- Created by: jasminep16
- Created on: 28-03-17 18:54
Distribution and types of cold environments
- Found at high altitudes and latitudes
Mass Balance/ Glacial budget
Glaciers ablate mass by melting asa resultof warm air temperatures or applied pressure, evapouration, wind erosion or by calving into icebergs.
In extremely cold and arid areas eg. Antartica, mass can also be losr by sublimation ie. the process where a solid changes directly into a gas.
Glaciers gain mass in the accumulation zone, the upper part of the glacier where input exeeds output.
Mass is lost in the lower ablation zone where output exeeds inputs.
At the transition point between the ablation and accumulation zones, the two zones equal each other. This is know as the equilibrium line. It aprox. coincides with the postion of the snowline. This can be mapped to track how the glacier changes.
Accumulation > ablation = Mass balance is positive (the snout will advance)
Ablation > accumulation = Mass balance is negative (the snout will retreat)
Types of Galciers
In continental zones the ice will flow outwards and downward and towards the valley floor in the form of snow.
Evaporation will also occour here from the snow/ice to the valley floor.
In the marine zones flow willbe more towards the edges where the ice shelves will form, these will then break off and fall into the sea
This ice will melt into water, which iwll then evaporate and will then fall as snow and start the cylce again.
Thermal classification of glaciers
- Partly warm, partly cold
eg. Iceland - on a constructive place boundry
Cold from above due to location, but warmed from below.
- Very very very very cold regions with low temperatures
eg. The poles (Artic, antartic)
- Only glacier and ice present because of the altitude (high up the mountain there's snow but lower down it'll be raining
eg. the apls, Kilemonjaro
Types of basal sliding
1) Enhanced basal creep - ice deformed by stresses created by jagged bedrock, bends round obstructions
2) Regelation (pressure by melting) - When ice presses against a small obstacle, but rather than deforming the ice melts and re-freezes on the lee side where pressure is lower.
3) Basal slip - slippage over a layer of water at bedrocks
When does it occour?
Sporadic movements, few cm at a time.
As it catches onto and is then released from small fozen areas of bedrock
It accounts for the majority of flow in the warm glaciers (steep gradients)
If no water is present basal sliding is reduced to basal creep
Slow creep due to slippage within and between ice crystals
Rate of deformation is greatest at the base of the glacier (greatest pressure)
Can occur in both polar and temerate glaciers
Bedrock deformation + Extra into on movement
Movement thruogh deformation of sediment or weak rock beneath the glacier
Type of movement is related to temperature of the ice:
- Basal sliding is most efficient if water is present for lubrication
- Bedrock deforamtion is more effective beneath temperate glaciers, as the underlying material would be saturated with water (reducing strength)
- Therefore the colder climates limit the amount of water which leads to movement in these environments mainly being mainly internal deformation.
Processes of erosion
When the melt water from a glacier freezes to the base rock and lumps of cracked and broken rock from the back wall.
Happen when the rocks which have frozen to the base of the ice and back of the glacier, scrape along the rock at the base -- Causing striations*
When melt water or rain gets into the cracks in the back wall of bedrock and freezes as temperatures drop at night, expanding and causing the crack to get larger, and eventually break away.
*Striations - start larger and end smaller (Showing which direction the glacier is moving)
Processes of erosion 2
Fracture and traction
- Crushing weight of the ice as it moves over rock and due to variations in pressures it leads to freezing and thawing of the melt water
- Basal melting, and aids in the base plucking process
- Occours as overlaying material is moved
- Causes fractures int he rock parallel to erosional surfaces
Melt water erosion
- The water is under hydrostatic pressure therefroe erodes rock
- And also chemically dissolves minerals and carry away the solute (especially with limestone)
Erosional landforms (Macro)
- hollow created in the hillside above a glacial valley
- Enlarged through plucking and abrasionas the ice rotates under gravity
- a narrow ridge between two corries (like a knife edge)
- as two corries become increasingly enlarged, the ridge between them gets narrower
- a sharp pointed hilltop
- Three or more corries are enlarged and the hilltop between them becomes more pointed
Erosional landforms (Macro) 2
Trough/ U shaped valley
- a steep-sided flat floored valley
- a pre-glacial river valleyis widened, through erosion, by an advancing glacier
- The pre-glacial interlocking spurs of a river valley are erdoed by the glacier as it moves through the valley
- a small valley high above the floor of the U shaped valley often with a waterfall
- Tributary glaciers with small amounts of ice could not erdoe all the way through to the valley floor (or as deeply as the main glacier), so are left higher up
Crag and tail
Ice hits a steep resistant outcrop of rock first, protecting the lee side of th obtsacle from erosion as the galcier has lost speed and power.
Asymetrical bare rock outcrop with a gently sloping stoss side where the glacier would have scraped up causing abrasion to happen. On the lee side it is sharp and jagged, because as the glacier passes over, it plucks at the rock.
