- Created by: Sarah_99
- Created on: 10-05-16 17:45
Different Cold Environments
Polar- these are the most extreme cold environments. Temps often drop to -50 degrees celcius. Polar environments are very dry with low amounts of snow but extensive areas of sea ice.
Countries - Antartica, Greenland.
Alpine- mountanous areas. Cold winters with lots of heavy snow- high altitude. Temps drop below -10 degrees celcius. Summers are warm.
Areas- Rockies, Alps.
Periglacial- edge of glacial. These areas are found on the fringe of polar or glacial environments. They have permaently frozen ground (permafrost). Breif warmer summers cause surface layer to melt- allows plants to grow. Not permaently covered by ice.
Countries- Siberia, Canada and Greenland.
Glacial- Specifically associated with glaciers. most of the worlds active glaciers are high up in alpine mountain regions. Heavy winter snowfall provides ice to feed glaciers. In summer meltwater lubricates the galcier helping them move.
Inputs, processes and outputs:
- Main input is snow. As it gets more compacted air is pushed out and it turns to high density clear glacial ice. Avalances are also inputs.
- The weight of the compacted ice combines with gravity to make the glacier move slowly downhill - it erodes the valley as it moves.
- The main output is meltwater. Other ouputs include evaporation and sublimation.
Top half of glacier. It is where there is a net gain of ice over the course of a year. Here the inputs (snow and avalanches) are greater than outputs. In winter accumulation is higher than ablation.
Bottom half of glacier. It is where there is a net loss of ice during a year. The losses (Melting- Meltwater, evaporation etc.) exceed the gains.
The boundary between the acccumulation and ablation zones is the equilibrium line.
Basal sliding - Occurs in warm glaciers. Meltwater helps to lubricate the base of the ice/ glacier. Increased pressure caused by obstacles on the valley floor causes localised melting of the ice - called pressure melting. The meltwater allows the ice to flow up and over the obstacle- often refreezes on downslope side- pressure is reduced.
Internal deformation - Ice crystals shift so that they are all pointing in the same direction (direction of flow.) This allows the ice crystals to slip and slide over each other. occurs in both cold and warm glaciers.
- Gravity - downhill force that encourages ice movement. The steeper the gradient the grester the pull of gravity.
- Friction - the friction on the ground need to be overcome so the ice can move.
- The mass of ice - The heavier the ice is, the more potential energy it has to move. Extra friction wil need over come from the weight
- Meltwater - lubricates ice allowing it to slip downhill. May help to overcome friction
- Temperature of ice - cold glaciers have ice frozen to bed rock, restricting movement. Warm glaciers have meltwater allowing it to move and sip downhill.
Variations in the rate of ice flow
A sudden change in gradient will cause the ice to flow faster and it may become thinner and streched, this is extensional flow. Streching can cause crevasses to form.
Reduction in gradient causes the ice to slow down causing it to pile up and become thicker. This is compressional flow. Open crevasses are now closed up.
Between the zones of extensional and compressional flow, the ice moves in a rotational manner around a certain point of gravity. This helps the formation of corries.
- Water seeps into cracks and pores in rock.
- Then when the temperature drops below freezing the water turns to ice.
- Ice expands by 9% widening and deepening cracks.
- Then the ice melts again.
- The process continues.
- Cracks get so large rock breaks away and pile up as scree at bottom.
The rocks can get trapped under glaciers and increase abrasion.
Process of chemical weathering that invloves the slow dissolving of clacium carbonate in some rocks e.g. limestone.
Carbon dioxide dissolved in water forms a week carbonic acid which dissolves the rock.
More effective the colder it is.
Galcial ice grinds over landscape. It dies this because of angular rock fragments. These create scratches on the bedrock - these are strations.
Meltwater freezes part of the underlying bedrock to the base of the glacier. Any lose rock fragments are then 'plucked' away when the glacier moves forward. Particularly common when a reduction in pressure under ice on the downslope side of an obstacle leads the the refreezing of meltwater.
This is a resistant rock outcrop that would be a obstacle to a glacier. The process of erosion erodes and smooths one side of the rock. The dowslope side is jagged due to plucking - pressure was released, water froze and as glacier moved forward lose rock is plucked out.
Corrie - Snow accumulates in an indentation in a valley side. Weathering and slumping enlarge the hollow on the mountainside. Rotational flow occurs eroding the rock below deepening the hollow. Plucking takes place on back wall making it steep. In post glacier conditions the glacier melts and there is a lake formed inside the corrie called a tarn.
Arete - Two neighbouring glaciers erode back into a mountain side. The ridge between them is called an arete. present in the Alps.
Pyramidal Peak - When three or more corries erode back into a mountain side, where the aretes meet at the top is called a pyramidal peak.
Glacial troughs - tend to be steep-sided and flat bottomed and straight because of the power of the glacier gauging it out.
