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Glaciation Flashcards

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1
Q

4 periglacial landforms

A

Ice wedges
Patterned ground
Pingos
Loess

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2
Q

Ice wedge polygons

A
  • downward narrowing masses of ice between 2-3m wide at base and extend below ground up to 10m
  • formed by refreezing of active layer during winter causing soil to contract and cracks open. During melting in summer cracks fill with meltwater and sediment then freeze the following winter, widening and deepening the crack
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3
Q

Patterned ground

A
  • frost push caused by hydrostatic pressure propels stone upwards, whilst frost heave causes stones to migrate outwards to form circles - this provides basis for all patterns
  • larger stones roll outwards due to gravity, leaving finer sediment in centre
  • relationship between type of patterned ground and slope angle
  • beyond 30 degrees angle, patterned ground can no longer form and rock avalanches may occur
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4
Q

Pingos

A

-ice cored hills
- growth of ice cores forces up overlying sediments, causing dilation cracks, once ice core is exposed it melts which causes top of Pingo to collapse, forming a crater
- smaller Pingos tend to have curved top
- melting of ice often forms crater which are sometimes filled with water =lake

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5
Q

7 macro features (<1km) glacial erosion all landforms

A
  1. Cirque/corrie/cŵn
  2. Arête
  3. Pyramidal peak
  4. Truncated spur
  5. U-shaped valley
  6. Hanging valley
  7. Ribbon lake
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6
Q

4 meso features (10m-1km, usually found in macro features)

Ice sheet scouring features

A
  1. Whalebacks
  2. Crag and tail
  3. Roche moutonneees
  4. Knock an’ Lochan
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7
Q

3 micro features (few metres and less)

A
  1. Chatter marks
  2. Striations
  3. Crescentic gouges
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8
Q

Milankovitch theory

(Long term climate change)

A

Earths orbit varies every 100,000 years. Elliptical to more circular

Means amount of solar radiation in summer and winter changes, impacts seasonal changes

Low eccentricity = low seasonality = glaciation, as a result temps at high latitudes in northern hemisphere decrease

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9
Q

Axil tilt = obliquity

(Long term climate change)

A

Varies between 21.8-24.4 degrees, does this over 41,000yr timescale

Impacts intensity of light received at the poles, so effects seasonality

Less tilt = warmer winters + cooler summers = glaciers don’t melt and advance = more solar radiation reflected so variations in ice volume.

Low obliquity = low seasonality so promotes glacation

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10
Q

Precession - wobble

(Long term climate change)

A

Earth wobbles on it’s axis over 21,000 year cycle, changing when earth is nearest to sun, increasing variation of irradiation of northern hemisphere

This impacts summer and winter temps which impact ice volume.

Glacation favored when direction of tilt means n. Hemisphere summers are at the largest earth-sun distance

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11
Q

Compressional flow

A

Ice mass thickens as slope gradient reduces and movement slows.
Potential for erosion increases

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12
Q

Extensional flow

A

Ice mass thins and movement increases when slope gradient gets steeper.
Erosion potential decreases

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13
Q

Factors controlling glacier movement

A

Lithology
Altitude
Slope angle
Size/thickness
Mass balance
Ice temp

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14
Q

Processes contributing to glacier movement

A

Basal sliding
Internal deformation
Regelation creep
Extensional and compressional flow

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15
Q

Basal sliding

A
  • temp water freezes at decreases under pressure
  • glacier moves and exerts pressure so there’s melting at base
  • meltwater acts as lubricant allowing glacier to move
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16
Q

Regelation creep

A
  • glacier encounters big obstacles
  • this increases pressure on ice and ice melts under pressure due to PMP, so meltwater forms
  • melt water acts as lubricant so glacier can move over and around obstacles
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17
Q

Internal deformation

A
  • most common movement in cold based
  • ice crystals change shape and position due to pressure
  • they move and slide past each other, allowing glacier to slowly move
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18
Q

Corrie

A

Macro

Snow accumulates in nivation hollow. Builds up year after year, snow gets compressed into ice.

Freeze thaw weathering and plucking of back wall steepens and deepens bottom

Ice eventually melts, can create lake

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19
Q

arete, pyramidal peak

A

Arête = 2 corries side by side
Pyramidal peak: 3+ corries erode on mountain

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20
Q

u shaped valley

A

Glacier carves through valley, widening and deepening it

Looks like stream that doesn’t fit the valley

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21
Q

Truncated spur

A

Pre-glacial interlocking spurs of river valley get widened and deepened by glacier.

Abrasion is dominant process and plucking, so sides of valley eroded to remove mountain spurs by cutting them off

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22
Q

Hanging valley

A

Main glacier erodes trough wider and deeper than smaller glacier joinin in.

