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Cold Climate Geomorphology > GP3: erosional forms and landscapes > Flashcards

GP3: erosional forms and landscapes Flashcards

1
Q

What are the 4 forms of categorising landforms by scale?

A

small (<1m), intermediate (1-100m), large (100-1000m), landscapes (>1000m)

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2
Q

What are landscapes of glacial erosion a record of

A

long-term regional patterns of glaciation

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3
Q

What are the two forms of small scale landforms?

A

Chattermarks/gouges and p-forms

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4
Q

What are chattermarks and gouges?

A

crescent-shaped fractures that face down-ice

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5
Q

What can chattermarks and gouges be used to reconstruct?

A

ice-flow direction

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6
Q

Why is the spacing between chattermarks usually even?

A

diurnal variations in subglacial water pressure causing periodic motion

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7
Q

What are p-forms?

A

plastically moulded forms in to the bedrock of a glacier

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8
Q

What are the 4 mechanisms for the formation of p-forms?

A

debris-rich basal ice
saturated till flowing between the ice and bedrock
subglacial meltwater under high pressure
ice-water mixtures

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9
Q

What do intermediate scale features reflect?

A

interactions between geology, topography and water/ice flow

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10
Q

What can intermediate scale features be used for?

A

yielding important insights in to former glaciological conditions

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11
Q

What are Roches mountains?

A

asymetric linear bedrock bumps

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12
Q

What are the names given to the up-ice and down-ice sides of a Roches mountains?

A

Up-ice: stoss side

Down-ice: lee side

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13
Q

Describe the landforms on the lee and stoss side of a Roches mountain

A 
Lee = quarrying/plucking
stoss = abrasion therefore striae
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14
Q

Why are there striae and plucking on the stoss and lee sides respsectively?

A

on the stoss side intense abration generated from ice flow occurs whereas on the stoss side the lee side the glacier refreezes after melting on the stoss side and so due to internal deformation the glacier cna pluck out material from the lee

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15
Q

How big can Roches mountains be?

A

<1 to hundreds of meters across

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16
Q

What strongly influences the shape of a Roche mountain?

A

Bedrock structure

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17
Q

What are the two theories for how Roches mountains form?

A

either under thin temperatre valley glaciers or near the melting margins of ice sheets as here the freezing process can occur

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18
Q

What are whalebacks and drumlins?

A

Elongated, approximately symmetrical smoothed bedrock bumps.

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19
Q

What differentiates whalebacks and drumlins from Roches mountains?

A

The former do not have quarried faces

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20
Q

What differentiates whalebacks from drumlins?

A

whalebacks form usually in bedrock whereas drumlins form as a result of deposition

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21
Q

What are common small scale features that are found on whalebacks and drumlins?

A

striae and p-forms

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22
Q

Why is there a lack of quarrying on whalebacks and drumlins?

A

because it is thought that these features are created by glaciers that are much thicker which therefore means the base is always at pressure melting point and does not refreeze and so cannot pluck the surface.

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23
Q

What are crag and tails?

A

elongated streamlined hills consisting of a blunt stoss side generated by resistant rock but then the downslope side is much smoother due to less resistant rock

24
Q

How are crag and tails formed?

A

Ice cannot erode the more resistant rock and so flows around it where it then encounters the less resistant rock which it then erodes to form a smooth slope down-ice

25
Q

Where are crag and tails commonly found?

A

Edinburgh

26
Q

What are relic channels?

A

Channels that formed at the base of the glacier

27
Q

What can relic channels tell us?

A

indicated the presence of meltwater at glacier base which then tells us the glacier must have been melting which can then tell us about the climate

28
Q

What are the two possible types of relic channel?

A

subglacial or ice-marginal

29
Q

What are subglacial channels called that erode in to the bedrock?

A

Nye channels

30
Q

What hinders interpretation of nye channels?

A

they are often eroded in to underlying sediment which does not preserve as well in the landscape.

31
Q

What is a key diagnostic for a nye channel?

A

An uneven surface featuring upslopes which the channel can only form when there is enough glacier pressure to force water upwards.

32
Q

What are ice-marginal channels?

A

Channels incised in sediment or bedrock by water draining along the margins of a glacier

33
Q

What do ice-marginal channels mark? and how can this be improved?

A

Former ice marginal positions. If we can date these channels then we can reconstruct the former ice margin extent.

34
Q

What allows ice marginal channels to be preserve well?

A

They form during glacier retreat

35
Q

What differentiates nye channels from ice marginal channels?

A

nye channels usually comprise only 1 or 2 channels that represent the flow line of the glacier whereas ice-marginal channels are a series of channels that provide a sequence of channels.

36
Q

What are 3 large scale landforms?

A

rock basins/overdeepenings
glacial troughs
cirques

37
Q

What are rock basins?

A

Overdeepenings eroded in to the bedrock at multiple scales. They are then commonly occupied by lakes.

38
Q

Where can you find a lot of rock basins in the UK?

A

Scotland - knock and lochan environments (essentially hilly and lakes environments)

39
Q

How are rock basins formed?

A

combination of mostly abrasion but also quarrying. The latter highlights the ice must be wet-based

40
Q

What are glacial troughs?

A

steep-sided flat bottomed valleys

41
Q

What are glacial troughs commonly referred to as?

A

U-shaped valleys

42
Q

How are glacial distinguished from fluvial troughs? What is this a testament to?

A

80% larger in CSA, 30% deeper. This is testament to the greater erosional capacity

43
Q

What are hanging glacial troughs?

A

a landscape dominated by fjords and valleys, and erosion in the main trough is greater than in the tributary glacier then as the main glacier retreats it can reveal the tributary glacier face which gives the impression of it hanging

44
Q

What are cirques? and how are they formed?

A

These are rounded overdeepenings caused by abrasion and plucking of the bedrock by a valley glacier.

45
Q

Where can you find cirques in the UK?

A

Lake district, wales and scotland

46
Q

What bounds cirques?

A

Upstream wall

47
Q

What environment do cirques form in?

A

local either small, subpolar glaciers, temperate glaciers or places where enhanced erosion occurs due to meltwater reaching bed through crevasses. This is because the glacier needs to be wet-based in order to carrying out quarrying

48
Q

What are glacial landscapes?

A

Vast landscapes of extensive glacial activity

49
Q

What are glacial landscapes commonly referred to as?

A

Knock and lochan landscapes

50
Q

What results in the uneven landscape?

A

Varying lithologies and structures that comprise the bedrock

51
Q

What is the relief of the dips created in the landscape?

A

<100m

52
Q

What processes cause the glacial landscapes?

A

widespread plucking and abrasion

53
Q

What is the alternative way that glacial landscapes can form?

A

selective linear erosion

54
Q

What is selective linear erosion and what evidence is there for it?

A

Linear erosion happens in very specific places due to the glacier response to extreme differences in rock resistance, more so than usual.

55
Q

What differentiates a glacial landscape generated by aerial scouring compared to one generated by selective linear erosion? why?

A

The former has low relief whereas the latter is characterised by more extreme relief. Because of how extreme the differences in extreme or less resistant rock are in a given landscape.

56
Q

What do troughs and plateaus indicate in a glacial landscape generated by selective linear erosion?

A

troughs mark the locations of former ice streams whereas plateaus mark former slow moving ice or cold–based ice

57
Q

What might be the source of possible positive feedbacks between processes amplifying features that characterrise a glacial landscape?

A

subglacial topography, ice velocity, basal temperature, rates of erosion

Cold Climate Geomorphology (10 decks)

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