permafrost) was first added to the 8th edition of ‘Keys to
Soil Taxonomy’ in 1998. Recognition of Gelisols was partly
to encompass soils with cryogenic properties in Alaska
(matching the adjacent Canadian classification for soils on
permafrost, the Cryosolic Soils) and also to accommodate
Antarctic soils. The USDA changed their definition of ‘soil’
to remove a requirement for organic matter so that the
Antarctic Gelisols could be considered ‘soil’ and therefore
included in Soil Taxonomy.
17.2 Soil Profile Genesis
Due to the cold dry environment, most soils in the Ross Sea
region have limited weathering and so largely retain the
inherited properties of the parent materials which are mainly
glacial tills. Although climate is the dominant influence on
soil genesis, parent material, topography, and time all have
recognisable influence. Organisms impact the soils markedly
only in a few isolated sites on coastal margins where penguin colonies occur or where summer meltwater supports
moss growth.
Soil desert pavement surfaces comprise gravels and
pebbles that are left behind as finer materials are eroded,
primarily by wind, until a protective layer of coarser material
remains at the surface preventing further erosion. Over time,
wind-blown sand and salt-weathering abrades and corrodes
the exposed rock surfaces. The abrasion, along with a small
amount of chemical weathering, particularly oxidation of
iron-rich minerals, leads to the formation of polished rock
surfaces with a ‘desert varnish’ coating. Ventifacts (rocks
carved and polished to smooth surfaces by the effects of
prolonged exposure to wind-blown particles) are evident at
many sites.
The older the land surface the more weathered the desert
pavement. Some high-altitude surfaces are thought to be
extremely (up to about 5 million years) old. Even though
weathering processes proceed only slowly in the Antarctic
environment, the long exposure time frames mean that desert
pavements on older surfaces are highly developed. Older
surfaces typically have a closely packed layer of gravel,
cobble, and boulder-sized material with ventifacted surfaces
that are pitted, and coated with desert varnish (Fig. 17.4).
In younger soils, the colours are often described as
‘lithochromic’. In other words, the soils are the colours of
the rocks or deposits from which they have formed as there
has been minimal chemical weathering. Soils are most often
formed in glacial tills that contain a poorly sorted mix of
sand, gravel, and larger pebbles and boulders that have been
broken up by physical weathering processes.
Ice lenses occur where small areas of ice accumulate in
the soil. Moisture tends to condense from the soil
atmosphere at the freezing front (the depth at which the
temperature in the soil is 0 °C), thus over time an
ice-enriched layer may form at the interface at the top of the
permafrost.
‘Patterned ground’ (Fig. 17.5) forms where contraction
cracks open in the extreme cold of winter forming polygons,
much like those formed by the cracks in a drying mud
puddle, but on a much larger scale. Patterned ground polygons are often 5–10 m across. Blowing snow tends to
accumulate in the cracks and thus meltwater seeps down,
then refreezes. Over time ice wedges up to about 2 metres
deep and 50 cm across may form (Fig. 17.2).
The Dry Valley landscape has been considered stable
over periods extending to millions of years particularly at
higher altitudes which have escaped some of the disturbance
of valley floors and walls that occurred during more recent
glacial advances and retreats. The older the surface the more
strongly weathered the soils. Older soils often contain visible
salt accumulation, redder soil colours, more clay, and
stronger weathering of surface soils. Exfoliation, cavernous
weathering, and ventifaction are often evident.
Salts accumulate in the soils because leaching does not
occur at most sites (through lack of water) and any moisture
that may dissolve and move salts eventually evaporates,
leaving the salts behind. In areas where snow accumulation
and melting lead to some surface or subsurface moisture
flow, the water may move and concentrate salts in lakes such
as Lake Vanda, or ephemeral ponds such as Don Juan Pond,
both of which are in the Wright Valley.
17.3 Soil-Landscape Relationships
17.3.1 Overview
The soils in the Ross Sea region of Antarctica have strong
relationships to the landscapes in which they form. At the
regional scale, the soils can be divided into three groups, the
coastal margins, the McMurdo Dry Valleys, and the isolated
ice-free areas at high altitudes in the Transantarctic Mountains and on the margins of the Polar Plateau. At local scales,
there are distinct relationships between topographic and
geomorphic position and the soils that form. The age of
landscape surfaces greatly influences the amount of weathering and the degree of soil development. Recently deposited, or mobile, material such as sand dunes, stream and
beach deposits, and the youngest glacial deposits, have soils
which exhibit minimal soil weathering or development
(Typic Haplorthels). Due to the cold dry environment, soils
on bedrock are generally shallow and classify as Lithic
Haplorthels. On older surfaces, weathering is more advanced
with iron oxides imparting dark brown colours to soil
17.1 Important Features of Antarctic Soils
271
Soil Taxonomy’ in 1998. Recognition of Gelisols was partly
to encompass soils with cryogenic properties in Alaska
(matching the adjacent Canadian classification for soils on
permafrost, the Cryosolic Soils) and also to accommodate
Antarctic soils. The USDA changed their definition of ‘soil’
to remove a requirement for organic matter so that the
Antarctic Gelisols could be considered ‘soil’ and therefore
included in Soil Taxonomy.
