Topic 2 - Glaciation EQ2

Question 1

What are glaciers, what type of system are they?

Answer 1

persistent body of dense ice that is constantly moving under its own weight

• are open systems with inputs and outputs

Question 2

Outline and explain the inputs of glaciers?

Answer 2

• precipitation in the form of snowfall is the man input, it is increasing compacted over many years forming high-density clear glacial ice
• avalanches from steep mountain sides (specifically with poleward aspect)
• wind deposition - strong winds at high altitudes blow snow onto accumulation zone

Question 3

Outline and explain the stores within glaciers?

Answer 3

Main stores are snow and ice, which vary seasonally specifically in more temperate regions (where there can be significant winter snowfall and summer melting)

Question 4

Outline and explain the flows/transfers within glaciers?

Answer 4

processes such as evaporation, sublimation, meltwater flow and glacial movement

• more pronounced and active in warmer environments

Question 5

Outline and explain the types of feedback loops?

Answer 5

Positive feedback loops - enhance and speed up processes, promoting rapid change

Negative feedback loops - regulate systems to establish balance and equilibrium

Question 6

Explain the dynamic equilibrium of glaciers?

Answer 6

Equilibrium line marks the boundary between accumulation zone and the ablation zone - will remain in place if inputs equal outputs

• equilibrium line moves up or down the glacier when balance shifts

Question 7

Outline and explain the ouputs of glaciers?

Answer 7

• main output is meltwater, result of melting close to glaciers snout (where temps are highest)
• calving - when ice extends over water, it causes huge chunks of ice to break off
• processes of evaporation and sublimation

Question 8

Outline and explain glacial mass balance?

Answer 8

Wether a glacier is growing or shrinking depends on the balance between accumulation and ablation - changes yearly

• ablation is greatest in summer and accumulation is greatest during winter

Question 9

Explain the accumulation zone of glaciers?

Answer 9

where there is a net gain of ice over the course of a year (inputs exceed outputs)

• if accumulation exceeds ablation it leads to positive mass balance, the glacier advances

Question 10

Explain the ablation zone of glaciers?

Answer 10

where there is a net loss of ice over the course of a year (outputs exceed inputs)

• if ablation exceeds accuulation it leads to negative mass balance, the glacier retreats (and potentially dies)

Question 11

Explain how the climate affects how a glacier works and the landforms it creates?

Answer 11

• cooler climate results in thicker ice which moves faster and advances - erodes and transports more vigorously
• warmer period causes glacier to shrink so the ice becomes thinner and retreats - less erosion and transport of debris (deposits more)

Question 12

Outline and explain how a positive feedback loop can enhance accumulation?

Answer 12

gain of ice increases surface albedo further lowering temperatures and leading to more snowfall - glacial mass increases

Question 13

Outline how glaciers move?

Answer 13

Their movement is dependent on the temperature of the ice (determines wether PMP is reached) if meltwater is present then they will move by processes called basal slip - otherwise by internal deformation

Question 14

Explain how temperate glaciers can move?

Answer 14

By basal slip - Melting point at surface of the glacier is 0 degrees, but due to pressure of overlying ice it is lowered - temperate glaciers meet PMP so meltwater produced which lubricates bedrock and glacial base, increasing rate of movement

• can also move by internal deformation

Question 15

Explain how polar glaciers can move?

Answer 15

PMP is not met due to temperatures being too cold - glaciers are frozen to the bedrock which prevents movement through processes like basal slip

• move instead by internal deformation

Question 16

Explain the process of basal slip?

Answer 16

Occurs when the base of the glacier is at the PMP, means that meltwater is present and lubricates the base - enables the glacier to slide rapidly over bedrock

• can be subdivided into other processes (eg surges, creep and regelation)

Question 17

Explain how the process of creep and regelation enhances basal slip?

Answer 17

Basal slip is enhanced by obstacles on the valley floor, large obstacles (over 1m) causes increase in pressure - so ice plastically deforms around the feature (creep), small obstacles cause PMP to be met - enhances basal slip

• ice refreezes on downward (lee) side of obstacles - process known as regelation

Question 18

Explain how the process of extending and compressing flow enhances basal slip?

Answer 18

Over steep slopes, rate of basal slip increases and the ice accelerates and thins (extending flow) over shallower slopes basal slip slows and the ice decelerates and thickens (compressing flow)

Question 19

Explain how the process of surges enhances basal slip?

Answer 19

• various causes for example earthquakes
• most common is enhanced basal slip triggered by the build up of meltwater at the ice-rock interface

Question 20

Explain how polar glaciers move?

Answer 20

Internal deformation - occurs when the weight of glacier ice and gravity causes ice crystals to deform - glacier moves downslope very slowly

Question 21

Explain the effects of different sized obstacles in creep and regelation?

