Geography- Cold Environments

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  • Created by: EnyaS
  • Created on: 26-09-15 16:14

Types of Cold Environments

1. Glacial Areas

Areas covered by ice sheets and glaciers e.g. Antarctica and Greenland

2. Periglacial / Tundra Areas

Exist in dry high-latitude areas not permanently covered by snow and ice. e.g. Northern Alaska and Canada, Siberia, and islands of the Arctic Ocean.

3. Alpine Areas

Areas contain small ice caps, mountain glaciers and tundra environmentse.g. Asia (Himalayas), Europe (Alps) and the Americas (Rockies, Andies)

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Climate Change

Evidence of Climate change:

Pollen Analysis - shape of grain and range of dispersial

Oxygen Isotope Measurements - heat and evaporation in ice

Drill Cores - locked inside ice are molecules and trapped air, which are preserved every year with more snowfall. Subtle changes in temperature can be measured from ice cores extracted in Antarctica.

Dendrochronology - tree rings show growth rate over a year. If it is warmer the tree will grow more, meaning the distance between the rings is wider. 20 years ago the rings were narrower, meaning it was cooler.

Rocks and Fossils - can be studied for information covering longer time periods. For instance, limestone found in Yorkshire would have been formed on the bottom of a warm seabed millions of years ago.

Glacial retreat - photos show that many mountain glaciers have retreated in the last 50 years. However this could partly be due to a lack of snowfall.

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Glaciers

A glacier is a slow moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles

Glacier Formation:

1. Snow flakes made of ice crystals fall to the ground

2. Each year snow falls, creating distinctive layers

3. The weight of the layers causes them to compress the crystals together

4. Further removal of air creates rock hard ice (meltwater seeps into these gaps and freezes, further compacting the mass)

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Glaciers as Systems

(http://www.acegeography.com/uploads/1/8/6/4/18647856/7326663_orig.jpg?432)

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Warm and Cold Glaciers

WARM (temperate glaciers)

  • Basal temperatures at or near PMP
  • Steep relief
  • Rapid movement 20-200m yr-1
  • High altitude
  • Outside Antarctica
  • Melt in summer
  • Erodes, transports and deposits

COLD (polar glaciers)

  • Basal temperatures below PMP
  • Low relief
  • Slow movement
  • High Latitude
  • Less erosion, transportation and deposition
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Other Glacial Keywords

Equilibrium Line Altitude (ELA):

Line / zone on glacier's surface where a year's ablation balances a year's accumulation

Snout:

Front of a glacier, lower part of ablation area

Pressure Melting Point (PMP):

Ice usually melts when temperature rises above 0 degrees celcius. However, due to the pressure of the ice above, ice at the base can melt at just below 0 degrees celcius.

WARM- Base is warmer than PMP = more erosion due to more ice melting

COLD- Base is colder than PMP = little erosion due to less melting

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Movements of Ice

Compressing Flow-

  • Reduction in gradient of valley floor = ice deceleration and a thickening of ice mass.
  • Erosion at its maximum

Extending Flow-

  • Valley gradient becomes steeper = ice accelerates and becomes thinner
  • Reduced erosion

Basal Flow-

  • Glacier moves over bedrock = friction
  • Lower ice under pressure + friction = melting
  • Meltwater = lubricant, cause ice to flow more rapidly 

Internal Flow / Deformation-

  • Ice crystals orientate themselves in direction of glacier's movement & slide past eachother
  • Surface ice moves faster = crevasses
  • Main flow of POLAR glaciers (no meltwater = frozen to beds)
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Movements of Ice (continued)

Rotational Flow-

  • Within the corrie = birthplace of glaciers
  • Ice moving downhill can pivot around a point = rotational movement
  • Plus increased pressure in rock hollow = more erosion & over-deepening of corrie floor

Creeps-

  • Stress builds up in glacier = ice behave with plasticity & flow, when obstacles are met

Surges-

  • Excessive build up of meltwater under glacier = move forward rapidly 250-300m / day
  • Hazard to people living below the snout

Crevasses-

  • Sides and base of glacier move at a slower rate than centre surface ice = ice cracks, producing crevasses
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