Physical - Glaciated Landscapes Flashcards
Abrasion
Abrasion involves the wearing down of rock surfaces by the grinding effect of rock fragments frozen into the base of glaciers. A good analogy of this process is sand papering and through its action it produces smoothed bedrock surfaces that often exhibit parallel sets of scratches (1-10mm diameter), called striations. Abrasion forms fine silt-sized particles (0 .1mm) known as rock flour, which causes the milky appearance of melt-water streams
Factors that influence abrasion
- Ice velocity: abrasion is greater beneath fast flowing glaciers since more debris passes a given point per unit of time
- Basal rock debris: abrasion can only occur if rock debris is present at the ice/rock interface. Clean ice cannot scour its rock bed and the rate of abrasion increases with basal debris concentration, furthermore, the abrading rock fragments must be harder than the bedrock surface beneath
- Removal of rock flour: in order to sustain abrasion rock flour needs to be flushed away from the glacial sole by a constant supply of meltwater, otherwise the ice/rock interface would clog-up with fine debris reducing the direct contact between abrading clasts and the underlying rock surface
Plucking
Plucking is the removal of well jointed or loosened blocks of bedrock by an overriding glacier. Blocks freeze onto the glacier sole and are then pulled clear of the rockmass as the ice moves forward. Once plucked the blocks become the grinding tools that cause abrasion. Plucking is particularly effective where a glacier flows over rock that has are ready been weakened by frost weathering
Crushing
Crushing occurs when the pressure exerted by basal rock fragments crushes the bedrock surface beneath to leave cresentic fractures called chattermarks
Meltwater erosion
The streams of meltwater that flow along the base of a glacier erode rock in the same way as surface streams, through the combined action of abrasion, hydraulic action, attrition, and solution. However,
there is one important difference, water at the base of a glacier is squeezed by the enormous weight of ice above (hydrostatic pressure). This causes meltwater streams to flow much faster, hence, the erosive
potential of meltwater streams is significantly greater than surface rivers
Freeze-thaw
Occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart
By how much does water expand when it freezes?
9-10%
Mass movement
The bulk movements of soil and rock debris down slopes in response to the pull of gravity
Slumping
- A form of mass movement that occurs when a coherent mass of loosely consolidated materials or a rock layer moves a short distance down a slope
- Occurs in sections
Sliding
This happens when a section of soil or rock suddenly gives way and moves down a slope
Rockfall
Bits of rock fall off the cliff face, usually due to freeze-thaw weathering`
Cirque
- An armchair-shaped hollow on a hillside above a glacial valley
- Pre-glacial hollow is enlarged by plucking and abrasion as ice moves in a rotational manner under gravity
Arête
- A narrow, knife-edge ridge between two cirques
- As two cirques erode backwards, the ridge between them becomes increasingly narrowed
Pyramidal peak
- A sharp, pointed hilltop
- As 3 or more cirques erode backwards/enlarge, the hilltop between them becomes increasingly sharp and pointed
- e.g. the Matterhorn, the Alps
U-shaped valley
- A steep-sided, flat-floored straight valley
- A pre-glacial river valley is widened and deepened by erosion from an advancing glacier
Truncated spur
- A steep and possibly rocky section of the side of a trough
- The pre-glacial interlocking spurs of the river valley are eroded by the much more powerful glacier
Hanging valley
- A small tributary valley high above the floor of the u-shaped valley, often with a waterfall
- Tributary glaciers with small amounts of ice did not erode their valley floor as deeply as the main glacier and so are left at a higher altitude
Roche Moutonnée
- Asymmetrical, base rock outcrop with a gently sloping side facing up-valley (smooth stoss, jagged lee)
- As ice crosses a resistant rock outcrop, the increased pressure causes melting and basal sliding and the up-valley side is smoothed by abrasion
- On the leeward side pressure is reduced, refreezing occurs and plucking takes place, causing a steep, jagged slope
Knock and lochan
A glaciated landscape of low relief which is made up of ice-moulded hillocks and intervening lochans (small lakes) eroded along zones of rock weakness
Crag and tail
A landform consisting of a rock hill and tapering ridge, which is produced by selective erosion and deposition beneath an ice sheet
- The crag is steep-sided and has cracks in it from plucking
- The tail is has a gentler gradient, due to it being made up of less-resistant rock; moraines are often deposited here
Lateral moraine
- A ridge of moraine along the edge of the valley floor
- Exposed rock on the valley side is weathered and fragments fall down on the the edge of a glacier. This is then carried along the valley and deposited when the ice melts
- Parallel to ice flow
Medial moraine
- A ridge of moraine down the middle of the valley floor
