Geology Reference
In-Depth Information
Table 8.1.
Active-layer thickness under different terrain conditions. (A) Depth of the active layer in ice-wedge polygon terrain in Yana-Indigirka
lowland of northern Siberia. (B) The increase in active-layer depth, thickness of permafrost thawed, and amount of ground subsidence at the site of
the 1968 forest fi re near Inuvik, NWT, Canada.
(A) Moisture conditions in central part of polygon
Depth of active layer (cm)
Latitude 70° N
Latitude 71° N
Relatively dry
30-34
23-25
Moist
38-41
31-33
Water layer, 7-10 cm deep in polygon centre
52-56
39-42
Water layer, 20-25 cm deep in polygon centre
62-69
51-53
Lake, 30
×
40 m with depth 25 cm or more
75
+
(B) Site
Mean increase since 1960 in
Mean thickness of
Mean ground
active-layer depth (approx)
permafrost thawed (cm)
subsidence (cm)
(approx.)
(approx.)
Unburned
From 42 cm to 52 cm in 1979
15
5
Burned
From 35 cm to 72 cm 1973
55
18
Burned:
Ridges
From 60 cm to 137 cm in 1988
116
39
Depressions
117
39
Unburned:
Hummocks
From 115 cm to 132 cm in 1981
26
9
Depressions
From 76 cm to 108 cm in 1981
48
16
Burned:
Hummocks
From 116 cm to 136 cm in 1979
30
10
Depressions
From 68 cm to 102 cm in 1979
51
17
Source: (A) Czudek and Demek (1970). (B) Mackay (1995a).
