GLACIOLOGY

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GLACIOLOGY

• Outlet Glacier Hanging Glacier Alaska Albert
  a G415-1 G415-3

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Definition of a Glacier

• a body of firn and ice
• consisting of
• recrystallized snow and refrozen meltwater
• lying wholly or partly on land
• and
• showing evidence of present or former flow.

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Nature of Glacial IceSources

• Precipitation
• Avalanches
• Rime ice (water vapor frozen on contact)
• Superimposed ice water frozen to glacier

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Nature of Glacial IceTransition of Snow to
Glacial Ice

• Overall conditions for formation
• Sufficient precipitation (need not be large)
• Low temperatures (especially in summer)

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Nature of Glacial IceTransition of Snow to
Glacial Ice
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Nature of Glacial IceTransition of Snow to
Glacial Ice
Fresh Snow Crystals Firn NAGT-9 NAGT-4
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Nature of Glacial Ice Transition of Snow to
Glacial Ice
G110-G1
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Nature of Glacial Ice Transition of
Snow to Glacial Ice

• FootnotesA in form of hexagonal crystalsB
  air expelled as density increasesC1 melting
  and refreezing due to pressure-temperature
  relationshipC2 melting point varies inversely
  with pressure.D ice crystals get larger
  with time.

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Nature of Glacial IceTransition of Snow
to Glacial Ice

• Other comments1. With ice near melting point,
  small increase in pressure causes melting.2.
  Meltwater flows to area of lower pressure,
  refreezes.3. This process is called
  regelation.4. Density of glacial ice lt density
  of ice formed by simple freezing due to trapped
  air.

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Nature of Glacial IceTransition of Snow to
Glacial Ice
Snowline Temple Glacier CrevasseG415-6
G415-17
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Nature of Glacial Ice Transition of Snow to
Glacial Ice Time and Thickness for
Conversions
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Nature of Glacial IceTransition of Snow to
Glacial Ice
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Nature of Glacial IceProperties of Glacial
IceNature and Orientation of Ice Crystals
Ice Surface
Hexagonal crystals
c - axis

• Note glide planes (along which crystals deform)

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Nature of Glacial IceProperties of Glacial Ice
G415-G18 333
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Nature of Glacial IceProperties of Glacial
IceHardness
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Nature of Glacial IceProperties of Glacial
IceCrushing Strength