17.2 Soil Profile Genesis
Due to the cold dry environment, most soils in the Ross Sea
region have limited weathering and so largely retain the
inherited properties of the parent materials which are mainly
glacial tills. Although climate is the dominant influence on
soil genesis, parent material, topography, and time all have
recognisable influence. Organisms impact the soils markedly
only in a few isolated sites on coastal margins where penguin colonies occur or where summer meltwater supports
moss growth.
Soil desert pavement surfaces comprise gravels and
pebbles that are left behind as finer materials are eroded,
primarily by wind, until a protective layer of coarser material
remains at the surface preventing further erosion. Over time,
wind-blown sand and salt-weathering abrades and corrodes
the exposed rock surfaces. The abrasion, along with a small
amount of chemical weathering, particularly oxidation of
iron-rich minerals, leads to the formation of polished rock
surfaces with a ‘desert varnish’ coating. Ventifacts (rocks
carved and polished to smooth surfaces by the effects of
prolonged exposure to wind-blown particles) are evident at
many sites.
The older the land surface the more weathered the desert
pavement. Some high-altitude surfaces are thought to be
extremely (up to about 5 million years) old. Even though
weathering processes proceed only slowly in the Antarctic
environment, the long exposure time frames mean that desert
pavements on older surfaces are highly developed. Older
surfaces typically have a closely packed layer of gravel,
cobble, and boulder-sized material with ventifacted surfaces
that are pitted, and coated with desert varnish (Fig. 17.4).
In younger soils, the colours are often described as
‘lithochromic’. In other words, the soils are the colours of
the rocks or deposits from which they have formed as there
has been minimal chemical weathering. Soils are most often
formed in glacial tills that contain a poorly sorted mix of
sand, gravel, and larger pebbles and boulders that have been
broken up by physical weathering processes.
Ice lenses occur where small areas of ice accumulate in
the soil. Moisture tends to condense from the soil
atmosphere at the freezing front (the depth at which the
temperature in the soil is 0 °C), thus over time an
ice-enriched layer may form at the interface at the top of the
permafrost.
‘Patterned ground’ (Fig. 17.5) forms where contraction
cracks open in the extreme cold of winter forming polygons,
much like those formed by the cracks in a drying mud
puddle, but on a much larger scale. Patterned ground polygons are often 5–10 m across. Blowing snow tends to
accumulate in the cracks and thus meltwater seeps down,
then refreezes. Over time ice wedges up to about 2 metres
deep and 50 cm across may form (Fig. 17.2).
The Dry Valley landscape has been considered stable
over periods extending to millions of years particularly at
higher altitudes which have escaped some of the disturbance
of valley floors and walls that occurred during more recent
glacial advances and retreats. The older the surface the more
strongly weathered the soils. Older soils often contain visible
salt accumulation, redder soil colours, more clay, and
stronger weathering of surface soils. Exfoliation, cavernous
weathering, and ventifaction are often evident.
Salts accumulate in the soils because leaching does not
occur at most sites (through lack of water) and any moisture
that may dissolve and move salts eventually evaporates,
leaving the salts behind. In areas where snow accumulation
and melting lead to some surface or subsurface moisture
flow, the water may move and concentrate salts in lakes such
as Lake Vanda, or ephemeral ponds such as Don Juan Pond,
both of which are in the Wright Valley.
17.3 Soil-Landscape Relationships
17.3.1 Overview
The soils in the Ross Sea region of Antarctica have strong
relationships to the landscapes in which they form. At the
regional scale, the soils can be divided into three groups, the
coastal margins, the McMurdo Dry Valleys, and the isolated
ice-free areas at high altitudes in the Transantarctic Mountains and on the margins of the Polar Plateau. At local scales,
there are distinct relationships between topographic and
geomorphic position and the soils that form. The age of
landscape surfaces greatly influences the amount of weathering and the degree of soil development. Recently deposited, or mobile, material such as sand dunes, stream and
beach deposits, and the youngest glacial deposits, have soils
which exhibit minimal soil weathering or development
(Typic Haplorthels). Due to the cold dry environment, soils
on bedrock are generally shallow and classify as Lithic
Haplorthels. On older surfaces, weathering is more advanced
with iron oxides imparting dark brown colours to soil
17.1 Important Features of Antarctic Soils
271