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GEO1020 > Mountain glaciers and climate change > Flashcards

Mountain glaciers and climate change Flashcards

1
Q

What are two hazards associated with mountain glaciers?

A

Avalanches

Outburst floods

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2
Q

What two resources do mountain glaciers provide?

A

Water

Minerals

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3
Q

What do glaciers show the impacts of?

A

Increasing air temperatures

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4
Q

How is ice formed?

A

Snow compacts to form ice

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5
Q

Why does snow compact?

A

Due to the weight of humans or the snow itself

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6
Q

In which direction does the ice in a glacier move?

A

It moves from the accumulation zone to the ablation zone

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7
Q

What happens when ice reaches the ablation area?

A

It melts

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8
Q

What can break off glaciers?

A

Icebergs

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9
Q

What are two ways in which mass balance can be measured?

A

By direct measurement or remote sensing

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10
Q

What are two forms of direct mass balance measurement?

A

Ablation stakes

Snow pits

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11
Q

How do ablation stakes work?

A

Drill into the ice and insert a pipe, overtime the ice will melt and the pipe will become more and more visible

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12
Q

What is an issue with ablation stakes?

A

They are time consuming

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13
Q

How do snow pits work?

A

Drill into the glacier with a chainsaw and see layers that show accumulation

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14
Q

What are the issues with direct measures of mass balance? (3)

A

It is difficult to scale up and there are variations in records.
In addition proximity to humans and accessibility is an issue

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15
Q

Why are there variations in records for direct measurement techniques?

A

Due to money

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16
Q

What is remote sensing?

A

This means finding out information about something without touching it

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17
Q

Why is remote sensing good?

A

Can cover large areas

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18
Q

What is an issue with remote sensing?

A

Compromises in terms of detail

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19
Q

What are 3 remote sensing methods?

A

Gravitimetry
Elevation change
SMB/D

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20
Q

How does gravitimetry work?

A

Look for changes in gravity

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21
Q

How does gravitimetry work?

A

If the density is known, the volume can be caluclated

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22
Q

How does elevation change work?

A

Use lasers to repeatedly enter the ice surface to get surface elevation changes?

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23
Q

What is SMB?

A

Surface mass balance

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24
Q

How does SMB work?

A

How much put in compared to how much out from models and compare to how much ice is coming out from outlet glaciers

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25
Q

For what size of glaciers is remote sensing best?

A

Large ones

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26
Q

What is SfM?

A

Structure from motion

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27
Q

What does SfM do?

A

Take photos and piece them together to make a model of the surface

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28
Q

Why is SfM useful?

A

Can get detailed info without having to be on the glacier itself

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29
Q

Why are tropical glaciers found in tropical areas?

A

Relics from past colder climates

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30
Q

Where is the vast majority of tropical glaciers?

A

The Andes but also high elevations in Indonesia and some (very little in Africa)

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31
Q

What will happen to tropical glaciers?

A

They will shrink and disappear

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32
Q

What percentage of the tropical glaciers have shrunk since 1970s?

A

Up to 50% of their surface area has gone since the 1970s

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33
Q

What is precipitation like in the inner tropics?

A

Similar precipitation all year round

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34
Q

What is precipitation like in the outer tropics?

A

Dry season May to September

Wet season is October to March

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35
Q

What type of weather is good for glaciers and why?

A

Wet snowy years

Albedo- more reflective

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36
Q

Why are glaciers in the outer tropics important?

A

Demand for water is needed all year round so glaciers act as a baseline throughout the wet and dry seasons

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37
Q

What is the mass balance of tropical glaciers due to?

A

Temperature and precipitation

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38
Q

When does snow and rain fall onto the tropical glaciers?

A

In the summer

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39
Q

When does melt occur on tropical glaciers?

A

In the summer

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40
Q

Give a location where debris covered glaciers are present

A

Himalayas

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41
Q

Where are the rock debris on debris covered glaciers from?

A

Surrounding hillslopes

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42
Q

What is an added danger as a result of debris on glaciers?

A

Avalanches and landslides

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43
Q

What features of the debris can have an effect on melting

A

Colour and packing

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44
Q

What does thick debris do to the ice?

A

Thick debris insulates the ice and reduces melt

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45
Q

What is the critical thickness?

A

This is the balance between thick and thin debris

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46
Q

What does a thin layer of debris do to the melt rate?

A

It increases it

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47
Q

Where on a glacier is melt highest?

A

Melt is highest at lower elevations

48
Q

Where on a glacier is melt lowest?

A

At higher elevations because it is colder

49
Q

What causes an inverted mass balance?

A

Melt being higher at lower elevations and lower at higher elevations

50
Q

In what sort of areas are debris covered glaciers located that could cause risks?

A

They are at the top of catchments for highly populated areas

51
Q

What is a feature of debris covered glaciers?

A

Ponds form on the glacier surface as water collects at the front of the glacier bordered by the moraines

52
Q

What is are two issues with ponds on the glaciers?

A

They are dark and therefore increase the melt rate

Lakes can easily burst leading to catastrophic effects

53
Q

Can sea ice contribute to sea level rise?

A

No

54
Q

What is UAV?

A

Unmanned Aerial Vehicle

55
Q

What do UAV surveys do?

A

Map the surface

56
Q

What do ground penetrating radars do?

