Permafrost

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Permafrost

• ESS 315

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What is Permafrost

• Any rock/soil at or below the freezing point of
  water.
• Remains below 0 degrees Celsius continuously for
  two years.
• Ice is not necessarily present.
• The active layer is the overlying surface that
  freezes in the winter, and thaws in the summer.

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Types of Permafrost

• Cold Permafrost Tolerates considerable heat
  without thawing. Remains between 10 30F.
• Warm Permafrost Introducing very little heat
  may cause thawing. Just below 34F.
• Ice Rich 20 - 50 visible ice.
• Thaw-Stable Permafrost in bedrock is
  well-drained. Coarse grained sediments.
• Thaw-Unstable Poorly drained, fine-grained
  sediment (clays and silts). Thawing results in so
  much moisture that it flows.

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Thermokarst Lakes

• Formed in depressions by melting from thawing
  permafrost
• Freshwater and usually Shallow

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• Solifluction - Slow down slope flow of saturate
  unfrozen earth minerals

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Ground Patterns
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Not juston Earth
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Zones of Permafrost

• Continuous Zone Permafrost is found almost
  everywhere in the zone.
• Discontinuous Zone Permafrost found in spots in
  the zone.
• Sporadic Zone Permafrost found isolated in
  small spots of the zone.

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Location of Permafrost in North
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Creation of Permafrost

• Deep permafrost takes thousands of years to
  create.

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Construction on Permafrost

• Heat from a building or other constructed article
  will cause thawing, and can result in sinking.
• Three solutions are common
• Using foundations on wood piles
• Building on a thick gravel pad
• Using anhydrous ammonia heat pipes

• Additionally, sinking can be prevented by using
  stilts that extend to a depth of over 15 meters

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Construction on Permafrost

• Additionally, sinking can be prevented by using
  stilts that extend to a depth of over 15 meters.

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The Alaska Pipeline

• Approximately 75 passes through permafrost
  terrain.
• Special designs are created to account for the
  movement, melting, and freezing characteristics
  of the ground.
• There are three principal designs used to
  construct the pipeline. The design varies from
  area to area.

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Pipeline Designs

• Above-ground pipeline
• Problems from melting are avoided in
  thaw-unstable areas by placing the pipeline on an
  elevated support system above ground.

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Pipeline Designs

• Below-ground, conventional burial
• In areas where thaw-stable or unfrozen ground is
  encountered, the pipeline can be buried with no
  special provisions.
• Below-ground, special burial
• Where thaw-unstable permafrost is encountered,
  but the pipeline must be buried for highways,
  animal crossings, rockslides/avalanches, etc.
• The pipeline is insulated so that the heat it
  produces does not promote melting.

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Ecological Problems

• Animals will not be able to effectively burrow or
  create dens.
• Plant roots are constrained to grow in a
  near-surface pattern

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Works Cited

• Alaska Pipeline- http//www.alyeska-pipe.com/pipel
  inefacts/Permafrost.html
• International Permafrost Association -
  http//ipa.arcticportal.org/
• http//planetparadigm.wordpress.com/2009/02/05/glo
  bal-climate-change-forget-the-climate-models-where
  s-the-real-evidence/
• http//www.uwsp.edu/geo/faculty/ritter/geog101/tex
  tbook/climate_systems/climate_change.html