Cryostatic pressures in nonsorted circles (mud hummocks), Inuvik, Northwest Territories

1976 ◽  
Vol 13 (7) ◽  
pp. 889-897 ◽  
Author(s):  
J. Ross Mackay ◽  
D. K. MacKay
Keyword(s):  
Northwest Territories ◽  
Active Layer ◽  
Water Loss ◽  
Time Span ◽  
Individual Identity ◽  
Soil Pressure ◽  
Field Evidence

Experiments were carried out during the 1967–1972 period in an attempt to measure cryostatic (frost-induced) pressures by means of soil pressure cells installed in nonsorted circles (mud hummocks) at Inuvik, N.W.T. Although slight soil pressure increases were measured in the hummocks during the freeze-back period, the field evidence shows that the hummock centers became desiccated, overconsolidated, and immobile rather than saturated, underconsolidated, and mobile, because of water loss to growing ice lenses at the top and bottom of the active layer. Cryostatic pressures during the freeze-back period are considered to be no more important than thaw displacement in the summer. The Inuvik mud hummocks appear to maintain considerable stability and individual identity over a time span of hundreds of years.

The origin of hummocks, western Arctic coast, Canada

1980 ◽  
Vol 17 (8) ◽  
pp. 996-1006 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Northwest Territories ◽  
Active Layer ◽  
Late Summer ◽  
Field Observations ◽  
Soil Pressure ◽  
Freeze Thaw ◽  
Fine Grained ◽  
Field Evidence ◽  
Upward Displacement ◽  
Upward Moving

Hummocks (nonsorted circles) are widely distributed in arctic and subarctic regions. The hummocks under discussion are composed of fine-grained frost-susceptible soils; the late summer frost table is bowl-shaped; and the hummocks grade from those which are completely vegetated (earth hummocks) to those with bare centres (mud hummocks). The mound form is usually attributed to an upward displacement of material resulting from cryostatic (freeze-back) pressure generated in a confined, wet, unfrozen pocket of the active layer. Theoretically, cryostatic pressure should not develop in a frost-susceptible hummock soil, because ice lensing at the top and (or) bottom of the active layer will desiccate the last unfrozen pocket so that the pore water is under tension, not pressure. Field observations carried out at Garry Island, Northwest Territories, for 1965–1979 and for 1967–1979 at Inuvik, Northwest Territories, involving: summer and winter excavations; the measurement of the deformation of tubes, soil pressure, soil temperature, soil heave, soil moisture migration; and observations on hummock stability provide no field evidence for the cryostatic theory. An alternative model of hummock growth, based upon field observations, is here proposed. The upward displacement of material is believed caused by freeze–thaw of ice lenses at the top and bottom of the active layer with a gravity-induced cell-like movement, because the top and bottom freeze–thaw zones have opposite curvatures. The cell circulation is evident from the grain-size distribution of hummock soils and from upward-moving tongues of saturated soil observable in late summer. The most active period is in late summer. Model experiments in the laboratory have been successful in producing mounds by freeze–thaw of a kaolin slurry in a bowl-shaped container in support of the proposed theory.

A reassessment of transport mechanisms of some rock avalanches in the Mackenzie Mountains, Yukon and Northwest Territories, Canada

1990 ◽  
Vol 27 (1) ◽  
pp. 129-144 ◽  
Author(s):  
P. K. Kaiser ◽  
J. V. Simmons
Keyword(s):  
Debris Flow ◽  
Northwest Territories ◽  
Valley Bottom ◽  
Flow Simulations ◽  
Rock Avalanches ◽  
Field Evidence ◽  
Debris Transport ◽  
Glacier Ice ◽  
Mackenzie Mountains ◽  
New Hypothesis

The transport mechanism of some rock avalanches of the Mackenzie Mountains in the Yukon and Northwest Territories of Canada is reassessed on the basis of evidence collected during fieldwork and by comparison with results from numerical simulations of the debris flow mechanism. A new hypothesis of glaciation-related transport is advanced as an alternate explanation of apparently very mobile rock avalanches with anomalous travel distances. By the example of the Avalanche Lake slide, it is demonstrated that the debris was most likely not deposited on the current topography but on valley glacier ice at an elevation of about 400–500 m above the valley bottom. This conclusion is supported by field evidence, an empirical runup relationship, and the results from numerical flow simulations. A qualitative interpretation of other debris deposits suggests that several events in the Mackenzie Mountains can be interpreted in the same manner. Key words: rock avalanches, rock slides, debris transport, debris flow modelling, Mackenzie Mountains, Northwest Territories.

Active-layer characteristics and summer climatic indices, Mackenzie Valley, Northwest Territories, Canada

2009 ◽  
Vol 20 (2) ◽  
pp. 201-220 ◽  
Author(s):  
Sharon L. Smith ◽  
Stephen A. Wolfe ◽  
Daniel W. Riseborough ◽  
F. Mark Nixon
Keyword(s):  
Northwest Territories ◽  
Active Layer ◽  
Climatic Indices

scholarly journals Report on 2015 field activities and collection of ground thermal and active layer data in the Mackenzie Corridor, Northwest Territories

2016 ◽  
Author(s):  
S L Smith ◽  
J Chartrand ◽  
C Duchesne ◽  
M Ednie
Keyword(s):  
Northwest Territories ◽  
Active Layer

Downward water movement into frozen ground, western arctic coast, Canada

1983 ◽  
Vol 20 (1) ◽  
pp. 120-134 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Soviet Union ◽  
Active Layer ◽  
Water Movement ◽  
Field Studies ◽  
Frozen Ground ◽  
Thermally Induced ◽  
The Soviet Union ◽  
Field Evidence ◽  
Hydraulic Gradients ◽  
Ice Content

Field studies carried out mainly since 1975 in permafrost areas of Alaska, Canada, China, and the Soviet Union have been combined with the results of laboratory investigations to show that in summer water can move from the thawing active layer into the subjacent frozen active layer and under certain conditions even into the top of permafrost. Direct field evidence discussed includes: data from drilling and neutron probe logging, which show a summer increase in the ice content of already frozen ground; summer heave of heavemeters, with heave occurring in the frozen active layer; and increase in the ice content of the subjacent frozen ground in both permafrost and non-permafrost areas, caused by snowmelt infiltration. Indirect field and laboratory evidence is also added to support the direct lines of evidence. The conditions that favor the downward migration of water from thawed to frozen ground are examined in terms of thermally induced hydraulic gradients, hydraulic conductivity, content of unfrozen pore water, temperature gradients, ice content, and gravity. Some geocryologic implications of the summer growth of ice in frozen ground, including the effects on water balance calculations and the origin of patterned ground, are briefly mentioned.

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