Glaciation Flashcards
Explain how meltwater has contributed to the formation of the proglacial features shown(shows a proglacial lake, outwash plain, the overflow from a lake of meltwater during the ice age). (6 marks)
Explain how glacial landforms can be used to help reconstruct former ice mass movement and extent. (8 marks)
Ice masses include glaciers and ice sheets.
The former extent of large ice sheets can be partly indicated by isostatic readjustment of the land surface which was depressed by the weight of the ice.
This method is only useful for large ice sheets not valley glaciers.
Far more accurate is the use of terminal moraine.
These mounds of glacial sediment can indicate the maximum extent of the glacier and ice sheets.
The Valparaiso moraine south of Chicago indicates the maximum southward extent of the last glacial period. Other landforms, such as eskers, are known to have formed englacially or sub-glacially so can indicate the area that had ice cover.
Eskers may also indicate flow direction assuming meltwater and ice flowed in similar directions. Large ice sheets have a meltwater plain or sandur in front of the ice which consists of meltwater channels and water deposited sediment.
The edge of the sandur can be used to infer the edge of the ice. One of the most useful indicators of ice flow direction are erratics.
These are rocks and boulders deposited in a location distant from their source rock because the rocks were carried by ice.
If the source outcrop can be identified then the flow direction can be inferred.
Striations, which are grooves cut into rock by abrasion, also indicated ice flow direction but only over short distances.
Evaluate the extent to which management can balance the demands of conservation and economic development in glacial environments. (20 marks)
There are some examples of glacial environments where conservation of biodiversity and unique landscape is placed well ahead of desires to develop area for their economic resources. The most famous example is Antarctica which has been protected under the Antarctic Treaty since 1961. All commercial exploitation of mineral resources is banned and fishing and tourism are strictly regulated. This works because there is an international consensus that Antarctica is a unique, pristine environment that should be the preserve of science not economic development. Elsewhere views are not so clear cut. The periglacial tundra of Northern Alaska, the Antarctic and ANWR are remote, isolated active glacial environments. Relict glacial environments such as the UK’s Lake District are much more accessible and consequently are under pressure from tourism. Tourism contributes up to 40% of the area’s economy and developing it creates jobs and economic development. However, fragile uplands are prone to trampling, litter and footpath erosion and the area’s carrying capacity may even be exceeded in summer months. The Lake District National Park authority manages the area using the ‘Sandford Principle’ meaning that conservation takes priority over economic development if the two conflict. While this helps preserve the glacial landscape it risks making people dependant on a small number of low paid, seasonal jobs. It also means large developments such as HEP reservoirs and quarries have no chance of being developed. In the Alps, which has active and relict landscapes, the fact that managing the area involves numerous different countries has meant that damage to the landscape from ski resorts, motorways and urbanisation has occurred despite the Alpine Convention that should protect the area. Overall, a balance is easier to strike in extreme, isolated environments with few or no residents. It is much harder tin accessible locations and where more than one country is involved.
SAM: Explain the factors that cause variations in the rate of accumulation. (6 marks)
Rates of accumulation and ablation vary with climate (1). Accumulation rates increase where
there are high levels of precipitation, low average temperatures, low levels of isolation, and
strong winds (1). Stronger winds at high altitudes cause snow to be blown into hollows and
basins so that snow accumulates (1). The highest rates of accumulation are therefore found at
high altitude (orographic effect) on slopes with poleward aspect (1). As temperatures are low,
sublimation and other losses are low, and meltwater is likely to refreeze (1). Positive feedback
cycles amplify change and if a glacier has a positive mass balance and the glacier surface
increases, there will be an increase in ice albedo. This will cause a further reduction in air
temperature, thus increasing accumulation and initiating a positive feedback cycle in which the glacier will continue to grow and advance(1).
Explain the factors that create a lowland depositional landscape. (6)
Lowland depositional landscapes are those away from mountains themselves, e.g. within U-shaped valleys, glacial outwash plains, and periglacial landscapes. A landscape is a unique combination of processes and landforms.