A

They go down through the ice to measure the thickness

57
Q

Why is it important to know ice thickness?

A

To know how long the glacier will last

58
Q

What are ice cliffs?

A

Areas of ice with string melting

59
Q

What do moraines show?

A

Previous extent of the glacier

60
Q

What are moraines made of?

A

Unconsolidated, weak sediment

61
Q

How do glacier lakes burst?

A

Through moraines

62
Q

When do glaciers flow?

A

On longer time scales

63
Q

In which direction do glaciers flow?

A

Downhill

From the accumulation zone to the ablation zone

64
Q

Why do glacial crevasses form?

A

When the ice flows too quickly and fractures

65
Q

Where is the fastest ice flow?

A

In the middle

66
Q

Why does the ice at the edges and the bottom flow smaller?

A

Friction

67
Q

What is the velocity at the top of the glacier?

A

0

68
Q

In which direction does the ice in the glacier flow?

A

Top to bottom

69
Q

What are 3 methods of ice flow?

A

Internal deformation
Basal sliding
Deformation of sediment under the glacier

70
Q

In what type of glacier does internal deformation occur?

A

All glaciers

71
Q

What is internal deformation?

A

Ice deforming under its own weight

72
Q

How does internal deformation occur?

A

Ice moves along boundaries of grains and recrystalises

73
Q

What factors affect the rate of deformation? (5)

A

Slope
Thickness
Temperature
Water content and crystal properties

74
Q

What does basal shear stress do?

A

It drives glacier flow

75
Q

What is basal shear stress caused by?

A

Density of ice and gravitational acceleration which are constant
Ice thickness
Ice surface slope

76
Q

What effect does ice thickness have on the movement of the glacier?

A

Thicker ice = faster movement- faster deformation

77
Q

What effect does ice surface slope have on glacier movement?

A

Steeper slope = faster movement - faster deformation

78
Q

What is ice thickness?

A

How much ice there is

79
Q

What does Glen’s flow law give?

A

The amount of deformation for a given amount of stress

80
Q

What is deformation also known as?

A

Creep

81
Q

How easily does warm ice deform?

A

Ice deforms easily when warm

82
Q

What type of glaciers are polar glaciers?

A

Cold- based

83
Q

What type of glaciers are temperate glaciers?

A

Warm- based

84
Q

What is PMP?

A

Pressure Melt Point

85
Q

What is the melt point dependent on?

A

Pressure

Temperature

86
Q

Why can liquid water be present at colder temperatures?

A

Because of pressure

87
Q

What is meant by cold-based glaciers?

A

They don’t reach PMP

88
Q

What is meant by warm-based glaciers?

A

They reach PMP

89
Q

In which type of glacier does basal sliding and sediment deformation occur?

A

Warm-based glaciers

90
Q

What are 6 factors that affect the PMP?

A 
Ice thickness
Accumulation rate
Ice surface temperature
Meltwater
Geothermal heat
Friction
91
Q

What are polythermal glaciers?

A

They have some warm ice and some cold ice so some parts are at the PMP but others aren’t

92
Q

In what two ways can basal sliding occur?

A

Enhanced basal creep

Regelation

93
Q

What is enhanced basal creep?

A

Ice hits an obstacle which increases the stress, causing the ice to deform more quickly around the obstacle

94
Q

What is regelation?

A

This involves transfer of heat

Ice heats an obstacle, causing it to melt. Once the obstacle has been overcome, the ice refreezes again

95
Q

What is sediment deformation?

A

Material at the bottom of glaciers is weak, watery and unconsolidated which allows the glacier to slide along on top

96
Q

What is glacial hydrology?

A

This is the movement of water through the glacier

97
Q

What is supraglacial water movement?

A

On top of the glacier e.g.streams

98
Q

What is englacial water movement?

A

Within the glacier (through cravasses and moulins)

99
Q

What is subglacial water movement?

A

Beneath the glacier

100
Q

What is proglacial water movement?

A

In front of the glacier

101
Q

What does glacial hydrology apply to?

A

All glaciers

102
Q

What is sheet flow?

A

A thin film of water at the bottom of the glacier

103
Q

What is channelised flow?

A

Channels of water that remove water efficiently by having an aborescent network

104
Q

What are the two types of channelised flow?

A

R channels

N channels

105
Q

Where are R channels?

A

Cut up into the ice

106
Q

Where are the N channels?

A

In the sediment

107
Q

What are linked cavities?

A

These are pockets under the glacier that are linked. Quite inefficient and hard to get the water out

108
Q

What are canals?

A

Networks cut down into the rock or sediment under the glacier

109
Q

Why is glacial hydrology important?

A

It has an effect on the melt rate and glacial flow

110
Q

What does the water interact with, making glacial hydrology important?

A

It interacts with the melt rate

111
Q

What is warmer, the ice or the water?

A

The water

112
Q

For channelised flow, is the effect of the ice or water stronger?

A

The effect of water is stronger which means that more water melts the ice as it is over a small surface area and causes the ice to expand, this leads to a low pressure

113
Q

What happens in linked cavities?

A

Water can’t expand the cavities quickly enough, causing the cavities to raise up and increases the pressure

114
Q

By how much can cavities raise up?

A

Cm to M

115
Q

What effect do linked cavities have on ice flow?

A

Increased speed of ice flow

GEO1020 (16 decks)

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