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geography: glaciation > unit two: types of ice masses and glacier movement > Flashcards

unit two: types of ice masses and glacier movement Flashcards

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1
Q

what is the cryosphere?

A

parts if the earth’s crust and atmosphere that are below 0 degrees for part of the year

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2
Q

what is morphology?

A

this is to do with the form, shape and structure of ice masses

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3
Q

what is climate?

A

controls annual temperature cycle of a region as well as amount of precipitation that falls as snow

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4
Q

what is topography?

A

the natural shape of the land

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5
Q

what is an unconstrained ice mass?

A

have a morphology and flow pattern that is not affected by the underlying topography

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6
Q

what is a constrained ice mass?

A

have a morphology and flow pattern that is dependent on the underlying topography

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7
Q

what is a thermal regime?

A

temperature of ice

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8
Q

what is a temperate glacier?

A

aren’t frozen to the bedrock

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9
Q

where are temperate glaciers found?

A

found outside the polar regions, usually high altitude, the temperature of the surface fluctuates above, below melting point

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10
Q

what is a polar glacier?

A

are permanently frozen to the bedrock, up to 500m thick

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11
Q

where are polar glaciers found?

A

found in high latitudes. the average temp is well below 0 degrees, due to temps of -20 to -30 degrees on the surface

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12
Q

what is pressure melting?

A

where ice will melt at temps below 0 degrees due to the pressure from the weight of the overlying ice

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13
Q

what is the pressure melting point?

A

the temp below 0 degrees at which ice melts due to pressure (weight) from overlying ice

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14
Q

what is regelation?

A

ice melts to water below 0 degrees on the application of pressure and refreezes back to ice when the pressure is removed

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15
Q

are valley glaciers constrained or unconstrained?

A

constrained

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16
Q

what is the rough size of valley glaciers?

A

3 - 1500km2

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17
Q

What is the description of a valley glacier?

A

glacier confined between valley walls, terminating in a narrow tongue, forms from ice sheets / caps and cwms. may terminate in sea as tide water glacier

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18
Q

What is an example of a valley glacier?

A

fraser glacier in alaska

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19
Q

is a cirque/cwm glacier constrained or unconstrained?

A

unconstrained

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20
Q

what is the rough size of cwm glaciers?

A

0.5 - 8km2

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21
Q

what is the description of a cwm glacier?

A

a smaller glacier occupying a hollow on the mountainside, it carves out a cirque, a smaller version is known as a niche glacier

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22
Q

what is an example of cwm glacier?

A

eel glacier on mt. anderson

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23
Q

is an ice shelf constrained or unconstrained?

A

constrained

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24
Q

what is the average size of an ice shelf?

