Cold Environments Flashcards
Where are cold environments found?
High altitudes (alpine areas) , High latitudes of 66.5 degrees
List three characteristics shared by all cold environments
1) low temperatures
2) abundance of snow and ice
3) little vegetation
What are the three main types of cold environment?
1) glacial environments
2) periglacial areas (tundra)
3) alpine areas
A glacier can be though of as a system. What are the four general components of such a system?
1) inputs
2) storage (represented by glacier)
3) transfer (the ice moving)
4) outputs
List two inputs of a glacier
Snow/ice and avalanches
List two outputs of a glacier
Water vapour and sublimation
What is sublimation?
Transition of a substance directly from solid to gas. Without passing through the intermediate liquid phase.
Define the zone of ablation
Where ablation is greater than accumulation
Define the zone of accumulation
Where accumulation is greater than ablation
What is the line of equilibrium
This is between the 2 zones. It represents the snow line. This separates net loss from net gain.
A phrase to describe the snout of a glacier moving down the valley
Glacial advance
What altitude is the snow line in Greenland?
Sea level
What altitude is the snow line at the equator?
6,000 metres
Why is the snow line higher on south-facing slopes in the Northern Hemisphere?
South-facing slope receives more insolation
4 stages of ice formation
1) snow falls as flakes, trapping lots of air
2) snow accumulation causes compaction of lower layers, forming névé
3) continued compaction, plus infiltration and freezing of water, forms a mass of solid ice
4) ice begins to flow in downhill directions, in form of glacier
Characteristics of a warm-based glacier
High rates of erosion, transportation and deposition.
Melts in the summer
Meltwater reduces friction. Therefore glacier moves more quickly.
Characteristics of a cold-based glacier
Movement of this type of glacier is slow as they are permanently frozen to the underlying ground surface.
This type of glacier moves predominantly by internal flow processes.
What two processes lead to meltwater forming near the base of a glacier?
Basal sliding and surges
What causes a glacier to flow?
Gravity
Mass
Where does a glacier flow fastest?
Down the centre and at the top
Where is the rate of erosion higher? The hollow or rock lip?
The hollow because a reduction in gradient of the valley floor leads to ice deceleration, therefore the ice thickens increasing mass.
What is the main erosion process occurring in cold environments?
Abrasion
Under what temperature conditions will freeze-thaw action take place?
Where temperatures rise during the day but drop below freezing at night
What important property of water means that ice will exert pressure on a crack as it freezes?
Water expands (takes up nearly 10% more space) when it freezes. Therefore occupying more space leading to cracking.
They have different densities.
Abrasion
Occurs at both the base and the sides of a glacier
Results in smooth, polished rock surfaces
Leaves striations
Plucking
Rock outcrops become frozen onto base of the glacier and are carried along with the glacier when it moves
Occurs mainly at base of glacier
Results in an uneven “jagged” landscape
Geometry of a Corrie
Usually found on N/NE/E face of slope
An armchair shaped rock hollow with a steepened back wall.
Has an over deepened basin with a rock lip
Formation of a Corrie
Formation of hollow
Snow compresses in the deepened hollow, forming ice
A shallow hollow is enlarged by nivation
The Corrie floor deepens and the back wall steepens, due to rotational ice movement
Why do Corries have a rock lip?
The thinner ice at edge doesn’t produce same downcutting power
Can result in a tarn
What feature forms when there are two corries?
Arrête
What feature forms when there are three Corries?
A pyramidal peak
In which three situations does over-deepening occur beneath a glacier, leading to rock-basin formation?
1) increased erosion at confluence of glaciers
2) areas of weaker rock
3) zones of well-jointed rocks
Why do rock steps form?
The hard rock is too resistant to be eroded
What is a trough end?
When a steep wall is found at the head of a glacier
Outline the two steps required to form a fjord
1) over-deepening below the present sea-level
2) sea level rising to submerge into these areas of glacial valleys
What is a Roche moutonnée
A particularly outcrop of rock
The stoss side
Up-valley side. Shallow gradient that has experienced abrasion.
Lee
Down-valley jagged side. Steep gradient and experiences plucking
When ice refreezes
Regelation
Long profile of a glacial valley
The Corrie (with rock lip) - hanging valley (with trough end) - main valley
What is till?
Material deposited directly by ice
How can till be differentiated from river or beach material?
Glacial till tends to be angular to sub-angular (river material is rounded)
What is an erratic?
