COLD ENVIRONMENTS Flashcards
What are the reason that an area may be cold?
- High latitude, receive less solar radiation because of the angle that the suns energy hits earth
- High altitude, air temperature decreases with increasing altitude, less of the suns energy is trapped making it colder and lower air pressures higher up causes a decrease in temperature
- Continentality – the sea heats the near land because in the winter it cools slowly but in the middle of continents the land does not get warmer by the sea making it colder
What are glacial environments?Where are glacial environments found?
Glacial environments are permanently covered by ice and only form where it’s really cold. Therefore glacial environments are found at high latitudes such as the Antarctic ice sheet and the Greenland ice sheet which are both above 60 degrees latitude. They are also found at high altitudes such as the Himalayan Mountains even though they’re at low latitude. Glaciers don’t form in the middle of continents because there is not enough snow.
What are Periglacial environments? Where are Periglacial environments found?
Periglacial environments are places where the temperature is frequently of constantly below freezing but not covered by ice. They contain a layer of permafrost on or below the surface. They form at high latitudes such as northern parts of Asia, North America and Europe, high altitudes e.g. the Tibetan Plateau in Asia and the Bolivian plate in South America, and in the interior of land masses e.g. Siberia and central Asia.
What are Alpine environments? Where are Alpine environments found?
Alpine environments are cold areas of land at an altitude above treeline, the limit of the area that trees can grow in. Alpine environments are always found at high altitudes often in mountain ranges, e.g. the Himalayas, the Andes and the Alps. They can exist at any latitude for example the rocky mountains in north America run north to south from above 50 degrees to around 30 degrees latitude. Alpine environments may include periglacial and glacial conditions, permafrost may be found below and above the treeline while glacial environments will be found higher.
What are polar environments? Where are polar environments found?
Arctic – high latitude, defined by the Arctic Circle or by the 10degress July isotherm. The areas around the North Pole is made up of sea ice which shrinks in the summer and refreezes in the winter. Much of the Arctic polar region is made up of the northern land areas of Asia, North America and Europe. The land-based polar environment can include glacial environments such as the Greenland Ice Sheet and Periglacial environments like northern Russia.
Antarctic – high latitude, the Antarctic Circle doesn’t go all the way around the land mass of Antarctica so the polar environment is defined by the 10 degree July isotherm. Some of the Antarctic environment is high altitude, some places it reaches an altitude of over 4000m. The interior is also affected by continentality which makes it cold. Most of the polar environment is on the land mass of Antarctica, the land based environment incudes glacial environments like the Antarctic ice sheet.
What is a glacier?
Glaciers are masses of ice that flow downhill, there are two main types – valley and corrie. Valley glaciers fill valleys and can be several kilometres long whereas corrie glaciers are smaller and found in bowl- shaped hollows high up in mountains.
Explain the glacial budget - Accumulation, ablation
The glacial budget is the balance between the inputs and outputs to a glacial system.
Accumulation is the input of snow and ice and ablation is the output of water from the glacier. There is more accumulation than ablation in the upper glacier or the zone of accumulation and there is more ablation at the zone of ablation in the low glacier. Where these are equal is given the name the equilibrium point. If there is more accumulation than ablation over a year the glacier has a positive regime however is there is more ablation the glacier has a negative regime.
Seasonally in the winter there is more ablation and a positive regime.
How have global temperatures affected the glacial budget?
Changes in global temperatures over long periods of time affected the glacial budget. In the 19th century temperatures were colder than the 18th so in general there was more accumulation meaning that many glaciers advanced. In the 20th century global temperature increased so glaciers tended to have a negative regime and retreat.
What are the inputs, stores and outputs of a glacial budget?
Inputs -Snow, Condensation of water vapour from air to liquid which then freezes, Sublimation of water vapour from the air directly to ice crystals, Bits of rock collected when the glacier carves away at the landscape
Stores - Ice, Melt water, on, in or below the ice, Debris carried by the glacier
Outputs - Ice can melt and flow out as melt water, Surface snow can melt and evaporate, Ice and snow can sublimate to water vapour, Snow can be blown away by strong winds, Calving, blocks of ice fall from the front of the ice mass into water to create ice burgs, in lakes and the sea
How is a glacier formed?
Snow settles but with weight of more snow falling on top it makes then snow denser and more granular. This is called firn. Air is squeezed out and particles of ice are compressed together by the continuing accumulation of snow and ice. Water melts and refreezes in the air spaces making the ice denser.
What are warm-based and cold-based glaciers?
