Geology Reference
In-Depth Information
Channel
Valley-side slope
Interfluve
Wind erosion and deposition
Waste mantle
Debris
production
Debris
transport
Debris
production
Debris
transport
Uplift or subsidence
Figure 1.7
A hillslope as a system, showing storages (waste mantle), inputs (e.g. wind deposition and debris production),
outputs (e.g. wind erosion), throughputs (debris transport), and units (channel, valley-side slope, interfluve).
export matter or energy. A
closed system
has bound-
aries open to the passage of energy but not of matter. An
open system
has boundaries across which energy and
materials may move. All geomorphic systems, including
hillslopes, may be thought of as open systems as they
exchange energy and matter with their surroundings.
destroy it. The events between the creation and the final
destruction are what fascinate geomorphologists.
Systems are mental constructs and have been defined
in various ways. Two conceptions of systems are impor-
tant in geomorphology: systems as process and form
structures, and systems as simple and complex structures
(Huggett 1985, 4-5, 17-44).
Internal and external system variables
Geomorphic systems as form and process
structures
Any geomorphic system has
internal
and
external vari-
ables
. Take a drainage basin. Soil wetness, streamflow,
and other variables lying inside the system are endoge-
nous or internal variables. Precipitation, solar radiation,
tectonic uplift, and other such variables originating out-
side the system and affecting drainage basin dynamics
are exogenous or external variables. Interestingly, all geo-
morphic systems can be thought of as resulting from
a basic antagonism between
endogenic
(
tectonic
and
volcanic
) processes driven by geological forces and
exo-
genic
(
geomorphic
) processes driven by climatic forces
(Scheidegger 1979). In short, tectonic processes create
land, and climatically influenced weathering and erosion
Three kinds of geomorphic system may be identified:
form systems, process systems, and form and process
systems.
1
Form systems.
Form
or
morphological systems
are
defined as sets of form variables that are deemed to
interrelate in a meaningful way in terms of system ori-
gin or system function. Several measurements could
be made to describe the form of a hillslope system.
Form elements would include measures of anything
on a hillslope that has size, shape, or physical prop-
erties. A simple characterization of hillslope form is
