study has shown Antarctic soils to be fascinating and complex with active physical, chemical, and biological processes. The most outstanding feature of soils in the Ross Sea
region of Antarctica is the presence of frozen soil materials
as a result of the extremely cold climate. Inland areas are
extremely dry, giving rise to a ‘cold desert’ environment.
Within the McMurdo Dry Valleys, extensive areas are
ice-free as evaporation exceeds precipitation. Similar conditions occur in other smaller areas in the Transantarctic
Mountains including the Britannia Range and Darwin
Mountains. Thus, where there is no permanent ice or snow
cover, the rock materials gradually weather to form soil.
Most of the soils in the Ross Sea region of Antarctica
comprise a surface desert pavement that overlies a seasonally thawed ‘active layer’ with permafrost at depth
(Figs. 17.1 and 17.2). Because of the cold climate, and lack
of moisture, physical weathering is dominant. Thus, most
soils have a gravelly sand texture with many larger boulders
and stones within the soil profile. Soils with noticeable clay
content are rare, and are generally formed from fine-textured
parent materials such as lake sediments.
The desert pavement comprises a surface layer of rocks,
gravel, and sand. The active layer is the near-surface soil that
thaws each summer, then freezes again in winter. The active
layer ranges in depth from about 1 m deep at warmer coastal
sites in the northern part of the Ross Sea region to no
thawing at all, and thus no active layer, in cold higher altitude sites on the margins of the Polar Plateau. The active
layer is thawed only for a few weeks at the height of the
Antarctic summer in late December and early January and at
other times may be frozen solid. Thus, the only way to
accurately determine the depth of the active layer is to install
temperature monitoring equipment.
Beneath the active layer is permafrost (‘permanently’
frozen ground). Permafrost is defined as having a temperature below 0 °C for at least two consecutive years. A ‘transition layer’ between the active layer and the permafrost is
increasingly being recognised where the soil occasionally
warms to temperatures >0 °C in a particularly warm summer. Where there is sufficient moisture (>about 10% gravimetric moisture), the permafrost is ice-cemented and is
consequently difficult to excavate and study. In some areas
solid ice, in the form of ground ice, ice lenses, or ice wedges,
may lie below the soil surface.
Ground ice is extensive in some areas where glaciers have
gradually ablated (through sublimation, or melting and
evaporation, of the ice). As the ice is melted and evaporated
a layer of mineral material, which was caught in the ice, is
left behind at the surface. Eventually, the mineral materials
accumulate to such a thickness that they insulate the
underlying ice and prevent further evaporation and melting
(Fig. 17.2). Some of the surfaces above ground ice are very
old and the mineral material can become highly weathered
with a strongly developed soil that, to the casual observer,
appears as terra-firma.
On some older high surfaces and inland parts of the
McMurdo Dry Valleys the environment is so dry that the
soils contain insufficient moisture to form ice-cement. Thus,
even where the temperature is well below 0 °C, the permafrost soil material is loose and easily excavated, and is
described as ‘dry permafrost’ (Fig. 17.1).
Antarctic soils are included in this book as New Zealand
has a strong interest in the Ross Sea region due to a territorial claim over the ‘Ross Dependency’, the area of
Antarctica directly south of New Zealand. Under the
Antarctic Treaty (to which New Zealand was one of the 12
original signatories in 1959), all territorial claims are put
aside and the Antarctic continent is managed in the interest
of peace and science. There has been a long history of New
Zealand research into soils in the Ross Sea region of
Antarctica, commencing with the expedition of John
McCraw and Graeme Claridge in 1959. Iain Campbell and
Graeme Claridge continued investigations into Antarctic
soils from the 1960s to 1990s. Their 1987 book is a classic
source of information related to Antarctic soils. In addition,
various historic exploration-era expeditions, including those
of Scott and Shackleton, operated from Christchurch in New
Zealand, as do modern research parties including US and
Italian Antarctic programmes. Hence, there is a
>100-year-long, enduring, connection between New Zealand
and Antarctica.
17.1.2 Areas of Occurrence
The Ross Dependency lies directly south of New Zealand
and stretches from latitude 60° S to 90° S (the South Pole)
and from longitude 160° E through to 150° W (Fig. 17.3)
with a total area of 450,000 km
2
. While most of the Ross
Dependency is sea- or ice-covered, it also contains the largest ice-free area in Antarctica. There are many small
ice-free areas scattered along the coast of the Ross Sea, and
on isolated outcrops (nunataks) and valleys within the
Transantarctic Mountains. The largest continuous area
(about 6,700 km
2 ) of exposed soil is in the McMurdo Dry
Valleys. The ice-free areas, on which soils develop, make up
less than 2% of the Ross Dependency region.
17.1.3 Variation Within Antarctic Soils
The variation within Antarctic soils is surprisingly large,
driven primarily by soil age, parent material, and moisture
availability. The New Zealand Soil Classification does not
extend to Antarctica so people working in Antarctica use
international soil classification systems to classify Antarctic
268
17 Soils in the Ross Sea Region of Antarctica
region of Antarctica is the presence of frozen soil materials
as a result of the extremely cold climate. Inland areas are
extremely dry, giving rise to a ‘cold desert’ environment.
