Permafrost in Canada
Permafrost is the thermal condition of the earth's crust when
its temperature has been below 32°F continuously for a number of years. Half of
Canada's land surface lies in the permafrost region--either in the
continuous zone where the ground is frozen to a depth of hundreds of feet, or in the
discontinuous zone where permafrost is thinner, and there are areas of unfrozen
ground.The existence of permafrost causes problems for the development of the
northern regions of all countries extending into the Arctic. Mining operations are
hindered by frozen ore which resists blasting and is difficult to thaw. Agriculture
is restricted by the presence of permafrost near the ground surface which limits the
soil available for plant growth. Engineering structures are also
affected by the low temperatures. Ice layers give soil a rock-like structure with
high strength. However heat transmitted by buildings often causes the ice to melt,
and the resulting slurry is unable to support the structure. Many settlements in
northern Canada have examples of structural damage or failure caused by permafrost.
In the construction and maintenance of railways, buildings, water and sewage lines,
dams, roads, bridges, and airfields, normal techniques must often be modified at
additional cost because of permafrost.For the last twenty-five years
scientific investigations and engineering projects have increased steadily in
Canada's permafrost region, and it is now technically possible to build any
structure or conduct any activity on the worst soils and under permafrost
conditions.This comprehensive analysis of permafrost--its origin,
definition, and occurrence, and the effect it has on industry and
agriculture--will be invaluable to the growing number of people working in the
north and to those interested in its development.
- Derechos de autor:
- 1970 University of Toronto Press
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