A large block of rock that has been moved from one area and deposited in another
Supraglacial debris means what?
Above
Subglacial debris means what?
Beneath
Englacial means what?
Inside
Where is medial moraine?
In the centre where two glaciers may have met
Where is ground moraine?
At the bottom of the glacier (in terms of deep down, not at the end)
Where is lateral moraine?
At the sides
What is a moraine?
A glacial accumulation of unconsolidated material/debris
What type of moraine represents the furthest extent of ice?
Terminal moraine
How does recessional moraine form?
Marks point where the retreat has halted for some time
What is a push moraine?
Where deposited moraine is shunted up into a mound
What kind of climate is needed to form push moraines?
A cool one. Where glacial advance can take place.
How do lateral moraines form?
As a product of rock fall.
Over-steepening of cliff or as a result of frost weathering
How do drumlins form at the base of a glacier?
1) beneath glacier
2) lodgement till/ground moraine
3) reduce in glacial energy therefore is unable to transport material
4) material deposits around rocky core
5) glacier continues to move over
Drumlins are elongated in the direction of ice movement. True or false?
True
The steep end of the drumlin is known as the Lee. True or false?
False
Drumkins can often be seen in swarms of smooth, oval shaped hills. True or false?
True
What is a fluvioglacial process?
A process as a result of meltwater from a glacier
Why might a river sourced from a melting glacier have a higher load capacity than a normal river of equivalent size?
It flows under considerable pressure, it has a high velocity and is very turbulent
Where do outwash plains form?
In front of the glaciers snout
What two forms of transport carry debris from the source to eventual deposition in an outwash plain?
1) glacial deposits
2) fluvioglacial deposits
How can varves be used to assess past climates?
A varve is when a layer of silt lives on top of a layer of sand. Shows 1 year of deposition.
Why are meltwater streams on the outwash plain often braided?
Seasonal changes in discharge leads to channels becoming choked with coarse material.
How does a kettle hole form?
When blocks of ice melt and leave a gap in the sediments. These are known as kettle holes.
How do eskers form?
Deposits made by subglacial streams
Stream restricted by ice walls - can carry load
Hydrostatic pressure allows the stream to flow uphill for short distance
Where to eskers form?
Parallel to the direction of ice advance
They are formed of sand and gravel
What causes kame terraces to form along the sides of glacial valleys?
When ice retreats further the delta collapses. Leaving only the sides.
Kames are delta deposits, formed when glacial rivers flow into lakes in front of the glacial snout. What commonly forms the dam that allows such lakes to form?
When recessional moraine deposits
Why does glacial meltwater have large amounts of erosive power?
Volume and large amounts of debris it carries
What is a proglacial lake?
Lake developing on the edges of ice
How can the presence of proglacial lakes eventually lead to the creation of new valleys and drainage systems?
When the ice damming these meltwater lakes totally melts, many of new valleys are left dry.
When overflows from these lakes which cross the lowest points of watersheds will create new valleys.
What is a periglacial area?
Not glaciated but exposed to very cold conditions
Provide an example of high-latitude area that is currently periglacial.
Alaska
Many current temperate areas have, in the past, been periglacial. Why might this be?
Spread of ice sheets and glaciers.
What is permafrost?
Permanently frozen ground
What conditions are required for permafrost to occur?
Where subsoil temperatures remain below zero for at least 2 consecutive years)
What is the active layer?
A layer that melts and refreezes
Provide three possible reasons that the ground surface becomes very wet during summer soil melting.
1) active layer melts
2) water cannot drain through permafrost
3) low temperature doesn’t encourage much evaporation
What are the three types of permafrost?
Continuous
Discontinuous
Sporadic
What landforms are created by freeze-thaw action?
Screes
Blockfield
What is nivation?
Takes place beneath patches of snow in hollows
What landform is formed by nivation?
A nivation hollow followed by a Corrie
Why do larger stones move to the surface during frost heave?
Ice crystals begin to develop. increase in volume of soil leads to upward expansion
Wha are the two types of patterned ground formed during frost heave?
Stone polygons and stone stripes
What causes solifluction?
When active layer thaws in the summer, excessive lubrication reduces the friction between soil particles
What landform is created as a result of solifluction?
Solifluction lobes
Describe the geometry of a pingo
Dome-shaped mound of earth-covered ice
Up to 7 metres hugh
Describe two ways in which groundwater freezing may create a pingo.
