Permafrost

1. Permafrost ESS 315

2. 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.

3. Types of Permafrost • 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.

4. Thermokarst Lakes • Formed in depressions by melting from thawing permafrost • Freshwater and usually Shallow

5. Solifluction - Slow down slope flow of saturate unfrozen earth minerals

6. Ground Patterns

7. Not juston Earth…

8. 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.

9. Location of Permafrost in North

10. Creation of Permafrost • Deep permafrost takes thousands of years to create.

11. 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

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

13. 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.

14. 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.

15. 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.

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

17. Works Cited: • Alaska Pipeline- http://www.alyeska-pipe.com/pipelinefacts/Permafrost.html • International Permafrost Association - http://ipa.arcticportal.org/ • http://planetparadigm.wordpress.com/2009/02/05/global-climate-change-forget-the-climate-models-wheres-the-real-evidence/ • http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/climate_systems/climate_change.html