Cold environments Flashcards
Three main reasons why an environment may be cold
High altitude
High latitude
Continentality (in the middle of a continent)
Why are high latitudes cold?
They receive less solar radiation
Why are high altitudes cold?
Because air temperature decreases with increasing altitude. (6-10 degrees colder every 1000m you go)
Why are middles of continents cold?
In summer the land heats up quickly, sea slowly, in winter the land cools quickly and sea cools slowly, so in winter the sea heats the coasts but not the centre of continents.
Where are glacial environments found?
High altitude and high latitude
2 main types of glaciers
valley and corrie
What are ice sheets?
Domes of ice covering huge areas of land
Example of glacial environment at high latitude…
Antarctic ice sheet and Greenland ice sheet (both above 60 degrees latitude)
Example of glacial environment at high altitude…
Himalayan mountain range
Why are glacial environments not found at centre of continents?
Not enough snow
Where are periglacial environments found?
High altitude, high latitude and in centre of continenents
What is a periglacial environment?
Places where the temperature is frequently or constantly below freezing, but not covered by ice. They contain a layer of permafrost on or below the surface.
Where are alpine environments found?
at high altitudes - above the tree-line. Often found above the tree-line in mountain ranges e.g. Himalayas
What is an alpine environment?
Cold areas of land at an altitude above the tree-line
What other conditions may be present in alpine areas?
Periglacial - may exist above and below tree-line
Glacial - may exist even higher up
Where are polar environments found?
Around the poles (one at North, one at South)
What are the two polar environments called and why are they cold?
Arctic - High latitude (66 degrees North)
Antarctic - High latitude (66 degrees South)
What is the areas around North Pole made of, and what happens to it in Winter and Summer?
Sea ice (frozen sea water) - Area of sea ice shrinks in Summer, leaving open sea, and refreezes in Winter
What environments can the Arctic include?
Glacial environments e.g. Greenland ice sheet
Periglacial environments e.g. Northern Russia.
2 other reasons why Antarctica is cold?
High altitude - in some places the ice is so thick it reaches an altitude of over 4000m
Continentality - Interior is cold as the centre is hundreds of km away from sea.
What environment is found in Antarctica?
Glacial e.g the Antarctic ice sheet
What are the inputs of a glacier?
Snow
Condensation of water vapour
Sublimation of water vapour to ice
Bits of rock collected when the glacier calves away the landscape
What are the stores of a glacier?
Ice
Meltwater (can be subglacial, englacial or supraglacial)
Debris
What are the outputs of a glacier?
Ice can melt and flow out of glacier as meltwater
Surface snow can melt and evaporate
Ice and snow can sublimate to water vapour
Snow can be blown away
With glaciers that end at the sea, blocks of ice fall from the snout of the glacier into water to create icebergs, this is called ‘calving’.
What is a glacial budget?
The balance between a glaciers inputs and outputs.It shows whether the glacier will advance or retreat
How does the glacial budget change throughout the year?
In summer ablation is greater as more melting will occur, in winter there’s more accumulation than ablation.
How will this affect the mass balance over a year?
The glacier may advance in winter but retreat in summer, so the volume of water in the glacier will stay the same.
How has the glacial budget changed over several years?
Temperatures in 19th century were colder than the 18th century so the glaciers would advance. However 20th century temperatures are higher meaning glaciers tend to retreat.
How do glaciers form?
1) Snow settles. It has a loose fluffy consistency
2) The weight of more snow falling on top turns the snow into denser, more granular snow called firn.
3) Air is squeezed out and particles of ice are compresses together
4) Ice melts and refreezes in air spaces, making the ice more dense.
In warm based glaciers the base is warmer than the melting point of ice, why?
Because of heat from friction caused by the glacier moving. Or because of geothermal heat from the earth.
What effect does a warm base have?
The ice at the base of the glacier melts and the melt-water acts as a lubricant, making it easier for the glacier to move downhill. Ice at the surface may also melt and move down through the glacier, lubricating it even more. Lots of movement means lots of erosion.
Explain the movement in cold based glaciers.
The ice is frozen to the base of the valley, so there’s very little movement. Cold based glaciers cause very little erosion.
What is basal sliding?
Meltwater underneath a glacier allows the glacier to slide over the ground. It is the main way that warm based glaciers move.
Why is flow faster around an obstruction than downstream?
There’s more melting around protruding bits of rock because there is pressure on the ice so melting point decreases. Meltwater can refreeze downstream so the glacier will slow down.
What is rotational flow?
Glacier move in an arc shape in a hollow, this is called rotational flow
What is internal deformation?
Where the ice bends and warps to flow downhill like a liquid. Its caused by ice crystals shifting past each other. Its the main way cold based glaciers move.
What is extensional flow?
At the head of the glacier the valley is steep, so there is a strong gravitational force pulling the ice downwards. This makes the ice move quickly, when ice moves quickly there’s more tension which causes the ice to fracture into layers, these layers then slip downwards.
What is compressional flow?
Lower down the valley the glacier is moving more slowly. The faster ice from the head of the glacier pushes down on the slower ice and compresses it. The high pressure causes the ice to fracture into layers, these then slip forwards.
What are the three main things that determine the speed at which a glacier flows?
Gradient of valley floor
Thickness of ice
Temperature at base of glacier
What parts of the glacier moves the fastest?
Surface and middle (see page 38)
What is a bergschrund?
When the glacier pulls away from the back wall the tension creates a large semicircular crevasse at the back of the glacier called a bergschrund.
What is plucking?
Ice in contact with rock surfaces can melt slightly then refreeze around protruding bits of rock. When the glacier moves forward it plucks the rock away.
What is abrasion?
Debris carried along by the glacier can scrape material off the valley walls and floor.