Within the McMurdo Dry Valleys, extensive areas are
ice-free as evaporation exceeds precipitation. Similar conditions occur in other smaller areas in the Transantarctic
Mountains including the Britannia Range and Darwin
Mountains. Thus, where there is no permanent ice or snow
cover, the rock materials gradually weather to form soil.
Most of the soils in the Ross Sea region of Antarctica
comprise a surface desert pavement that overlies a seasonally thawed ‘active layer’ with permafrost at depth
(Figs. 17.1 and 17.2). Because of the cold climate, and lack
of moisture, physical weathering is dominant. Thus, most
soils have a gravelly sand texture with many larger boulders
and stones within the soil profile. Soils with noticeable clay
content are rare, and are generally formed from fine-textured
parent materials such as lake sediments.
The desert pavement comprises a surface layer of rocks,
gravel, and sand. The active layer is the near-surface soil that
thaws each summer, then freezes again in winter. The active
layer ranges in depth from about 1 m deep at warmer coastal
sites in the northern part of the Ross Sea region to no
thawing at all, and thus no active layer, in cold higher altitude sites on the margins of the Polar Plateau. The active
layer is thawed only for a few weeks at the height of the
Antarctic summer in late December and early January and at
other times may be frozen solid. Thus, the only way to
accurately determine the depth of the active layer is to install
temperature monitoring equipment.
Beneath the active layer is permafrost (‘permanently’
frozen ground). Permafrost is defined as having a temperature below 0 °C for at least two consecutive years. A ‘transition layer’ between the active layer and the permafrost is
increasingly being recognised where the soil occasionally
warms to temperatures >0 °C in a particularly warm summer. Where there is sufficient moisture (>about 10% gravimetric moisture), the permafrost is ice-cemented and is
consequently difficult to excavate and study. In some areas
solid ice, in the form of ground ice, ice lenses, or ice wedges,
may lie below the soil surface.
Ground ice is extensive in some areas where glaciers have
gradually ablated (through sublimation, or melting and
evaporation, of the ice). As the ice is melted and evaporated
a layer of mineral material, which was caught in the ice, is
left behind at the surface. Eventually, the mineral materials
accumulate to such a thickness that they insulate the
underlying ice and prevent further evaporation and melting
(Fig. 17.2). Some of the surfaces above ground ice are very
old and the mineral material can become highly weathered
with a strongly developed soil that, to the casual observer,
appears as terra-firma.
On some older high surfaces and inland parts of the
McMurdo Dry Valleys the environment is so dry that the
soils contain insufficient moisture to form ice-cement. Thus,
even where the temperature is well below 0 °C, the permafrost soil material is loose and easily excavated, and is
described as ‘dry permafrost’ (Fig. 17.1).
Antarctic soils are included in this book as New Zealand
has a strong interest in the Ross Sea region due to a territorial claim over the ‘Ross Dependency’, the area of
Antarctica directly south of New Zealand. Under the
Antarctic Treaty (to which New Zealand was one of the 12
original signatories in 1959), all territorial claims are put
aside and the Antarctic continent is managed in the interest
of peace and science. There has been a long history of New
Zealand research into soils in the Ross Sea region of
Antarctica, commencing with the expedition of John
McCraw and Graeme Claridge in 1959. Iain Campbell and
Graeme Claridge continued investigations into Antarctic
soils from the 1960s to 1990s. Their 1987 book is a classic
source of information related to Antarctic soils. In addition,
various historic exploration-era expeditions, including those
of Scott and Shackleton, operated from Christchurch in New
Zealand, as do modern research parties including US and
Italian Antarctic programmes. Hence, there is a
>100-year-long, enduring, connection between New Zealand
and Antarctica.
17.1.2 Areas of Occurrence
The Ross Dependency lies directly south of New Zealand
and stretches from latitude 60° S to 90° S (the South Pole)
and from longitude 160° E through to 150° W (Fig. 17.3)
with a total area of 450,000 km
2
. While most of the Ross
Dependency is sea- or ice-covered, it also contains the largest ice-free area in Antarctica. There are many small
ice-free areas scattered along the coast of the Ross Sea, and
on isolated outcrops (nunataks) and valleys within the
Transantarctic Mountains. The largest continuous area
(about 6,700 km
2 ) of exposed soil is in the McMurdo Dry
Valleys. The ice-free areas, on which soils develop, make up
less than 2% of the Ross Dependency region.
17.1.3 Variation Within Antarctic Soils
The variation within Antarctic soils is surprisingly large,
driven primarily by soil age, parent material, and moisture
availability. The New Zealand Soil Classification does not
extend to Antarctica so people working in Antarctica use
international soil classification systems to classify Antarctic
268
17 Soils in the Ross Sea Region of Antarctica