Flashcards in Ice On Land Deck (82):
A long standing mass of ice that moves very slowly downhill.
Where are glaciers found?
Low altitude and high latitudes.
What do glaciers do?
They erode, transport and deposit huge quantities of material.
What is the formation of a glacier called?
The formation of a glacier and the process by which they shape the landscape sound them is called glaciation.
Is a period of ice advance associated with falling temperatures.
Is a period of ice retreat associated with rising temperatures (currently Holocene period).
What is internal deformation?
Is when the weight of the ice causes the deformation of ice crystals.
This takes place most readily where pressures are highest.
What is basal sliding?
When meltwater at the base of a glacier acts as a lubricant and the glacier slides over the land
When do glaciers move fastest?
-Increasing thickness of ice
-Increasing meltwater at the base a glacier
What is eccentricity?
A change in the Earth's orbit
What is obliquity?
The tilt of the Earth's axis
What is precession?
The Earth's axis tilt
How are glaciers formed?
1. As SNOW falls it becomes compacted as more snow falls on top of it
2. Air is expelled and each individual ice snowflakes turn into GRANULAR ICE crystals
3. The ice becomes denser turning into FIRN
4. Then the firn turns into GLACIAL ICE
What are the outputs of a glacier?
-Ablation: usually occuring at the snout where temperatures are their highest (or on surface in the summer (melting!))
-Calving: where chunks of ice break away at the snout
-Evaporation: water liquid to water vapour
-Sublimation: water solid to water vapour
What are some inputs to the system?
Avalanches of snow and ice can also provide inputs to the system
What happens when the glacial budget is positive?
What happens when the glacial budget is negative?
What is the impact of the short term temperature changes?
-Summer: negative glacial budget as ablation EXCEEDS accumulation
-Winter: positive glacial budget as accumulation EXCEEDS ablation
What is the impact of the long term temperature changes?
-Interglacial: negative glacial budget as ablation EXCEEDS accumulation
-Glacial: positive glacial budget as accumulation EXCEEDS ablation
What are long term changes that will effect the glacial budget?
-Glacial and interglacial periods
What is the Glacial Budget?
The glacial budget is the balance between accumulation and ablation in a glacier. It determines whether the glacier will advance or retreat
What is a Corrie glacier?
-It is the smallest type of glacier
-Rotational slip causes the ice to retreat from the back wall, creating a crevasse (which forms a corrie)
-E.G. Jasper National Park
What is a Valley glacier?
-A moving mass of ice confined within a valley
-Broad V shape
-Steeped wall (U-shaped Valley)
-E.G. Tongos National Forest: Alaska
What is an example of an Ice Cap and an Ice Sheet?
-Senrial Rang (Antartica)
What is abrasion?
-A process of erosion in which rocks carried in the bottom of the ice wear away the surface rock over which the ice passes
-Leaving behind striations (the depth of these depend on the resistance of the bedrock in comparison to the debris that are eroding the bedrock
When are the rates of abrasion the greatest?
-Large amount of debris
-Thick ice (greater pressure)
-Rock debris are most resistant than the bedrock it is eroding
-Glacier travelling at a greater velocity
-Meltwater creates faster basal sliding with means the glacier has greater eroding power
(However if there is excess under pressure this reduces the contact between the contact between debris and bedrock which actually reduces abrasion
What is plucking?
A process of erosion in which blocks of rock are torn away from the bed rock as the ice moves away
When are the rates of plucking the greatest?
-The bedrock is well jointed (rocks that interlock together)
-Large amounts of meltwater, more re-freezing can take place
-Thick ice (greater frictional drag)
Describe freeze-thaw weathering
1. Water enters the joint or crack in the rock
2. Temperatures reach below 0 degrees and the water freezes and expands. This exerts pressure on the rock prising the joints apart
3. Temperatures reach above 0 degrees in the daytime causing the ice to melt
4. This process is repeated, weakening the rock and eventually causing it to break apart
-This can from basal debris used in abrasion
-Also helps to 'prepare' the rock for erosional processes by loosening and fracturing the rock providing weaknesses that can be exploited through processes such as plucking
What is physical subglacial meltwater erosion?
-Meltwater carries sediment under pressure, eroding the underlying bedrock
-If the sediment is more large and coarse the bedrock will be eroded faster and more effectively
What is chemical subglacial meltwater erosion?
