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Deep Thaw Above
Shallow Thaw Above
Unfrozen
Permafrost (>3.0 m)
Permafrost (>1.0-3.0 m)
Based Upon
Active Layer Above
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Permafrost (≤1.0 m)
100 m
Limited Data
a. Characteristic depths of thaw and the locations of zones that are unfrozen from the surface into
bedrock. Small, shallow drainageways and gullies are not identified on this map. These areas may
locally exceed thaw depths by two or three times the cited depths. Completely thawed areas have
peripheral shallow and deep thaw zones, which, unless quite wide, are omitted from the map to
reduce clutter.
Figure 10. Preliminary maps of the Canol Road area. Maps made from unrectified aerial photo-
graphs taken on 20 May 1993. Interpretations are based upon GPR and borehole data and ground
observations.
mon within former channels, swales or sloughs,
Unfrozen areas of former sloughs and swales are
resulting in an arcuate pattern that reflects the
commonly vegetated by large birch and aspen or
past alluvial activity in this area (Fig. 10). Thaw
poplar.
depths adjacent to such unfrozen areas are deeper,
Permafrost extends from about 7 m depth near
but often become shallow rapidly with distance
the base of Birch Hill to over 35 m south of the
away from them (Fig. 11).
Truck Fill Stand and west of Canol Road (Fig. 12).
Vegetation can tell us the approximate range
Permafrost generally thickens, and depths to its
of thaw depth in some areas. Stunted black spruce,
base increase, with distance south of Birch Hill.
for example, are usually growing on an active
Where unfrozen materials occur above bedrock,
layer that is less than 1 m thick. Larger, healthy
we presume that the bedrock is unfrozen at depth
spruce, sometimes mixed with birch, may grow
as well. The depth to bedrock ranges from several
within areas having deeper annual thaw zones.
meters to over 40 m in the same area (see Fig. 13).
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