26
Climatic Geomorphology
altitude, the air becomes more rarified and solar radiation increases. In these conditions,
the rocks are subjected to more intense thermal effects (Tricart and Cailleux, 1965).
A height increment of 1000 m in the Alps is equivalent to a decrease of temperature
experienced during a 1000 km journey toward the North Pole. This thermal drop is
normally accompanied by altitudinal and latitudinal variations in vegetation (Bfidel, 1977,
1982). Also with increasing altitude, a characteristic succession in the morphology
and size of patterned soils commonly occurs, as reported for the Swiss Alps and
Karakoram by Furrer (1972). Similar cases have been described in other mountainous
areas, constituting a reliable proof of the altitudinal gradient. Precipitation varies with
height, displaying an initial increasing trend, which after a maximum, diminishes upwards.
All the big mountains are characterized by a more rainy and cloudy intermediate step.
Another important effect is that displayed in the north-facing areas at mid-latitudes where
snow is preserved during long periods, thereby impressing a periglacial landscape within
the altitudinal variation. In the intertropical zone, the windward areas are more humid
than those located to the leeward, which are generally dry (Tricart and Cailleux, 1965).
On the other hand, it can be pointed out that at scales of 106-107 km 2 the variety of
landscapes is better explained by climatic differences; at scales of 104-105 km 2, landscape
variability is dominated by structural and bedrock lithology variations; and at scales of
102 km 2 the landforms are the result of the activity of different erosive processes (Chorley
et al., 1984).
5. The main morphoclimatic zones
The differentiation of the different morphoclimatic areas must take into account the
dominant working processes in each of these areas, but it is also essential to consider
the possible occurrence of inherited Quaternary and Tertiary landforms. This interest in
climatic change was already manifest for Penck and Bruckner (in 1901-1909) in their
dissertation on the ages of the alpine glaciations. Similarly, Passarge (1904), in his work
on the Kalahari desert, found clear evidence of environments of alternating arid and
savannah conditions. Bfidel (1948) insisted on the importance of paleo-landforms, and in
1963 proposed the term climatogenic geomorphology to define the discipline of the study
of relic landforms developed under different climatic conditions, and for the deduction
of the succession of climatic environments over time. Obviously climatic change is
particularly relevant in mid-latitude areas. Also, Birot (1960) pointed out that the
influence of climatic change during Tertiary and Quaternary times extended from the
Arctic to the Equator. The distinction between modem and ancient inherited landforms
is essential to understanding landscape evolution in climatic terms, but in fact, numerous
misinterpretations of landscape development may actually arise.
The division of the Earth surface into different morphoclimatic areas, for different
reasons, has always been a complex task. There are different parts of the world for which
our knowledge of the main morphoclimatic controls is very limited (central Asia, South
America, etc.) and therefore it is difficult to trace precise boundaries between them (Tricart
and Cailleux, 1965). The increasing use of satellite imagery, however, has partially solved
this problem. On the other hand, it is necessary to keep in mind that a morphoclimatic map
does not exactly come from the total or partial overlapping of existing climatic, vegetation
Climatic Geomorphology
altitude, the air becomes more rarified and solar radiation increases. In these conditions,
the rocks are subjected to more intense thermal effects (Tricart and Cailleux, 1965).
A height increment of 1000 m in the Alps is equivalent to a decrease of temperature
experienced during a 1000 km journey toward the North Pole. This thermal drop is
normally accompanied by altitudinal and latitudinal variations in vegetation (Bfidel, 1977,
1982). Also with increasing altitude, a characteristic succession in the morphology
and size of patterned soils commonly occurs, as reported for the Swiss Alps and
Karakoram by Furrer (1972). Similar cases have been described in other mountainous
areas, constituting a reliable proof of the altitudinal gradient. Precipitation varies with
height, displaying an initial increasing trend, which after a maximum, diminishes upwards.
All the big mountains are characterized by a more rainy and cloudy intermediate step.
Another important effect is that displayed in the north-facing areas at mid-latitudes where
snow is preserved during long periods, thereby impressing a periglacial landscape within
the altitudinal variation. In the intertropical zone, the windward areas are more humid
than those located to the leeward, which are generally dry (Tricart and Cailleux, 1965).
On the other hand, it can be pointed out that at scales of 106-107 km 2 the variety of
landscapes is better explained by climatic differences; at scales of 104-105 km 2, landscape
variability is dominated by structural and bedrock lithology variations; and at scales of
102 km 2 the landforms are the result of the activity of different erosive processes (Chorley
et al., 1984).
5. The main morphoclimatic zones
The differentiation of the different morphoclimatic areas must take into account the
dominant working processes in each of these areas, but it is also essential to consider
the possible occurrence of inherited Quaternary and Tertiary landforms. This interest in
climatic change was already manifest for Penck and Bruckner (in 1901-1909) in their
dissertation on the ages of the alpine glaciations. Similarly, Passarge (1904), in his work
on the Kalahari desert, found clear evidence of environments of alternating arid and
savannah conditions. Bfidel (1948) insisted on the importance of paleo-landforms, and in
1963 proposed the term climatogenic geomorphology to define the discipline of the study
of relic landforms developed under different climatic conditions, and for the deduction
of the succession of climatic environments over time. Obviously climatic change is
particularly relevant in mid-latitude areas. Also, Birot (1960) pointed out that the
influence of climatic change during Tertiary and Quaternary times extended from the
Arctic to the Equator. The distinction between modem and ancient inherited landforms
is essential to understanding landscape evolution in climatic terms, but in fact, numerous
misinterpretations of landscape development may actually arise.
The division of the Earth surface into different morphoclimatic areas, for different
reasons, has always been a complex task. There are different parts of the world for which
our knowledge of the main morphoclimatic controls is very limited (central Asia, South
America, etc.) and therefore it is difficult to trace precise boundaries between them (Tricart
and Cailleux, 1965). The increasing use of satellite imagery, however, has partially solved
this problem. On the other hand, it is necessary to keep in mind that a morphoclimatic map
does not exactly come from the total or partial overlapping of existing climatic, vegetation