-Meltwater is made up of different chemicals (nature of the minerals found in the sediment that it transports)
-These chemicals may react with the bedrock, dissolving the bedrock through an erosional process called 'solution'
-An example could be the acidic meltwater, dissolves the bedrock since it is made out of chalk/limestone
Describe the formation of a corrie
1. Snow collects on a hollow on a mountainside and subsequent snowfall leads to compaction and the formation of a corrie glacier
2. Moraine is added to the top of the corrie glacier by freeze-thaw weathering on the mountainside, this falls through the crevasses
3. As the glacier moves further downslope, it tears away rock from the back wall, through plucking, steepening the back wall
4. Rock fragments from plucking, as well as that from freeze-thaw weathering are lodged at the bottom of the glacier, enhancing the glacier's abrasive power. Through abrasion, which is the sandpapering effect of the ice as it moves away, the base of the corrie is overdepeened
5. Glacial ice is less thick at the snout of the glacier and so the erosional power is smaller here. Rotational slip gouges out the overdeepend hollow leaving behind the typical 'armchair' shape of a corrie. A rock lip is also formed as a result
5. During an interglacial period the ice melts leaving behind a tarn
Describe an arête
-A sharp edged two sided ridge on the top of the mountain
-This is formed when two neighbouring corries have eroded back to back. As each glacier erodes either side of the ridge, the ridge becomes narrower
Describe a pyramidal peak
-A three-sided slab of rock which forms a mountain peak. Steep slopes on at least three sides and a sharp summit
-Formed when three or more corries erode back t back so far that they produce arêtes with a pyramidal peak in between
Describe the formation of a hanging valley
-A tributary valley left high above the main valley floor so that its stream flowing down the main valley sides falls as a waterfall
1. It is formed when the floors of a tributary valley were not eroded at the same rate as the main valley (slower)
2. This is because it contained a smaller glacier whose erosional power meant that it was not as deeply eroded as the bigger glacier in the main glacier trough
Describe the formation of a ribbon lake
-A long narrow lake in the floor of a glaciated valley
1. Formed when a glacier moves over an area containing alternating sections of hard and soft rock
2. The soft rock is less resistant than the hard rock and so it is eroded quicker creating a rock basin
3. The hard rock acts as dams between which rainwater accumulates after the ice age, filling up the rock basin creating a ribbon lake
What is glacial transportation?
-Glaciers carry a huge amount of material and transport very large volumes of material over very large distances. The rate of transport will depend on the supply of material and the velocity of the glacier
-This unconsolidated debris (rock material carried by a glacier known as moraine) is called moraine
-Materials transported by glaciers can come from processes such as plucking, abrasion, rocksfalls from weathering of the surrounding slopes, bulldozing action, wind blown materials, avalanches, and FTW
Describe the formation of a glacial trough
-A flat-floored steep sided valley formed by a glacier often also refereed to as a U shaped valley
1. Before the glacial period the landscape was shaped by erosional powers of rivers resulting in a 'V' shaped valley
2. During an interglacial period the ice begins to occupy a former river valley
3. Since the ice is a solid it is unable to wind around the interlocking spurs.
4. Therefore as the glacier moves downhill it erodes these. The glacier uses abrasion in which it uses its loads to wear away the rock and the glacier also uses plucking. This is when the glacier pulls away material beneath it and to the side of it. The subglacial moraine also aids the abrasion process
5. This gives a very steep valley side where the spurs have been truncated and this also widens and deepens the valley floor
What is a misfit stream?
-A misfit stream is a smaller river which flows over the wide valley floor of a glaciated valley; its size is out of scale with that of the valley
-It is formed in the interglacial period and did not erode the valley
Describe the formation of truncated spurs
-Higher areas of the straight rocky sides of the glaciated valley
1. Snow collects in a series of hollows at the side of the valley and subsequent snowfall leads to compaction and the formation of ice
2. The ice moves from the corries down the mountainside into a valley once occupied by a river.
3. The valley is V-Shaped and has interlocking spurs, which are alternating tongues of land that jut out on either side
4. The ice is solid so is unable to wind around the spurs like the river. Therefore via abrasion and plucking it erodes the material form the spurs and then bulldozes it out of the way.
