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Geography - Glaciers > Unit 5 > Flashcards

Unit 5 Flashcards

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1
Q

What is meant by the term periglacial?

A

describes a landscape that undergoes seasonal freezing and thawing, typically on the fringes (PERImeter) of past and present glaciated regions

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2
Q

What type of soil are periglacial areas usually found in?

A

these areas often contain permafrost (ground that has been frozen for 2 consecutive years)

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3
Q

What % of the Earth’s landscape contains permafrost?

A

25% of exposed land surface in the northern hemisphere e.g. Russia and Greenland

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4
Q

What is the mean annual ground surface temp needed for permafrost to occur?

A

(-4 to -6 degrees)

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5
Q

How deep can permafrost be?

A

1500m

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6
Q

What is the active layer?

A

this is a thin layer of soil, which thaws in summer and refreezes in winter
(30 to 200cm)

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7
Q

What are the problems caused by permafrost?

A

flooding, destroy habitats, houses subsiding infrastructure ruined

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8
Q

What are the potential opportunities in areas with permafrost?

A

freshwater supplies
agriculture can arise

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9
Q

What are some of the factors that could explain variations in permafrost globally?

A
  • temp
  • altitude and latitude
  • precipitation
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10
Q

What is meant by continuous permafrost?

A

forms in the coldest areas of the world where avg. annual temps are below -6 degrees, and can extend down hundreds of meters

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11
Q

What is meant by sporadic permafrost?

A

occurs at the margins of periglacial environments and is highly fragmented and only a few meters thick

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12
Q

What is meant by discontinuous permafrost?

A

same as continuous, the only difference is that it is more fragmented and often thinner

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13
Q

What is meant by Talik?

A

unfrozen ground between permafrost

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14
Q

What are the three types of ground ice?

A
  • pore ice
  • needle ice
  • ice lenses
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15
Q

How does pore ice develop?

A

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

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16
Q

How does needle ice develop?

A

consists of narrow ice slivers that are up to several cm long, they normally form in moist soils when temps drop below freezing overnight

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17
Q

How do ice lenses develop?

A

are bodies of ice formed when moisture, mixed within soil and rock, accumulates in the localised zone

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18
Q

What are ice wedge polygons?

A

are downward narrowing lens of ice that can grow up to 3m wide at the surface and extend beneath the ground surface up to10m

(lens of ground ice can lead to the formation of ice wedge polygons)

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19
Q

What happens in the first winter where ice wedged polygons begin to form?

A
  • ground temp is = -10 degrees or below
  • ground splits to form cracks
  • as the ground temp falls below -20 degrees, the soil contracts and enlarges
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20
Q

What happens in the first summer where ice wedged polygons begin to form?

A
  • in the summer the ice melts, liquid from the active layer fills the crack, more water fills the crack, water refreezes as winter hits
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21
Q

What happens in the second winter of when ice wedged polygons being to form?

A

-cryostatic pressure causes the water to expand by 9%, this causes the cracks in the ground to expand, pushing the soil upwards and creating a bulge

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22
Q

What happens to ice wedged polygons after several winters of the previous processes?

A
  • new cracks form, older cracks enlarge as liquid water refreezes
  • each summer, more and more water seeps into the cracks, meters in depth
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23
Q

What is meant by patterned ground and how does this form?

A
  • the surface of periglacial areas is categorised by the presence of stone arranged in symmetrical and geometric shapes
  • these features are collectively known as patterned ground
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24
Q

What is meant by frost heave?

