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faulting, form one focus of this chapter. Despite
recognition that many elements of the geomor-
phic system in alluvial settings are linked to
each other, each element does not have a similar
response time or sensitivity to changes imposed
on it (Whipple and Tucker, 1999). Reconsider,
for example, a drainage basin (Fig. 1.3) and the
hierarchy of sensitivity of its landscape elements
to imposed changes. In order to change the
catchment area, the interfluves have to be shifted
laterally, but in order to shift the interfluves,
the hillslopes that define where the interfluves
are located have to migrate in space. Changes in
the shape of hillslopes and removal of material
from them are typically most sensitive to slope
angle, with higher angles leading to less slope
stability and more rapid material transport
(Fig. 7.3). Changes in the slope angle itself are
related to changes in the altitudinal differences
between the interfluves and the river channels.
If the river channel is lowered by incision ero-
sion, adjacent hillslope angles are steepened,
rates of creep should increase, and the hillslope
may become unstable and prone to landsliding.
Thus, the erosion or aggradation of river chan-
nels will strongly influence hillslope responses.
In a drainage basin, a hierarchy of sensitivity
to  most tectonically imposed changes would
look like this: catchment area (least sensitive)
to  interfluves to hillslopes to channels (most
sensitive).
Another way to envision the sensitivity of a
landscape is to consider the impact on it that a
relatively small, tectonically induced, change
might have. For example, if folding causes a
region to be tilted 1 ° , what difference would this
make to various elements in the drainage-basin
hierarchy? The catchment area and interfluves
would be insensitive to such changes at short
time scales. If hillslopes were poised at maxi-
mum stable slope angles, then some of them
could be destabilized by such tilting, but, under
most circumstances, they, too, would be largely
unaffected. River channels, on the other hand,
typically have equilibrium gradients of consider-
ably less than 1 ° . Our hypothesized slope
increase of 1 ° , therefore, would greatly increase
the stream power due to its proportionality to
slope (Box 2.2). A river could respond very
quickly to this increased power by starting to
erode its bed. In a sense, landscape elements
like catchment areas and interfluves can be
characterized as having considerable geomor-
phic inertia , such that they tend to change
slowly, whereas the dynamic nature of rivers
and their rapid responses to changing external
controls indicate that they have little inertia. In
terms of examining the impact of tectonism on
Holocene landscapes, those elements that have
little geomorphic inertia provide the clearest
responses.
It is useful to keep in mind the magnitude of
typical deformation rates. Most vertical deforma-
tion occurs at rates of a fraction of a millimeter
per year. Uplift at 1 mm/yr yields 10 m of uplift
during the Holocene. Very rapid and sustained
bedrock uplift rates are seen in ranges like the
Himalaya (Burbank et al ., 1996b; Zeitler et al .,
2001b), the Southern Alps of New Zealand
(Tippett and Hovius, 2000), and the Central
Range of Taiwan (Dadson et al ., 2003; Willett
et  al ., 2003), where rates as high as 10 mm/yr
have been described. We have already seen that
such rates in the Himalayan foreland have driven
more than 100 m of vertical displacement of
Holocene river terraces (Fig. 7.25). Rates of
horizontal displacement on strike-slip faults can
be much more rapid (>30 mm/yr) and might
be  expected to perturb geomorphic systems
even more. Indeed, such faults cause significant
lateral displacements of features at Holocene
time scales (Liu et al ., 2004; Sieh and Jahns,
1984). Because strike-slip faults may induce
little differential vertical movement, however,
the millennial-scale stability of hillslopes and
the profiles of streams along strike-slip faults
are  typically less affected than in settings
dominated by dip-slip faulting.
Given (i) the hierarchy of sensitivity to change
within terrestrial geomorphic systems, (ii) the
magnitude of deformation during Holocene tec-
tonism, and (iii) the relative impacts of vertical
versus horizontal displacements, an examination
of Holocene landscape responses to deforma-
tion in terrestrial settings focuses naturally on
fluvial systems. River channels typically extend
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