Geoscience Reference
In-Depth Information
work on any engineering construction associated with
economic development, e.g. housing, industrial plant,
roads, railways, airstrips or pipelines for oil and natural
gas. The thickness of the permafrost in the subsoil is
sensitive to any change in surface vegetation and the
building of human-made structures. If the insulating
cover of vegetation is removed or a heated building placed
directly upon the ground surface, it is hardly surprising
if the permafrost thaws, causing subsidence and distortion
of the building. Subsidence is a more serious problem with
ice-rich poorly draining soils such as gleys and peats.
Coarse sands and gravels are well draining and present less
of a problem.
Many historic buildings show the effects of subsidence,
as in the Klondike gold-rush town of Dawson in the
Yu ko n (
Plate 24.20
).
It can be overcome by supporting
buildings on 'piles' drilled into the permafrost, allowing
cold air to circulate between the ground surface and the
floor of the building, so that the heated building does not
come into contact with the ground. Large buildings
(industrial plant, power stations, oil storage facilities)
require a thick pad of well draining aggregate. The
insulating power of the pad can be enhanced with
fibreglass insulation, and by metal pipes through it which
permit air to circulate in winter. Pads are also used for
roads, airport runways and railway tracks.
Impact of oil and gas fields
Recurring political crises in the Middle East have
persuaded governments and companies to exploit the
significant supplies of oil and natural gas located in the
Arctic regions of Alaska, Canada, Norway and Russia.
The operation and drilling of wells for oil and natural gas
carry great environmental risks, which are compounded
by the transportation of the hydrocarbons by tankers
and pipelines across the tundra or through polar seas to
'Southern' markets. There is also the necessity to service
the needs of remote polar communities with fuel and
supplies. Inevitably there have been many accidental spills
of crude oil, diesel oil, petrol and jet fuel kerosene as oil
and gas deposits have been developed in the Arctic. The
spills have gone into marine ecosystems from offshore
well sites, ocean-going vessels and shore-based facilities,
and into terrestrial ecosystems from exploration wells,
production wells, storage tanks and oil pipelines. Fondahl
(1997) gives the astonishing estimate that there are 36,000
oil pipeline ruptures per annum in Russia alone, or ninety-
six per day! She states further that the pipeline rupture in
the Komi Republic of Russia in 1994 spilt 270,000 tonnes
of crude oil (US estimate) compared with the Russian
estimate of 15,000 tonnes. This pipe had evidently been
leaking since 1988.
At present the technology for clearing up spills is not
adequate to remove oil from ice-covered waters, and there
must be a high probability of a major environmental
disaster in Arctic waters. An oil spill is much more
persistent in polar regions, as oil degrades ten to twenty-
five times more slowly at 5
C than at 25
C. Ice cover
reduces the spreading and evaporation of the oil
(spreading is two-thirds faster in the absence of ice), and
thus organisms are exposed to oil for much longer periods
than in temperate waters. The direct effects of exposure
to oil on marine mammals and birds are lethal; very
serious population crashes can occur if oil hits at breeding
time. The colonial nesting habit of birds and the colonial
gatherings of marine mammals make them particularly
This street in Dawson, Yukon, dates from Klondike gold rush
days in the early 1900s. The out-of-alignment facades of
buildings show how melting of the permafrost causes
differential subsidence and tilting.
Photo: Bill Barr
