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Dynamic Earth: Physical Geography > Glaciation > Flashcards

Glaciation Flashcards

(98 cards)

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1
Q

how much more frequent is nuisance flooding today than 50 ya?

A

300-500%

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2
Q

how many people live in areas below the projected tideline by 2050

A

150 million people

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3
Q

how much has the sea level risen since 1850

A

21-24cm

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4
Q

since when has the ocean been warming rapidly causing thermal expansion?

A

1980s/90s

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5
Q

where is much of the ice loss occurring?

A

fringes of the antarctic ice sheet-> up to 10m a year

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6
Q

what are ice shelves

A

ice connected to the ground sheet but extending over the ocean (floating)
- thinner and more likely to melt

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7
Q

effect of ice shelves on the flow of the overall glacier

A

slow the flow and therefore ice loss

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8
Q

compare the east and west antarctic ice sheets

A

east antarctic ice sheet contains more ice but may be more stable than the west antarctic ice sheet which is mostly on land below sea level

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9
Q

last time temperatures were similar to today, what level were the seas?

A

6-9m higher

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10
Q

when was the last time CO2 was as high as present?

A

the Pliocene-> sea levels at least 6m higher

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11
Q

what occurred to sea levels about 20,000 yrs ago?

A

global warming event after ice age, meltwater pulse 1A caused 15m change in levels over a few 100 yrs

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12
Q

what sea do the antarctic ice sheets flow into?

A

Ross Sea

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13
Q

in what way can warming actually lead to ice sheet build up>

A

more snow

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14
Q

5 ways that glaciers impact humans

A
  1. meltwater= source of freshwater
  2. changes to ecosystems due to glacial changes
  3. driver of local tourism
  4. power from meltwater
  5. glacier floods= hazards
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15
Q

what is a glacier

A

a piece of ice that persists year on year and is massive enough to deform under its own weight

