-Glaciers-
Glaciated Systems and Landscapes
A glacier can be views as an open system, with inputs and outputs to
external systems, such as atmospheric and fluvial systems.
- Inputs: the primary input is snow. It becomes increasingly
compacted over many years, turning from low density(snowflakes)
to high density (clear glacial ice). Another input can be avalanches.
- Outputs: the main output from a glacial system is liquid water from
melting of ice close to the snout where temperatures are higher.
Where ice extends over the water (e.g ice shelves in antarctica)
huge chunks of ice may break off to form icebergs. This is a process
called calving. Other outputs include processes of evaporation and
sublimation.
- Energy: the glacier’s mass combines with the force of gravity to
generate potential energy. As the glacier moves, this energy is
converted into kinetic energy, enabling the glacier to carry out
processes such as erosion, transportation and ultimately deposition.
- Stores/Components: the main stores are snow and ice. There may
be seasonal variations in the magnitude of these stores, especially
in temperate regions (= significant winter snowfall and summer
melting).
- Flows/transfers: some of these processes such as evaporation,
sublimation, meltwater flow and the processes of glacial movement
(internal deformation and basal sliding). These flows are more
pronounced and active in warmer environments where there are
significant variations in temperature.
- Dynamic equilibrium: in a glacial system, an equilibrium line can be
drawn between the accumulation zone and ablation zone. If the
glacier is in a state of balance were inputs equal outputs, the line
will remain In the same place.
Present day distribution of cold environments:
- Polar- areas of permanent ice. E.g. vast ice sheets of antarctica and
Greenland.
- Periglacial (tundra) – the edge of permanent ice, characterised by
permafrost (frozen ground).
, - Alpine- mountain areas – high altitudes result in cold conditions.
- Glaciers- found at the edges of ice sheets, particularly in
mountainous regions.
Physical characteristics = Soil development:
Soil is a mixture of weathered rock, rotted organic matter, living
organisms (biota), gases (mostly oxygen) and water. Weathering is limited
due to the lack of liquid water and the lack of vegetation, which means
there is little organic matter and few decomposers. As a result, soil
formation is extremely slow, and soils that do develop are thin, acidic,
sometimes waterlogged and mostly frozen.
Climate:
All cold environments experience periods when temperatures are
close/below freezing. Liquid water is limited to certain times of the year
and sometimes completely absent. Snowfall varies and frequent strong
winds add wind chill and absorb precious moisture from plants. These
factors limit the development of soils and vegetation.
Periglacial environments are characterised by tundra vegetation
consisting of low growing plants, including mosses, lichens, grasses
sedges and dwarf shrubs. their small, waxy leaves are well adapted to
retain warmth and reduce water loss caused by exposure to strong winds.
They maximise the short, warmer summers by flowering and setting seed
in just a few weeks. Additionally, they have shallow root systems to cope
with the thin, frozen soil.
Glacial Budgets:
The glacial budget considers the balance between the inputs and outputs.
Accumulation zone: where there’s a net gain of ice over the
course of a year. Here the inputs exceed the outputs.
Ablation zone: where there is a net loss of ice during a year.
The losses exceed the gains.
This mass balance varies during the course of a year, in the summer,
ablation will be at its highest due to rapid melting of ice. During the
winter, higher amounts of snowfall + limited melting will result in
accumulation being greater than ablation.
If accumulation exceeds ablation (positive mass balance) = likely advance
If ablation exceeds accumulation (negative mass balance) = likely retreat
The snout is often marked by a terminal moraine -a ridge of sediment,
that is pushed ahead of the glacier. If the glacier is retreating, the terminal
moraine is left abandoned.
Glaciated Systems and Landscapes
A glacier can be views as an open system, with inputs and outputs to
external systems, such as atmospheric and fluvial systems.
- Inputs: the primary input is snow. It becomes increasingly
compacted over many years, turning from low density(snowflakes)
to high density (clear glacial ice). Another input can be avalanches.
- Outputs: the main output from a glacial system is liquid water from
melting of ice close to the snout where temperatures are higher.
Where ice extends over the water (e.g ice shelves in antarctica)
huge chunks of ice may break off to form icebergs. This is a process
called calving. Other outputs include processes of evaporation and
sublimation.
- Energy: the glacier’s mass combines with the force of gravity to
generate potential energy. As the glacier moves, this energy is
converted into kinetic energy, enabling the glacier to carry out
processes such as erosion, transportation and ultimately deposition.
- Stores/Components: the main stores are snow and ice. There may
be seasonal variations in the magnitude of these stores, especially
in temperate regions (= significant winter snowfall and summer
melting).
- Flows/transfers: some of these processes such as evaporation,
sublimation, meltwater flow and the processes of glacial movement
(internal deformation and basal sliding). These flows are more
pronounced and active in warmer environments where there are
significant variations in temperature.
- Dynamic equilibrium: in a glacial system, an equilibrium line can be
drawn between the accumulation zone and ablation zone. If the
glacier is in a state of balance were inputs equal outputs, the line
will remain In the same place.
Present day distribution of cold environments:
- Polar- areas of permanent ice. E.g. vast ice sheets of antarctica and
Greenland.
- Periglacial (tundra) – the edge of permanent ice, characterised by
permafrost (frozen ground).
, - Alpine- mountain areas – high altitudes result in cold conditions.
- Glaciers- found at the edges of ice sheets, particularly in
mountainous regions.
Physical characteristics = Soil development:
Soil is a mixture of weathered rock, rotted organic matter, living
organisms (biota), gases (mostly oxygen) and water. Weathering is limited
due to the lack of liquid water and the lack of vegetation, which means
there is little organic matter and few decomposers. As a result, soil
formation is extremely slow, and soils that do develop are thin, acidic,
sometimes waterlogged and mostly frozen.
Climate:
All cold environments experience periods when temperatures are
close/below freezing. Liquid water is limited to certain times of the year
and sometimes completely absent. Snowfall varies and frequent strong
winds add wind chill and absorb precious moisture from plants. These
factors limit the development of soils and vegetation.
Periglacial environments are characterised by tundra vegetation
consisting of low growing plants, including mosses, lichens, grasses
sedges and dwarf shrubs. their small, waxy leaves are well adapted to
retain warmth and reduce water loss caused by exposure to strong winds.
They maximise the short, warmer summers by flowering and setting seed
in just a few weeks. Additionally, they have shallow root systems to cope
with the thin, frozen soil.
Glacial Budgets:
The glacial budget considers the balance between the inputs and outputs.
Accumulation zone: where there’s a net gain of ice over the
course of a year. Here the inputs exceed the outputs.
Ablation zone: where there is a net loss of ice during a year.
The losses exceed the gains.
This mass balance varies during the course of a year, in the summer,
ablation will be at its highest due to rapid melting of ice. During the
winter, higher amounts of snowfall + limited melting will result in
accumulation being greater than ablation.
If accumulation exceeds ablation (positive mass balance) = likely advance
If ablation exceeds accumulation (negative mass balance) = likely retreat
The snout is often marked by a terminal moraine -a ridge of sediment,
that is pushed ahead of the glacier. If the glacier is retreating, the terminal
moraine is left abandoned.
