ESS 315

 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.

 Cold Permafrost: Tolerates considerable heat without thawing. Remains between 10 – 30°F.  Warm Permafrost: Introducing very little heat may cause thawing. Just below 34°F.  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.

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

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

 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.

 Deep permafrost takes thousands of years to create.

 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

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

 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.

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

 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.

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

 Alaska Pipeline- pipe.com/pipelinefacts/Permafrost.htmlhttp:// pipe.com/pipelinefacts/Permafrost.html  International Permafrost Association  05/global-climate-change-forget-the-climate- models-wheres-the-real-evidence/ 05/global-climate-change-forget-the-climate- models-wheres-the-real-evidence/  1/textbook/climate_systems/climate_change.ht ml 1/textbook/climate_systems/climate_change.ht ml