Geology Reference
In-Depth Information
Figure 5.6. Distribution of permafrost in the northern hemisphere. From Brown et al. (1997),
courtesy of the United States Geological Survey.
(Kudryavtsev et al., 1978). In the northern hemisphere, nearly one-half of Canada
and 80% of Alaska are underlain by permafrost (Figure 5.6). In Russia, nearly 50% is
underlain by permafrost, most occurring in the forest zone east of the Yenesei River. In
China, permafrost occurs on the Tibet Plateau and in northeast China.
Typical permafrost thickness and mean annual air temperatures data are indicated in
Table 5.3. In North America, the permafrost distribution is broadly governed by climate;
the southern limit of continuous permafrost generally coincides with the position of the
8 °C mean annual air temperature isotherm (Brown, 1960, 1966, 1967a; Péwé,
1966b). The southern boundary of continuous permafrost extends east from the Seward
6 °C to
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