Glaciers Flashcards
Tundra/ Peri-glacial areas
Dry, high latitude areas, covered in ice for part of year (Canada, N. Alaska) permafrost.
In summer surface layer thaws, warmer
Alpine areas
High altitudes, small ice caps, mountain glaciers, tundra environments (Himalayas, Alps, Andes). Very cold winters, heavy snow. High altitude (less than 10c/ warm summer more than 20c).
Climate changes
World is nearing end of warming pattern.
Reasons for climate change
- Milankovitch Cycles
- Changes in ocean currents
- Volcanic dust and aerosol
- Variation in sunspot activity
- Carbon and methane trapping
Milankovitch cycles
Orbital and axial variations influence initiation of climate change in long term natural cycles of ‘ice ages’ and warm periods.
Changes in ocean currents
Oceans move heat around planets, but confined by land masses so transport more localised and channeled into specific regions.
Volcanic dust and aerosol
These warm/cool the earths surface depending on how sunlight interacts with volcanic material.
Dust: temporary cooling, cooling depends on amount of dust. Duration of cooling depends on size of particles (dust blocks sunlight).
Sulfur hazes: cooling
Flood basalt volcanoes: inc CO2: warming
Variation in sunspot activity
More sunspots increased temperature.
Therefore, more greenhouse gases: fossil fuels.
Carbon and methane trapping
Methane from frozen ground of tundra.
Greenhouse gases.
Ablation
Removal of snow or ice from evaporation/melting.
Accumulation
Gradual gathering of something.
Calving
Chunk of ice breaks off from end of glacier.
Firn line
Intermediate stage in transformation of snow to glacial ice.
Glacial budgets
Glacier ice recedes or accumulates depending on balance of ablation and accumulation.
Glacial advance
Moves forward faster than melting.
Glacial retreat
Melts more than moves.
Glacier mass
Mass of glacier
Steady state
Glacier in equilibrium with climate
Sublimation
Transition of solid directly to gas.
No liquid phase.
Inputs
Snow (compacted to ice)
Avalanches (weight and ice makes movement)
Outputs
Melting Evaporation Ice Meltwater Sediment Sublimation Calving
Source of glacier
Zone of accumulation
More inputs than outputs: Higher up, more snowfall. Lower temp. Less melting. New snow: reflective: absorb less heat: slower melting. Lower temps. Less sublimation.
Snout
Zone of ablation
Less snowfall.
Higher temps.
More melting, sublimation, evaporation, calving.
Glacial landforms
Corries Arêtes Pyramidal peaks Horns Glacial trough/ribbon lakes Hanging valleys Misfit river Roche moutonne Nivation hollow Striations
Freeze-thaw
Water in rock.
Water freezes, rock expands by 9%.
Water melts, rock shrinks.
Frost shattering
Same as freeze thaw but, when water melts the rock breaks: scree.
Mass movement
Movement of material downhill under influence of gravity.
How glaciers erode?
Abrasion as ice holds scree.
Plucking.
Abrasion
Angular material is carried by glacier or is embedded in glacier (moraine) which scours the valleyside and base.
Small material smoothes rock it passes.
Large material causes big scratches: striations (worn down to rock flour).
Plucking
Water at the bottom of the glacier freezes to rock on valley base. As glacier moves, rock on valley base is pulled away from base.
Mainly occurs when rock is well-jointed (lots of cracks) and at base of glacier where pressure causes meltwater.
Occurs in warm based glaciers (basal flow needs meltwater which cold based glaciers don’t have).
Nivation
Snow that stays all year round.
Underneath: frost-shattering, some chemical weathering on rock which disintegrates rock into softer rock.
Forms nivation hollows.
Corrie formation
Corries: deep round hollows with a steep back wall and a rock basin.
Form when snow accumulates in hollows on hill sides, with less sunny, north-facing aspect.
Snow into ice and ice moves downwards. Freeze-thaw and frost shattering loosened and removed material from back of hollow, making steep back wall. Moraine dragged along the base of glacier deepens the floor of hollow by abrasion = rock basin. Rock lip forms from deposition of moraine (natural dam for meltwater).
Arêtes and pyramidal peaks formation
When two or more corrie walls develop back to back.p, they erode backwards towards each other. Land between them narrows so a knife-edge ridge (arête is formed).
Three or more corrie glaciers cut back into same mountain is a pyramidal peak/horn.
Glacial/ Polar Areas
Covered by ice sheets and glaciers.
Mainly land-based (Antarctica) but can be sea-based too (Arctic).
