5.2: the processes that case glacier movement

Question 1

What is the fundamental cause of ice movement?

Answer 1

Gravity

Question 2

What is the accumulation zone?

Answer 2

the area above the firn line, where snowfall accumulates and exceeds the losses from ablation

Question 3

What is the Firn Line

Answer 3

A line across the glacier, from edge to edge, that marks the transition between exposed glacier ice and the snow-covered surface of a glacier

Question 4

What is the ablation zone

Answer 4

Refers to the low-altitude area of a glacier or ice sheet below firn with a net loss in ice mass due to melting, sublimation, evaporation, ice calving, blown snow, avalanche, and any other ablation.

Question 5

Describe what shear stress is

Answer 5

force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress.

Question 6

Describe how a glacier moves.

Reference the accumulation zone, ablation zone, shear stress

Answer 6

As ice mass builds up in an accumulation zone the weight of the snow and ice exerts an increasing downslope force due to gravity - known as shear stress
Shear stress increases as the slope angle increases
Once the shear stress is great enough to overcome the resisting forces of ice strength and friction, the glacier ice pulls away and moves downward away from the zone of accumulation where it eventually looses mass

Question 7

Where are warm based glaciers found?

Answer 7

temperate maritime climates

Question 8

Warm wet based glaciers experience greater snowfall in winter and more rapid ablation in the summer; therefore the imbalance between accumulation and ablation zones is …? so the glacier ice must move downslope more rapidly to maintain …? with the slope angle

Answer 8

1. greater
2. equilibrium

Question 9

In cold based polar glaciers the slower the rates of accumulation, and especially ablation, result in a …? gradient of equilibrium and ..? ice movement

Answer 9

1. smaller
2. slow

Question 10

Basal Sliding relates to the presence of …? beneath a glacier

Answer 10

meltwater

Question 11

Basal sliding is movement that only applies to …? based glaciers?

Answer 11

warm-based glaciers

it can’t occur where the glacier is frozen to the bed

Question 12

Describe the process of basal sliding

Refer to meltwater and friction in your explanation

Answer 12

The meltwater acts a lubricant reducing friction with both the entrained debris and underlying bedrock (this is known as slippage)

Question 13

Regelation Creep (sometimes known as …?), occurs as basal ice deforms under …? when encountering obstructions such as rock steps. As a glacier moves the pressure on the basal ice will increase and it will ..?. Once the glacier had flowed over the obstruction the pressure is …? and the water refreezes

Answer 13

1. slip
2. pressure
3. melt
4. lowered

Question 14

What base type of glaciers move by internal deformation?

And what region of the world are they found in?

Answer 14

Cold-based polar glaciers

Question 15

internal deformation which has 2 main elements:

1. Intergranular flow
2. Laminar flow

Explain them both

Answer 15

1. Intergranular flow when individual ice crystals deform and move in relation to each other
2. Laminar flow when there is movement of individual layers within the glacier

Question 16

When ice creep can’t respond quickly enough to a glaciers speed of movement what occurs

Answer 16

ice faulting occurs causing crevasse’s at the surface

A crevasse is a deep crack that forms in a glacier or ice sheet that can be a few inches across to over 40 feet

Question 17

Warm based glaciers have a …? velocity of movement than the …?-based glaciers because of the addition of basal sliding to internal deformation. Even greater velocities are reached when a warm-based glacier moves over deformable …?

Answer 17

1. greater
2. cold
3. sediment

Question 18

What 5 factors impact glacial movement?

Answer 18

1. Altitude
2. Slope
3. Lithology
4. Size
5. Mass balance

Question 19

How does Altitude impact glacial movement?

Answer 19

affects the temperature and precipitation inputs

Question 20

How does Slope impact glacial movement?

Answer 20

is directly related to flow - steeper slopes lead to faster speeds

Question 21

How does Lithology impact glacial movement?

Answer 21

can affect basal processes and the possibility

Question 22

How does Size impact glacial movement?

Answer 22

can affect the rapidity of the response

Question 23

How does Mass Balance impact glacial movement?

Answer 23

affects the equilibrium of the glacier and also whether its advancing or retreating

Question 24

What are outlet glaciers?

Answer 24

Outlet glaciers are valley glaciers that originate in ice sheets, ice caps, and ice fields.