Glacial depositional landscapes might include different types of till / moraine (e.g. subglacially, terminal, and lateral moraines) because perhaps because glaciers have stopped moving/come into contact with surfaces.
When glaciers open out onto a plain, till is deposited as swarms of rounded hummocks (drumlins), the shape of which are streamlined so that their long-axis lie parallel to the ice movement.
Fluviglacial depositional landforms, might include kames (where material is deposited in depressions on the surface) and eskers (where materials was deposited by rivers flowing underneath the ice).
Periglacial environments might include sand dunes and loess, formed by sediment drying in the summer, and being transported by wind to other locations.
Other landscape features might include Erratics are deposited by melting glaciers after being transported hundreds of kilometres, often from regions of different geology.
Explain how changes in the position of the snout of the Mer de Glace may provide evidence for changing climate. (6)
AO1:
Glacial mass balance system and the relationship between accumulation and ablation in the maintenance of equilibrium.
The process of accumulation such as direct snowfall, avalanches, and wind deposition.
The reasons for the variations in the rates of accumulation and ablation, and the impact these variations have on the mass balance over different timescales.
AO2:
The resource shows that between 1570 and 1610, the length of the glacier increased by over 1500m showing evidence of changing climate as northern European temperatures fell due to the end of the Medieval warm period and the onset of the Little Ice Age possibly caused by variations in sunspot activity.
Between 1610 and 1830, in what has often been described as the Little Ice Age, there are fluctuations in the length of the Mer de Glace from a maximum of 1700m from the 1570 snout position to a minimum of 500m from the 1570 position in 1710 showing evidence
of changing climate possibly caused by variations in sunspot activity caused by 13-year cycles of solar activity.
Between 1830 and 1930 the snout of the Mer de Glace retreated to its 1570 position a decrease of over 1500m as the Little Ice age ended and the Industrial age started showing evidence of a changing climate.
Between 1930 and 2010 there has been a rapid retreat of the snout of up to 1500m which is further evidence of changing climate associated with anthropogenic global warming.
Yet there are several periods such as between 1650 and 1690 when the small-scale fluctuation in the length of the Mer de glace is more likely the result of changes in meteorological conditions as
opposed to climate as retreats are likely to be associated with increases in summer temperatures leading to greater rates of ablation whilst advances are likely to be associated with increases in winter snowfall leading to greater rates of accumulation.
Explain the processes that affect the mass balance of temperate glaciers. (6)
AO1
Glacial mass balance system and the relationship between accumulation and ablation in the maintenance of equilibrium.
The processes of accumulation such as direct snowfall, avalanches, and wind deposition
The process of ablation such as melting, calving, evaporation, sublimation, and avalanches.
AO2
The mass balance of temperate glaciers is a consideration of the inputs to the system (accumulation) and the outputs of the system (ablation). The mass balance of a glacier is said to be positive if accumulation exceeds ablation whilst the mass balance of temperate glaciers is said to be negative if ablation exceeds accumulation.
Direct precipitation is the most widespread process of accumulation as precipitation that falls directly onto the glacier surface can over time form neve and then firn and then glacier ice. As this transformation occurs, loosely consolidated ice crystals with interconnecting air passages transforms into larger ice crystals with little or no air passages.
Accumulation in temperate glaciers can also be associated with snow-fall associated with the process of the orographic uplift of humid air. As humid air rises, the air cools and condenses and so increases the precipitation level.
Surface melting is the most widespread process of ablation. Surface melting occurs when the ice surface already at 0C receives further heat. This heat is derived from exposure to radiation and heat exchange with the air in contact with the ice.
The efficacy of solar radiation in melting is largely determined by whether it is fresh snow covering the ice which has a high albedo of 0.6 to .09 or ice which has a lower albedo of 0.2 to 0.4.
Internal and basal melting are also important processes in temperate glaciers as temperate glaciers are isothermal and are at pressure melting points throughout their depth.
Accept other explanations of accumulation such as the processes of avalanches, wind-blown snow, and superimposed ice.
