Geology Reference
In-Depth Information
()
a
()
b
()
i
Thermokarst lake
Dilation
crack
Lifting force
(hydrostatic pressure)
Permafrost
Unfrozen
saturated sands
Permafrost
()
ii
Lake drains
Residual pond
Permafrost
Ice
body
Pore water
under hydrostatic
pressure from
pore water expulsion
Permafrost
Permafrost
aggradation
Permafrost
aggradation
Dilation crack
()
iii
Pingo ice
Sub-pingo
water lens
Ta l i k
Unfrozen
pore water at < 0°C
Total uplift volume of
pingo ice and pore ice
()
iv
()
v
Collapsing pingo
Pond
Figure 11.4 Pingo formation. (a) Closed-system pingo produced after the infilling of a lake. (b) Open-system pingo.
Sources: (a) Adapted from Mackay (1998, 8); (b) Adapted from Müller (1968, 846)
occur in central Alaska, the Alaskan coastal plain, and the
floor of the Beaufort Sea, in the Canadian Arctic. Active
pingos occur in central Alaska and coastal Greenland,
and the north of Siberia, particularly in deltas, estuar-
ies, and alluvial areas.
forms are seldom higher than 2 m and between 15
and 50 m in diameter. They are used as owl perches
and stand out as fairly dry sites. Their origin is unclear
as they bear no apparent relationship to topography.
Even smaller hydrolaccoliths, which are never more than
1 m high or about4mindiameter, occur in parts
of the North American Arctic, including Southampton
Island, in North West Territories, Canada, and Alaska,
USA. These features seem to result from the segregation
of ice.
Bugors
Bugors and bugor-like forms are small and short-lived
mounds that occur in the active layer. In Siberia, Russia,
bugors (the Russian word for knolls) are gently rising oval
mounds or hydrolaccoliths that occur in scattered groups.
They are 5-10 m high, 50-80 m wide, and 100-5,000 m
long. Similar, though slightly smaller, hydrolaccoliths
occur in the North American Arctic. These bugor-like
Palsas, peat plateaux, and string bogs
A palsa is a low peat hill, commonly conical or dome-
shaped, standing some 1-10 m high and having a
 
Search WWH ::




Custom Search