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Geography - Glaciers > Unit 2 > Flashcards

Unit 2 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

not affected by the underlying topography

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6
Q

What is a constrained ice mass?

A

dependent on the underlying topography

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7
Q

What is a thermal regime?

A

temperature of the ice

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8
Q

What is a temperate glacier? Where are they found?

A

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

(these glaciers AREN’T frozen to the bedrock)

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9
Q

What is a polar glacier? Where are they found?

A

found in high latitudes, glacier IS permanently frozen to the bedrock, up to 500m thick. The average temp is well below0 degrees, due to temps of -20 to -30 degrees on the surface

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10
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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11
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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12
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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13
Q

Are valley glaciers constrained or unconstrained?

A

constrained

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14
Q

What is the rough size of valley glaciers?

A

3 - 1500km2

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15
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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16
Q

What is an example of a valley glacier?

A

Fraser glacier in Alaska

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17
Q

Is a cirque/cwm glacier constrained or unconstrained?

A

unconstrained

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18
Q

What is the rough size of cwm glaciers?

A

0.5 - 8km2

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19
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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20
Q

What is an example of cwm glacier?

A

Eel glacier on Mt. Anderson

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21
Q

Is an ice shelf constrained or unconstrained?

A

constrained

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22
Q

What is the average size of an ice shelf?

A

10 - 10,000km2

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23
Q

What is the description of an ice shelf (sea ice)?

A

large area of floating glacier ice extending from the coast where several glaciers have reached the sea

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24
Q

What is an example of an ice shelf?

A

Ward hunt in Canada

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25
Q

Are piedmont glaciers constrained or unconstrained?

A

constrained

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26
Q

What is the average size of piedmont glaciers?

A

3 - 1000km2

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27
Q

What is the description of a piedmont glacier?

A

This is a valley glacier that extends beyond the end of a mountain valley into a flatter area and spreads out as a fan

28
Q

What is an example of a piedmont glacier?

A

Malaspina glacier in North America

29
Q

Are Ice sheets constrained or unconstrained?

A

unconstrained

30
Q

What is the average size of an ice sheet?

A

50,000km2

31
Q

What is the description of an ice sheet?

A

complete submergence of regional topography, forms a gentle sloping dome of ice several km thick in the centre

32
Q

What is an example of an ice sheet?

A

Greenland ice sheet

33
Q

Is an ice field constrained or unconstrained?

A

unconstrained

34
Q

What is the average size of an ice field?

A

10 - 10,000km2

35
Q

What is a description of an ice field?

A

Ice covering an upland area but not thick enough to bury topography, many don’t extend beyond highland source

36
Q

What is an example of an ice field?

A

Seller glacier in Antarctica

37
Q

Is an ice cap constrained or unconstrained?

A

unconstrained

38
Q

What is the average size of an ice cap?

A

< 50,000km2

39
Q

What is the description of an ice cap?

A

occupies upland areas, a smaller version of an ice sheet, outlet glaciers drain both ice sheets and ice caps

40
Q

What is an example of an ice cap?

A

Vatnajokull (covers more than 8% of island nation)

41
Q

What is a cold based glacier? Where are they found?

A

This glacier is permanently frozen to the bedrock (internal deformation), so there is no debris in the basal layer.

Found in high latitude areas

42
Q

What is the average size of a cold based glacier and what are the temperatures needed?

A

size = up to 500m thick

temp = ice temp is well below 0 degrees, average surface temperature is -20 and -30 degrees

43
Q

What is a warm based glacier? Where are they found?

A

They are found at high altitudes.

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

44
Q

What are the temperatures needed for warm based glaciers and how does movement occur?

A

temperatures at the surface fluctuate above and below melting point

80% of movement comes from basal sliding and the rest from internal deformation

45
Q

What is the melting point of ice at normal atmospheric pressure?

A

0 degrees

46
Q

How does the pressure melting point change?

A

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

47
Q

What happens to pressure as you increase the depth?

A

Pressure increases

48
Q

What is basal sliding? Does it occur under warm or cold based glaciers?

A

Warm based glaciers

meltwater at the base of the glacier acts as a lubricant, reducing friction between the base of the glacier and underlying bedrock, enabling movement

49
Q

What is the bedrock under glacier like? How does enhanced basal creep work?

A

Bedrock is rarely smooth and ice often protrudes the overlying ice

As the ice comes into contact with obstacles on glacier bed, the ice/crystals deforms around it (but doesn’t reach PMP)

50
Q

What is plastic flow?

A

ice forms around obstacles

51
Q

How does regelation slip work?

A
  1. when the temp of the basal ice is close to the PMP 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

52
Q

What is the continual melting and refreezing of ice also known as?

A

regelation ice slippage

53
Q

In which glacier does internal deformation occur? How many mechanisms are there?

A

Polar (cold) based glaciers

x2 mechanisms:
1. intergranular flow
2. laminar flow

54
Q

What is intergranular flow?

A

involves displacement of ice grains in relation to each other, it is the rotation of grains

55
Q

What is laminar flow?

A

involves layers of ice within the glacier slipping over each other (internal slipping)

56
Q

What is ice faulting and how does it occur?

A

when either warm/cold based glacier moves on a steep slope, its unable to deform quick enough

-> this causes ice faulting, which is when a variety of crevasses form on the surface of the glacier

57
Q

What happens when the slope gradient the ice is travelling on is increased?

A

there is an acceleration of ice movement = produces EXTENTIONAL flow (occurs in the zone of accumulation

58
Q

What happens when the slope gradient the ice is travelling on is reduced?

A

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

59
Q

In which type of glaciers does subglacial bed deformation occur?

A

warm based glaciers

60
Q

How does subglacial bed deformation occur?

A

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

61
Q

How does the velocity of ice movement vary?

A

rate of glacial movement varies enormously from one glacier to another but typically lies in the range of 3 - 300 meters per year

62
Q

What are the two factors that impact on the rate of glacial movement?

A
  1. Slope angle
  2. Thermal regime
63
Q

How does the slope angle affect the rate of glacial movement? (2 ways)

A
  1. if the slope is steep, the ice movement will accelerate (when the slope gradient is increased)

-> extentional flow - occurs in zone of accumulation

  1. if the gradient is reduced, the leading ice slows down allowing ice behind to catch up

-> compressional flow (slower movement)

64
Q

How does the thermal regime of a glacier affect the rate of movement?

A

a warm based glacier contains more meltwater, which means it moves faster

a cold based glacier contains less meltwater, which means it moves slower

65
Q

What is a surge?

A

period of rapid movement, when a glacier snout advances up to 1000 times faster than normal

66
Q

Why do surges occur?

A

as a result of change in the flow pattern of sub-glacial meltwater

67
Q

What are the six stages of a surge?

A
  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. PMP 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 - Glaciers (4 decks)

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