- When two valley glaciers converge, two lateral moraines combine to form a medial moraine. Material is carried and deposited when melting occurs
- Parallel to ice flow
Terminal moraine
- A ridge of moraine extending across the valley at the furthest point the glacier has reached
- Advancing ice carries moraine forward and deposits it at the point of the maximum advance when it retreats. The up-valley (ice contact) side is generally steeper than the other side as the advancing ice rose over the debris
- Transverse to ice flow
Recessional moraine
- A series of ridges running across the valley behind the terminal moraine
- Each recessional moraine represents a still-stand during ice retreat. They are good indicators of the cycle of advance and retreat that many glaciers experience
- Transverse to ice flow
Drumlins
- Egg-shaped hills of deposited material that occur in swarms (‘basket of eggs’ topography)
- The material is deposited by the glacier, and then moulded into a stream-lined shape when the glacier advances, allowing us to see glacier movement direction
- e.g. Ribble Valley in Lancashire
Till plains
An extensive flat plain of glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place, depositing the sediments it carried
Lodgement till
Material that has been eroded from the underlying rock by the ice, and is moved by the ice (stuck under the ice)
Ablation till
This was carried on or near the surface of the glacier and was deposited as the glacier melted
Englacial
Situated, occurring, or formed inside a glacier
Subglacial
Situated, or occurring, underneath a glacier or ice sheet
Supraglacial
Situated, or occurring, on top of a glacier
Which landforms can be used to reconstruct former ice extent, movement and provenance?
- Erratics
- Moraines
- Crag and tail
- Drumlin orientation
Environmental value of glacial environments
- The need to maintain a genepool of wild organisms to ensure the maintenance of genetic variety (global seed bank in Svalbard)
- The need to retain wilderness so that animal communities can remain in their natural environment, for example providing sanctuary for the migratory bird and animal communities of the Alaskan North Slope
- To use wholly natural communities that still exist as control systems for comparison with exploited mismanaged systems elsewhere
What % of the world’s people live in polar and mountainous and upland regions?
8%
Economic value of glaciated environments - farming - country examples
- Nepal
- Bolivia (Altiplano)
- Ethiopia (Bale Mountains)
What % of Bolivia’s population lives in the High Andes?
70%
What activities do communities in Bolivia partake in?
- Growing crops: potatoes, quinoa, beans
- Rearing llamas and alpacas
What % of the country’s GDP do communities living in the High Andes in Bolivia earn?
30%
What % of Bolivia’s population are living below the poverty line? How many of these are indigenous Indians living in the Altiplano?
60%, almost all of the %
How has the development of technology helped indigenous communities in the High Andes?
It has provided many opportunities for cottage industries, such as weaving and knitting co-operatives, and ecotourism
What year was the Antarctic Treaty created?
1959
In the International Polar Year of 2007-09, the UN’s Environmental Programme reported that how many countries and how many researchers took part in scientific research in Antarctica?
60 countries, 10,000 people
In the International Polar Year of 2007-09, the UN’s Environmental Programme reported that scientific research cost hoe much in Antarctica?
$1.5 billion
Research projects in Antarctica
- Understanding global change (past, present, future) by looking at ice cores
- Researching ‘life on the edge’ to explore how ecosystems cope with intensely harsh conditions
- Investigating subglacial Lake Vostock and other lakes beneath the ice sheet
- Developing sustainable food webs in the Southern Ocean ecosystem
- Studying the Earth’s upper atmosphere and its links to the lower atmosphere and the Earth’s climate
- Understanding how the Antarctic ice is melting, in terms of scale and pace, using satellites and field data
Farming in alpine areas in developed countries (economic)
- Primarily pastoral because of the above-average precipitation, rugged terrain with steep slopes and stony, shallow soils, which together make cultivation difficult
- In truly Alpine areas, animals are grazed in the summer because meadows are snow free and grass is high quality, and the grass in the valley bottoms can be made into animal feed for the winter
Silviculture
- The planting of trees for commercial forestry
- Carried out by the Forestry Commission and private investors in the UK, with the main type of tree being Sitka spruce (softwood timber, wood pulp, paper)
- Occurs in the uplands due to the struggle of hill farming
Mining and quarrying
- Glacial erosion plays an important role of removing regolith (loose overlaying soil) and vegetation to remove economically valuable rocks
- Glaciated mountains are made from slates, so high deposits of igneous and metamorphic rocks
- Lowland areas - outwash deposits from Pleistocene ice sheets provide a very important source of sand and gravel for the building industry (concrete)
How many HEP stations does Switzerland have?
