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glacier Flashcards

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1
Q

what are fluvioglacial landforms

A

those that are created by the work of meltwater streams in front of an often retreating glacier
created largely through deposition but also by erosion

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2
Q

how does meltwater change glacial sediments

A

glacial deposits tend to be unstratified (have no layers)
meltwater changes the glacial sediment or till be sorting them by size, stratifying them into layers and rounding the sediments

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3
Q

how does discharge and sediment load of meltwater streams vary

A

in summer discharges will be very high as meltwater arrives from many meltwater streams
in winter meltwater discharge may even stop as temperature may never rise above the pressure melting point
also varies on a daily basis, greatest discharges coinciding with highest daily temperatures

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4
Q

where are contemporary fluvioglacial landscapes found

A

warm based glacial systems (for example in alpine regions)
in areas that tend to have meltwater (ones that have activity at lower elevations like valleys or outwash planes

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5
Q

under what conditions will a glacier deposit materials

A

exceeding the carrying capacity - when the vector can no longer carry the material e.g. melting
losing energy: shrinking ~(not advancing) and change in relief (flat ground loses spread)

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6
Q

what are erratics

A

glacier-transported rock fragment that differs from the local bedrock. Erratics may be embedded in till or occur on the ground surface and may range in size from pebbles to huge boulders weighing thousands of tonnes

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7
Q

what is till

A

unsorted material deposited directly by ice (boulder clay)

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8
Q

what is lodgement till

A

material lodged on the valley e.g. subglacial debris

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9
Q

what is ablation till

A

combination of englacial and supraglacial debris, dropped in situ as the glacier begins to melt

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10
Q

what is an outwash plain

A

Outwash plains are formed in front of a glacier and are where material is deposited over a wide area
the till levels out the landscape creating a characteristically flat topography

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11
Q

what are moraines

A

a general term for unstratified and unsorted deposits of sediment that form through the direct action of, or contact with, glacier ice

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12
Q

define a corrie

A

a deep hollow in a mountain side left behind by a glacier - characterised by a steep back wall and over deepened base

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13
Q

define arête

A

a knife edge ridge separating two or more corries
e.g. striding edge, lake district

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14
Q

define pyramidal peak

A

sharp summit and steep sides between 3 or more corries that have continuously eroded backwards

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15
Q

what is a roche moutonnée

A

a mass of resistant rock which has a smooth, rounded up (stoss) slope facing against the direction of the ice flow and a steep, jagged face on the far (lee) side

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16
Q

define glacial trough

A

also known as a u shaped valley
high, steep sided walls wis a flat, wide base
formed due to glaciers eroding the whole SA of valley much faster than the valley river

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17
Q

define misfit stream

A

rivers in a glacial trough that did not erode to form the valley

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18
Q

define hanging valley

A

remnants of river tributary valleys
smaller valleys that sit high on the sides of glacial troughs

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19
Q

define truncated spur

A

former interlocking spurs that have been sawn off (truncated) by the glacier
end in an abrupt steep edge

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20
Q

define ribbon lake

A

long and narrow lake found in a glacial trough
formation begins when a glacier moves over an area containing alternate sections of hard and soft rocks
soft rock is less resistant and erodes faster than hard rock, creating a rock basin, the hard rock acts as a dam where rain water accumulates

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21
Q

define weathering

A

the breakdown of rock or parent material by external processes in situ

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22
Q

what is physical/mechanical weathering

A

disintegration of rock without a chemical change
e.g. freeze thaw/exfoliation
often results in piles of angular rock fragments known as scree that can be found at the foot of a mountain

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23
Q

what is chemical weathering

A

the decomposition of rocks caused by a chemical reaction with it e.g. acidic rainwater can react with and dissolve certain rocks and minerals

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24
Q

what is biological weathering

A

involves the actions of flora and fauna e.g. plant roots expanding cracks in the rocks

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25
Q

define mechanical weathering

A

creating a fragmented or angular landscape with loose material called scree

26
Q

what is freeze thaw/frost shattering

A

A crack in a rock can fill with water which then freezes as the temperature drops. As the ice expands, it pushes the crack apart, making it larger
requires temperature fluctuation below and above freezing

27
Q

what is carbonation

A

the mixing of water with carbon dioxide to make carbonic acid

28
Q

what is nivation

A

an umbrella term used to cover a range of processes associated with patches of snow that result in the formation of hollows
the collection of seasonal snow in hollows which encourage frost weathering beneath them

29
Q

describe the process of nivation

A

Snow and ice build-up on sheltered/shaded sloped areas. These patches often remain through the summer months. Compact névé snow can develop when snow melts and refreezes. Firn ice can develop over time in these shallow depressions, and when movement occurs, the ice can pluck small bits of loosened rock from the back surface of the area.

Freeze-thaw cycles around the edges and below the snow patch cause frost shattering.

When thawing occurs, the smaller pieces of frost shattered rock are moved down the slope by meltwater, solifluction and gelifluction.

As a result of these processes, nivation hollows are formed, over time these can develop into corries.

