Module 10

Question 1

explain how alpine and continental glaciers form and move: snow is transformed from firn into glacial ice

Answer 1

-Glaciers form by continual accumulation of snow above the snowline, followed by compaction, melting, and refreezing that compresses air space within snow pack
-Snow that persists throughout the summer and into the following winter becomes firn; Ongoing compaction, melting and refreezing slowly transforms firn into glacial ice
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Question 2

Link glacier motion to mass balance; distinguish between accumulation and ablation processes; distinguish between internal deformation and basal slip

Answer 2

The movement of glaciers through cyclical processes of melting and freezing

Rate of internal deformation is related to ice temperature: ‘warm’ ice flows more rapidly than ‘cold’ ice
Movement of ‘warm’ ice is assisted by presence of meltwater beneath glacier; serves to lubricate the bed– basal slip

Accumulation processes: Snow fall; melting and refreezing; deposition of water vapour
Ablation processes: Melting of ice (at surface, within glacier, at base of glacier); calving of icebergs; sublimination

Question 3

Describe glacial erosion; distinguish between plucking and abrasion

Answer 3

Erosion caused by the movement of glaciers

Plucking–stress applied by glacier against the bed overcome the strength of rocks; releases large, angular rock clasts

Abrasion– rock clasts in transport at bed of glaciers are used to cut into and/or polish the rock surface; produces striations

Question 4

Describe glacial deposition: distinguish between lodgement and ablation (melt out)

Answer 4

Deposition occurs when glacier is no longer able to transport debris

Lodgement occurs in response to an increase in ice pressure applied to debris moving in the subglacial environment
Melt-out occurs in response to supply of geothermal heat in the subglacial environment and solar radiation in the supraglacial environment

Question 5

Describe the distribution of permafrost; distinguish between continuous and discontinuous permafrost

Answer 5

Permafrost regions are divided into two zones: continuous zone and discontinuous zone

• Continuous permafrost (mean annual isotherm -7°C)
• Discontinuous permafrost (mean annual isotherm -1°C)

Question 6

Define the term talik. Why are these features important in permafrost?

Answer 6

Talik is unfrozen ground that may occur above, below, or within a body of discontinuous permafrost or beneath a water body in the continuous zone

Water flowing through taliks can introduce energy for permafrost thaw and can serve to limit downward progression of the freezing front in the winter

Question 7

Identify three different types of ground ice.

Answer 7

(1) Pore ice is ice occurring in the pores of soils and rocks
(2) Wedge ice is when soils contract, creating cracks in the ground surface that fill with water, which freezes
(3) Massive ground ice is large formulations of ice in the permafrost

Question 8

Describe landforms associated with each type of ground ice

Answer 8

Pore ice: associated with formation of sorted stone circles
Ice wedge: associated with formation of ice wedge polygons
Segregated ground ice: associated with the formation of palsas
Massive ground ice: associated with of formation pingos

Question 9

Define the term cryoturbation and describe how this process works

Answer 9

If sufficient groundwater freezes, the saturated soil and rocks are subjected to frost heaving (vertical movement) and frost thrusting (horizontal movement)
In some periglacial regions, the expansion and contraction of soils (cryoturbation) results in the movement of soil particles, stones, and small boulders into distinct shapes known as sorted stone circles