Over 500
What % of electricity is derived from HEP in Norway and New Zealand?
90%
What % of electricity is generated from HEP in Switzerland?
70%
Activities tourists partake in in Alpine landscapes?
- Hill walking
- Climbing
- Mountaineering
- Skiing
Aletsch Glacier, Bernese Overland, Swiss Alps
Jungfrau railway to Jungfraujoch (3454m); access by road tunnel; all year round tourism
Mer de Glace, Chamonix, French Alps
Cable car to Aiguille du Midi for glacier viewing and hiking; visit to ice cave beneath glacier
Columbia Icefield and Athabasca glacier, Alberta, Canada
Brewster snow coach and glacier walk; access by icefield; parkway and ice centre
Franz Josef glacier and Fox glacier, Fjordland National Park, NZ
Guided walks, heli-rides and heli-skiing
Everest base camp and ascent, Himalayas, Nepal
Trekking to Everest base camp (Kleenex trail); huge pressure on Everest itself as permitted numbers are allowed to rise and concentrated during a relatively short season
Torres del Paine National Park, Chile/Argentina
Glacier viewing platform, glacier hikes
Southwest Iceland
Ski and snowcat rides on the glacier
Approximately what % of the world’s freshwater is locked up in ice?
75%, meaning glaciers contain 2% of all water overall
How many gallons of water does the Arapaho glacier provide for the city of Boulder in Colorado per year?
260 million gallons, used for irrigation and drinking
Example of plants what thrive in glaciated areas?
Purple saxifrage and Arctic poppy
Thermokarst
- A form of periglacial topography resembling karst, with hollows produced by the selective melting of permafrost
- Toxic chemicals/acid rain from coal mines in Svalbard
- Metal smelting in the Kola Peninsula (Russia)
Value of polar ecosystems
- Fisheries
- Wild Foods
- Genetic resources
- Fresh water
- Carbon sequestration
- Climate regulation
- Aesthetic value
- Spiritual value
Lahar
A mixture of meltwater from snow and ice on top of an active volcano and tephra (volcanic material such as ash) from eruptions that travels very quickly down existing river valleys, reaching some distance away from the volcano
1985 Nevado del Ruiz, Columbia lahar
- Rushed down Lagunillas Valley to a town called Armero 50km downstream
- Mudflow deposit of 3-8m deep
- Killed more than 23,000
Glacial outburst flood
- These are when the heat of a volcano melts the snow and ice in a glacier, causing heavy and sudden floods
- These can suddenly release large amounts of water, rock, gravel and ice that can be extremely dangerous as they can flood and damage land and structures
Iceland glacial outburst flood
Heat from Grímsvötn volcano beneath the Vatnajökull ice cap melts the ice and creates a subglacial lake within its cauldron - when reaching critical size, it forces its way through subglacial tunnels
- Total discharges of 0.5-3.5km³ approximately every 3-6 years
- 5th November, 1996 - US$15 million damage to infrastructure
Avalanches/landslides
- When shear stress exceeds shear strength of a mass of snow located on a slope
- Result from two types of snow pack failure: loose snow and slab avalanches
Loose snow
Acts rather like dry sand; a small amount slips out of place and starts moving down a slope
Slab avalanches
Occurs when a strongly cohesive layer of snow breaks away rom a weaker underlying layer. A run of higher temperatures followed by refreezing creates ice crusts, which provide a source of instability. Slabs can be as large as 100,000m³ and can bring down 100 times the initial volume of snow and cause huge danger
Aspect of slope for avalanches
In excess of 30 degrees
How many people are killed each year by avalanches (mostly in the Rockies and Alps)?
200
In 1970, what towns were destroyed in Peru?
Yungay and Ranrahirea were destroyed by an eathquake-induced ice and rock avalanche from Mount Huascarán
In 1970, how many people were killed in Peru?
18,000
Traditional culture groups
- Sami of Lapland
- Inuit of Greenland
Antarctica - number of tourists that visit every year?
40,000 - limited by International Association of Antarctica Tour Operators (IAATO)
How have the number of tourists to polar environments increased?
