materials and salt accumulating within the profile and under
pebbles and gravel in the desert pavement (e.g. forming Salic
Anhyorthels).
The availability of moisture in soil has a major impact on
the soil processes and resulting soil profile form. Moisture
availability is related to both the wider regional landscape
(including distance from sea and influence of katabatic
winds) and the local topographic position. Examples are
discussed in the following sections.
17.3.2 Antarctic Coastal Margins
Due to the sea acting as both a temperature moderating
influence, and a source of moisture, soils in the coastal
margins are generally warmer and wetter than soils at sites
further inland. The coastal margins receive greater precipitation and, because of the warmer, more humid, environment, more of the snow that falls melts, rather than directly
sublimating, as is common further inland. For a few weeks,
every summer many coastal soils may have water flowing
over or through the soil. The marine ecosystem is the source
of the food chain for all the wildlife along the coast and the
ice-free coastal areas provide important resting and breeding
sites for birds. Thus, the activity of birds transfers some
nutrients into the coastal soils from the marine ecosystem.
The major landscape units of coastal areas include raised
beaches, areas of glacial till, and exposed bedrock. Because
of isostatic rebound, many sites along the coast have a series
of raised beach-ridges. The soils on raised beaches comprise
weakly weathered, highly rounded and smoothed, pebbles
and gravels in a sandy matrix with occasional shells or other
marine-derived material.
The glacial drift deposits on coastal margins have generally been exposed by glacial retreat over the last few thousand years so are only weakly weathered. The lithology tends
to be dominated by the local geology. For example, soils are
marble-dominated at Marble Point, gneiss-dominated at
Gneiss Point, and granite-dominated at Granite Harbour.
However, a mixture of lithologies, including granites, sandstones, and dolerite occurs at all sites indicating that some
materials have been carried some distance. The tills are
poorly sorted, ranging from angular to sub-rounded large
(> 1 m diameter) boulders, all the way through to fine sands.
On Ross Island, the bedrock comprises scoriaceous basalt.
Being porous, meltwater penetrates into the scoria and
freeze-thaw processes break the clasts so soils comprise rock
fragments interspersed with gravels and sands.
In the relatively moist coastal environments, all soils
contain enough water to form ice-cemented permafrost. On
younger surfaces, weak patterned ground cracks are visible.
However, on some of the older surfaces, such as the foot
slopes of some hills, there are areas with strong patterned
ground development. The availability of moisture can lead to
stronger biological (moss, algae, and lichen) growth in the
coastal regions than in other areas (Sect. 17.4.4).
17.3.3 The McMurdo Dry Valleys
The McMurdo Dry Valleys are unique (Fig. 17.6) and are
considered the closest environment to Mars that we have on
Earth. In the dry valleys, evaporation exceeds precipitation;
hence, the absence of snow and ice that covers most of the
Antarctic continent. Evaporation is enhanced by strong
katabatic winds that flow down off the Polar Plateau through
the dry valleys. Precipitation is low because the dry valleys
are shielded from water sources by the Ross Ice Shelf to the
east, the Transantarctic Mountains to the north and south,
and the Polar Plateau to the west. Thus, the McMurdo Dry
Valleys are a ‘cold desert’ environment and the soils share
many properties with soils of hot deserts including minimal
organic matter, accumulation of salts, and sand-dominated
soil textures.
Within the McMurdo Dry Valleys, the main landscape
drivers that impact the soils are the availability of moisture,
the microclimate, the surface age (with older surfaces tending to occur at higher altitudes), and the underlying parent
materials.
Soil moisture levels are higher on the margins of the Polar
Plateau (due to inputs of blowing snow) and nearer the coast
because of higher snow fall. The driest areas tend to be in the
dry valley floors and in upland areas that are sheltered from
the wind-blown snow associated with polar cold air drainage. Within the valley walls and floors, there are areas that
receive intermittent moisture in the summer from the
ephemeral streams that carry meltwaters from the high valley
walls down into the valley floors. Moist soils are also found
on the margins of lakes and streams where moisture is drawn
up into the adjacent soil under capillary forces where it
evaporates, often leaving a salt margin (Fig. 17.7).
Where there is sufficient moisture, the soils contain
ice-cemented permafrost and strong patterned ground features tend to form. Ice-cored moraine (where a mineral soil is
formed over remnant glacier ice) occurs in a number of areas
—for example at Beacon Valley, where mineral material
overlies and insulates underlying glacier ice. The surface
soils on ice-cored moraine can be relatively highly weathered, with strongly oxidised and weathered surface pavements, and may contain dry permafrost material that overlies
the ice core. A distinctive feature of ice-cored moraine is the
presence of large-scale patterned ground that often has patterned ground cracks 1–2 m deep between the polygons.
Increased melting, resulting in greater subsidence, occurs in
the crack area, and hence generates an extremely hummocky
surface which is somewhat difficult and tedious to walk over.