- Truncated spurs - when a glacier cuts through interlocking spurs.
- Ribbon lake - if a glacier encounters a weaker bedrock or if a tributary glacier joins
- Hangging valley - smaller glacier may increase vol of ice, but has less erosive power. So when ice melts the tributary valley is left perched abouve the main valley.
- Lateral - consist of frost-shattered rocks that have falled onto a glacier from the valley sides.
- Medial - tributary glacier joins the main glacier, two lateral morains join up to form a medial moraine. tis line of debris then continues its journey toward the centre of the main glacier.
- Englacial - rock trapped within the ice, having been buried over the years by fresh snow and ice
- Terminal - marks the furthest extent of a glacier. Glacier stops moving - less pressure - depositis material at snout.
Outwash plain- Found beyond the terminal moraine. It is a vast expnase of sand ang gravel deposited by braided meltwater rivers from the glacier.
Till - Glacier retreats when it finally melts, the material carried on or in the ice is dumped on the ground moraine - this unsorted rock debris is a till.
Drumlins - Egg shaped hilloks that occur in clusters. Thought to be formed by the moulding of rock debris on the valley floor by ice moving over it. One side is streamline the other is jagged.
Fluvioglacial Landforms - Eskers
- Eskers are ridges of deposited material.
- They run parallel to the valley sides - close to valley sides
- 30 meters high
- Several km wide and long
- Meandering shape
- Sorted material deposited by meltwater largest first - rocks, grain, sand
How you would draw in an exam:
Fluvioglacial Landforms - Kames
- Terrace kame - results from infilling of a margional glacial lake - ice melts, ridge abandoned
- Delta kame - formed when a stream deposits material on entering a margional lake - velocity decreases. They are small hills on the valley floor.
- Crevasse kame - Material deposited into a crevasse. Ice melts - material deposited onto valley floor to form small hummocks- similar to freeze thaw.
How you would draw in an exam:
Fluvioglacial Landforms - Outwash plain
- Extensive gently sloping area of sands and gravel that forms infornt of a glacier behind terminal moraine.
- Seasonal - summer
- Stratified - sediment is layed down in layers in periods of higher discharge - summer
- Braided streams of meltwater rivers
- Lateral erosion from streams help create flat texture.
- Huge - tens of km long and wide.
- Created by both erosion and depisition by meltwater.
- Meltwater emerges from snout and looses energy - no longer under hydrostatic pressure.
- Material is deposited - largest first forming alluvial fan.
- When a number of these emerge an outwash plain is formed - finest sediment is carried furthest sorting sediment by size.
Fluvioglacial Landforms - Meltwater Channels
- The major erosion landform created by melt water are Melt water channels – also known as glacial overflow channels.
- These 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 melt water from glaciers).
- These huge releases of water had much energy to erode and carve out deep gorges using processes such as abrasion and hydraulic action, which today are occupied by streams too small to have created the valleys they flow in.
- Examples are well documented – Newtondale and Lake Pickering, Lake Lapworth and Ironbridge Gorge.
Periglacial Processes - Permafrost
In areas where temperatures rarely rise above 0 degrees celcius, the ground can become permanently frozen to depths of over 100 meters.
The upper surface of the permafrost is called the permaforst table. Above this the soil may temporarily melt durning summer when temperatures breifly rise above 0 degrees C. This melted layer is called the active layer. In the winter it refreezes.
The thickness of permafrost decreases the further away from the arctic you go.
In extreme conditions permafrost can be over 1000 meters deep - Siberia.
Periglacial Processes - Frost Shattering and Frost
When water expands in rocks making them break apart and causinga rock-strewn landscape called felsenmeer.
It also leads to the accumulation of scree at the base of cliffs.
Frost shattering is the most effective when there are daily fluctuations in temperature. However, it can operate over a much longer time period - if freeze thawing only occurs seasonally.
Frost heave is where water in the soil just below the surface freezes and causing the surface to expand and it pushes up the ground above.
Ice crystals can raise individual particles to forma spiky surface.
Periglacial Processes - Nivation
Nivation includes the effects of frost shattering, which operates around the edges of the snow - gradually causing the underlying rock to disintergrate.
Then in the simmer meltwater removes any weathered rock debris to reveal an ever-enlarging nivation hollow.
Slumping may also take place during the summer when the saturated debris collapses due to the force of gravity when it is no longer frozen into place.
As long as the weathered material is removed by meltwater or slumping the hollow will continue to grow larger.
In simpler terms:
Nivation is where the effects of frost shatter operates causing rock debris to form which are then removed by either melt water or slumping to reveal a hollow that will continue to grow as long as the debis is removed by meltwater or slumping.
Periglacial Landforms - Ice Wedges
When permafrost contracts in extremely low temperatures, cracks develop.
