L2 - Glacier Motion

Question 1

What material does ice behave like?

Answer 1

Plastic

Question 2

What occurs during Glacier Flow?

Answer 2

There is a transfer of mass from High to Low Elevation

Question 3

What 3 factors influence Glacier Flow?

Answer 3

1. Accumulation of Mass
2. Physical Ice Properties and Topography
3. Stress and Strain

Question 4

What does mass transfer aim to achieve?

Answer 4

An equilibrium

Question 5

What is Stress?

Answer 5

The weight of the ice and the slope of the bed

Question 6

What is Strain?

Answer 6

The response of the ice to the stress

Question 7

What are the 3 mechanisms of Strain?

Answer 7

1. Ice Deformation
2. Glacier Bed Deformation
3. Basal Sliding

Question 8

What is the name of the fastest flowing glacier in the world and where is it located?

Answer 8

Jakobshavn Isbrae in Western Greenland

Question 9

What influence does ice thickness and steepness have on stress?

Answer 9

It increases with thickness and steepness

Question 10

What does stress respond to?

Answer 10

Topography

Question 11

What causes ice deformation?

Answer 11

Movement within or between individual ice crystals

Question 12

What type of sediments leads to increases movement and deformation?

Answer 12

Soft bed sediments

Question 13

Name the 3 types of glacier thermal regime

Answer 13

1. Warm
2. Cold
3. Polythermal

Question 14

What must be true for basal sliding to occur?

Answer 14

The basal ice must be at the pressure melting point

Question 15

What is the p.m.p?

Answer 15

The pressure melting point

Question 16

What are the 2 sliding process?

Answer 16

1. Regelation Sliding

2. Enhanced Plastic Flow

Question 17

What is Enhanced Plastic Flow also referred to as?

Answer 17

Enhanced Creep

Question 18

What is Creep? (With Citation)

Answer 18

A way that snow or ice can move by deforming its internal structure (NSIDC, 2016)

Question 19

Who raised the theory (with a date) that glaciers can slide over their beds because of melting on the upstream side and freezing on the downstream side?

Answer 19

Weertman, 1964

Question 20

What is the principle of Enhanced Plastic Flow?

Answer 20

Creep is enhanced in the vicinity of obstacles due to higher strain rates

Question 21

What is Hydraulic Jacking?

Answer 21

When ice is lifted up from the bed and then hovers, which removes friction and increases flow

Question 22

What are the 3 effects that water pressure can have on sliding processes?

Answer 22

1. Submergence of small bed roughness features
2. Increased local stress over obstacles
3. Hydraulic Jacking

Question 23

What are the 3 factors that cause velocity variations between different types of glaciers?

Answer 23

1. Mass Balance Gradients
2. Ice Temperatures
3. Bed Conditions

Question 24

What type of glacier is typically slow flowing?

Answer 24

Cold Based Glaciers

Question 25

What type of glaciers are usually fast flowing?

Answer 25

1. Polythermal Outlets
2. Ice Streams
3. Surging Glaciers

Question 26

Are ice streams topographically controlled at the surface or at the bed?

Answer 26

At the Bed

Question 27

What are the two modes for a surging glacier?

Answer 27

1. Quiescent

2. Surging

Question 28

Name 2 locations where surging glaciers are common

Answer 28

1. Svalbard

2. Alaska

Question 29

What must happen for a surge to start?

Answer 29

The critical basal shear stress threshold must be passed and the gravitational driving forces exceed the friction at the bed

Question 30

How long to surging events last and how often do they occur?

Answer 30

Last 1-5 years and occur every 10-100 years