Page 34 - Fundamentals of Geomorphology

WHAT IS GEOMORPHOLOGY? 17

c
() Form system () Flow or cascading () Process–form or
a
b
system process–response 123
system
Cliff
Cliff
Cliff Rockfall Cliff
Covered
Covered
cliff face
Talus Talus cliff face
at time 2 2
at time
Lower Lower Time
slope slope
3
2
1
Figure 1.8 A cliff and talus slope viewed as (a) a form system, (b) a flow or cascading system, and (c) a process–form or
process–response system. Details are given in the text.

shown in Figure 1.8a, which depicts a cliff with a the system processes. A hillslope may be viewed in
talus slope at its base. All that could be learnt from this way with slope form variables and slope process
this ‘form system’ is that the talus lies below the cliff; variables interacting. In the cliff-and-talus example,
no causal connections between the processes linking rock falling off the cliff builds up the talus store
the cliff and talus slope are inferred. Sophisticated (Figure 1.8c). However, as the talus store increases
characterizations of hillslope and land-surface forms in size, so it begins to bury the cliff face, reduc-
may be made using digital terrain models. ing the area that supplies debris. In consequence,
2 Process systems. Process systems, which are also the rate of talus growth diminishes and the sys-
called cascading or flow systems, are defined as tem changes at an ever-decreasing rate. The process
‘interconnected pathways of transport of energy or described is an example of negative feedback, which
matter or both, together with such storages of energy is an important facet of many process–form systems
and matter as may be required’ (Strahler 1980, 10). (Box 1.2).
An example is a hillslope represented as a store of
materials: weathering of bedrock and wind deposi- Geomorphic systems as simple or complex
tion add materials to the store, and erosion by wind structures
and fluvial erosion at the slope base removes mate-
rials from the store. The materials pass through the Three main types of system are recognized under this
system and in doing so link the morphological com- heading: simple systems, complex but disorganized
ponents. In the case of the cliff and talus slope, it systems, and complex and organized systems.
could be assumed that rocks and debris fall from the
cliff and deliver energy and rock debris to the talus 1 Simple systems. The first two of these types have
below (Figure 1.8b). a long and illustrious history of study. Since at
3 Form and process systems. Process–form systems, least the seventeenth-century revolution in science,
also styled process–response systems, are defined astronomers have referred to a set of heavenly bod-
as an energy-flow system linked to a form system in ies connected together and acting upon each other
such a way that system processes may alter the system according to certain laws as a system. The Solar
form and, in turn, the changed system form alters System is the Sun and its planets. The Uranian