Discontinuous permafrost - water seeps into upper-layer of ground and then freezes. Therefore it expands ( open system )
Continuous permafrost, ground water can be trapped by freezing from above and permafrost from beneath. When water freezes it will expand
How does an ice wedge form?
Beneath active layer
Repeated process of open crack freezing and thawing. Gets deeper and wider!
Indigenous people’s living in cold environments traditionally perform which economic activities?
Hunting and fishing
Would you describe the traditional lifestyle of indigenous peoples in cold environments as sustainable?
Yes - examples such as Inuit and Lapps have developed strategies to survive in a difficult natural environment
How did newcomers first exploit the Southern Ocean?
Sealing, whaling, trapping for fur and mining
When did the exploitation of the southern ocean begin?
18th century onwards
What problems did this activity cause?
Made the lifestyle of indigenous population harder. Affecting sustainability. By 1800 fur seals were wiped out.
Which economic exploitation of the region began in the 19th century?
Whaling
Why did the northern hemisphere nations need to come to the southern ocean to carry out this activity?
Whale population of North Atlantic reduced by massive exploitation. Therefore used southern ocean. Whaling is a very profitable business
Why did this activity largely stop in the mid-twentieth century?
Establishment of the international whaling convention in 1946 led to end.
What economic activity took over in the mid-twentieth century?
Fishing
What concerns were raised about this activity?
The number of fish being taken. Particularly krill - which underline the whole food web
Why do tourists generally visit Antarctica?
To see glacial landscapes
For its remoteness, isolation, chance to tear oneself
Historic sound (McMordo sound)
Expeditions
What is the purpose of the trans-Alaska pipeline?
To transfer oil to the USA. Demand was increasing.
It was built between 1974-77
Why is the pipeline raised above the ground?
So heat isn’t conducted into ground surface
Allows structure to move sideways as a protection against ground movement
Resist being jacked up by successive years of frost heave
Where is he pipeline buried?
Under roads
Avalanche sensitive areas
Major caribou migration routes
When the pipes are buried, how is the permafrost protected?
It is covered by think insulation
Refrigeration units to keep the ground frozen
Why is tundra considered a fragile environment?
It’s climate and limited productivity
Why do plants in the tundra environment have difficulty adapting to changed conditions?
Limited productivity.
Slow plant growth.
Any disruption causes problems.
Why might reducing the number of lemmings in a tundra environment impact on the Arctic fox population?
It’s predator, the arctic fox, cannot find food and therefore may struggle to survive.
What aspects of human efforts to settle in cold environments act to thaw the permafrost?
vegetation cleared (for construction)
Vehicle tracks
Describe thermokarst landscape, as formed when permafrost thaws.
Topographic depressions characterised by extensive areas irregular hummocky ground interspersed with waterlogged hollows.
And three methods used to insulate human constructions from the underlying permafrost.
1) elevate smaller buildings
2) larger structures use aggregate pads
3) use of utilidors
What is the purpose of the trans-Alaska pipeline?
To transfer oil to the USA. Demand was increasing.
It was built between 1974-77
Why is the pipeline raised above the ground?
So heat isn’t conducted into ground surface
Allows structure to move sideways as a protection against ground movement
Resist being jacked up by successive years of frost heave
Where is he pipeline buried?
Under roads
Avalanche sensitive areas
Major caribou migration routes
When the pipes are buried, how is the permafrost protected?
It is covered by think insulation
Refrigeration units to keep the ground frozen
Why is tundra considered a fragile environment?
It’s climate and limited productivity
Why do plants in the tundra environment have difficulty adapting to changed conditions?
Limited productivity.
Slow plant growth.
Any disruption causes problems.
Why might reducing the number of lemmings in a tundra environment impact on the Arctic fox population?
It’s predator, the arctic fox, cannot find food and therefore may struggle to survive.
What aspects of human efforts to settle in cold environments act to thaw the permafrost?
vegetation cleared (for construction)
Vehicle tracks
Describe thermokarst landscape, as formed when permafrost thaws.
Topographic depressions characterised by extensive areas irregular hummocky ground interspersed with waterlogged hollows.
And three methods used to insulate human constructions from the underlying permafrost.
1) elevate smaller buildings
2) larger structures use aggregate pads
3) use of utilidors
What is an energy resource?
Any part of the environment that can be used to meet human needs. Can be classed as renewable or non-renewable
