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The surface of the Prudhoe Bay oil field consists of a flat,
treeless, desert plain of approximately 69,000 square miles
covered by a thin mat of vegetation and organic material called
tundra. Beneath the tundra is a layer of permafrost that extends
to a depth of 1,800 to 2,000 feet.
From mid-May through mid-September, the sun does not set on
the North Slope. Summer temperatures may reach 80 degrees
Fahrenheit. From June through September, when the tundra thaws
to a depth of 12 to 18 inches, vehicular traffic on the tundra is
prohibited unless authorized by permit and may be conducted only
in specially designed vehicles called Rolligons.
During summer, the permafrost traps water on the tundra
surface, and the North Slope becomes a wetlands with thousands of
shallow lakes and abundant wildlife, including numerous migratory
birds and animals.
In winter, North Slope temperatures fall to -70 degrees
Fahrenheit, the tundra freezes, blizzards and whiteouts are
common, and darkness prevails for much of the day. In late
November, the sun dips below the horizon and does not reappear
until mid-January.
In spite of harsh winter conditions, some work on the North
Slope is better performed during winter because frozen tundra
provides a better foundation for vehicular traffic than tundra
that, during the summer, may not be passable.
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Last modified: May 25, 2011