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GEO1020 > Glaciated landscapes and glaciers of the past > Flashcards

Glaciated landscapes and glaciers of the past Flashcards

1
Q

What are past ice masses due to?

A

Sea level rise

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2
Q

What was sea level like 16,000 years ago?

A

120 m lower than it is today

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3
Q

What can past measures be used to do?

A

Predict future levels- speed and extent of sea level rise

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4
Q

What type of response is not ideal?

A

A non-linear response

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5
Q

What can ice masses that are no longer here give information about?

A

See how quickly they disappear and if there is evidence of non-linear behaviour which can be applied to Greenland and Antarctica as there were ice sheets over Europe and America in the past

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6
Q

Why is it important that we have knowledge of past glaciers in terms of their glacier bed?

A

To see its flow and how they impact on the landscape

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7
Q

What are the 3 types of Milankovitch cycles?

A

Eccentricity
Obliquity
Precession

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8
Q

How long do glacials last?

A

90,000 years

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9
Q

How long do interglacials last?

A

10,000 years

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10
Q

How long does eccentricity last?

A

100,000 years

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11
Q

What is eccentricity?

A

How elpitical the earth’s orbit is

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12
Q

What is obliquity?

A

The tilt of the Earth’s axis

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13
Q

How long are obliquity cycles?

A

41,000 years

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14
Q

What is precession?

A

The wobble of the Earth on its axis

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15
Q

How long do precession cycles last?

A

27,000 years

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16
Q

What do the Milankovitch cycles affect?

A

How much radiation the Earth receives

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17
Q

Which Milankovitch cycle affects interglacial cycles?

A

Eccentricity

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18
Q

Which Milankovitch cycle is the weakest?

A

Eccentricity

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19
Q

When did these Milankovitch cycles take place?

A

During the quaternary

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20
Q

How many cycles have there been in the quaternary?

A

21 glacial-interglacial cycles

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21
Q

What is at the end of the quaternary?

A

The holocene

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22
Q

What is the holocene?

A

The current interglacial

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23
Q

How long has the holocene lasted so far?

A

12,000 years so its a bit long

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24
Q

When was the last glacial period?

A

100-12 ka

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25
Q

What was the last glacial called?

A

Weichselian

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26
Q

When was the last glacial maximum?

A

26-18 ka

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27
Q

What was the ice like in the last glacial period?

A

It was much more extensive covering N America, N Europe

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28
Q

Where was the Laurentide ice sheet?

A

Over N America and Canada

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29
Q

Where was one of the big ice streams on the Laurentide?

A

Hudson Bay

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30
Q

What did the Hudson Bay ice stream do?

A

Discharge icebergs into the North Atlantic every 7000 years

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31
Q

What does IRD stand for?

A

Ice-rafted debris

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32
Q

How was IRD found?

A

Through ice cores

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33
Q

What is IRD?

A

Debris that are too big to be carried by ocean currents and are instead transported by icebergs. This gets deposited when the iceberg melts

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34
Q

How many layers of IRD have been found?

A

About 6

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35
Q

What are these events of iceberg discharge called?

A

Heinrich events

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36
Q

What is the periodicity of Heinrich events?

A

7.2 ka

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37
Q

What is surprising about these Heinrich events at the Laurentide ice sheet?

A

They occurred during relatively cold periods

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38
Q

What is the binge phase?

A

This is where as much ice is accumulated as possible

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39
Q

What are stadials?

A

Short periods of cold

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40
Q

What are interstadials?

A

Short warm events

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41
Q

During what period (interstadial or stadial) did Heinrich events occur?

A

Stadial

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42
Q

What is the purge phase?

A

Loss of ice

Sediment thaws resulting in rapid movement and therefore iceberg lost

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43
Q

What happens if there is lots of thick ice?

A

The base of the ice melts

44
Q

How much water did Hudson Bay release over 250 years?

A

2.3 million km3

45
Q

What is the binge-purge theory?

A

Binging phase causes ice to build up
Ice underneath melts
Causes a purge

46
Q

What is another theory about Hudson Bay Heinrich events?

A

Global cooling

47
Q

Explain the global cooling theory

A

Ice accumulated as a result of global cooling.

As it grew, icebergs had to remove some ice

48
Q

What are two issues with the global cooling theory?

A

Never explains why the cooling happened

No explanation of time frame

49
Q

What is the external forcing and isostatic uplift theory?

A

The Laurentide advanced in cooling periods, then ocean warming flooded in and caused iceberg discharge, now there is less ice so the pressure underneath is not as much, causing the ice to move up and cut off the warm water supply

50
Q

What is the evidence for external forcing and isostatic uplift theory?

A

From one ice core, far away from the site

Reliability?

51
Q

What have Heinrich events shown?

A

The non-linear response to climate

52
Q

What was the name of the last interglacial?

A

Eemian

53
Q

When was the last interglacial?

A

115,000-130,000 BP

54
Q

What was the mean temp. of Eemian?

