Glacial Processes

Question 1

What is the mass balance (budget) of a glacier? (4 things)

Answer 1

The difference between accumulation (inputs) and ablation (outputs).

If accumulation > ablation, the glacier advances.
If ablation > accumulation, the glacier retreats.
If accumulation = ablation, the glacier is stationary.

Question 2

What are the 5 key inputs (accumulation) in a glacier?

Answer 2

• Snowfall & precipitation
• Avalanches (snow & rock)
• Meltwater that refreezes
• Wind-blown deposits
• Rock fragments from weathering and erosion

Question 3

What are the 4 key outputs (ablation) in a glacier?

Answer 3

• Meltwater streams (especially in summer)
• Sublimation & evaporation
• Calving (ice breaking off into lakes/oceans)
• Loss of solar energy due to albedo effect

Question 4

What is the equilibrium line (firn line) on a glacier?

Answer 4

The point where accumulation equals ablation, marking the transition between the accumulation zone and the ablation zone.

Question 5

What 4 factors affect glacial movement?

Answer 5

• Mass balance: Areas of accumulation move slower than areas of ablation.
• Slope gradient: Steeper slopes result in faster flow.
• Lithology: Softer rocks erode faster, influencing movement.
• Altitude: Higher glaciers have more potential energy but often remain frozen longer.

Question 6

What is basal slip? (2 things)

Answer 6

• Occurs in temperate glaciers due to pressure melting at the base.
• A thin film of water forms between the glacier and the bedrock, reducing friction and allowing the glacier to slide.

Question 7

What is regelation creep? (2 things)

Answer 7

• When a glacier encounters an obstacle, pressure increases, melting ice upstream.
• The water refreezes downstream, allowing the glacier to move over obstacles.

Question 8

What is internal deformation? (3 things)

Answer 8

• The ice crystals in a glacier realign and slide past each other.
• Occurs mostly in cold-based glaciers, as they lack basal meltwater for movement.
• Movement happens along cleavage planes (weaknesses in ice).

Question 9

What are the four main erosional processes in glaciers?

Answer 9

1. Crushing: High pressure from rock fragments embedded in ice crushes the bedrock.
2. Plucking (quarrying): The glacier pulls out weakened bedrock, forming steep cliffs.
3. Abrasion: Rock debris in ice scrapes bedrock like sandpaper, creating striations.
4. Basal melting: Meltwater under pressure increases erosion.

Question 10

How does freeze-thaw weathering contribute to glacial erosion? (2 things)

Answer 10

• Water enters cracks in rocks, freezes and expands, breaking the rock apart.
• Creates angular debris that glaciers use for abrasion.

Question 11

What is mass movement, and how does it affect glaciers?

Answer 11

• Rockfalls and landslides supply glaciers with debris, which aids erosion.
• Forms moraines when deposited.

Question 12

How does positive feedback impact glacial systems? (2 facts with both 4/5 chains of reasoning)

Answer 12

• Increased snowfall → higher albedo → further cooling → more accumulation.
• Rising temperatures → more melting → glacier thins → more heat absorption → increased melting.

Question 13

How does negative feedback impact glacial systems? (Give 5 chains of reasoning)

Answer 13

• Higher temperatures → increased evaporation → more precipitation → more snowfall → maintains glacial mass.

Question 14

What are the 2 spatial variations in a glacial budget?

Answer 14

• Upper glacier (accumulation zone): Cold temperatures result in net accumulation.
• Lower glacier (ablation zone): Warmer temperatures lead to net ablation.

Question 15

What are the 2 seasonal variations in a glacial budget?

Answer 15

• Winter: Net accumulation → glacier expands (positive balance).
• Summer: Net ablation → glacier retreats (negative balance).