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Glaciated Landscapes > Unit 5 Notes > Flashcards

Unit 5 Notes Flashcards

1
Q

What % of the earth’s landscape contains permafrost?

A

25%.

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2
Q

How deep can permafrost go?

A

Up to 1.5km deep.

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3
Q

What parts of the world is permafrost found in?

A

High-altitude, and high-latitude areas.

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4
Q

Which factors affect the variation in permafrost globally?

A

Gulf stream, North atlantic drift, volcanic activity.

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5
Q

What is sporadic permafrost?

A

Occurs at the margins of periglacial environments, is highly fragmented, only a few metres thick.

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6
Q

What is discontinuous permafrost?

A

More fragmented, thinner permafrost, forming in colder areas.

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7
Q

What is continuous permafrost?

A

Forms in the coldest areas of the world, average annual temperatures are below 6 degrees, extend down hundreds of metres.

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8
Q

Why does the melting of permafrost lead to a negative feedback loop?

A

As permafrost contains methane, there is dead organic matter found within it, meaning that as ice thaws, the gas will escape. Methane causes more warming, leading to more permafrost being defrosted.

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9
Q

What are the ground ice landforms?

A

Pore ice, needle ice, ice lenses.

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10
Q

What is pore ice?

A

Develops in pore spaces between soil/sediment particles where liquid and water can accumulate and freeze.

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11
Q

What is needle ice?

A

Consists of narrow ice slivers, up to several centimetres long, forming in moist soil

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12
Q

What is an ice lense?

A

Bodies of ice formed when moisture, mixed within soil or rock, accumulates in a localised zone.

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13
Q

What is the first step in ice wedge formation?

A

As seasons change, a crack forms in the ground, and as temperature falls to around -20 degrees, soil contracts and enlarges.

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14
Q

What is the second step in ice wedge formation?

A

In summer, ice melts and liquid from the active layer fills the crack, and water refreezes when winter hits.

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15
Q

What is the third step in ice wedge formation?

A

Cryostatic pressure causes water to expand by 9%, when freezing, causing cracks to expand, pushing soil upwards, creating a bulge.

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16
Q

What do temperatures have to be for an ice wedge to form?

A

-10 degrees, but preferably -20.

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17
Q

How do stones move to the surface in periglacial environments?

A

Frost heave.

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18
Q

What are the first 2 steps in frost heave?

A

Freezing progresses down from surface, accompanied by upward expansion, lifting the stone by freezing onto the upper surface. Freezing front progresses down space created below stone, as it is lifted.

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19
Q

What are the third and fourth steps in frost heave?

A

Ice crystals grow into the space, pushing up the stone. Thawing progresses down from the surface, contraction and lowering of surface level, but the stone is still supported by ice crystals.

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20
Q

What are the last two steps in frost heave?

A

Thawed sediment collapses around the stone, supporting it. Stone held in thawed sediment, while ice crystals melt, and space is filled by collapsing sediment.

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21
Q

What is the first step in formation of a stone sorted polygon?

A

Ground freezes from the surface downwards, stones cool down faster than surrounding soil, Moisture around stones freezes and expands by 9%, Stones are raised due to Cryostatic pressure.

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22
Q

What is the second step in stone sorted polygon formation?

A

Stones are raised high enough to break through ground surface, frost heave results in doming of overlying ground, Forms a mound because of increased volume, wet slumps into the gap below the stone, preventing it from going back to its original place.

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23
Q

What is the final step in stone sorted polygon formation?

A

Rocks accumulate at edge, stones slip or roll onto the base, rocks form patterns, steeper gradients cause striped patterns, gradual gradients cause stone polygons.

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24
Q

What is the first step in open system pingo formation?

A

Liquid groundwater is confined below impermeable permafrost, if it finds a weakness in overlying permafrost, it will rise into the crack, due to artesian pressure.

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25
Q

What is the second step in open system pingo formation?

A

As the water rises through the permafrost, it begins to cool, and in some cases, freeze. If rising water reaches active layer in summer, it may form a spring.

26
Q

What is the third step in open system pingo formation?

A

During winter, or prolonged periods of time with cold temperatures, rising water will freeze before reaching the surface, forming an ice lense.

27
Q

What is the fourth step in open system pingo formation?

A

As more ground water continues to rise from below the permafrost, it feeds the ice lens, causing it to grow. Ice lense displaces overlying sediment, forming domed ice.

28
Q

What is the first step in closed system pingo formation?

A

In cold periglacial environments, frost dominates in summer months, lakes form within the active layer. As winter approaches, it begins to freeze from the top down.

