Glacier Systems and Processes

Question 1

What type of system is a glacier?

Answer 1

Open system

Question 2

How are glaciers formed?

Answer 2

Thin, granular snow called névé (or firn) compacts to form a large mass of ice.

Question 3

What is the glacial budget?

Answer 3

The difference between annual accumulation and ablation (mass balance).

Question 4

What are the three states of budget (mass balance) within a glacier?

Answer 4

• Positive
• Neutral
• Negative

Question 5

What is the equilibrium line?

Answer 5

The boundary between the zone of accumulation and the zone of ablation.

Question 6

What is the snow line?

Answer 6

The boundary between snow-covered areas and areas with no snow cover.

Question 7

What is accumulation?

Answer 7

The addition of mass to a glacier.

Question 8

What is ablation?

Answer 8

The loss of mass from a glacier.

Question 9

What are the two types of glaciers?

Answer 9

• Cold-based (polar)
• Warm-based (temperate)

Question 10

What are the main features of a cold-based glacier?

Answer 10

• Large area
• Low precipitation and melting
• Internal deformation
• Glacier frozen onto bedrock

Question 11

What are the main features of a warm-based glacier?

Answer 11

• Small area
• High precipitation and melting
• Internal deformation and basal sliding
• High levels of erosion and deposition

Question 12

Why is subglacial meltwater present within warm-based glaciers?

Answer 12

Basal temperatures are at or above the PMP.

Question 13

What is the PMP?

Answer 13

Pressure melting point
- The temperature at which ice melts under pressure.

Question 14

What are the two types of weathering in cold environments?

Answer 14

• Frost action
• Nivation

Question 15

What is frost action?

Answer 15

Water enters cracks in rocks during the day and freezes overnight, before expanding by 9% which exerts pressure and causes rock fragments to break off.

Question 16

What is nivation?

Answer 16

A common process in periglacial environments where the alternating freezing and thawing of snow and ice causes erosion beneath patches of snow.

Question 17

What are the five types of ice movement in cold environments?

Answer 17

• Internal deformation
• Basal sliding
• Compressional flow
• Extensional flow
• Rotational slip

Question 18

What is internal deformation?

Answer 18

The pressure exerted by a glacier causes ice crystals to align and slide over one another, causing ice movement.

Question 19

What is basal sliding?

Answer 19

The lubrication provided by subglacial meltwater causes ice movement.

Question 20

What is compressional flow?

Answer 20

A glacier will slow down, compress and thicken when it reaches a shallower gradient.

Question 21

What is extensional flow?

Answer 21

A glacier will speed up, extend and become thinner when it reaches a steeper gradient.

Question 22

What is rotational slip?

Answer 22

Compressed ice within a hollow/depression rotates and causes erosion due to gravity and meltwater.

Question 23

What are the 2 types of erosion in cold environments?

Answer 23

• Plucking
• Abrasion

Question 24

What is plucking?

Answer 24

A glacier becomes frozen on to rock outcrops and pulls away pieces of rock as it moves.

Question 25

What is abrasion?

Answer 25

Rocks within a glacier scrape the valley sides and floor, leaving behind striations.

Question 26

When does deposition occur?

Answer 26

- Ice melting at the glacial snout - During the change between compressional and extensional flow

Question 27

What are the characteristics of glacial deposits?

Answer 27

- Unstratified - Unsorted - Angular

Question 28

What are the characteristics of fluvioglacial deposits?

Answer 28

- Stratified - Sorted - Smooth/rounded

Question 29

What are the characteristics of meltwater channels?

Answer 29

- High discharge - Turbulent flow - High erosive power

Question 30

What is permafrost?

Answer 30

Ground that is permanently frozen below 0°C for more than two consecutive years.

Question 31

What are the three categories of permafrost?

Answer 31

- Continuous - Discontinuous - Sporadic

Question 32

What is the active layer?

Answer 32

The thin top soil layer of permafrost which thaws in summer and causes waterlogging.

Question 33

What are the three types of periglacial mass movement?

Answer 33

- Solifluction - Scree - Frost heave

Question 34

What is solifluction?

Answer 34

The slow downslope movement of soil particles as they become saturated due to waterlogged soils in summer months.

Question 35

Why does the active layer become waterlogged?

Answer 35

The permafrost below is impermeable and rainwater/meltwater cannot percolate through it.

Question 36

What is scree?

Answer 36

Scree gathers at the base of steep cliffs/slopes due to freeze-thaw weathering.

Question 37

What is frost heave?

Answer 37

Anomalous expansion of water to ice crystals in the active layer causes the upward expansion of the soil surface.

Question 38

What is the difference between lodgement till and ablation till?

Answer 38

Lodgement till is deposited underneath the ice, whereas ablation till is deposited by melting ice.

Question 39

Where are subglacial meltwater channels present?

Answer 39

Between the base of the ice and the bedrock.

Question 40

Where are englacial meltwater channels present?

Answer 40

Confined in tunnels within the ice.

Question 41

Where are supraglacial meltwater channels present?

Answer 41

On the surface of the ice in meltwater channels.

Question 42

What is the difference between the grading of glacial and fluvioglacial sediments?

Answer 42

Glacial sediments are poorly graded, whereas fluvioglacial sediments are well-graded (larger material is deposited first).