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Physical Geography - Structures > Glacier- Formation > Flashcards

Glacier- Formation Flashcards

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1
Q

What is glacier formaiton dependent on?

A

Balance of input/output

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2
Q

What is temperature change dependen on?

A

Specific heat capacity

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3
Q

Specific heat capacity for ice is?

A

1.751J at -50C or 2J at -10C

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4
Q

Specific heat capacity for H2O?

A

4.127J at 0C.

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5
Q

Which state changes release energy?

A

Evporation and freezing

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6
Q

Watts

A

Equal to one joule per second, measured against surface area per square metre

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7
Q

What is energy flow of a glacier compose dof?

A

Incident Solar Radiation
Reflected Infrared Radiation
Letent Heat transfer by condensation
Latent Heat consumed or released during melting and freezing

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8
Q

Why does TOA atmospheric radiation decrease with altitude?

A

Diffusion and filtration.

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9
Q

Optical Depth

A

This is an extinction coefficienct of an atmospheric layer inegrating distance, humidity, cloudiness and concnetration of other particles.

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10
Q

What does incidient SW radiaiton depend on with declination?

A

Latitude, slope gradient and time of day.

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11
Q

What is an example of influence of clouds on energy balance?

A

Where clear air, SW up to 1200Wm-2, whilst cloudiness reduced to few percent

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12
Q

What is the equation of radiant flux?

A

Emissivity multiplied by SB constant multiplied by temperature^4

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13
Q

What does sensible heat depend on?

A

Gradient between atmosphere and glacier, transfer of molecular momentum

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14
Q

What does the atmosphere-glacier gradient depend on?

A

Turbulence and convectionf of boundary level air

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15
Q

What is glacial energy most variable with?

A

Higher temperatures, strong winds and rougher surfaces.

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16
Q

Why are glaciers blue?

A

Perferential ABSORPTION of blue light

17
Q

Why is ice temperature variable?

A

Because its meltin point varies with temperature, decreasing with increasing pressure.

18
Q

What is the melting point of the base of a glacier?

A

at -1.27C if 2000m thick about 17.6MPa

19
Q

What is ice temperature regulated by?

A

Atmospheric surface energy exchange, geothermal heat flux at bed, frictional heat at bed by sliding.

20
Q

Why might glacial temperature rise occur in winter?

A

Refreeze of meltwater with released energy.

21
Q

How may snow reduce conductivity?

A

Air bubbles with less conductive ability.

22
Q

How is geothermal heat flux generated?

A

Radioactive decay, increasing basal ice temperature

23
Q

How is frictional heat on ice generated?

A

Sliding at the base

24
Q

What does dT/dt equal?

A

Shear stress x shear strain rate divided by ice density x specific heat capacity of the ice

25
Q

Basal Sliding

A

This is the act of a glacier sliding over the bed due to meltwater under the ice acting as a lubricant

26
Q

What are the three types of glacial structure?

A

Temperate
Cold
Polythermal

27
Q

Temperate Glaciers

A

Where melting point is everywhere except a surface layer a few metres thick, due to seasonal temperatures.

28
Q

Where do temperatre glaciers exist?

A

Where winter snowfall and summer melt is highest, as snow insulates ice from low winter temperatures.

29
Q

Cold Glaciers

A

These are everywhere below melting point, thus frozen to their beds.

30
Q

Polythermal Glaciers

A

These are composed of both cold and warm ice

31
Q

Orographic Lift

A

This occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain

32
Q

What is the most prominent source of accumulation?

A

Snow precipitaiton, but also supercooled water carreid from winds.

33
Q

How does ice formation occur?

A

Compaction of multitude of layers, filling air-pores and increasing bulk density.

34
Q

H2O differential densities per cubic metre?

A

40-200kg for snow, 830-910 fir ice and 1000kg for liquid water at 0c

35
Q

What is requried for firn-ice transformation?

A

Density increase, filling of air pores, compacting bubbles, pressure.

36
Q

How does compression form ice?

A

Restructuring of crystals

37
Q

How do melt and refreeze increase copaction rate?

A

Water percolation into pores of the snow force air outwards, and frezing.

38
Q

Dynamic Recrystallization

A

This involves nucleation of new dislocation-free grains followed preventing propogation of cracks.

39
Q

What causes reduction in glaciers?

A

Melting, evaporation, sublimation, wind scouring, iceberg calving

Physical Geography - Structures (10 decks)

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