Warm-based glacier -The base is warmer than melting point because of heat from friction or geothermal heat. The ice at the bottom melts which acts as a lubricant making it easier for the glacier to move downhill. Lots of movement means there is lots of erosion.
Cold-based glacier - The base is cold so there is little melting, the ice is frozen to the base so there is very little movement and very little erosion.
How do glaciers move? (5 ways)
Basal sliding - Meltwater under the glacier allows the glacier to slide over the ground, this is the main way that warm based glaciers move. There is more melting around bits of protruding rock because of the pressure on the ice, the water can refreeze downstream of the obstruction where there is less pressure. Thus movement is slower downstream where there is less obstructions.
Rotation flow - The movement of glaciers in an arc shape when in a hollow by basal sliding
Internal deformation - When the ice bends and warps to flow downhill like a liquid. Ice crystals shift past each other in order to move the glacier. This is the main way that cold-based glaciers move.
Extensional flow - The valley is steep near the head of the glacier so there is a strong gravitational force pulling the ice downwards making the ice move quickly. When ice moves quickly there is more tension causing the ice to fracture into layers which then slip downwards.
Compressional flow - Lower down the glacier the ice is moving slowly because the gradient of the valley is decreasing. The faster ice from above pushes down on the slower ice and compresses it. The induced high pressure causes the ice to fracture into layers which slip forwards.
What is the speed of a glacier determined by?
Gradient of the valley floor – steeper = faster
Thickness of the ice – thicker = faster, more internal deformation in cold based and more pressure causing melting in warm based
The temperature of the base – warmer = faster
Explain crevasses in a glacier
Stresses and strains cause cracks called crevasses to form in the glacier. Stress can be caused by extensional and compressional flow, calving or tension between the ice and the valley sides. The tension caused by the glacier pulling away from the ice attached to the back wall produces a bug semi-circular crevasse at the back of the glacier called the bergschrund
What are the erosional process of a glacier?
- Plucking – ice in contact with rock surfaces can thaw slightly then re-freeze around rocks protruding from the valley sides and floor. When the glacier moves it plucks away rocks from the valley sides and floor
- Abrasion – debris carried by the glacier can scrape material off valley walls and the floor
- Meltwater – streams are powerful enough to erode the valley floor and sides by normal fluvial processes
- Weathering – frost shattering breaks rocks off he back and side walls of a valley. Meltwater from the snow gets in the valet walls and the freezes, which causes it to expand and exerts a pressure on the rock causing bits to fall off, onto or into the glacier, adding to the abrasion of the valley.
What are the transportation process of a glacier?
Glaciers carry a large amount of debris which has been gathered by plucking or fallen onto the glacier. Sediment can range in size and can be transported in 3 main ways
• Supraglacial – carried on top of the glaciers surface
• Englacial – carried within the body of the glacier
• Subglacial – material moved along the base of the glacier
What are the depositional processes of a glacier?
Unsorted mixture of material deposited by the glacier is called till and includes everything from massive boulders down to pebbles and clay. Till points in the direction that the glacier is flowing and is often deposited as landforms called moraines.
• Lodgement till – spread onto the valley floor beneath the ice by moving glaciers
• Ablation till – dropped by the glacier as it melts, this till is mainly deposited close the glacier snout
Erosional landform - corrie/cirque/CWM
Corries are basins created by the formation of glaciers. Glaciers usually form on one side of a mountain where there is least sun and the coldest winds, this is where there is the most accumulation.
Basal sliding with abrasion and plucking deepen the hollow into a corrie, when the ice in the hollow is thick enough it flows over the lip and downhill as a glacier. Frost shattering and plucking steepen the back wall of the corrie.
Erosional landform - arête
An arête is a steep sided ridge formed when two glaciers flow in parallel valleys, the glaciers erode the valley sides which sharpens the mountain ridge in between them.
Erosional landform - pyramidal peak
A pyramidal peak is a pointed peak with at least three sides, formed when three or more corries form back to back.
Erosional landform - Glacial trough
Glacial troughs or u shaped valleys are steep sided valleys with flat bottoms formed by the erosion of a v-shaped valley by glaciers.
Erosional landform - truncated spur
Truncated spurs are formed when ridges of land that stick out into the main valley are chopped off as the main valley glacier moves past.
Erosional landform - hanging valley
Hanging valleys are formed by tributary glaciers, they erode the floor less deeply because they are smaller. When the glaciers melt the valleys are left at a higher level than the main valley. Waterfalls are common from the hanging valley into the main valley
Erosional landform - Valley steps
Steps in the glacial trough formed when the glacier erodes the valley floor more deeply where another glacier joins it of where there is less resistant rock.
