Geology Reference
In-Depth Information
Evolution of a Normal-faulted Range
40
Schematic of
Tectonic Setting
land surface
w/ exaggeration
0
Horst
-40
-80
normal fault
without
exaggeration
-120
A
v ertical exagg e ration : 10 4
Fig. 11.17 Numerical model of
topographic evolution of a
normal-fault-bounded range.
The numerical model ZSCAPE
(Densmore et al. , 1998; Ellis
et al. , 1999) of a normal-fault-
bounded range in which erosion
is driven by a suite of surface
processes, including bedrock
landsliding. Resolution of the
model = 100 m. A. Cross-section
of the tectonic forcing of the
system with two opposing
normal faults driving both
vertical and horizontal
deformation fields. Dislocations
dip 60
20 km
Landscape Evolution
Model (LEM)
Elevation (m)
1000
500
0
-500
-1000
°
. B. Resulting topography
after one million years.
Precipitation pattern is uniform.
Channels are self-formed, and
incise at rates driven by local
stream power. Landsliding
dominates the hillslope evolution.
Triangular facets form on both
faulted mountain fronts. Adapted
from Densmore et al. (1998).
B
allowed the hillslopes to come down at the rate
dictated by the incision rate of the local channel.
Flexure was taken into account in two dimen-
sions, allowing both the topographic envelope
and the crustal response to erosional unloading
to be followed through time.
Densmore et  al . (1998) incorporated more
realistic landsliding rules in their model, dubbed
ZSCAPE (Fig. 11.17). The tectonic component of
this model is based on the Gomberg and Ellis
(1993, 1994) and Gomberg (1993) 3DDEF
boundary element code for tracking the dis-
placement field to be expected from a set of
prescribed dislocations in an elastic medium.
The setting addressed by Densmore et al . (1998)
and by Ellis et al . (1999) is the Basin and Range
province of western North America. High-angle
normal faults are prescribed. The surface pro-
cesses for which model components exist in the
code include regolith production, diffusion of
regolith, landsliding, fluvial sediment transport,
and fluvial bedrock incision. The code is flexi-
ble enough to deal with spatially non-uniform
precipitation. The 100-m pixels resolve many-
fold more details than Anderson's (1994) model.
Initial conditions of a flat or a slightly tilted
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