30
Q

where are nivation processes most active

A

at the edges of snow patches because the exposed rock with low albedo absorbing more energy

31
Q

define abrasion

A

when rock fragments frozen to the glacier base smooth and sandpaper the bedrock as the glacier moves over it

32
Q

define plucking

A

as a glacier moves meltwater gets into cracks and freeze
this rips or plucks out rock fragments from bedrock
plucking can also occur on the headwall of a corrie, where the glacier is attached to the mountain

33
Q

define dynamic equilibrium

A

All natural systems are in this state state
it means changing balance
for glaciers, as inputs are constantly changing due to climate, the system needs to adjust to the changes in order to reach a new state of balance

34
Q

glacial budget

A

The balance between inputs and outputs
the glacial budget is constantly changing
the amount of ice in the glacier

35
Q

what is accumulation

A

inputs > outputs so glacier grows in size

36
Q

what is ablation

A

outputs > inputs so glacier will retreat and reduce in size

37
Q

what is a mass balance

A

accumulation - ablation
positive balance
accumulation > ablation
negative balance
ablation > accumulation

38
Q

what is net balance

A

annual mass balance of a glacier over a year
a negative balance means the glacier snout is reterating
a positive balance means that the glacier snout is advancing
balance is a steady state or equilibrium

39
Q

describe the temporal variation in glacial budget

A

winter - positive balance = acculmulation = snout advance
greater precipitation input
reduced melting due to lower temperatures

summer - negative balance = ablation = snout retreat
reduced precipitation input
increased melting, sublimation and calving due to raised temps
moving faster, more energy, higher rates of erosion

40
Q

describe the spatial variation in glacial budget

A

ice caps/sheets: accumulation zone is in the centre
ablation zone is in the periphery
valley glaciers:
accumulation zone - high altitudes
ablation zone - snout

41
Q

what is humus

A

processed organic matter
dead organic matter that has been broken down

42
Q

what is regolith

A

inorganic material and weathered down material (rocks)
often helps with drainage

43
Q

what is biota

A

living plants and animals in soil

44
Q

what are adiabatic temperature changes

A

changing temp without adding or subtracting heat. result of compressing air or allowing allowing to expand

45
Q

what is the difference between isostatic and eustatic changes

A

Isostatic change is a local rise or fall in land levels. Eustatic change involves a rise or fall in water levels caused by a difference in the volume of water

46
Q

define a periglacial landscape

A

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

47
Q

how does base temperature determine glacial movement

A

Warm based glaciers have a higher temperature at base than the pressure melting point this means that water that would’ve previously been frozen exists as liquid
this leads to an increase in melt water which lubricates the base reducing friction and causes increased basal sliding
a buildup of this meltwater can cause a surge (300m in a day)
warmer temperatures also result in enhanced basal creep which is when an object in the path of the glacier causes increased pressure resulting in a higher PMP and therefore more meltwater

In cold-based glaciers there is a lower temperature PMP so they do not experience as much basil sliding
they move through internal defamation which is when the weight of the ice causes the ice crystals to stretch resulting in the downward motion of the glacier
in some cold temperatures ice could freeze and attach to bedrock meaning subglacial internal deformation is the only force of movement

cold temperature glaciers move much slower than warm temperatures

48
Q

what is the difference between ice creep and basal creep

A

Ice creep is when ice crystals slide past each other advancing the ice surface
enhanced basal creep is the increased pressure from an obstacle in the path of the glacier leading to a low-pressure melting point and more meltwater
ice creep happens everywhere whereas basal creep happens sub glacially

49
Q

where within the glacier is basal creep fastest

A

Ice cream happens fastest at the top/surface and the middle away from sides because there is the least friction with the sides and bedrock

50
Q

how does ice overcome obstacles

A

Through enhanced basal creep and basal slippage enhanced basal creep is caused by an obstacle which causes pressure whereras basal slippage is caused by increased pressure from ice and lower PMP so it travels more rapidly

51
Q

what is the difference between extending and compressing flow

A

extending flow is when a steeper gradient causes ice to move faster so the ice mass stretches becoming thinner
compressional flow is where the gradient is less steep so the ice mass slows, backs up and crevasses close

52
Q

when will a surge occur

A

when excessive meltwater builds up at base and the glacier moves 300m in a day

53
Q

when and where does basal slippage occur

A

in temperate glaciers
more frequent in summer

54
Q

how does bedrock permeability affect glacier speed

A

movement is faster over impermeable surfaces rather than permeable. This is because impermeable surfaces don’t allow meltwater to escape and it stays at the base of the glacier. This decreases friction which allows the glacier to advance at faster rates

55
Q

what are the different kinds of permafrost

A

Continuous permafrost covers the largest areas with temperatures below -5°C
Discontinuous permafrost occurs over smaller areas with temperatures between -5°C and -1.5°C
Sporadic permafrost covers the smallest areas where temperatures are between -1.5°C and 0°C
Permafrost can be classified as continuous (>90% of land area underlain by permafrost), discontinuous (90%-50%), sporadic (50%-10%)

56
Q

what is solifluction

A

the progressive movement of a mass down a slope caused by freeze-thaw activity

57
Q

define erosion

A

The wearing away and removal of rock by external agent

58
Q

define regelation

A

Regelation is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced

59
Q

What are the names of the mechanical and chemical processes of subglacial melt water erosion

A

mechanical is fluvial abrasion
Chemical is corrosion Corrosion is the process of slowly eating up metals by gas and water vapours present in the atmosphere due to the formation of certain compounds like oxide, sulphides, carbonate, etc

60
Q

define pressure release

A

aka dilation
When the overlying mass is removed by weathering, the confining pressure decreases, allowing the rock to expand

61
Q

what is a rock step

A

outcrop or platform that is caused by a difference in type of rock hard/soft

62
Q
A

Geography (10 decks)

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