Grooves on exposed rock caused by abrasion from rocks embedded in the base of the glacier as it passes over bare rock.
- sorted fluvio-glacial deposits, largest to smallest
- the largest are heavier so are dropped off higher upstream
- Stoss end up-glacier, elongated and tapering down-glacier
Till fabric for boulder clay (Mirco)
- analysis of the stones may show orientaion parallel to ice advance, and rock type can be helpful to determine from where the glacier came
- large boulders of rock which are dropped by the glacier, prime examples of glacial entrainment.
Depositional features 2
- Glacial streams are found under the ice and are loaded with debris
- as the ice retreats the rivers deposit their loads beneath the glacier.
Kettle hole lakes
- Small clustered lakes
- Ice moves over the land forming a depression which is then filled in with water
Material derived from freeze-thaw weathering of valley sides, and is carried at the side of the glacier
Found in the centre of the glacier and is the resultog two lateral moraines joining together
Material dragged beneath the glacier
Marks the maximum advance of the glacier. (Rock material deposited at the snout of the glacier)
These form behind and parellel to the terminal moraine, marking stages of retreat.
Kames and eskers
Scientific research - Antarctica (Case study)
Polar regions ahve beome living labs for many research scienticst
- designated the continet of peace and science in 1959 (Antartica treaty)
- understanding global change, through looking at ice cores
- researching life on the edge, exploring how ecosystems cope with intensly harsh conditons
- Subglacial lakes beneath ice sheets (Lake Volstock)
- Developing sustainable food webs in the southern ocean ecosystem
- Studying the eaths upper atmosphere and its links to the lower atmosphere (earth's climate)
- Understand how the ice is melting at its impact
Farming -developing countries (Economic value)
Developing nations have few transport links up into the high mountains, thereofre there is limmited access to supplies and employment is also restrictive.
Countries such as Nepal, Bolivia and Ethiopia the highlands are mainly inhabited by idigenous communities whose way of live is dependant on subsistance farming.
In Bolivia 70% of the population live sin the Andes growing crops such as potatos, quiona and beans to feed themselves. They also rear lamas and alpacas for clothing and meat. However these people only earn 30% of the countries GDP per capita. Almost all those living under the poverty line in Bolivia are indigenous Indians living in the mountains.
In these developing regions technological leap-frogging with internet access and mobile phones has created oppotunites Cottage industry like weaving and knitting cooperatives.
It has also meant that there can be a much wider market and targetting of ecotourism in the area.
Farming -developed countries (Economic value)
In Alpine regions in developed countries, the agriculture in upland glaciated regions is primarily pastoral because of the high precipitaion, jagged steep landscape and shallow soils, make cultivation exeedingly difficult.
In truly Alpine areas transhumance (the act of moving livestock acorss areas) takes advantage of the climate cycle.
In the Summer animals are grazed at high altitudes in the meadows, as the snow melts and provides high quality grass.
At the same time the grass in the valley can be made into hay for winter feeding.
During the snowy witers animals are brought to the vlley and housed near farms houses and are fed on hay or grazed on lower pasturs.
Forestry (Economic value)
Hillside afarming is a struggle,especially in those areas where farm prices are exeedingly high and there are few government support sydetems (EU rural payments).
Thus many regions and uplands are being used increasingly for siviculture (forestry).
In the UK this is carried out both by the Forestry Commision and private investors, with the main type of tree being non-native, fast growing conifers, such as Sitka spruce grown for softwood timber, wood pulp and even paper.
These conifers tolerate harsh climates and acidic soils taht would not be sutiable for other land uses.
(However this creates monoculture etc etc..)
Mining and quarrying (economic value)
Glacial erosion plays are large role in the removing of lose overlying soil and vegetation to expose economically vaulabe rocks.
In many active or relict area there are mine and quarries of mineral deposits and ores. Rocks such as slates and metamorphic rocks also form much of the glaciated moutains.
In lowland areas outwash deposits from Pleistocene Ice sheets proved a very important source of sand and gravel from building and industry. (Eg. Concrete)
Hydroelectricity (economic value)
HEP is a major use of water sources derived from glaciers.
Both Norway and New Zealand derive over 90% of their electricity from this source. HEP can be provided by natural ribbon lakes or dams and resoviors in a glaciated valley. Switzerland has over 500 HEP stations producing 70% of its overall electricity.
HEP is a renewable resource, but there are issues with the reliablity of the water supplies and environmental concerns over damming of rivers.
In developing countries liek Nepal or Bolivia micro-hyrods can revolutionise the quality of life for many villages.
Tourism (Economic value)
Tourism has develop and grown massively over the past two or three decades, which has brought massive economic benefit to moutainous regions, with people attracted to the spectacular scenery of the past and present glaciated landscapes.