Extremes: winter: -50degrees C
Striations
Scratches and grooves from debris in ice being dragged along surface at great pressure
Roche Moutonne
Resistant rock left on valley floor as not removed.
Hanging valleys
Truncated spurs
Glaciers down river valley: erosion along valley sidea may remove tips of preglacial interlocking spurs leaving cliff like features - truncated spurs.
Glacial trough
Ribbon lakes
Glacier moves down valley - changes in geology, soft rock eroded easily, hard rock eroded slowly.
Post-glaciation, holes from eroded soft rock, fill with water - ribbon lakes.
Fluvio-glacial material
Deposits from meltwater streams
Till
Unsorted, angular debris/material
Fluvio
Sorted, rounded material
Periglaciation
Permafrost- 25% earths surface, permanently frozen ground.
High latitude, circumpolar locations.
In summer surface layer thaws: active layer
Frost heave forms sorted stone polygons
Active layer refreezes: ice crystals expand: upward expansion of soil surface - uneven domes.
Solifluction forms Lobes
Mass movement.
Summer: Meltwater: no percolation as frozen ground: saturates soil: reduced friction: highly mobile.
Pingos
Open system
Rounded hill, ice cored.
Forms:
Permafrost discontinuous, water seeps into upper layers of ground then freezes.
Ice lens created which causes overlying sediments to heave upwards into dome shaped feature: pingo.
Found mainly in sandier soils.
Pingos
Closed system
On site of lake with sediment at bottom.
Sediment insulates ground - allowing water to collect underneath.
Sediment freezes in winter, water confined and pressure increases.
Trapped water freezes, expands and forces sediment upwards to form pingos.
Ground water contraction forms ice wedge polygons
Refreezing of active layer during winter, soil contracts, cracks on surface.
Melting in summer, cracks fill with meltwater Nd fine sediment - helps partially fill crack.
Repetition for many years - widens and deepens crack to form ice wedge (1m wide, 3m deep).
Talik
Unfrozen ground
Scree
Rock debris
Felsenmeer
Water expands when into ice - breaks apart rocks and sediments: forms rock-strewn landscapes.
Till Description
Unsorted, angular deposits of rock sand and clay.
Till formation
Mainly unsorted subglacial materials deposited by melting glaciers.
Terminal moraine description
Narrow ridge of unsorted material extending across a valley.
Terminal moraine formation
Mounds of boulders deposited at maximum advance of the ice.
Recessional moraine description
Series of narrow ridges extending across a valley.
Recessional moraine formation
Moraine deposited during a standstill in the retreat.
Lateral moraine description
Unsorted material found along the sides of glaciers and glaciated valleys.
Lateral moraine formation
Material found along the sides of a glacier or a valley as a result of frost shattering.
Medial moraine description
Mounds of material found in the centre of glaciers.
Medial moraine formation
Formed by the meeting of two lateral moraines.
Push moraine description
Unsorted material found across a valley (with stones tilted at an angle due to readvance).
Push moraine formation
Materials already deposited on the valley floor pushed upwards by a temporary readvance.
Drumlins description
Small elongated mounds with a steep end facing upvalley, a streamlined shape and found in swarms.
Drumlins formation
Materials deposited by ice when englacial material is too heavy to be carried by the melting glacier.
(When glacier retreating)
Erratics description
Rocks which are not native to the area in which they are found.
Erratics formation
Rocks carried by glacier from their source to an area of different rock.
Kettles description
Small, shallow lake containing stratified material.
Kettles formation
Blocks of detached, dead ice left by a melting ice-sheet, later surrounded by fluvioglacial material, melts and forms a lake.
Esker description
A long, winding ridge of sorted material.
Esker formation
Deposited by subglacial streams.
Kame description
And kame terrace
Mounds of sorted material deposited by meltwater along the valley sides or as a delta at an ice front.
Kame formation
Material deposited where meltwater streams are in contact with the ice.
Outwash plain description
Sorted deposits of gravel, sand and clay spread over a low land area.
Outwash plain formation
Meltwater spreads out over low-lying areas, decreases in velocity and deposits its load of gravels, then sands and clays.
Formation of glacial trough
Ice occupies a former river valley. There may be some reference to the formation of ice within corries – the origin of the glacier in the trough. The ice removes the interlocking spurs of the former river valley, via processes of abrasion (where moraine within the ice to the sides has a sandpapering effect on both sides and base) and plucking (where the ice following melting under pressure, freezes to the rock and tears part of it away when it moves) at the base especially and bulldozing as the material is pushed out of the way. Thus, the valley widened and deepened – but the latter to varying extents due to the presence of extensional (when ice goes down steeper parts, thins and flows faster) and compressional (where the ice goes down a shallower gradient, thickens and erodes more) flow – the latter leading to deeper sections.