A

Mean temps 1 degrees C warmer

1.5 in certain places

55
Q

Was the Greenland ice sheet bigger or smaller in the last interglacial?

A

It was smaller

56
Q

What was the sea level like in the last interglacial?

A

5-7m higher

57
Q

What was the CO2 concentration like in the last interglacial?

A

Much lower

58
Q

What was found under Trafalgar Square?

A

Animal remains from animals you would expect to see in Africa- must have been warmer in the past

59
Q

What are glacial landforms created by?

A

Glacial deposition or glacial erosion

60
Q

What are two forms of glacial erosion?

A

Abrasion

Plucking

61
Q

What is abrasion?

A

Glacier has rock stuck in the bottom and scrape out the landscape

62
Q

What is plucking related to?

A

Basal sliding

63
Q

What is plucking?

A

Ice under high pressure melts, water flows round the rock and refreezes onto the top of the rock but as it is still moving downhill it rips the rock away

64
Q

Where can glaciers move material?

A

Over the top at the surface
Through the bottom on the bed
Within the glacier

65
Q

Where is most glacial deposition seen?

A

At the margins of the glacier

66
Q

What do the characteristics of the deposited material depend upon?

A

Source e.g the atmosphere/ glacier bed
Route e.g supraglacially
Where it is deposited

67
Q

Is supraglacially moved material severely modified?

A

No, it is barely modified

68
Q

What happens to subglacial material?

A

It becomes very modified

69
Q

What do glaciers deposit?

A

Till

Diamtic

70
Q

What is till?

A

A generic name

71
Q

What is diamtic

A

Material that is definitely known to be from a glacier

72
Q

What are the characteristics of till?

A

Heterogeneous grain size
Large clasts, silt and clay matrix
Unsorted pebbly mud

73
Q

What is a terminal moraine?

A

A moraine that marks the extent of the glacier

74
Q

What information do moraines give?

A

Ice extent in the past

Retreat pattern of glaciers that exist- can tell the speed of retreat and other info

75
Q

What are lateral moraines?

A

Moraines at the side of glaicers

76
Q

What do lateral moraines tell us?

A

The area and height of the glacier

77
Q

What do drumlins have?

A

A steep front and long tail at the end

78
Q

Which side of the drumlin is upstream?

A

The steep side

79
Q

What do drumlins show?

A

The flow characteristics

80
Q

What are fast flow features important for?

A

The stability of the glacier

81
Q

What are mega scale glacier lineations?

A

They are essentially bigger versions of drumlins

82
Q

How do we know that drumlins and mega scale glacier lineations give information about glaciers?

A

They are found at areas of recent glaciation

83
Q

What do eskers relate to?

A

Subglacial hydrology

84
Q

What are eskers?

A

Casts of subglacial channels

85
Q

What is needed for eskers to form?

A

Lots of water

86
Q

What are eskers an indication of?

A

An ice margin that was retreating rapidly

87
Q

What are P forms?

A

Erosional froms of eskers

88
Q

How are P forms formed?

A

They are scraped out of the rock by water under high pressure which erodes the rock

89
Q

What scale are U shaped valleys?

A

Landscape scale

90
Q

What is the theory of Gamburtsev Mountains, why haven’t they changed?

A

They are seen as the birth place of East Antarctica. Theory is that the ice grew really quickly and encased the mountains

91
Q

What happened to the English-Irish ice sheet at the start of the interglacial?

A

It retreated very quickly

92
Q

What is the bedrock responsible for?

A

Difference in the bedrock topography caused a difference in the response of the glacier to climate change.
The bedrock topography is to do with the history of the glaciers

93
Q

How are ice cores sampled?

A

Drill into the centre of the ice sheet to avoid deformation of the ice core

94
Q

What do the layers show in ice cores?

A

Accumulation, then melt then accumulation the next year to give layers over each year

95
Q

What can be used to date ice cores?

A

Tephrachronology

96
Q

What is special about tephra?

A

It has a unique fingerprint

97
Q

What happens to the annual layer thickness as the depth of the ice core increases?

A

As the depth gets deeper, annual layer thickness decreases

98
Q

What are the records like for Greenland?

A

Shorter time scale but higher resolution

99
Q

What are the records like for Antarctica?

A

Longer time scale but smaller resolution

100
Q

How deep can the ice cores be collected in Greenland?

A

3000m

101
Q

How many years ago can we get ice cores in Greenland for?

A

123,000 years ago

102
Q

How deep can the ice cores be collected in Antarctica?

A

3000m

103
Q

How many years ago can we get ice cores in Antarctica for?

A

800,000 years

104
Q

What is a key thing that ice cores can tell us?

A

Atmosphere at that time (gaps between the snow trap the atmosphere in bubbles)

105
Q

What do ice cores allow comparison of?

A

Atmosphere and ice volume which can be linked

106
Q

What can ice cores show changes of?

A

Pollution and ice flow

107
Q

Why does a cage need to be put up?

A

In case of electrical storm

GEO1020 (16 decks)

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