17.3 Soil-Landscape Relationships
273
pebbles and gravel in the desert pavement (e.g. forming Salic
Anhyorthels).
The availability of moisture in soil has a major impact on
the soil processes and resulting soil profile form. Moisture
availability is related to both the wider regional landscape
(including distance from sea and influence of katabatic
winds) and the local topographic position. Examples are
discussed in the following sections.
17.3.2 Antarctic Coastal Margins
Due to the sea acting as both a temperature moderating
influence, and a source of moisture, soils in the coastal
margins are generally warmer and wetter than soils at sites
further inland. The coastal margins receive greater precipitation and, because of the warmer, more humid, environment, more of the snow that falls melts, rather than directly
sublimating, as is common further inland. For a few weeks,
every summer many coastal soils may have water flowing
over or through the soil. The marine ecosystem is the source
of the food chain for all the wildlife along the coast and the
ice-free coastal areas provide important resting and breeding
sites for birds. Thus, the activity of birds transfers some
nutrients into the coastal soils from the marine ecosystem.
The major landscape units of coastal areas include raised
beaches, areas of glacial till, and exposed bedrock. Because
of isostatic rebound, many sites along the coast have a series
of raised beach-ridges. The soils on raised beaches comprise
weakly weathered, highly rounded and smoothed, pebbles
and gravels in a sandy matrix with occasional shells or other
marine-derived material.
The glacial drift deposits on coastal margins have generally been exposed by glacial retreat over the last few thousand years so are only weakly weathered. The lithology tends
to be dominated by the local geology. For example, soils are
marble-dominated at Marble Point, gneiss-dominated at
Gneiss Point, and granite-dominated at Granite Harbour.
However, a mixture of lithologies, including granites, sandstones, and dolerite occurs at all sites indicating that some
materials have been carried some distance. The tills are
poorly sorted, ranging from angular to sub-rounded large
(> 1 m diameter) boulders, all the way through to fine sands.
On Ross Island, the bedrock comprises scoriaceous basalt.
Being porous, meltwater penetrates into the scoria and
freeze-thaw processes break the clasts so soils comprise rock
fragments interspersed with gravels and sands.
In the relatively moist coastal environments, all soils
contain enough water to form ice-cemented permafrost. On
younger surfaces, weak patterned ground cracks are visible.
However, on some of the older surfaces, such as the foot
slopes of some hills, there are areas with strong patterned
ground development. The availability of moisture can lead to
stronger biological (moss, algae, and lichen) growth in the
coastal regions than in other areas (Sect. 17.4.4).
17.3.3 The McMurdo Dry Valleys
The McMurdo Dry Valleys are unique (Fig. 17.6) and are
considered the closest environment to Mars that we have on
Earth. In the dry valleys, evaporation exceeds precipitation;
hence, the absence of snow and ice that covers most of the
Antarctic continent. Evaporation is enhanced by strong
katabatic winds that flow down off the Polar Plateau through
the dry valleys. Precipitation is low because the dry valleys
are shielded from water sources by the Ross Ice Shelf to the
east, the Transantarctic Mountains to the north and south,
and the Polar Plateau to the west. Thus, the McMurdo Dry
Valleys are a ‘cold desert’ environment and the soils share
many properties with soils of hot deserts including minimal
organic matter, accumulation of salts, and sand-dominated
soil textures.
Within the McMurdo Dry Valleys, the main landscape
drivers that impact the soils are the availability of moisture,
the microclimate, the surface age (with older surfaces tending to occur at higher altitudes), and the underlying parent
materials.
Soil moisture levels are higher on the margins of the Polar
Plateau (due to inputs of blowing snow) and nearer the coast
because of higher snow fall. The driest areas tend to be in the
dry valley floors and in upland areas that are sheltered from
the wind-blown snow associated with polar cold air drainage. Within the valley walls and floors, there are areas that
receive intermittent moisture in the summer from the
ephemeral streams that carry meltwaters from the high valley
walls down into the valley floors. Moist soils are also found
on the margins of lakes and streams where moisture is drawn
up into the adjacent soil under capillary forces where it
evaporates, often leaving a salt margin (Fig. 17.7).
Where there is sufficient moisture, the soils contain
ice-cemented permafrost and strong patterned ground features tend to form. Ice-cored moraine (where a mineral soil is
formed over remnant glacier ice) occurs in a number of areas
—for example at Beacon Valley, where mineral material
overlies and insulates underlying glacier ice. The surface
soils on ice-cored moraine can be relatively highly weathered, with strongly oxidised and weathered surface pavements, and may contain dry permafrost material that overlies
the ice core. A distinctive feature of ice-cored moraine is the
presence of large-scale patterned ground that often has patterned ground cracks 1–2 m deep between the polygons.
Increased melting, resulting in greater subsidence, occurs in
the crack area, and hence generates an extremely hummocky
surface which is somewhat difficult and tedious to walk over.
17.3 Soil-Landscape Relationships
273