extends from the
Wasatch Mountains in eastern Utah to the Sierra Nevada along
the border of California and Utah (Figure 18.3a). It is character-
ized by numerous mountain ranges and intervening valleys that
are generally aligned from north to south (Figure 18.3b). The
relief between the crests of mountain ranges and the adjacent
basins can be as much as about 3050 m (10,000 ft), resulting in
a distinctive view from the air (Figure 18.3c).
The Basin and Range Province began to form about
20 million years ago when the North American crust started
to stretch in this part of the continent due to upward pressure
(b)
(c)
Figure 18.3 The Basin and Range Province.
(a) The Basin and
Range Province extends over much of the American Southwest.
(b) Satellite image of the Basin and Range Province. Notice the
semilinear network of mountain ranges (darker shades) and in-
tervening basins that lie between the Wasatch Range and Sierra
Nevada. (c) Panoramic view of a portion of the Basin and Range
Province. Note the distinct mountain ranges and the intervening
basins.