Answer 21

• Obstacles larger than 1m causes an increase in pressure, which make the ice plastically deform around the creep
• obstacles smaller than 1m cause pressure-melting which increases ice movement by basal slip

Question 22

Explain how internal deformation occurs in depth - give both types of movements?

Answer 22

• Inter-granular movements, where individual ice crystals slip and slide over each other
• intra-granular movements, where individual ice crystals become deformed or fractured (due to stresses within ice) - mass of ice deforms and moves downhill

Question 23

Explain subglacial bed deformation?

Answer 23

Occurs locally when a glacier moves over relatively weak or unsolidated rock - sediment can deform under weight of glacier, moving the ice on top along with it

Question 24

Outline 4 factors which affect the rate of glacial movement?

Answer 24

• altitude
• gradient of slop
• presence of meltwater
• ice thickness

Question 25

Explain how ice thickness can affect glacial movement?

Answer 25

When ice is 50m thick plastic flow begins - greater thickness creates more pressure in the ice, allows for PMP to be met - meltwater produced

Question 26

Explain how altitude affects rate of glacial movement?

Answer 26

Altitude affects precipitation and temperature - greater precipitation and lower temperature, the greater increase in mass balance - glacier advances

Question 27

Explain how slope gradient can affect the rate of glacial movement?

Answer 27

Gravity encourages ice to move, steeper gradient the greater the pull of gravity

Question 28

Explain how the presence of meltwater affects glacial rate of movement?

Answer 28

Meltwater present in temperate glaciers where PMP is met, lubricates the base of the glacier enabling it to slide through process of basal slip

Question 29

Explain in depth how rock type (lithology) affects glacial movement?

Answer 29

movement is faster over impermeable surfaces than permeable, because basal meltwater is retained – aiding slippage - if bedrock is permeable then meltwater percolates away, slowing the movement of the glacier

• easily eroded rocks (heavily fractured rock) are more prone to bed formation

Question 30

Outline and explain the 2 main types of glacial erosions?

Answer 30

• abrasion - angular frost-shattered material scours the landscapes and large rocks cause striations
• plucking/quarrying - occurs when meltwater freezes bedrock to glacier base, causing loosened rocks to be plucked away with forward movement

Question 31

Outline and explain 3 ways material is transported by glaciers?

Answer 31

Supraglacial - weathered material carried on top of ice

Englacial - once supraglacial material, now buried by fresh snow and carried within ice

Subglacial - material carried below ice, dragged by overlying glacier

Question 32

outline the role of water in the transport of material within glaciers?

Answer 32

In temperate environments water flows on top of glaciers (leads to fluvial transport) - water can also flow down crevasses in the ice (moulins) and transport material into and beneath the glacier

• meltwater streams flow under ice, carrying material to snout

Question 33

Outline and explain what subglacial landforms are, what processes are present and what are formed?

Answer 33

• occur below a glacier or ice sheet
• abrasion and plucking active here
• forms striations and Roche mountée
• meltwater below the ice and subglacial deposition can create eskers

Occur at micro-scale

Question 34

Outline and explain what marginal landforms are, what processes are present and what are formed?

Answer 34

• occur at sides or ends of glacier and ice sheets
• weathering and deposition active here
• create landforms like moraines

Occur at mirco or meso-scale

Question 35

Outline and explain what proglacial landforms are, what processes are present and what are formed?

Answer 35

• occur in front or just beyond the glacier/ice sheets margin
• fluvioglacial processes (meltwater eroding, transporting and depositing sediment) operate here
• create outwash plains, meltwater channels and proglacial lakes

Question 36

Outline and explain what periglacial landforms are, what processes are present and what are formed?

Answer 36

• exist at edges of glaciers/ice sheets
• processes operating associated with frost, ice and meltwater
• create landforms like blockfields, ice wedges and pingos
• occur on a extensive scale (macro-scale)

Question 37

Explain the distribution of glacial landforms - include upland and lowland regions?

Answer 37

• upland areas characterised by erosional landforms (eg corries and hanging valleys)
• lowland areas tend to have more depositional landforms (eg outwash plains)

Question 38

Explain what entrainment is in regard to transport?

Answer 38

Process where surface sediment is incorporated into fluid flow by supra and subglacial processes (eg air,water or ice) part of process of erosion

• small rock fragments are trapped (entrained) by basal ice freezing around them applying drag to pull them along
• results in abrasion

Question 39

Explain supraglacial and subglacial sources?

Answer 39

Supraglacial - include material falling from hillsides being washed or blown on to the glacial from surroundings

Subglacial - material eroded from the glacier bed and valley walls and englacial material which has worked its way down through glacier

Question 40

Outline the types of scales of landforms?

Answer 40

• micro - small scale, up to 1m long (features like striations and glacial grooves)
• meso - medium scale, roches moutonées, ribbon lakes, drumlins and eskers
• macro - large scale, glacial troughs, terminal moraines and knock and lochan