5. In this way, the interlocking spurs are cut off to from truncated spurs which mark the sides of the glacial trough
What is bulldozing?
The pushing of deposited sediment at the snout by the glacier as it advances
What is a moraine?
All the material deposited after having been transported by ice
What is subglacial transportation?
Is material carried along the base of the glacier e.g. in a subglacial moraine
-Source of the material: glacial erosion, englacial material that has gradually worked its way down through the ice
What is englacial transportation?
Is material carried within the glacier itself e.g in an englacial moraine
What is supraglacial transportation?
Is material carried on top of the ice.
Can eventually become englacial if it gets 'buried' by further accumulation
-Source of material: can come from falling debris from surrounding slopes e.g. in a lateral moraine or medial moraine
What is a ground moraine?
Surface deposits left by glaciers and ice sheets; the surface formed is uneven and hummocky
What is a lateral moraine?
Pile of scree or boulder clay deposited in a line along the sides of a valley
What is a medial moraine?
Pile of loose material carried and deposited in the centre of the ice
What is a terminal moraine?
Pile of boulder clay in a line across the valley of lowland, dumped by the ice at the furthest point reached
What are moraines in a retreating glacier?
Describe the deposition of a glacier?
-Glaciers will always reach a point where they will start to melt (usually die to higher temperatures as they descend in height down the valley)
-As the ice melts it cannot carry as much material and so this is deposited. The load EXCEEDS the glacier's carrying capacity
-The main depositional feature is a terminal moraine and recessional moraine and eventually they will leave behind a lateral, medial and unconsolidated ground moraines
Describe the formation of a moraine
1. Ice carries material within it and beneath it and this material is called moraine
2. It falls onto the surface due to freeze-thaw weathering from the sides and moves within the ice, and it gets into the ice via a large number of crevasses on the surface
3. Plucking and abrasion and the base leads to further material beneath the glacier
4. This material is pushed to the font of the glacier where it is moved along and this is called bulldozing
5. As the glacier melts for example when it reaches lower land, so there are higher temperatures, the load will exceed the glacier's carrying capacity leaving behind a terminal moraine, or recessional moraine
What is a landform of deposition?
-Drumlins are egg-shaped hills made of boulder clay up to about 40m high and 400m long; many usually occur together forming a 'basket of eggs' scenery
-The accepted theory is that the ice becomes overloaded with sediment and the competence (ability to carry sediment) of the glacier is reduced (e.g. by meting ice/ablation) and material is deposited
Describe the formation of a drumlin
1. The melting glacier meets a small obstacle, which is enough to encourage deposition of boulder clay (till) from the ice
2. On first meeting the obstacle more deposition takes place forming the blunt (stoss) end
3. The moving ice moulds the boulder clay into shape around the obstacle, which forms the tapered (lee) end
4. Over time the material is re-shaped by further ice movements
What is a fragile environment?
A fragile environment is an environment that is easily unbalanced and damaged by natural or human factors. Alpine environments are fragile environments and need careful, sustainable management. They take a long time to recover if something is changed or damaged
What is sustainable management?
Sustainable management is a management approach that conserves the environment for future generations to enjoy as it is today
What are the economic impacts of glacial retreat?
-If glacier is completely melted, the meltwater decreases and industries that rely on meltwater, such as agricultural irrigation and hydroelectric power, will loose money and shut down
-There will be no more winter sports, and so fewer tourists will come which will damage the local economy and jobs
-Permafrost melting is to make cable cars and ski lifts which increases maintenance cost
What are the social impacts of glacial retreat?
-In some settlements the water supply will be reduced
-HEP is disrupted leaving people with unreliable power supply
-As unemployment increases as businesses shut down, local people will have to move away to find work. Young people in particular will move away leaving behind older family members
-If an areas population declines, local services and recreational facilities will shut down
-The ice will no longer be available as recreational sue for locals e.g. for trekking and ice climbing
What are the environmental impacts of glacial retreat? (unreliable snowfall)
-Glacial retreat is linked to an increase in natural hazards, rapid melting can cause flooding, rockslides and avalanches. These hazards destroy habitats and disrupt food chains
-Meltwater from retreating glaciers contributes to rising sea levels, water is no longer stored as ice n land and returns to the sea. RSL destroy coastal habitats by causing flooding and erosion
-Fish species that have adapted to live in the cold meltwater that comes from glaciers may die out
-Harmful pollutants can be trapped in glacial ice and rapid melting releasees them into the environment polluting streams and lakes
-(Damaged vegetation has not enough time to recover if it is at a higher altitude as then there is a shorter growing seasons due to increasing temperatures
-Ski on thin layer of ice can cause soil erosion and vegetation damage)
What are some of the solutions for glacial retreat and unreliable snowfall?