A

the upward dislocation of soil and rocks by the freezing and expansion of soil water

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25
What is the process of frost heave and how does it work?
1. freezing progresses down from the surface accompanied by the upward expansion, lifting stone by first freezing onto the upper surface 2. freezing front progresses down the space created below stone, as it is lifted 3. ice crystals grow into space and push up stone 4. thawing progresses down from surface, contraction and lowering of surface level, but stone is still supported by ice crystals 5. thawed sediment collapses around stone, supporting it 6. stone held in thawed sediment while ice crystals melt and space is filled with thawed sediment
26
What is an example of patterned ground?
Stone Sorted Polygons
27
What is the first stage in stone sorted polygons formation?
- stones are pushed towards the surface, through frost heave - the ground begins to dome due to expansion form growing ice beneath the stones
28
What is the second stage in stone sorted polygons formation?
- stones begin to slip, slide and roll to the base of the dome, starting to form patterns - the repeated process of frost heave eventually allows stones to appear on the surface
29
What is the third stage in stone sorted polygons formation?
- the type of patterned around depends on the gradient of the ground surface - steeper gradients cause stone stripes to form, whereas more gradual or flatter gradients will form = stone sorted polygons
30
What is a pingo?
they are circular ice-cored hills, that have an ice lens at the core of pingos, which is thought to develop due to 2 reasons.
31
What are the 2 reasons as to why ice cores develop in a pingo?
-> artesian groundwater flow (open system) -> cryostatic pressure (closed system)
32
How does an open system pingo form? (beginning phase in the summer)
(draw the diagram) - groundwater moves up through talik - this groundwater is then confined below the impermeable permafrost, rises into the crack due to artesian pressure - as the water rises through the permafrost, it begins to cool and in some cases, freeze - if the ground water reaches the active layer in summer, it can form a spring
33
How does an open system pingo form? (in the winter, with the ice lens)
- during the winter months, where there are prolonged periods of cold temperatures, the rising groundwater will freeze before reaching the surface to form an ice lens - as more groundwater continues to rise from below permafrost, it feeds the ice lens causing it to grow - as the ice lens grows it displaces the overlying sediment forming a dome shaped ice core hill = open system pingo
34
What is meant by Talik?
a layer of year round unfrozen ground found in permafrost regions, with unfrozen sediment found in it
35
How does a closed system pingo form? (in the summer)
- in the summer of periglacial environments, lakes will form within the active layer, as winter approaches the lake will freeze top down - the unfrozen lake water and lake sediment beneath the ice acts as an insulator for the underlying ground - this prevents the ground from freezing and results in talik
36
How does a closed system pingo form? (in the winter)
- the permafrost will advance and encroach on the overlying talik, consequently liquid water contained within the talik will freeze, forming an ice lens - as the ice lens grows it will exert cryostatic pressure and rise upwards displacing the overlying lake
37
What is meant by artesian pressure?
the water rises, without the need to pump, because it is under a lot of pressure (is forced out)
38
What is meant by cryostatic pressure?
pressure exerted on rocks and soil when freezing occurs
39
What is a thermokarst landscape?
is a land surface, which is characterised by irregular surfaces of marshy hollows and depressions formed, as permafrost thaws due to warming climate
40
What is meant by solifluction and in what type of landscape does it occur?
occurs in thermokarst landscape solifluction = saturated soil that flows under the force of gravity
41
How do pingos collapse?
- an increase in temperature, causes the surface of ground to thaw - solifluction occurs and cracks will form in the sediment covering the ice dome - this allows the ice lens to begin warming and thawing, causing the dome to collapse in on itself - as the ice lens continues to thaw, the meltwater will form a lake within the crater as the impermeable permafrost layer hold the water in place
42
What is the case study for a thermokarst landscape?
Batagay crater in Russia
43
What proportion of Russia is covered in permafrost? What are the problems causes by melting permafrost?
over half - Collapsed hospitals, destabilising infrastructure - positive feedback cycles, as permafrost melts, methane is released
44
What are the 6 types of frost shattering landforms?
- Nirvation Hollow - Blockfields - Scree Slopes - Protalus Ramparts - Solifluction Lobes - Frost Creep and Terracettes
45
How do nirvation hollows form?
