626
Climatic Geomorphology
experienced numerous cyclic advances and recessions (Clark, 1994). The retreat of the ice
sheets produces abundant landforms, such as kames and kettles, fluvioglacial landforms,
(eskers and pitted sandar) and glaciolacustrine, drumlins. All these landforms occupy their
largest extension within the successive boundaries of the icecap. Excellent examples exist
in central Canada (Figure 24.8), where the dividing line of the ice was located in the
eastern part and was covered by ribbed moraines, drumlins and eskers. The western
periphery is characterized by outcrops of the substrate and a thin layer of glacial materials
(Aylsworth and Shilts, 1989). These spectacular examples can be recognized in Labrador
in eastern Canada, Scandinavia, Finland and in the Kola Peninsula of Russia (Figure 5.13).
Benn and Evans (1998) tried to make a generalization, at least for the Laurentide ice
sheet, of the evolution of these depositional landforms for the last glacial retreat. The first
times were characterized by successive advances and retreats of the ice, producing the
deposition of a great quantity of sediments and their restructuring, as well as lakes
dammed by ice. After that, ice masses suddenly receded and moraines and discontinuous
eskers were generated on bedrock. Meanwhile, new dams produced marginal lakes.
During the last retreat stages, moraines were more extensive and an important network of
eskers, which indicate the flow direction, were produced.
4. Valley and cirque glaciers retreat
Alpine glacier valleys are characterized by very deep vertical slopes, where cryoclastsy
acts intensely, providing clasts to the margins and bottom of the valley. Generally, these
troughs were developed from periglacial valleys.
In historic times, valley inhabitants worried about the fluctuations of the glaciers,
because they produced many disasters affecting human life and properties. The catastrophic events were caused by advances of a glacier tongue and mainly by bursts of lakes
dammed by ice or landslides (Tufnell, 1984). This information about the historical events
in alpine valleys provides relevant data on the evolution of the valleys (Grove, 1979,
1988). Comparison of paintings and engravings of the 18th and 19th centuries with recent
and current photographs supplies relevant data on the fluctuation of the glaciers (Lamb,
1977; Stroeven et al., 1989). On the other hand, during the past few decades precise works
on mass balances have been carried out. In those works the variations of glaciers have been
related to climate change (Oerlemans, 1989a,b).
Alpine regions are characterized by a landscape with pyramid peaks (horns), edges
between glaciers, cirques, and longitudinal profiles with frequent over-excavations. In
areas that have undergone large retreats, or that also have limited supply, the predominant
landscape is the one with glacial cirques (Figure 24.9). These landforms were developed
in all aspects, although shady places are the most prone, because they are sheltered from
solar radiation and, therefore, from the thaw of the ice. Often after ice thaw, rock glaciers
arise in the cirques.
Valley glaciers are the most spectacular landforms, which reflect the great capacity for
erosion of these masses of ice. One of the most significant features is the lateral moraines,
which join with terminal ones and generate moraine ridges. These ridges reach a greater
thickness if the glacier is stable, although generally, melt water erodes the ridges little by
little. In some glaciers, as in the Nigardsbreen glacial valley of Norway, the terminal parts
Climatic Geomorphology
experienced numerous cyclic advances and recessions (Clark, 1994). The retreat of the ice
sheets produces abundant landforms, such as kames and kettles, fluvioglacial landforms,
(eskers and pitted sandar) and glaciolacustrine, drumlins. All these landforms occupy their
largest extension within the successive boundaries of the icecap. Excellent examples exist
in central Canada (Figure 24.8), where the dividing line of the ice was located in the
eastern part and was covered by ribbed moraines, drumlins and eskers. The western
periphery is characterized by outcrops of the substrate and a thin layer of glacial materials
(Aylsworth and Shilts, 1989). These spectacular examples can be recognized in Labrador
in eastern Canada, Scandinavia, Finland and in the Kola Peninsula of Russia (Figure 5.13).
Benn and Evans (1998) tried to make a generalization, at least for the Laurentide ice
sheet, of the evolution of these depositional landforms for the last glacial retreat. The first
times were characterized by successive advances and retreats of the ice, producing the
deposition of a great quantity of sediments and their restructuring, as well as lakes
dammed by ice. After that, ice masses suddenly receded and moraines and discontinuous
eskers were generated on bedrock. Meanwhile, new dams produced marginal lakes.
During the last retreat stages, moraines were more extensive and an important network of
eskers, which indicate the flow direction, were produced.
4. Valley and cirque glaciers retreat
Alpine glacier valleys are characterized by very deep vertical slopes, where cryoclastsy
acts intensely, providing clasts to the margins and bottom of the valley. Generally, these
troughs were developed from periglacial valleys.
In historic times, valley inhabitants worried about the fluctuations of the glaciers,
because they produced many disasters affecting human life and properties. The catastrophic events were caused by advances of a glacier tongue and mainly by bursts of lakes
dammed by ice or landslides (Tufnell, 1984). This information about the historical events
in alpine valleys provides relevant data on the evolution of the valleys (Grove, 1979,
1988). Comparison of paintings and engravings of the 18th and 19th centuries with recent
and current photographs supplies relevant data on the fluctuation of the glaciers (Lamb,
1977; Stroeven et al., 1989). On the other hand, during the past few decades precise works
on mass balances have been carried out. In those works the variations of glaciers have been
related to climate change (Oerlemans, 1989a,b).
Alpine regions are characterized by a landscape with pyramid peaks (horns), edges
between glaciers, cirques, and longitudinal profiles with frequent over-excavations. In
areas that have undergone large retreats, or that also have limited supply, the predominant
landscape is the one with glacial cirques (Figure 24.9). These landforms were developed
in all aspects, although shady places are the most prone, because they are sheltered from
solar radiation and, therefore, from the thaw of the ice. Often after ice thaw, rock glaciers
arise in the cirques.
Valley glaciers are the most spectacular landforms, which reflect the great capacity for
erosion of these masses of ice. One of the most significant features is the lateral moraines,
which join with terminal ones and generate moraine ridges. These ridges reach a greater
thickness if the glacier is stable, although generally, melt water erodes the ridges little by
little. In some glaciers, as in the Nigardsbreen glacial valley of Norway, the terminal parts