A

10 - 10,000km2

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25
what is the description of an ice shelf (sea ice)?
large area of floating glacier ice extending from the coast where several glaciers have reached the sea
26
what is an example of an ice shelf?
ward hunt in canada
27
are piedmont glaciers constrained or unconstrained?
constrained
28
what is the average size of piedmont glaciers?
3 - 1000km2
29
what is the description of a piedmont glacier?
this is a valley glacier that extends beyond the end of a mountain valley into a flatter area and spreads out as a fan
30
what is an example of a piedmont glacier?
malaspina glacier in north america
31
are Ice sheets constrained or unconstrained?
unconstrained
32
what is the average size of an ice sheet?
50,000km2
33
what is the description of an ice sheet?
complete submergence of regional topography, forms a gentle sloping dome of ice several km thick in the centre
34
what is an example of an ice sheet?
greenland ice sheet
35
is an ice field constrained or unconstrained?
unconstrained
36
What is the average size of an ice field?
10 - 10,000km2
37
what is a description of an ice field?
ice covering an upland area but not thick enough to bury topography, many don’t extend beyond highland source
38
what is an example of an ice field?
seller glacier in antarcita
39
is an ice cap constrained or unconstrained?
unconstrained
40
what is the average size of an ice cap?
< 50,000km2
41
what is the description of an ice cap?
occupies upland areas, a smaller version of an ice sheet, outlet glaciers drain both ice sheets and ice caps
42
what is an example of an ice cap?
vatnajokull (covers more than 8% of island nation)
43
what is a cold based glacier?
this glacier is permanently frozen to the bedrock (internal deformation), so there is no debris in the basal layer
44
where are cold based glaciers found?
high latitude areas
45
what is the average size of a cold based glacier?
up to 500m thick
46
what are the temperatures needed for a cold based glacier?
ice temp is well below 0 degrees, average surface temperature is -20 and -30 degrees
47
what is a warm based glacier?
due to increased pressure of the overlying ice, pressure melting occurs and therefore water exists as a liquid at the base. The effects of pressure, geothermal energy and percolation of meltwater = these glaciers aren't frozen to the bedrock
48
where are warm based glaciers found?
high altitude areas
49
what are the temperatures needed for warm based glaciers?
temperatures at the surface fluctuate above and below melting point
50
how does movement of a warm based glacier occur?
80% of movement comes from basal sliding and the rest from internal deformation
51
what is the melting point of ice at normal atmospheric pressure?
0 degrees
52
how does the pressure melting point change?
as pressure increases the temperature at which ice melts will fall below 0 degrees at a rate of 1 degree for every 100km/cm2 of pressure
53
What happens to pressure as you increase the depth?
pressure increases
54
what is basal sliding?
meltwater at the base of the glacier acts as a lubricant, reducing friction between the base of the glacier and underlying bedrock, enabling movement
55
Does basal sliding occur under warm or cold based glaciers?
warm based glaciers
56
what is the bedrock under glacier like?
bedrock is rarely smooth and ice often protrudes the overlying ice
57
how does enhanced basal creep work
as the ice comes into contact with obstacles on glacier bed, the ice/crystals deforms around it (but doesn’t reach pressure melting point)
58
what is plastic flow?
ice forms around obstacles
59
how does regelation slip work?
1) when the temp of the basal ice is close to the pressure melting point then this increases pressure on the up - glacier side of an obstacle will induce melting 2) allows the glacier to slip and as the meltwater flows around the obstacle to the downside glacier 3) pressure is reduced on the down side causing meltwater to refreeze
60
what is the continual melting and refreezing of ice also known as?
regelation ice slippage
61
in which glacier does internal deformation occur?
polar (cold) based glaciers
62
what and how many mechanisms are there that cause internal deformation?
1) intergranular flow 2) laminar flow
63
what is intergranular flow?
involves displacement of ice grains in relation to each other, it is the rotation of grains
64
what is laminar flow?
involves layers of ice within the glacier slipping over each other (internal slipping)
65
What is ice faulting?
a variety of crevasses form on the surface of the glacier
66
how does ice faulting occur?
when either warm/cold based glacier moves on a steep slope, its unable to deform quick enough
67
what happens when the slope gradient the ice is travelling on is increased?
there is an acceleration of ice movement = produces extentional flow (occurs in the zone of accumulation)
68
what happens when the slope gradient the ice is travelling on is reduced?
the ice slows down in movement = compression flow occurs, enabling the ice behind to catch up. this leads to the thickening of ice, often the following ice pushes up and over the moving, leading ice
69
in which type of glaciers does subglacial bed deformation occur?
warm based glaciers
70
how does subglacial bed deformation occur?
when a glacier (warm based) moves over weak or unconsolidated rock, the sediment can deform under the weight of glacier moving the ice on top of it
71
How does the velocity of ice movement vary?
range of 3 - 300 meters per year
72
what are the two factors that impact on the rate of glacial movement?
- slope angle - thermal regime
73
How does the slope angle affect the rate of glacial movement? (2 ways)
1) if the slope is steep, the ice movement will accelerate (when the slope gradient is increased) > extentional flow - occurs in zone of accumulation 2) if the gradient is reduced, the leading ice slows down allowing ice behind to catch up > compressional flow (slower movement)
74
How does the thermal regime of a glacier affect the rate of movement of a cold based website?
a cold based glacier contains less meltwater, which means it moves slower
75
How does the thermal regime of a glacier affect the rate of movement of a warm based website?
a warm based glacier contains more meltwater, which means it moves faster
76
what is a surge?
period of rapid movement, when a glacier snout advances up to 1000 times faster than normal
77
why do surges occur?
as a result of change in the flow pattern of sub-glacial meltwater
78
what are the six stages of a surge?
1) pressure builds up underneath glacier during phase of normal glacier flow, increase of ice in accumulation zone 2) during winter, meltwater channels are closed = increases ice accumulation 3) during summer the weight of the ice accumulation is so great that the meltwater channels don’t open. 4) pressure melting point and the subglacial water separates the basal ice from its bed , lubricating it, causing the overlying ice to flow more steadily 5) abundant water increased the pore water of the sub glacial sediment, which adds to the rapid movement 6) the surge occurs and the glacier resumes normal flow, cycle occurs as frequently as every 10 - 20 years

geography: glaciation (9 decks)

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