Modelling Landscape Evolution - Environmental Modelling: Finding Simplicity in Complexity - page 312

Plateau Degradation Escarpment Retreat

100 Ma

60 Ma

Present-day

0.0 0.5 1.0 1.5

Elevation (km)

2.0 2.5 3.0

Figure 19.6 Topography and drainage patterns predicted by the Cascade landscape-evolution model for two modes of escarpment
development, designed to simulate the evolution of the SE African margin. Both models start out with an initial plateau at 3-km
elevation and an instantaneous base-level drop at the frontal edge of the model as in Figure 20.3, but the 'Plateau degradation'
model includes a pre-existing drainage divide (100 m higher than the plateau) 120 km from the frontal edge, whereas the plateau in
the 'Escarpment retreat' model is horizontal. Panels show snapshots of predicted topography at 100 Ma, 60 Ma and the present-day
for a rifting event and associated base-level drop at 130 Ma. The model used is the same as in Figure 20.3; model parameters are:
κ =

1m 2 y − 1 ; K s = 10 − 3 my − 1 10 − 3 my − 1 0 . 2 × for the 'Plateau degradation' model and 5 × for the 'Escarpment retreat' model;

L f 100 km. Note similar initial and final conditions, but strongly differing evolution (Based on van der Beek, P.A., Summerfield,

M.A., Braun, J. et al . (2002) Modeling post-break-up landscape development and denudational history across the southeast African
(Drakensberg Escarpment) margin. Journal of Geophysical Research , 107, 2351 with permission).

=