Geocryology: The study of earth materials having a temperature below 0°C

Includes: glacial ice and permafrost

Periglacial cold-climate features formed adjacent to the Pleistocene ice sheets (Lozinski, 1909): now used for any cold climate condition or feature

• Quantitative definition is ill-defined; French definition = mean annual air temp
• Permafrost (perennially frozen ground): general characteristic of a periglacial regime
• The ground is characteristically divided into two permafrost zones:
  • active layer: The upper layer that is seasonally thawed and frozen
  • permafrost zone: The lower layer that is perennial frozen
  • permafrost table: the boundary between the active and permafrost zones

Processes

• frost wedging
• upfreezing
• ice-lense formation
• needle ice
• polygonal cracking and ice-wedging

Features

• patterned ground
• solifluction and creep
• extensive scree slopes
• pingos
• thermokarst
• string bogs
• lacustrine ice-push ridges
• oriented lakes; differential thawing of permafrost, controlled by dominant wind direction: parallel or perpendicular to dominant wind direction 

Permafrost formation and survival:The formation and survival of permafrost is dependent on the rate at which heat can be conducted from the earth or from the surface

• Heat flow equation Q=K h/l A
  • Q=quantity of heat flowing through a cross-sectional area (cal per sec)
  • K=coefficient of diffusivity=thermal conductivity
    • varies according to vegetative cover, composition and texture of soil, water-ice vs. air content, snow or ice cover etc.
  • h/l =thermal gradient

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Lindley Hanson (email) Last Modified 4/22/03