- 1990s - 1 million
- 2014 - 2 million
How many cruise ships visited Svalbard in 2015?
50
Number of landing sites in polar environments
200
How much has cruise ship tourism increased growth rates (%) in Greenland since 2004?
200%
Costs of polar tourism in 2015?
£12-14,000
Disturbance of wildlife
- Breeding birds, hauled out seals
- Education and impose minimum approach distances
Litter, waste, fuel spills
- Damages land-based ecosystems, marine wildlife become entangled in rubbish of coated in fuel
- Could ensure ship operation confirms to international maritime standards, that they’re ice-strengthened and have ice-navigation equipment, that they have an oil spill response plan
- Could limit size of tourist vessels entering Antarctic waters
Environmental degradation
- Fragile moss mats
- Could limit numbers going ashore, avoid sensitive areas, brief tourists
Removing historic artefacts, fossils, bones
- Tell tourists not to collect souvenirs
- Brief tourists
Disruption of important scientific research
- Research stations, field study sites
- Allow only a few visitors per season, brief tourists, guide tourists
Damage to plants
- Smaller leaf area
- Smaller stem area
- Less photosynthesis
- Less growth- biomass
- Less water and nutrients drawn up through plants
Soil compaction
- Fewer spaces in the soil
- Less air in the soil
- Less water held in the soil
- Fewer soil animals (e.g. worms)
- Fewer nutrients in the soil
- Fewer seeds germinate
- More difficult for roots to grow
What % of glaciers on the eastern slopes of the Rockies have been lost since 1850?
25-75%
What % of Himalayan glaciers are in rapid retreat?
95%
Example of a Himalayan glacier? Retreat?
Khumbu glacier, has retreated over 5km since 1953
Glaciers in Peru and Bolivia have shrunk by what % in the last 30 years?
25%
Less ice → what? (flow chart)
Less ice → less albedo → reduced reflection → more atmospheric warming → more melting
Which rivers are fed by Himalayan meltwater?
Yangtze, Mekong, Brahmaputra, Ganges, Hwange Ho
How many farmers are dependent on the glaciers of the TIbetan Plateau in Western China (semi-desert area)?
350 million
What % of people in China rely on the glaciers in the Tibetan Plateau?
42%
Reduction of meltwater flowing into the Ganges-Brahmaputra system is likely to result in how many people facing water shortage?
500 million people
Reduction of meltwater flowing into the Ganges-Brahmaputra system is likely to result in what % of irrigated land being affected?
40%
Andean ‘tropical glaciers’ have declined by around what % since 1970?
16%
Which Andean glacier has disappeared?
Cotacachi in Ecuador
Which Andean glacier has nearly disappeared?
Chacaltaya in Bolivia - 82% gone
What number of people in Bolivian urban centres (La Paz, El Alto) rely on glacier meltwater for what % of their drinking water supply?
2.5 million people, 40% of their drinking water supply
What % of drinking water is supplied by glacier meltwater in Quito, Ecuador? Population?
50% for 2 million people
What % of total energy in Ecuador comes from HEP?
50%
What % of total energy in Peru comes from HEP?
80%
What greenhouse gas is released in large amounts by the melting of permafrost?
Methane
How does climate change affect our life support systems of water and carbon cycles?
Water insecurity will increase for many people and communities for a variety of reasons and, with the melting of permafrost and the loss of masses of methane, there will be losses in the carbon stores and the potential for instability within the carbon cycle
Following climate change, which of active or relict landscapes will see worser impacts?
Active
By the end of the 21st century, how much are sea levels expected to rise by? How will this affect the human population?
0.5-0.75m - this puts 100 million lives at risk
How will global warming affect oceanic circulation?
Its predicted that there will be a 20-50% collapse of the thermohaline circulation as ice sheets melt and icebergs cool the water - this partially blocks the passage of currents such as the Gulf Stream
Tipping point
The point at which climate changes occur irreversibly and at an increasing rate
Actions of individuals to mitigate against climate change?
Lifestyle and consumption changes
Local actions to mitigate against climate change?
Local government strategies for planning, recycling, transport, micro-energy, green homes
National actions to mitigate against climate change?
General policies and legislation e.g. on energy mix, transport, taxation
Global and international actions to mitigate against climate change?
International agreements, e.g. Kyoto co-operation to control emissions and agree targets for carbon dioxide emissions