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16
Q

what is an ice sheet

A

over 50,000 km2, any changes in underlying topography dont impact ice flow

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17
Q

what is an ice cap

A

less than 50,000 km2, still not impacted by underlying topography

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18
Q

what is an ice stream

A

channel of relatively fast flowing ice-> flow from middle to edges

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19
Q

what are calved pieces of ice also known as

A

ice bergs

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20
Q

what is the constraining factor on alpine glaciers

A

topography

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21
Q

3 essential factors to form a glacier

A

land surface, persistent cold temperatures, precipitation

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22
Q

what is glacial mass balance

A

how the mass of the glacier changes over time

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23
Q

what occurs in the accumulation zone

A

snow falls and persists at the top of the glacier

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24
Q

equilibrium line

A

usually corresponds with the freezing level

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25
in which zone does the glacier melt
ablation zone
26
what occurs when the equilibrium line goes up
the glacier decreases
27
what happens when the equilibrium line goes down
the glacier increases
28
supraglacial water
on top of the glacier
29
englacial water
through the glacier
30
moulins
near vertical shafts that allow supraglacial water to enter the glacier
31
subglacial water
water below the glacier
32
N-channels versus R-channels
N-channels-> cut down into the channel | R-channels-> cut up into the (warmer) ice
33
how can we measure or detect subglacial drainage systems
radar
34
what is the effect of water at the base of the glacier
increases flow
35
why do cracks form on the surface of glaciers
less pressure on top than below
36
regelation
freezing point decreases due to pressure when approaching an obstacle. water flows around obstacle and refreezes on downslope side
37
what is the process by which glaciers move under their own weight
ice deformation
38
surging glaciers
meltwater builds up in subglacial reservoirs before overflowing, causing a rapid increase in sliding
39
what occurs to clasts when entrained and carried by glacier over time
they go from angular to smoothed
40
why is less work done on the landscape in v cold polar regions
ice only moves by internal deformation
41
what do glacial troughs and hanging valleys mark
where glacier tributaries once joined the main glacier
42
stoss and lee features
subglacial features caused by regelation debris cracked off during refreezing forms gentle slope up and steep cracked slope down
43
rouche moutonées
small stoss and lees
44
eskers
r-channels fill with sediment over time and are left behind when glacier melts
45
how can eskers climb hills?
high pressure forces water upwards
46
where are drumlins common
areas which had warm fast flowing ice
47
flutes
like stoss and lee forms but the cavity side gets filled with sediment
48
what is left behind by pro-glacial lakes
glacial flour, builds up in layers
49
what is surface-exposure dating?
atoms from deep space hit the surface of rocks and make a reaction that expels some subatomic particles- measure how many were removed... (shows when the rock was deposited by the glacier)
50
in a warmer climate, is there a higher or lower proportion of 18O than a cooler climate?
higher
51
what other gas matches quite closely with ice core proxy data
methane
52
where does most mass come to ice sheets from
smaller, faster flowing ice streams or outlet glaciers
53
nivometric component
percentage of precip falling as snow in an area
54
give 5 controlling factors on distribution of ice and snow
latitude, altitude, relief, aspect, continentality
55
snowline
where fresh snow still lies- retreats up glacier by late summer
56
firn
wetted/compacted snow over a year old
57
2 zones of the accumulation zone
dry-snow zone: no melt | wet-snow zone: entire snowpack is saturated by end of summer
58
superimposed ice
water that refreezes at the base of the glacier
59
how does snow transform to ice when water is present
melting, percolation and refreezing-> fast changes
60
how does snow turn to ice when no water
slow process, packing and settling, changes to ice crystal size and shape from sublimation and deformation
61
warm ice
at pressure melting point and contains water
62
cold ice
at temps below pressure melting point, doesnt contain liquid water
63
what does the thermal regime of the glacier control
the water system and range of processes that can occur at the bed of the glacier
64
3 types of thermal regime
temperate glacier, cold glacier, polythermal glacier
65
4 main morphologies of subglacial water systems
1. thin sheet flow 2. network of channels 3. linked cavities 4. braided system of canals
66
what can cause R channels to close up
ice creep
67
at what time of year are water pressures highest in r channels
spring, melting
68
where do linked cavities form
downstream of bedrock bumps
69
is water in a large canal at higher or lower pressure than a smaller canal
higher
70
where are canals likely to occur
where low-slope glaciers overlie soft sediment
71
how many glaciers mapped under the Antarctic ice sheet
over 400
72
3 mechanisms of glacier flow
internal deformation, sliding, bed deformation
73
what two factors cause drag at the bed
bed roughness (form drag) and rock to rock friction (frictional drag)
74
enhanced creep
increased compressive stress upstream side of obstacle, most effective for larger obstacles
75
Glens flow law
creep rate proportional to the 3rd power of the stress
76
how fast are fast flowing glaciers
100-1000m a yr
77
glacial crushing
direct fracturing of the bedrock due to weight of ice
78
5 ways glacial crushing might occur
stress concentration due to stones in basal ice, pre existing weaknesses in bedrock, repeated cycles of loading and unloading, freeze-thaw, pressure release due to large amounts of rock removal
79
product of glacial crushign
large, angular rocks
80
outcome of chemical erosion due to meltwater
decomposition of minerals to ionic constituents
81
3 factors that control erosion rates
changes in basal temp, glacier velocity, bedrock properties
82
how much on average do valley glaciers erode each year
1mm
83
how are the sediments resulting from glacial deposition classified
by the process of their deposition
84
till
sediment deposited from a glacier
85
lodgement till
frictional resistance between clast in transport at the base exceeds the drag imposed by the ice- grain by grain plastering
86
deformation till
pre-existing subglacial materials folded, sheared and partially homogenised by movement above of debris rich ice
87
meltout till
ice surrounding sediment melts
88
flow till
continuous supply of water in summer, poor draining, common sediment flows, particle sorting
89
crag and tail features
features of erosion: resistant rock left standing proud of surface, smaller cavities form behind more resistant rock
90
chatter marks
formed when ice moves over the bed with stick-slip motions
91
push moraines
glacier pushes sediment up to form a ridge
92
dump moraines
ridges formed transverse to the flow from material delivered to the margin of the glacier by ice flow
93
lateral moraines
parallel to sides of glaciers from dumped and frost-shattered matter
94
hummocky moraines
irregular mounds of material from meltout of supraglacial or englacial matter
95
de Greer moraines
linear ridges of sediment, transverse to the flow where a retreating ice mass borders on a glacial lake
96
crevasse-fill ridges
glacier with deep crevasses sinks into soft water saturated sediments
97
kettle holes
depressions from melting stagnant ice
98
kames
mound of sediment forme when a hole in a melting stagnant ice mass becomes filled with sediment

Dynamic Earth: Physical Geography (11 decks)

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