Glaciation Pack E

Question 1

What role does moving ice play in transforming the landscape?

Answer 1

It causes erosion and depositional landforms

Question 2

What is weathering?

Answer 2

The breakdown or decay of rocks at the Earth’s surface creating regolith (broken up rocks)

Question 3

What are the three types of weathering?

Answer 3

• Physical
• Chemical
• Biological

Question 4

Which types of weathering are more common in cold places?

Answer 4

• Physical
• Chemical

Question 5

How does freeze thaw weathering create debris?

Answer 5

• Water enters cracks or joints in the rock
• Water freezes in the joints and expands by up to 90%
• This wedges rocks apart and breaks them to form angular debris

Question 6

What weather conditions are needed for freeze thaw weathering?

Answer 6

There must be frequent temperature fluctuations around the melting point, where temperatures must rise above melting point during the day and drop below freezing point at night

Question 7

What about the landscape and rock type make freeze-thaw weathering more common?

Answer 7

• Jointed and permeable rocks
• Lots of water
• Frequent temperature fluctuations

Question 8

What is erosion?

Answer 8

The wearing away and transport of rocks by ice and meltwater

Question 9

What are the three types of erosion?

Answer 9

• Abrasion
• Plucking
• Meltwater erosion

Question 10

What is abrasion?

Answer 10

The process where the material a glacier is carrying wears away the valley floor and sides

Question 11

What is plucking?

Answer 11

When rocks and stones become frozen to the base of the glacier as water refreezes and are pulled from the ground or rock face as the glacier moves

Question 12

How does abrasion work and what are the ideal conditions for it?

Answer 12

• Rocks scrape the bedrock as the ice moves
• In warm based glacier as there is meltwater
• Thick, fast moving glaciers with weak bedrock are ideal

Question 13

How does plucking work and what are the ideal conditions for it?

Answer 13

• Joints are initially widened by fracture
• The large downwards pressure from the weight of the glacier and friction between the basal ice of the glacier and the rock below causes melting
• Water refreezes to obstacles
• Ice frozen to the valley sides moves
• Rocks are detached and chunks are removed from the bedrock and entrained in ice
• Highly jointed and permeable rock is best

Question 14

What is subglacial meltwater erosion?

Answer 14

Erosional processes caused by meltwater running under the base of the glacier

Question 15

Where does subglacial meltwater erode rock?

Answer 15

• Valley base and sides
• Snout (as there is more meltwater)

Question 16

How does subglacial meltwater erosion erode rock?

Answer 16

Solution - where the meltwater dissolves minerals and carries them away
Hydraulic action - forces air and water into joints and pores which dislodges rock before it is taken away
Attrition - where material being carried hits each other

Question 17

How is subglacial meltwater erosion powerful?

Answer 17

• Meltwater streams flow faster
• As they are under hydrostatic pressure from surrounding ice
• More erosive power

Question 18

What is nivation?

Answer 18

The different processes that occur under snow (e.g. when freeze thaw and chemical weathering create material which is then flushed out by meltwater creating small nivation hollows which then form the start of a corrie)

Question 19

What factors affect the rate of erosion?

Answer 19

Basal thermal regime:
- Warm based glaciers have increased erosion potential
- Pressure melting point has to be reached to provide meltwater for sliding
- Water must refreeze (regelation)
- Cold based glaciers protect underlying rock

Ice velocity:
- Faster moving glaciers are more erosive
- Pass over a larger area

Ice thickness:
- Thicker ice increases pressure and erosion potential
- More weight pressing on the underlying material makes abrasion more effective

Confluence:
- At a confluence more mass is added
- More erosion

Resistance of rock:
- Harder bedrock will erode less easily
- Harder rock entrained in the glacier will cause more erosion

Bedrock permeability:
- More permeable rock will erode more
- Water exerts pressure

Bedrock jointing:
- More plucking when more joints

Available debris:
- More weathered debris available leads to more erosion

Debris characteristics:
- Large, hard or angular rocks will cause more erosion

Topography:
- Steep mountainous areas lead to increased erosion
- More energy

Temporal control:
- More time that there is moving ice means more erosion

Question 20

What is congelifraction?

Answer 20

Freeze thaw weathering that splits soil not rock

Question 21

How is congelifraction different to freeze-thaw weathering?

Answer 21

Happens on the surface not under the glacier

Question 22

What is fracture, traction and dilation?

Answer 22

• Fracture and traction happen as a result of the crushing effect of the weight of moving ice
• Dilation occurs as overlying material is moved so fractures in the rock are parallel to erosion surfaces