Accept other explanations of ablation such as the processes of calving, evaporation sublimation, and avalanches.
Explain the role of glacial meltwater in creating distinctive landforms. (8)
AO1
The distinctiveness can be associated with the form, position, and the deposits forming the feature as well as ice the distinction between ice contact and pro glacial features.
Eskers are linear features that often show a close correspondence with the recent direction of ice movement. Eskers are often formed within ice-walled tunnels by meltwater reworking sediment (often coarse-grained, water-laid sand and gravel) that was found at the base of the glacier. Eskers often form at the time of the glacial maximum when glacier movement is slow. Once the retaining ice walls have melted away, these meltwater reworked debris are deposited as distinctive
long winding ridges such as those found in Rothiemurchus. They are also distinctive to glacial deposits as they are stratified and sorted and often have distinct bedding of the sediments.
Kames are irregularly shaped hills consisting of sand, gravel, and till. They are associated with a retreating glacier when material resting on the glacier is reworked by meltwater. Kames form in zones of melting ice such as crevasses, moulins, and larger cavities. As the ice melts, the kame begins to emerge as a low hill such as those found in Gleann Einich. Bedded and sorted sand and gravel predominates but often sharp lateral variations are apparent in the calibre of the material,
indicating rapid changes in flow velocity. They are distinctive as they have an irregular pattern as compared to drumlins which often occur in swarms.
Kame terraces are also thought to be landforms formed that are parallel to the ice flow. Kame terraces form when sediment accumulates in ponds and lakes trapped between lobes of glacier ice
or between a glacier and the valley side. As the glacier retreats, they are deposited on the valley sides. Typically, the sediment comprises well-bedded and sorted sand and gravel. They are distinctive as they can form steps leading down to the valley floor.
Kettle holes are formed by blocks of ice that are separated from the main glacier. The isolated blocks of ice then become partially or wholly buried in glacial meltwater outwash material. When the ice blocks eventually melt they leave behind holes or depressions that fill with water to become kettle holes such as Lochan Deo.
Pro glacial lakes are ephemeral lakes created where glacier ice blocks a valley or embayment and ponds the glacial meltwater. The lakes may drain through the ice barrier or via spillways through cols. Drainage of these lakes may form sculpted bedrock surfaces and leave behind poorly-sorted boulder gravels.
Sandurs are found in glaciated areas, such as Svalbard, Kerguelen Islands, and Iceland. Glaciers and icecaps contain large amounts of silt and sediment, picked up as they erode the underlying rocks when they move slowly downhill, and at the snout of the glacier, meltwater can carry this sediment away from the glacier and deposit it on a broad plain. The material in the outwash plain is often size sorted by the water runoff of the melting glacier with the finest materials, like silt, being the most distantly re-deposited, whereas larger boulders are the closest to the original terminus of the glacier.
Meltwater channels – also known as glacial overflow channels – are the product of erosion. Glacial meltwater flowing away from the glacier front is often heavily charged with debris and moving at high velocities. Like normal rivers but with high and fluctuating discharges, these proglacial channels are capable of rapid deepening of channels, even in bedrock. Large amounts of meltwater have much energy to erode and carve out deep gorges that today are occupied by streams too small to have created the valleys they flow in. These also form as the original course followed by a river before glaciation may be blocked by ice or as an overflow from a proglacial lake (one that results from meltwater from glaciers). Examples include Newtondale and Lake Pickering, Lake Lapworth, and Ironbridge Gorge.
Accept other explanations of how glacial meltwater can contribute to
the formation of recognised fluvio-glacial features.
Evaluate the view that tourism poses the greatest threat to both active and relict
glaciated landscapes. (20)
AO1:
Human activities (leisure and tourism, reservoir construction, urbanisation) are threats to glaciated landscapes.
Human activity can also degrade the landscape and fragile ecology ofglaciated landscapes (soil erosion, trampling, landslides, deforestation).
Glaciated landscapes face varying degrees of threat from natural hazards (avalanches and glacial outburst floods).
