Chapter 2
Glaciers
1. Introduction
Since Precambrian times, several ice ages have occurred in Earth history and have
been printed in the geologic registry by erosive and sedimentary features (Eyles, 1993)
(Fig. 2.1). Within this general perspective, the Quaternary encompasses a glacial period
that began to develop fundamentally in upper Tertiary. The remaining ice accumulations
at the present time are left occupying only --~ 10 per cent of the terrestrial surface above sea
level, whereas in the last glacial maximum about 18,000 years ago, they covered almost a
third of the continental areas (Flint, 1971; Sugden and John, 1976). The activity of the
glacier masses is, therefore, reflected by different erosive and depositional landform
modelling as an important activity of the planet.
Investigations on the activity of past and present glaciers occur in different fashions.
Works on glacial geology are carried out by Quaternary researchers, who fundamentally
worry about glacial stratigraphy and chronology; whereas geomorphologists analyse
glacier processes and model the results of ice mass performance, as well as its
evolution. Glaciologists are interested in the study of the nature, physical behaviour, and
work done by glaciers (Lliboutry, 1965). In most cases, glaciologic investigations and
those carried out by glacial geomorphologists show a clear disconnection, although
there seems to be some overlap (Sugden and John, 1976). This union of methods is
necessary because glaciers constitute a means of rapid activity, with modifications in
days or months, and are therefore suitable for studying present-day processes and the
resulting forms.
In the past few decades a new field of work related to glacial geomorphology
has been opened within planetary geology. Thus on Mars, snow and ice sheets covering
30 per cent of its surface are recognized as occurring during winter and being reduced
to residual ice caps in summer, occupying a single 1 per cent. Also, the interpretation
of some Martian channels as originating by valley glacier activity has been expressed.
Some investigators establish for this planet a climatic change similar to that of Earth's
during upper Cenozoic (Cutts et al., 1979; Baker, 1981a; Carr, 1981). These
investigations of planetary geomorphology can provide important data for a greater
understanding of our glacial ages.
2. Past and present extension of glaciers
The present-day glacial ice occupies an approximate surface of 15.8 million km 2
(Table 2.1), or about 10 per cent of the total emergent terrestrial surface above sea level.
Glaciers
1. Introduction
Since Precambrian times, several ice ages have occurred in Earth history and have
been printed in the geologic registry by erosive and sedimentary features (Eyles, 1993)
(Fig. 2.1). Within this general perspective, the Quaternary encompasses a glacial period
that began to develop fundamentally in upper Tertiary. The remaining ice accumulations
at the present time are left occupying only --~ 10 per cent of the terrestrial surface above sea
level, whereas in the last glacial maximum about 18,000 years ago, they covered almost a
third of the continental areas (Flint, 1971; Sugden and John, 1976). The activity of the
glacier masses is, therefore, reflected by different erosive and depositional landform
modelling as an important activity of the planet.
Investigations on the activity of past and present glaciers occur in different fashions.
Works on glacial geology are carried out by Quaternary researchers, who fundamentally
worry about glacial stratigraphy and chronology; whereas geomorphologists analyse
glacier processes and model the results of ice mass performance, as well as its
evolution. Glaciologists are interested in the study of the nature, physical behaviour, and
work done by glaciers (Lliboutry, 1965). In most cases, glaciologic investigations and
those carried out by glacial geomorphologists show a clear disconnection, although
there seems to be some overlap (Sugden and John, 1976). This union of methods is
necessary because glaciers constitute a means of rapid activity, with modifications in
days or months, and are therefore suitable for studying present-day processes and the
resulting forms.
In the past few decades a new field of work related to glacial geomorphology
has been opened within planetary geology. Thus on Mars, snow and ice sheets covering
30 per cent of its surface are recognized as occurring during winter and being reduced
to residual ice caps in summer, occupying a single 1 per cent. Also, the interpretation
of some Martian channels as originating by valley glacier activity has been expressed.
Some investigators establish for this planet a climatic change similar to that of Earth's
during upper Cenozoic (Cutts et al., 1979; Baker, 1981a; Carr, 1981). These
investigations of planetary geomorphology can provide important data for a greater
understanding of our glacial ages.
2. Past and present extension of glaciers
The present-day glacial ice occupies an approximate surface of 15.8 million km 2
(Table 2.1), or about 10 per cent of the total emergent terrestrial surface above sea level.