Challenges of tundra to humans
- low temps
- low precipitation
- permafrost
- short summers so less growing
- blizzards
Inuit population
- economic activities: hunting (seals, caribou), fishing
- nomadic
- sustainable - adapted to climate and limited resources
What is the trans-alaskan pipeline?
From Prudhoe Bay to Valdez.
Help with intensity of demand for oil.
Cost $8 billion
Environmental responses of trans-alaskan pipeline
Pipe above ground so doesn’t melt permafrost.
Pipe is zigzag to allow movement.
Pilings: resist frost heave so land doesn’t lift up.
Buried and insulated on caribou migration routes so not blocked.
1002 lands
Coastal plain
Debating whether to drill for oil.
More than decade supported by most alaskans and the government but environmentalists against it.
Impacts of recent tundra development on permafrost
Cleared vegetation: decreased isolation.
Repair of active layer.
Buildings foundations transfer heat to ground - thermokarst.
Water logged depressions formed.
Trans-alaskan pipeline:
How can permafrost be protected?
Elevate buildings on piles driven into permafrost. Build larger structures on aggregate pads to reduce heat transfer. Build utilidors (insulated boxes above ground for heating purposes).
Modern changes of the Vuntut Gwitchen
Economic: gravel quarry, 2003; jobs available in gov services (policing).
Lifestyle: not nomadic
Less sustainable: snow-mobiles and rifles
Old Crow Flats
North of Arctic circle
January: -35C, July: 15C
Annual precipitation: 200mm
Old crow flats
Plain: 5000km2, 300m elevation Continuous permafrost Ponds, lakes, marshes Only settlement in region Population 300
Oil drilling in Alaska
250,000 jobs created
75% alaskans support
Oil development not harmed wildlife in prudhoe bay
But coastal plain is habitat for caribou which are for vuntut gwitchen
Tourism in Alaska - White Mountains
400,000 hectares protected by White Mountains National Recreation Area which encourages responsible tourism.
All hunters need a permit.
Vehicle routes network, soil protection, prevent permafrost melting and water logging.
ANWR
Arctic National Wildlife Refuge
Antarctica
Ice covered land mass
Remote
Wildlife
Ice field
Ice on land
Ice shelf
Laters of ice that are floating on the sea water that are fed by the flow of ice on the continent.
Antarctic treaty
Signed 1959
12 nations
For access and research rights so countries can work together for common causes of of scientific research. Used for peaceful purposes. No military activity.
How is sustainable tourism achieved in antarctica?
Code of conduct
Small groups
No litter
Little stress on penguins
Concerns about tourism in Antarctica
Fragile ecosystem- footprints remain for decades
Tourist season during breeding season
Demand for fresh water hard to meet
Madrid protocol
Balance between protecting continent from development and allowing exploitation of resources.
Noise pollution bad for birds.
Minerals may be exploited some day.
Protocol conceded due to depletion of resources around the rest of the world and increasing demand for resources.
Internal flow
Movement within glacier - ice crystals align and slide over each other.
Clod based glaciers/polar.
At top of glacier.
Basal flow/slippage
Glacier slides over bedrock - meltwater from pressure acts as lubricant at bottom of glacier.
Regelation slip
This type of flow occurs when a glacier meets a small obstacle.
As glacier moves over obstacle there is pressure on the upglacial side.
This leads to melting which helps the ice slip over the obstacle.
Once over the obstacle, on the downglacier side the meltwater refreezes as the pressure is lower.
Creep
Occurs when stress builds up within the glacier, causing the glacier to be more plastic and flow.
Tends to occur when a glacier meets a large obstacle and results in the glacier creeping or flowing around the obstacle.
Extensional flow
Occurs above firn line as downvalley ice is pulling away from upvalley ice.
Occurs when slope steepens.
Ice accelerates and thins as stretches so crevasses form.
(Thin ice=less erosion)
Compressional flow
Below firn line. Ice from upper valley pushing against down valley ice and when valley is less steep glacier slows and thickens.
So ice erosion is at its maximum.
Rotational flow
Between the two zones of extensional and compressional flow, ice moves in a curved or rotating manner. This movement occurs within a corrie - the birthplace of many glaciers.
Ice slides down an armchair shaped hollow about a central point of rotation.