As it retreats, leaves large trough with hanging valleys along side, can have waterfalls on them

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23
Q

Ribbon lake

A

After deglaciation, water fills hollows in glacial trough, often on impermeable ground

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24
Q

Ice contact Depositional features

A

Medial moraines
Terminal moraines
Lateral moraines
Recessional
Drumlins
Erratics
Till plains

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25
Recessional moraines
Marks position where glacier gradually melted away
26
Terminal moraines
Debris dumped at glacier’s snout, marks maximum position of ice
27
Medial moraines
Produced when 2 valley glaciers meet to form one larger glacier. Their lateral moraines merge and run down middle of larger glacier
28
Lateral moraines
Along edge of valley glaciers where ice meet valley wall
29
Erratics
Rocks transported from source region to area of different geology
30
What show evidence of ice movement direction
Crag and tail ; angle of long axis shows direction of movement, tail points down stream Erratics ; match rock found to source to see where ice came from Drumlins ; stops points upstream, lee points downstream
31
Drumlins
Oval mounds caused by glaciers dropping basal debris load due to friction. Found in clusters
32
Till plains
Where large section of ice detaches from glacier and melts, depositing debris, forms large plain of unsolved till
33
Types of till
Deformation till - weak underlying rock gets defined by glacier sediment Ablation till - deposited by melting ice, carried into ablation zone deposited near snout. Lodgement till - deposited under ice sub glacial debris lodged in bed Flow till -
34
Knock And Lohan
Alternating bands of hard and soft rock
35
Roches Moutonnées
Formed beneath warm-based ice. Abrasion on stoss side and plucking on lee side - ice erode softer rock
36
Crag and tail
Erosion and deposition under ice sheet. Hill (crag) stronger so resists erosion.
37
Whaleback
Glacier passes over, abrasion on stows and lee(steep) sides Beneath thick slow WB glacier w lot mwater
38
Ice Contact Features Fluvio-Glacial Landforms (3 Features)
Kames - Formed as meltwater streams emerge onto outwash plain/proglacial lake at glacier snout. Velocity falls suddenly and deposits Esker- Subglacial streams carry a lot of sediment due to hydrostatic prsssure inside subglacial tunnels. Glacier retreats and deposits at consistent rate, forming ridge KT - Valley sides heat up in summer melting edge of glacier, forming meltwater stream that deposits sediment, when glacier retreats sediment falls to floor
39
4 proglacial features
Outwash plain - flat expanse sediment in front of snout. Mwater emerge from glacier lose energy and deposit Proglacial lake - meltwater trapped against ice sheet/damming action of terminal moraine Meltwater channels - Narrow channel cut into bedrock/deposits along/infront ice margin. High hydrostatic pressure means meltwater can erode deep channels Kettle holes - blocks detached dead ice separated from glacier, buried by sediment then melt and leave hollow fill w water
40
Loess
Glacier erode bedrock - rock flour and mwater streams carry this to end of glacier
41
Plucking
Basal ice freezes in rock surface cracks. Main body of glacier moves and material around the ice in cracks is pulled and plucked out
42
Abrasion
Physical wearing/grinding of surface through friction + impact by material carried in ice/water
43
Meltwater erosion
Since water under hydrostatic pressure, meltwater can dissolve minerals and carry them away, especially in limestone
44
Crushing
Glacier moves and due to its weight erodes soil and rock it sits on.
45
Erosion types
Plucking Abrasion Meltwater erosion Crushing
46
Periglacial processes
Nivation Frost heave Solifluction Freeze thaw *
47
Nivation
Weathering and erosion around/beneath snow. Accumulates in hollow and doesn’t melt due to cold temp, grows year after year and layers compact to ice. Eventually ice moves under own weight and erodes ground (forms nivation hollow)
48
Frost Heave
Upward movement of sediment and soil due to freeze thaw in soil. Can cause stones to rise through soil as larger material rises and smaller moves down
49
Solifluction
Movement of wet soil down a slope. During summer active layer melts
50
Freeze thaw
Temp are often around freezing point where water enters the cracks in rocks freezes causing pressure and then the rock to break off. Often creating Scree
51
Ablation
Loss of mass from glacier. Includes: meltwater, avalanches calving, sublimation, evaporation. Occurs at snout
52
Accumulation
Addition of mass to glacier. Usually snow/precipitation. Mainly occurs at high altitudes and top of glacier
53
Sublimation
Solid turn to gas without urning to liquid first
54
Calving
Chunks of ice break off end of glacier
55
Avalanches
Can be worsened by humans(tourism=skiing)
56
Wind Deposition
Sediment gets blown and deposited
57
Entrainment
Sub supra en
58
Where periglacial
High altitude high latitude -6 to 6 for freeze thaw to happen
59
Physical threats:
Avalanche: weak layer in snowpack disturbed (Human skiing worse tho Switzerland 2019) rapid flow snow down slope Lahar: mix water and rock, fast moving. CC: melt of glacier and pfrost= arctic amp +ive FB loop Jokulhlaups: glacial outburst floods mwater caused by heating of volcanic eruptions, 1996 destroyed ring rd in Iceland
60
Human threats
Tourism: Svalbard litter waster, pollution, environmental degradation. Ski = avalanche Cc: human induced Mining: exploit natural resource pollution, conflict indigenous communities Greenland cultural erosion. Bad for environment Svalbard coal mining.

Geography (6 decks)

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