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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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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Transition of Snow to Glacial Ice
Temp. in degrees C

Depth
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Nature of Glacial IceProperties of Glacial Ice
G415-G18 333
Shrinking glacier how can you tell?
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Thermal RelationsHeat Flow Across Glaciers
Boundaries
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Thermal RelationsTemperature Gradient Antarctica
Degrees C

G
Depth (m)
A
Glacier bed
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Glacial MovementHow a Glacier Flows
Vs
Can we determine how much movement is by ice
creep vs basal slip?
Vi
Ice creep
bs
Velocity curve
Vb
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Glacial MovementGlen Flow Law

• Velocity of Glacier at Surface Vs 1/32 (?g)3
  (sin?3) b4Rapid increase in V, with slight
  increase in b or ?.? must be steep near
  glaciers terminus because b is less.

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Glacial MovementBasal Slip
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Glacial Movement

• Direction of Flow and Variations in VelocityFlow
  occurs to distribute accumulation.
  Longitudinal Section Plan View

Zone of Accumulation
Equilibrium Line
Equilibrium Line
Zone of Ablation
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Glacial MovementDirection of Flow and Variations
in Velocity

• Transverse Sections Above EL
• Below EL

V
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Glacial MovementVariations with Time

• 4) Surges Sudden, spectacular movements. Velocit
  y increase of 10 to 100 times normal. No new
  ice added. Response to intrinsic
  threshold. Often periodic. Explanations Ice-d
  amming Behind stagnant ice. Thickness
  increases. Stress increases release
  occurs. Re-establishment of equilibrium
  profile.

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Glacial Movement Variations with Time

• Hydraulic lifting
• Water buildup along base. Pore pressure
  increases. Friction reduced until threshold
  crossed. Surge takes place.

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Mass Balance of Glaciers Diagrams of
Relationships
Zone of accumulation
Zone of ablation
Equilibrium line
Zone of Erosion
End moraine
Zone of Transportation
Zone of Deposition
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Mass Balance of Glaciers Diagrams of
Relationships
Equilibrium line
Equilibrium line
Icebergs
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Mass Balance of Glaciers Relationship to Movement

• Large accumulation means high flow rates, even if
  the glacier is in equilibrium. Results in
  more erosion, transportation.Favorable
  conditions 1) temperate conditions 2)
  maritime climatesPosition of terminus related to
  mass balance 1) positive advance 2) negative
  recession 3) equilibrium stationary (favors
  forming end moraine)

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Crevasse
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Terminology Used in the Study of Glaciology

• Basal slip
• Cirque glacier
• Cold ice
• Compressive flow
• Continental ice sheet
• Crevasse
• Equilibrium line
• Extending flow
• Firn
• Glacial ice
• Ice creep

• Mass balance
• Ogive
• Polar glacier
• Stratification
• Surge
• Temperate glacier
• Valley glacier
• Warm ice
• Zone of ablation
• Zone of accumulation

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Student Responsibilities on Glaciology

• What is a glacier, and under what conditions does
  it form? Trace the steps in the formation of
  glacial ice, including the changes in properties.
  How is heat interchanged between a glacier and
  the surrounding environment, and what is the
  importance of these thermal relations in respect
  to the movement of glaciers? What are the
  mechanisms of glacial movement, and how does
  movement vary throughout a glacier? What is a
  surge? What do we mean by mass balance, and how
  does that relate to glacial movement? What are
  some of the common ice structures?

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The end.