-If there is less snow resorts may purchase snow cannons: however these create a negative economic impact as they are very expensive and the chemicals in the snow may contaminate water supplies and they create noise pollution
-Provide alternative ski tourism e.g. museums
-May develop of a higher terrain: however it is very expensive and there will be short term closure which will reduce tourism and construction will mean pollution and noise and they build in environmentally sensitive areas which create a negative impact on the environment
What is some evidence for the effect of glacial retreat and unreliable snowfall?
-15% of the French ski areas are covered by snow cannons
-The ski industry has a turnover of more than 20billion euros in France. Closure of resorts would devastate economies
-Accumulation of fresh snow has halved in the last 40 years, leading to glacial retreat
-Currently an estimated 15% of Switzerland's ski resorts are deemed to have unreliable levels of snowfall
What is an avalanche?
-An avalanche is a rapid downhill movement of a mass of snow, ice and rocks, usually in a mountainous environment
-Impact can be major or minor
-Most likely to occur at a gradient of 30-45 degrees
Describe a powder avalanche
1. Develop in cold dry conditions
-Powder snow is often blow by the wind and deposited on the lee side of the mountain. Usually happens after heavy rainfall
2. Especially common where powder snow falls onto a hard surface crust
-The crust acts as a certain slide, down which the snow moves at speeds >45m/s
3. Part of the powder avalanche flows along the ground, and part becomes airborne, producing a white cloud of snow and dust moving down a hillside at high speeds (can be >300km/hr).
-The avalanche creates a powerful air blast in front of it
Describe a slab avalanche
1. Large blocks of snow fracturing away from the main plain of mountainside because the surface layer is not securely stuck to the lower layer of snow
2. The avalanche begins in the surface layer of the snow, but frequently lower layers can also begin to collapse.
-90% of fatalities are caused by slab avalanches
Describe wet avalanches
1. Common in the spring or anytime when the snow begins to thaw
2. The meltwater soaks up the snow pack and melts the bonds that make the ice grains stick together
3. When the air spaces are filled with water, the grains can begin to flow at gradients >20 degrees
4. Wet avalanches flow turbulently and pick up soil, vegetation, and rocks , leading to frozen deposits sometimes 30m thick
Describe the difference between a powder and a slab avalanche?
1. A powder avalanche usually starts from a single point on the hillside and involves loose, powdery snow
2. In contrast a slab avalanche, involves a large slab of ice and snow shearing away from the hillside and moving rapidly downhill. It is the more deadly and dangerous of the two types of avalanche
3. A powder avalanche is formed in dry cold conditions, and as it falls downhill some stays on the ground whilst some becomes airborne
4. Whereas a slab avalanche is a result of the different layers of snow having different freezing rates and so are not stuck securely
5. This means a slab avalanche has blocks of snow falling and a powder avalanche has powder snow descending downhill or in the air (airborne) creating a 'white cloud'
What are the physical causes of an avalanche?
-Heavy snowfall: adds weight to earlier snowfalls. Uneven freezing rates, together with occasional melting, can create distinct layers within the snow and ice making slab avalanches more likely to occur as on layer slips over another
-Steep slopes: avalanches are more likely to occur on steep slopes in excess of 30 degrees
-Temperature rise: sudden rises in temperatures and associated melting often lead to avalanches in the spring
-Heavy rainfall: this can lubricate a slope and trigger an avalanche
What are the human causes of an avalanche?
-Tree removal: the removal of trees for ski developments enable avalanches to move downhill unimpeded. When present on a hillside, trees can break up an avalanche and prevent it from becoming too large
-Off-piste skiing: often involves skiing in areas of fresh snow that have not yet been assessed for the avalanche risk
What are the impacts of avalanches?
-Social: deaths, injuries, property damage
-Environmental: trees uprooted, biodiversity disrupted
-Economic: ski resorts lose business and rebuilding costs
What are the management strategies for avalanches?
