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GEO1020 > Permafrost and periglacial landscapes > Flashcards

Permafrost and periglacial landscapes Flashcards

1
Q

Define periglacial environment

A

Cold but non-glacial, regardless of proximity to glaciers

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2
Q

Define permafrost

A

Soil or rock that remains at or below zero degrees C for at least two consecutive years

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3
Q

What are the 3 layers of permafrost?

A

Active layer
Permafrost
Talik

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4
Q

What does the active layer of permafrost do?

A

Freezes and melts with the seasons

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5
Q

What is an issue with humans and the active layer of permafrost?

A

Can’t build infrastructure

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6
Q

What is the talik?

A

Thawed area below the permafrost

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7
Q

Why does talik occur?

A

Because of geothermal heat

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8
Q

How deep can permafrost be?

A

Over 1km deep in places

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9
Q

What 4 things can control permafrost characteristics?

A

Geothermal heat
Land cover e.g. trees/ buildings
Mean annual temperature (colder = thicker permafrost)
Ground conductivity

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10
Q

Where can permafrost be found?

A

Polar permafrost

Alpine permafrost

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11
Q

What percentage of the Earth does permafrost cover?

A

20%

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12
Q

Why is permafrost found in polar environments?

A

Due to high latitude

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13
Q

Why is permafrost found in alpine environments?

A

Due to high altitude

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14
Q

What are the 3 types of permafrost?

A

Continuous
Discontinuous
Sporadic

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15
Q

What are the continuous permafrost temperatures?

A

-6 to -8

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16
Q

What is the discontinuous permafrost temperature?

A

-1

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17
Q

How much permafrost should there be in order to be classed as continuous?

A

90-100%

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18
Q

How much permafrost should there be in order for it to be classed as discontinuous?

A

50-90%

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19
Q

How much permafrost should there be in order to class it as sporadic?

A

Less than 50%

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20
Q

What is ground temperature related to?

A

Air temperature

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21
Q

What is the general trend for polar permafrost?

A

Ground temp is linked to permafrost. Colder towards the poles. For areas where this is not the case this could be due to vegetation or geothermal heatflux

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22
Q

What is the general trend for alpine permafrost?

A

Lower elevations have less permafrost in the Northern Hemisphere (less sunlight)

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23
Q

What is another unexpected location for permafrost?

A

Under the ocean

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24
Q

What is GPR?

A

Ground Penetrating Radar

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25
Q

What does GPR look at?

A

At the structure of the subsurface. It reflects off of things on the subsurface e.g. water or layers of rock or soil

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26
Q

What does GPR allow you to see?

A

How deep the permafrost is and where the gaps are

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27
Q

What are 4 engineering challenges?

A

Frost heave
Thawing and subsidence
Saturation
Freezing of buried pipes

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28
Q

How does frost heave work?

A

Water freezes and expands, this causes the building to be lifted up. In the summer, when it melts the building will move down. Here the permafrost will be uneven.

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29
Q

How does thawing and subsidence work?

A

Can cause a big gap, causing the buildings to fall downwards. Likely to be uneven

30
Q

How does saturation work?

A

Melting in summer leads to water, however this is trapped and cannot move. Essentially like building on a lake

31
Q

What is the issue of freezing of buried pipes?

A

Liquid freezes and expands, could cause the pipe to burst

32
Q

What is the passive strategy of permafrost?

A

Minimise disturbance

33
Q

Give an example of a passive strategy?

A

Drill supports for houses into the permafrost

34
Q

Where does the passive strategy work?

A

In areas with thick, continuous permafrost

35
Q

What is the active permafrost strategy?

A

Destroy permafrost- get rid to build on solid ground

36
Q

Where are methods of active strategy effective?

A

In sporadic areas

37
Q

Why are roads ventilated?

A

To make sure they don’t get too hot

38
Q

Why is insulation installed in permafrost?

A

To stop it from getting too hot

39
Q

How long is the Trans-Alaskan pipeline?

A

1285km long

40
Q

What does the Trans-Alaskan pipeline transport?

A

Oil

41
Q

Why can’t the Trans-Alaskan pipeline be put underground?

A

Oil flows best at 70 C which would melt permafrost so they have to put it on stilts

42
Q

How long is the Tibet railway line?

A

1100km long

43
Q

Why is the Tibet railway is important?

A

It is one of the only ways to get across Tibet

44
Q

How is the Tibet railway adapted to permafrost?

A

It is on stilts and is insulated from the permafrost

45
Q

What is freeze thaw?

A

Ground freezes and expands, then refreezes and contracts, this causes rocks to crack

46
Q

What is frost creep?

A

When it freezes it moves upwards at a right angle in the active layer but when it melts it sinks back down due to gravity

47
Q

What is gelifluction?

A

Active layer melts in summer and becomes fluid, as the bit below is frozen, it has to flow downhill

48
Q

What are braided rivers?

A

Lots of different channels that transport material. Very seasonal in terms of meltwater inputs (high in summer, low in winter)

49
Q

Where do ice wedge polygons form?

A

In areas of continuous permafrost

50
Q

What temperature is required for ice wedge polygons to form?

A

-15 C

51
Q

How are ice wedge polygons formed?

A

Water enters a crack in the summer, freezes in the winter and pushes it a part. Continuous process creates a big crack in the landscape

52
Q

What are the 2 types of pingo?

A

Closed system pingos (hydrostatic)

Open system pingos (hydraulic)

53
Q

How are closed system pingos formed?

A

A lake has frozen sediment underneath, when the lake drains the top starts to freeze and expand, pushing up the ground to form lumps

54
Q

How are open system pingos formed?

A

Water drains through the ground and hits an area through which it can’t drain because of the permafrost. Here it freezes and pushes the land up

55
Q

What is a thermokarst?

A

An uneven landscape with hollows filled in of water with patches of thaw and frozen areas

56
Q

What could thermokarsts be important for?

A

Greenhouse gases

57
Q

Why are the impacts of warming bigger in the Arctic?

A

Due to feedbacks with sea ice and albedo

58
Q

What is meant to happen to the air temperature and what other temperature will this affect?

A

There is expected to be major air temperature warming and therefore major ground temperature warming

59
Q

What is likely to happen to the permafrost this century?

A

It is likely that a lot of permafrost will be lost (worst case scenario)

60
Q

What will happen if permafrost is lost in terms of greenhouse gasses?

A

There will be more CO2 and CH4 in the atmosphere

61
Q

What are large parts of the Russian Arctic affected by?

A

Permafrost melt

62
Q

What is an impact of the release of extra greenhouse gases?

A

Economic impacts

63
Q

How could ecosystems change as a result of permafrost loss?

A

Drunken trees
Fires
Insect infestation

64
Q

What is the warming like across the Alps?

A

Consistent and substantial

65
Q

What is an issue with warming in the Alps?

A

Mountain hazards and landscape stability

66
Q

What is the issue with landslides?

A

They are difficult to predict

67
Q

What is released as a result of permafrost thaw?

A

Hydrates

68
Q

Why are hydrates released?

A

Through gradual thaw of the permafrost- soil under lake can be thawed very quickly

69
Q

What is the issue with climate change?

A

Can have rapid and unpredictable events

70
Q

What happens to the active layer as a result of increased air temperatures?

A

It thickens

GEO1020 (16 decks)

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