Global warming is having a major impact on glacial mass balances, which in turn risks disruption of the hydrological cycle (meltwater, river discharge, sediment yield, water quality).
AO2:
A key reason why tourism poses the greatest threat to active glaciated
landscapes is the increase in tourism. Arctic tourism has increased from 1 million in 1990’s to over 2 million in 2017. As most arrive by ship, the Arctic landscape has been degraded by the building of new port facilities such as at Honningsvag and roads such as the E69 for visitors to see North Cape.
Furthermore Arctic tourism to Svalbard has also rapidly increased leading to damage to the pristine Artic landscape of Ny-Alesund and Magdalena Bay – so much so that in 2015 large cruise ships were banned from these pristine Arctic sites.
Moreover, other Arctic areas are also suffering damage to their fragile landscapes - Greenland and Alaska have also seen large increases in tourist pressure with Greenland recording increases of 400% in visitor numbers and Alaska over 1 million by 2017. This has led to degradation and damage of these Artic landscapes particularly by the use of snowmobiles in honeypot sites such as Glacier Bay National Park.
In addition, trekking in summer in popular sites such as Denali National Park has led to pleas for hikers not to GPS coordinates of their hikes to reduce the impact of trails on the landscape.
Yet tourism to other polar landscapes has, to now, been less of a threat. Although there are 40,000 visitors to Antarctica per year, due to protocols adopted in 1966 and subsequently added to in the Antarctic Treaty there is now a framework to manage tourism in Antarctica reducing the potential for damage to the landscape.
Furthermore, strict protocols have meant that all waste is removed from this area, even wastewater, and so any damage is being minimized.
However, there are concerns as the tourism is both spatially and temporally concentrated in Antarctica with concerns raised over the impact on the Patriot Hills area where heated tents and a runway are constructed every year.
Importantly relict glaciated landscapes are also under threat from tourism with trekking causing damage to the fragile mountain ecosystems with some plant communities such as tundra flower meadows only needing 25 people a week before damage can occur.
Mountain biking and pony trekking are also thought to have even greater impacts on relict landscapes particularly in those areas of steep fragile soils such as the Lake District.
It is important to remember, however, that other human activities also pose threats to both active and relict glaciated landscapes. Deforestation on exposed slopes has been found to cause increased damage to the landscapes such as in the Canadian Rockies whilst over-cultivation and overgrazing is also thought to cause damage to the landscapes in Andean areas.
Furthermore urbanization, mineral exploitation and reservoir construction also pose threats to glaciated landscapes with pollution and toxic waste being threats from hastily built urban areas and the damage to the landscape of glaciated areas through mineral exploitation and reservoir construction often taking decades to recover.
There are also natural threats such as avalanches, landslides and glacial outburst floods which are a threat too glaciated landscapes such as the 2016 landslide in Glacier Bay when a ½ mile square rock face collapsed and flowed more than six miles.
Climate change is also thought to be a threat to glaciated landscapes with recent studies showing that most glaciers are currently retreating with only maritime glaciers in Scandinavia showing glacial advances. This retreat will threaten landscapes due to the changes in the hydrological cycle that this will bring as well as the increased chance of glacial outburst floods.
Overall, tourism can pose a significant threat to both active and relict glaciated landscapes to a greater or lesser degree. It can be thought of a more serious threat than other anthropogenic threats such as urbanization, forestry and reservoir construction due the scale of the threat with millions of visitors to active landscapes and tens of millions to relict landscapes. Yet careful management can reduce these threats such as the protocols adopted in Antarctica as well as the sensitive management of National Parks. Natural threats such as landslides can be considered as to be less of a threat as they are naturally occurring processes that occur in glaciated landscapes and so are part of the processes that that make such landscapes distinctive. Yet, the impacts of climate change could be the biggest threat as it will threaten most of the glaciated areas in the world but at present the exact scale of the threat has yet to accurately quantified. So at present tourism probably does pose the greatest threat to glaciated landscapes.
