Climatic geomorphology
19
research. This fact has triggered a metamorphosis and breaking up of the discipline
(Chorley, 1978; Thorn, 1988a). As indicated by the first author, geomorphology today has
been submerged in a processes syndrome. The subjacent problem is related to translating
the detailed-scale studies of processes research to broad-scale landscape evolution
(Barsch, 1990). This is the motive as to why geomorphology should carry on research at a
wide variety of temporal and spatial scales, in an attempt to better understand the different
workings of landscape development at different scales (Chorley, 1978). In addition there is
hope that modem computer simulations will also be able to merge surface process research
with landscape evolution studies.
3. Climatic geomorphology: processes and morphoclimatic zonation
Climatic geomorphology can be defined as the discipline that identifies climatic factors
such as the intensity, frequency and duration of precipitation, frost intensity, direction
and power of wind, and it explains the development of landscapes under different climatic
conditions (Ahnert, 1996). It is noteworthy that in this recent definition the magnitude and
frequency of surface processes are taken into account. Initially, in the pioneering work of
Peltier (1950) only two climatic parameters (mean annual temperature and total annual
precipitation) were considered in establishing their relation with five key geomorphic
processes: chemical weathering, frost action, pluvial erosion, mass movement and wind
action (Fig. 1.5). For Peltier, "this set of graphics simply represents the schematic
illustration of a concept." As a whole, he distinguished two different morphogenetic
elements, which are weathering processes and the transport agents of the resultant
materials. From this perspective this author postulated nine different morphogenetic
regions (Fig. 1.6), which may be distinguished by a characteristic assemblage of geomorphic processes. Distinctions made by Peltier were mainly qualitative and very
subjective (Derbyshire, 1973b). A similar approach was that developed by Leopold et al.
(1964). Wilson (1968, 1969) also developed a comparable approach, but he changed the
frost action graphic for a mechanical weathering one, modified the fields for relative
intensities of geomorphic processes defined by Peltier, and distinguished six climatic
regimes denominated as climate-process systems. Wilson underlined the monthly
variation of temperature and precipitation (seasonality), as well as its influence on the
activity of geomorphic processes (Fig. 1.7).
Tanner (1961) used potential evapotranspiration instead of temperature as a climatic
variable, because this factor gives us a more realistic idea of moisture availability and, in
addition, is linked to the proportion of vegetal cover. Likewise, Tanner also assumed the
four main morphogenetic regions to be glacial, temperate, arid and selva, but also added
tundra, savannah, and semiarid regimes.
An interesting approach is that proposed by Common (1966) in his work about
landslides and morphoclimatic regions. He considered that mass movement is a part of the
denudational process and may be used to recognize different landscapes. Instead of using a
large number of involved variables, Common elaborated three global maps based upon
particular characteristics of precipitation and temperature of geomorphic interest
(i.e. precipitation regimes, intervals of total precipitation and temperature).
19
research. This fact has triggered a metamorphosis and breaking up of the discipline
(Chorley, 1978; Thorn, 1988a). As indicated by the first author, geomorphology today has
been submerged in a processes syndrome. The subjacent problem is related to translating
the detailed-scale studies of processes research to broad-scale landscape evolution
(Barsch, 1990). This is the motive as to why geomorphology should carry on research at a
wide variety of temporal and spatial scales, in an attempt to better understand the different
workings of landscape development at different scales (Chorley, 1978). In addition there is
hope that modem computer simulations will also be able to merge surface process research
with landscape evolution studies.
3. Climatic geomorphology: processes and morphoclimatic zonation
Climatic geomorphology can be defined as the discipline that identifies climatic factors
such as the intensity, frequency and duration of precipitation, frost intensity, direction
and power of wind, and it explains the development of landscapes under different climatic
conditions (Ahnert, 1996). It is noteworthy that in this recent definition the magnitude and
frequency of surface processes are taken into account. Initially, in the pioneering work of
Peltier (1950) only two climatic parameters (mean annual temperature and total annual
precipitation) were considered in establishing their relation with five key geomorphic
processes: chemical weathering, frost action, pluvial erosion, mass movement and wind
action (Fig. 1.5). For Peltier, "this set of graphics simply represents the schematic
illustration of a concept." As a whole, he distinguished two different morphogenetic
elements, which are weathering processes and the transport agents of the resultant
materials. From this perspective this author postulated nine different morphogenetic
regions (Fig. 1.6), which may be distinguished by a characteristic assemblage of geomorphic processes. Distinctions made by Peltier were mainly qualitative and very
subjective (Derbyshire, 1973b). A similar approach was that developed by Leopold et al.
(1964). Wilson (1968, 1969) also developed a comparable approach, but he changed the
frost action graphic for a mechanical weathering one, modified the fields for relative
intensities of geomorphic processes defined by Peltier, and distinguished six climatic
regimes denominated as climate-process systems. Wilson underlined the monthly
variation of temperature and precipitation (seasonality), as well as its influence on the
activity of geomorphic processes (Fig. 1.7).
Tanner (1961) used potential evapotranspiration instead of temperature as a climatic
variable, because this factor gives us a more realistic idea of moisture availability and, in
addition, is linked to the proportion of vegetal cover. Likewise, Tanner also assumed the
four main morphogenetic regions to be glacial, temperate, arid and selva, but also added
tundra, savannah, and semiarid regimes.
An interesting approach is that proposed by Common (1966) in his work about
landslides and morphoclimatic regions. He considered that mass movement is a part of the
denudational process and may be used to recognize different landscapes. Instead of using a
large number of involved variables, Common elaborated three global maps based upon
particular characteristics of precipitation and temperature of geomorphic interest
(i.e. precipitation regimes, intervals of total precipitation and temperature).