- forms on a north facing slope = they receive little to no insolation - frost shattering provides a supply of loose material - firn forms, this snow then remains in hollow all year, enlarged by nirvation - rock debris removed by meltwater stream or by solifluction in summer
46
How do blockfields form?
a surface covered by large, angular rocks product of freeze thaw weathering on flat surfaces
47
What is an example of a blockfield?
Snowdonia, on the Glyder Plataeu around the pyramidal peak at Glyder Fawr
48
What is a scree slope?
an accumulation of freeze thaw weathered rock fragments at the base of a cliff
49
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52
How do scree slopes form?
(draw the diagram) - before freeze thaw weathering occurs. slopes will have a steep gradient - freeze thaw weathering occurs as temps fluctuate around 0 degrees - this weathered material falls to the bottom of the slope through mass movement - overtime the debris that is creates, accumulates at the bottom of the slope, which reduces the slope angle
53
What is a protalus rampart, and how does it differentiate from scree slopes?
(draw a diagram) - a ramp shaped mound of scree that forms in a similar way to a scree slope - it differs in formation from a scree slope as it involves ice and snow being present on a valley slope
54
How does a protalus rampart form?
- freeze thaw weathering occurs at temperatures that fluctuate around 0 degrees - forms the same way as a scree slope - HOWEVER, the mound will be much more pronounced towards the base of the slope, material is deposited further up the slope = protalus rampart - when the ice melts this accumulation of scree is left, forming this distinct feature
55
What is meant by mass movement?
downslope movement of weathered material under the influence of gravity
56
What are solifluction lobes?
when the surface becomes waterlogged and active - solifluction = saturation of soil that flows under the influence of gravity - typically a slow movement (rarely exceed 10cm per year)
57
Where are solifluction lobes most likely to occur?
under periglacial conditions where vegetation is limited
58
How are solifluction lobes formed?
in winter = frozen ground in summer = the surface layer thaws whilst the underlying layer remains frozen and impermeable - the surface layer becomes active and waterlogged as a result - this thawed layer moves downslope slowly over the frozen ground - (solifluction sheets and lobes can be formed) - as material moves downhill the slope angle is reduced with the material from higher elevations flowing down and being redeposited closer to the slope base
59
What are frost creeps and Terracettes?
when mass movement occurs in periglacial environments, due to repeat freezing and thawing of the active layer + process called soil creep
60
What is meant by soil creep?
over a large area the frost heaving process (expansion of the soil), produces features known as terracettes
61
How do frost creep and terracttes form?
1. Active layer thaws 2. Active layer freezes = it expands outwards (frost heaving) parallel to the surface 3. Active layer thaws again = soil particles drop vertically downwards, resulting in downward movement of particles
62
Where can examples of periglacial landforms be found
Nant Ffrancon Valley in Snowdonia (Unit 4b)
63
What happens in periglacial environments in terms of the action of water?
freezing and thawing of the active layer - permafrost ground beneath the thawed surface remains frozen, where there is very little or no infiltration or percolation ground = impermeable
64
Where do dry valleys usually develop?
in regions of permeable rock, such as chalk and limestone, which would usually allow water to infiltrate and percolate into the ground
65
How do dry valleys form?
- they show evidence that the periglacial landscape was previously influenced by flowing water - due to the permafrost being impermeable, this prevents percolation, leading meltwater to pool and run over the ground surface - as the ice masses retreat, and warmer conditions develop, high levels of river runoff occur eroding and deepening the valley - once the conditions are warmer, the permafrost will melt = more infiltration and percolation reducing runoff = dry valley
66
What is meant by Loess deposits?
is fine rock debris (sand, silt and clay) transported and deposited by glacial winds - derived from glacial abrasion and transported by meltwater rivers during summer to the sandurs
67
What are glacial winds known as?
Katabatic winds
68
How do Loess deposits, actually work?
1. the cold dense Katabatic winds pass over the glacier ice sheet 2. pass over the sandur containing fine rock of silt and clay 3. they are then transported and deposited by wind = a process called deflation
69
What do deflation winds cause? What type of landscape?
winds will pick up and transport the loess many miles eventually depositing it as thick sediment, creating a flat plateau landscape
70
Where in the world can loess deposits be found?
Present day Ukraine, where there are good quality agricultural soils

Geography - Glaciers (8 decks)

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