During the summer meltwater flows into these cracksand fills them up.
The meltwater refreezes in the winter to form ice wedges, which expand and force the crack to widen.
Over and long period of time repeated cycles of freezing and thawing, the ice wedges increase in size.
They also start to form small ridges on the surface die to frost heave.
In the summer, ponds of meltwater can form on the hollows between the ridges.
Periglacial Landforms - Patterned Ground
Patterned ground from ice wedges and their ridges:
A ice wedges become more extensive, a polygonal pattern may be formed on the ground surface - with ice wesges and their ridges marking the sides of the polygons.
Stone patterned ground:
Stone polygons tend to form of shallow slopes and are directly assosiated with ice wedges.
Frost heave causes the expansion of the ground and lifts the soil particles upwards.
This process is particularly effective for larger particles that can be thrust upwards by lenses of ice in the soil.
Any smaller particles will probably be removed by meltwater or wind - leaving larger stones lying on top of the ice wedges, marking out the polygonal pattern.
if the ground is more steeply sloping the rocks may gradually slide downslope - this can lead to the formation of stone stripes rather than polygons.
Periglacial Landforms - Pingos
A pingo is a an ice-cored rounded hill that is a common feature in Northern Canada.
A lake fills with sediment which insulates the ground and allows liquid water to collect underneath it.
As the sediment gradually refreezes during early winter, the water that has collected becomes increasingly confined - and its pressure increases,
Eventually, the trapped water eventually freezes and expands when it does forcing the sediment lying on top of it upwards to form the characteristic pingo mounds.
In the summer when the core ice melts the centre collapses to form a central depression. This can sometimes become filled with water.
Pingos can reach up to 60 meters in height and 600 meters in diameter.
There are round 1400 pingos in the Mckenzie delta region of Canada.
Exploitation - Indigenous people
About 1.3 million indigenous people live in the Arctic and tundra environments.
They have lived a sustainable, largely subsistence, way of life there for thousands of years - depending on hunting, gathering and herding for thier survival.
80% of the 370 indigenous settlements are costal - inuits spend their winters hunting seals and other animals on the forzen land and surrounding sea ice. In summer they use small boats to fish in open costal waters - Greenland.
Today many indigenous people hav access to modern - high velocity rifles and snowmobiles.
Most remaining indigenous settlements are found along river valleys in Russia and Scandanavia, where people concentrate on herding animals like raindeer.
Exploitation - Early resource exploitation
For thousands of years, the Arctic Ocean provided rich fishing grounds for both indigenous peoples and also fishermen from countries further south.
Early visitors hunted seals and whales, as well as catching marine and freshwater fish.
Northern European nations, such as the UK, Norway and Iceland, made huge profits from wahling and from the fishing industry, particularly for cod.
Exploitation - Recent developments
Oil and gas exploitation has lead to significant industrial developments in the Arctic region - new roads have been constructed, pipelines laid, and settlements established to service the new energy industries.
These have already had negative impacts on the Arctic's indigenous peoples - by interfering with the migration and hunting of caribou, and by threatening fragile marine ecosystems and fisheries - e.g. through oil spills (Exxon Valdez, Alaska)
Other human developments in the Arctic include - mining, hydroelectric power, and even bombing ranges. The former Soviet Union used to use the Arctic as a nuclear testing ground.
Nowadays, the number of tourism to the Arctic region is increasing.
Even though remains an important industry in the Arctic, poor fishery management has led to over-exploitation and a collapse of fish stocks, particularly for cod.
The greatest development presuure is in Northern Scandinavia, where holiday cabin resorts, road construction, HEP and wind farms all threaten the access of Sami raindeer herders to their traditional grazing areas. An estimated 35% of trafitional grazing land has been affected and by 2050 as much as 78% of costal ranges will be unavailable for them to use.
Exploitation - Resources and sustainable managemen
Drilling for oil in Alaska began in the early 1900's. They discovered Prudhoe Bay oilfield in 1967 - oil exploitation really took off there. Largest oil field in America - produced upto 20% of N.Americas oil requirements.
The trans-Alaskan oil pipeline was constucted in 1974 due to the presence of winder sea ice. The pipeline goes right across Alaska to the tanker port of Valdez, where there is a giant oil refinery.
In order to prevent the warm oil in the pipe from melting underlying permafrost, and to allow caribou to migrate, the pipe was built on stilts.
The oil reserves in Prudhoe Bay began to decline, increasing pressure oil companies and politicians to develop alternative sites in the region.
In 1923, the Western Arctic Reserve was designated as an area that could be developed for oil and gas in an emergency.
However, people dont belive this should happen because of threatened species that live there and the groups of indigenous people who depend on the animals for food.
So if this area was expolited, there would have to be great care not to damage the environment and minimise impact on the indigenous people.