29
Q

What is the second step in closed system pingo formation?

A

Unfrozen lake water and lake sediment beneath ice acts as an insulator for underlying ground, preventing the ground from freezing, resulting in talik.

30
Q

What is the third step in closed system pingo formation?

A

During prolonged periods of cold, permafrost will advance and encroach on overlying talik, Liquid water contained in talik freezes, forming an ice lense.

31
Q

What is the fourth step in closed system pingo formation?

A

As this ice lense grows, it exterts cryostatic pressure, rising upwards, displacing overlying lake sediment that used to be at the bottom, now lowers. Raised ice core will be formed.

32
Q

What is Thermokast?

A

A land surface characterised by irregular surfaces of marshy hollows and depressions formed as permafrost thaws due to a warming climate.

33
Q

What are the first two steps of pingo collapse?

A

Warming climate, solifluction in active layer. Solifluction continues, reducs size of ice lens.

34
Q

What are the final two steps of pingo collapse?

A

Most of ice lens has melted, slumping of active layer. Lake where ice lens used to be, lake can’t drain away, as permafrost is impermeable.

35
Q

What is an example of a thermokarst?

A

Russia - Batagay Crater. Over half of Russia has permafrost, which causes buildings to sink into the ground.

36
Q

What are the causes of the Batagay crater?

A

Longer, hotter summers, permafrost thawing.

37
Q

Why is the melting of permafrost bad?

A

Methane could be released.

38
Q

What is an example of Blockfields?

A

Glyder Plateau.

39
Q

What are the steps of scree slopes forming?

A

Freeze thaw weathering begins to occur, there is nothing to start with, more continues, and freeze thaw occurs. Rocks begin to collect, more freeze thaw occurs, scree slope builds up.

40
Q

Where are solifluction lobes more obvious?

A

It can take place on slopes with a gentle gradient, but is more obvious on slopes of between 10-20 degrees.

41
Q

How fast do solifluction lobes move?

A

Between 0.5-5cm per year.

42
Q

What happens to the active layer during summer?

A

It thaws, and the underlying layer remains frozen, and impermeable. The surface layer becomes waterlogged and active as a result.

43
Q

Why does frost creep occur?

A

Repeated freezing and thawing of active layer, repeated frost heave causes terracettes.

44
Q

What does repeated frost heave do?

A

Active layer expands outwards, parallel to the surface. When active layer thaws, soil particles drop vertically downwards, resulting in down slope movement of particles.

45
Q

Where are the examples of scree slopes, protalus ramparts, and terracettes?

A

The Nant Ffrancon valley.

46
Q

What do brief warm summers lead to in periglacial environments?

A

Thawing of the surface, producing an active layer.

47
Q

What happens to permafrost during this time?

A

It remains frozen, and little infiltration can occur.

48
Q

What is infiltration?

A

Movement of water into ground surface.

49
Q

What is percolation?

A

Downward movement of water through the ground.

50
Q

Why is there no infiltration or percolation in permafrost areas?

A

Permafrost is impermeable.

51
Q

What are the first two steps of dry valley formation?

A

Dry valleys are relict periglacial landforms, showing evidence that the landscape was previously influenced by flowing water. They develop in regions of permeable rock, such as chalk or limestone, allowing water to infiltrate.

52
Q

What are the third and fourth steps of dry valley formation?

A

When permafrost is present, frozen ground prevents percolation, meaning that meltwater pools run over ground surfaces. As ice masses retreat, high levels of river runoff occur, eroding river valleys.

53
Q

What is the final step of dry valley formation?

A

Once warm interglacial conditions have developed, water from the surface infiltrates and percolates, reducing surface runoff.

54
Q

Where are loesses derived from?

A

Glacial Abrasion.

55
Q

What are loesses transported by during spring and summer?

A

Meltwater rivers.

56
Q

What happens to meltwater rivers during autumn and winter?

A

Flow of these rivers is reduced, large parts of the sandur will dry out.

57
Q

What does deflation create?

A

Creates a flat surface plateau landscape. e.g. Ukraine.

58
Q

Which landforms are created by only frost shattering?

A

Blockfields.

59
Q

Which landforms are created only by mass movement?

A

Solifluction lobes, terracettes.

60
Q

Which landforms are created by both mass movement and frost shattering?

A

Nivation Hollows, Scree slopes, protalus ramparts.

61
Q

Which landforms have been created by neither process?

A

Loess, Dry valley, ice wedge, pingos.

Glaciated Landscapes (13 decks)

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