A large rang of outdoor activities are avaliable in Alpine landscapes;
Glacial and periglacial landscapes make huge contributions to the world's life support systems.
- 75% of all freshwater is locked up in ice
- Glacial eroded valleys in many mountainous regions form natural ways for water collection. (Eg. the lake district)
- Glaciers are also valuable as a source of water for irrigation as they produce most water in the late spring and summer. The USA Arapaho glacier currently produces about 260million galloons of drinking water per year for the city of Boulder, Colorado. As well as irrigating huge areas of crops.
Threats to: Avalanches
When the stress put on snow outweighs the strength of the snows resistance. The strength of the snow pack is related to its density and temperature.
Types of snow pack failure:
- Loose snow acts like dry sand; a small amount of snow slips out of place and starts to move downhill
- Slab avalanches occour when a layer of snow breaks away from a weaker underlying layer. A run of higher temperatures followed by refrezing creates ice crusts, which provide instability. Slabs can bring down 100 times the initial volume of snow and cause huge damage.
Types of avalanche motion:
- powder avalanches (Most hazardous)
- dry flow
- wet flow (Which occour mainly in spring time)
Avalanche - Case study
1970 - Peru
- The towns of Yungay and Ranrahirea
- Destroyed by an ice and rock avalanche caused by an earthquake
- It travelled 16km down the valley as a muddy flood killing over 18,000 people
In 2015 the Neplaese earthquake set off many ice and rock avalanches that killed some mebers of expeditions at Everest base camp.
Threats to: Glacial Outburst floods
A powerful flood caused by the sudden discharge of a subglacial or ice moraine dammed lake. These types of floods can take place wherever melt water collects behind an ice or moraine obstruction.
Ways they can be triggered:
- Increase of ice melt causing water level rise
- Overflow and melting of an ice dam (Climate warming has a large effect on the frequency of these)
- Breakdown of an ice dam because of tectonic activity
- Irreversible overtopping of a moraine dam by large tsunami style waves caused by Avalaches or landsides into the lake
- Enlargement of pre-existing tunnels beneath the ice dam because of increased water pressure
This type of flooding can also affect periglacial landscapes during melt season.
Glacial outburst flood - Case study
These are particularly frequent in Iceland due to the fact that the volcanic activity generates meltwater beneath the glacier, while acting as a trigger for ice instability, which can lead to a sudden release of melt water.
Heat from Grimsvotn volcano beneath an ice cap melts the ice and creates a subglacial lake in its cauldron. When the lake reaches a critical size it forces its way through subglacial tunnels and the lake drains catasrophically in hours.
In 1996 the eruption of the volcano broke through the ice and sent up a huge collumn of ash into the sky, melting a large amount of the ice. Then on 5th November the melt water burst through the glacier causing USD$15 million in damage to infrastructure.
Chamonix - case study
The council has developed a policy of ‘integrated tourism’, which educates and involves visitors and local people in the protection of the Alpine environment.
It includes :
• System of avalanche barriers maintained.
• Avalanche awareness courses.
• Daily bulletins for tourists.
• Free public transport (reduce car usage) .
• Pollution from public transport reduced as buses are low emission.
• Encouraging local farming .
• Some hotels fitted with solar panels to heat water and systems to automatically turn lights off. CO2 emissions reduced.
• Education about the Mer de Glace
The Rhone glacier - Case study (Economic)
Temperatures have risen by 1⁰C over the last century and has risen by 3⁰C over 1,800 metres in the last 40 years and the Mer de Glace is 500 metres shorter than it was in 1994. Furthermore Winter snowfall is unreliable and the lower Alps is receiving less total snowfall overall.
• Some resorts will no longer be viable as Winter resorts- this is a real problem in the southern Alps.
• Fewer sightseers and ice climbers will be a problem in all resorts.
• Less tourism will result in less income for the area .
• However, the big, high-altitude resorts, should prosper as people are forced to go to them. They have the facilities and amenities already and the ability to make artificial snow.
• Agriculture could benefit from a higher snowline and warmer summers – a longer growing season.
The Rhone glacier - Case study (Social and environ
• Jobs could be lost if tourist numbers fall – higher unemployment.
• With no jobs, young people will leave to find work – change in the population structure .
• Services could decline, but the elderly that remain will demand more.
• The Alps is a ‘fragile environment’, which means it is easily damaged.
• A delicate balance exists, so the increase in temperatures/ loss of snow could mean that it is uninhabitable for some species.
• Less water, so river levels will drop that have their source in the Alps. More avalanches .
• Flooding from melting glaciers .
• Rock falls as the ground thaws.
Threats from people - quick fire
- Population demographic and size
- Avalanches caused by skiiers and pollution
- Biodiversity being destroyed by the presence of humans, the building of structures/settlements and the planting of monoculture (Lake district)
- The aesthetics of an area may be affected and tainted by human activity (Chamonix)
- Climate change (The Rhone glacier)