-Snow fences and walls: reduce accumulation on less slopes (prevent snow from drifting across upwind slopes)
-Barriers: impede and stop avalanches ad protect major instalments e.g. roads
-Afforestation: anchors snow on slopes during the winter season and impede the avalanche
-Large, flat, free urban areas: provides space for snow to deposit on
-Land use: can be zones by planners to avoid development in areas prone to avalanches and tell skiers not to go there
-Explosive: to artificially trigger avalanches
What are the responses to avalanches?
-Short term: helicopters to locate survivors
-Long term: Instructors warn skiers, stricter rules, more equipment and skiers are made to wear avalanche transceivers
Describe the Athabasca Glacier
-Location: North America, Canada in Jasper National Park, surrounded by the Rocky Mountains
-Covers an area over 6 km squared and 6 km long
What is the evidence that the Athabasca Glacier retreated?
-19th Century AD extended to the current Sunwapta Lake and parts of the icefield parkway
-Previously joined with the Dome Glacier but now they have both retreated to become parallel lines of separate glaciers
-Parks Canada Agency placed markers on walk up to glacier, to show how far the glacier reached in previous years
-Line of lateral moraine on valley floor
Why did the Athabasca Glacier retreat?
-Natural Heating: between AD100 and AD1300 glacier had shrunk to only 3 km long. By 1850 the glacier had advanced by nearly 5 km
-Mid 19th Century Industrial Revolution: enhanced GHG effect, industry and production increased and so more fossil fuels were burnt and so more GHG were released and so more heat was absorbed and re-radiated back to Earth and so the Earth's atmosphere began to heat up which increased temperatures and so the glacier melts and therefore retreats
-Location: Alpine area located in South-Eastern France with 5 million visitors a year
What are the winter and summer attractions in Chamonix?
-Skiing and snowboarding
-Mer de glace: 7 km long and 200m deep
-Heated swimming pools and spas
-Rafting and canoeing and paragliding
-350 km of marked hiking trails
-40 km of mountain biking
-Outdoor cafes and live music
What are the social impacts of tourism in Chamonix?
-Local people benefit from improvements e.g. public transport
-Many jobs are available
-Tourist developments increase the avalanche risk
-Narrow roads become congested and polluted and ruins scenery
-Tourist orientated shops
What are the environmental impact of tourism in Chamonix?
-Chamonix of kept attractive (well lit)
-local materials are used for building so blends into scenery
-Construction decreases soil stability, increases the run off, more erosion to surrounding hillsides
-Energy is used to run facilities (more CO2 emissions, which increases Global Warming) and fly
-Erosion to mountain footpaths ruin the landscape
-Cigarettes of tourists: contaminate water, damage local wildlife, trapped in still mountain air (smoke) causes lung problems for locals
What are the economic impacts of tourism in Chamonix?
-Tourism provides employment (facilities and construction)
-Companies make money
-Local services are supported (e.g. shops)
-Inflated price: locals pay more for everyday items
-Housing prices are increased and second homes, this makes it harder for locals
-Employment can go to foreigners
What are some of the management strategies in Chamonix? (1)
-Promotes responsible tourism, as a means of balancing the demands of tourism with the need to conserve and protect the environment
-(However it is hard to please both as tourism will ultimately harm the environment)
-Chamonix Municipality (local authority) provides environmentally friendly transport service with clean energy buses and free public transport
-(Positive as it manages traffic whilst being environmentally friendly)
-Espace Mont Blanc involves a cooperation between France, Italy and Switzerland on issues of international transport, nature conservation, forests and water resources
-(Positive as it deals with important overall issues with three economies and powers, making a bigger positive impact)
What are some of the management strategies in Chamonix? (2)
-Tomorrow's Valley brings together representatives from the local community and tourist groups to plan for sustainable management. Current projects include:
-Burying service networks such as electricity lines underground (safer and more attractive for locals and tourists)
-Renovating and preserving historic buildings and monuments
-Preserving natural wetlands and peat bogs
-Minimising the impact of skiing on the landscape by planting trees and suing local building materials that blend in with the natural environment
-Maintaining and way-marking foot-paths and cleaning rivers (provides seasonal employment for local people and makes them involved)
-Supporting local traditional employment sectors, particularly farming