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Geography > Extreme Environments > Flashcards

Extreme Environments Flashcards

1
Q

Whats permafrost?

A

Impermeable permanently frozen ground for at least 2 consecutive years

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2
Q

What’s thermokast?

A

Depressions caused by subsidence due to the melting of permafrost - leads to waterlogged soil

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3
Q

What is thermokast caused by? (4)

A
  • change in vegetation affects albedo affect
  • shifting of stream channels
  • fire which destroys permafrost
  • disruption of vegetation
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4
Q

What are the 3 different types of permafrost?

A
  • continuous (-5/-50)
  • discontinuous (-1.5/-5)
  • sporadic (0/1.5)
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5
Q

What is plucking?

A

Occurs at the base of the glacier

Water seeps into joints of rock, freezes onto the rock and is ripped out by the moving glacier

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6
Q

What is abrasion?

A

Debris carried by glacier scratches sides of rocks leaving striations

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7
Q

What does the rate of erosion depend on?

A
  • local geology
  • the amount of load carried by glacier
  • weight and thickness of glacier
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8
Q

How do Cirques form?

A

1) periglacial hollow is enlarged by freeze-thaw
2) Ice accumulates in the hollow
3) After reaching a certain height, ice moves out in a rotational way which erodes rock around it by abrasion and plucking
4) Cirques keeps enlarging due to freeze-thaw and sometimes forms a lake

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9
Q

How are arretes and pyramidal peaks formed?

A

Due to headward recession (cutting back of 2 or more cirques)

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10
Q

How are hanging valleys formed?

A

Formed by tributary glaciers, which are left suspended over

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11
Q

What is drift?

A

Refers to all fluvioglacial and glacial deposits left after ice has melted

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12
Q

What is till and what are its two types?

A

Till refers to deposit that is angular and unsorted
Lodgement till - from a moving glacier
Ablation till - from a stagnant glacier

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13
Q

What are the characteristics of till? (5)

A
  • poor sorting/stratification
  • mixture of rock type
  • many particles of striations
  • compaction of deposits
  • sub-angular particles
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14
Q

What are erratics?

A

Large boulders that don’t belong with the local geology

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15
Q

What is moraine? What are the 3 types of moraine?

A

Lines of loose rocks, weathered by the valley side and carried by the glacier

  • terminal moraine
  • lateral moraine
  • medial
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16
Q

What is medial moraine?

A

When two glaciers merge and two lateral moraines form in between the enlarged glacier

17
Q

What is froze heave?

A

When water freezes in soil lifting up individual soil particles to the surface

18
Q

What is solifluction?

A

Water freezes rocks and soil under. This melts and flows downhill. It doesn’t infiltrate the soil because of the impermeable permafrost. When it’s deposited it forms solifluction lobe.

19
Q

What is frost creep?

A

Movement of sediments from frost heave, moving downhill due to gravity

20
Q

What is patterned ground?

A

Patterns in ground such as circles, stripes that are found in soil coming from intense frost action

21
Q

What are pingos?

A

Isolated, conical hills only found in periglacial areas formed by freezing water under pressure- expansion of permafrost

22
Q

What are the two types of pingos?

A

Open system pingos

Closed system pingos

23
Q

What is salt crystallisation?

A

Causes the deposition of rocks by solutions of salt

24
Q

What are the two main types of salt growth?

A
  • areas of temp. change, where sodium sulphate expands creating pressure of joints
  • water evaporates and leave salt crystals (salt expands when heated)
25
Q

What is disintegration?

A

Rock heats up during the day and expands, then contracts at night which causes stress in outer layer- exfoliation occurs

26
Q

What do flash floods do?

A

Carry sediments which have large erosive force, flowing through canyons which leads to deposition

27
Q

What is an exotic/ exogenous river?

A

Comes from a wetter environment but flows through a desert

28
Q

What is an endoheic river?

A

Those that drain inland lake or sea

29
Q

What is an ephemeral river?

A

Those that flow seasonally or after storms

30
Q

Dunes shape and size depends on what factors? (4)

A
  • supply of sand
  • direction of wind
  • nature of the ground surface
  • presence of vegetation
31
Q

What is deflation?

A

Progressive removal of small material leaving behind larger materials forming stony deserts

32
Q

What is abrasion (wind)?

A

Erosion carried out by wind-borne particles (acting like sandpaper) Usually within 1 metre of the ground where the largest, heaviest, most erosive particles are carried

Geography (1 decks)

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