Modes of profile flow

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Modes of profile flow

• Total Velocity
• Internal Velocity
• Laminar
• Sum of processes
• Basal Slip
• Not if frozen to bed
• Bed Deformation
• If not rock

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Observed bed deformation

• Inferred from structures in till
• Measured from markers emplaced in basal sediment
  and recovered

3
Structures of glaciers

• What structures do you see here?Grinnell
  Glacier
• Lenses, layers, fractures
• How do they form?

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Schematic mountain glacier

• Plan View
• Cross-section

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Schematic mountain glacier

• Detailed section
• Terminus

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Example Malaspina Glacier

• Note accommodation of Malaspina and Agassiz
  glaciers into increasing space
• Longitudinal compression

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Unsteady Flow I

• Flow is NOT constant
• Varies with season (snow load increases strain
  rate)
• Varies with bed resistance f(water)?
• Varies unpredictably!

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Unsteady Flow II - Ogives
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Unsteady Flow III Kinematic Waves

• Thickening increases depth linearly
• Depth increases stress linearly
• Stress increases strain (flow) exponentially
• Therefore, a pulse propagates through the glacier.

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Unsteady Flow IV - Surges

• Many glaciers (10) surge
• Stagnant for years
• Increase in thickness
• Surge!
• Decouple from the bed?
• Surface fracturing
• Thrusting?

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Surging Terminus
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Brittle Deformation - Crevasses

• Long observed
• Results from rapidly-applied stress
• Form many distinctive patterns

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Mechanics of Crevassing

• Observed patterns relate observed strain directly
  to the mechanics of stress couples

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Crevasse Examples

• Depth lt10m
• Tensional and marginal
• Terminal splays
• Complex systems

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Crevasse Examples
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Icefalls
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Icefalls
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Summary of Flow Process I
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Summary of Flow Process II
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Remember flow is one-way!