Some mechanical aspects of pingo growth and failure, western Arctic coast, Canada

1987 ◽  
Vol 24 (6) ◽  
pp. 1108-1119 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Elastic Plate ◽  
Plate Theory ◽  
Early Growth ◽  
Thin Elastic Plate ◽  
Normal Faulting ◽  
Overburden Thickness ◽  
Changing Roles ◽  
Western Arctic ◽  
Arctic Coast ◽  
Spring Flow

Many closed-system pingos are underlain by sub-pingo water lenses, and the same is probably true of numerous open-system pingos. In the early growth stage the bending of the frozen overburden of a pingo by a sub-pingo water lens can be compared to the bending of a thin elastic plate. Although the assumptions of elastic plate theory do not apply fully to a growing pingo, because time-dependent plastic and creep deformation are involved, the application of elastic plate theory nevertheless helps to explain the peripheral normal faulting and spring flow of pingos, summit failure, the ease with which elongated pingos appear to collapse, and the changing roles played by the radius and overburden thickness of pingos from early growth to the cessation of growth.

scholarly journals Pingo Growth and collapse, Tuktoyaktuk Peninsula Area, Western Arctic Coast, Canada: a long-term field study

2002 ◽  
Vol 52 (3) ◽  
pp. 271-323 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Freezing Point ◽  
Growth Data ◽  
Long Term Study ◽  
Western Arctic ◽  
Mound Growth ◽  
Arctic Coast ◽  
Spring Flow ◽  
Potential Use ◽  
Term Field

Abstract Growth data from precise surveys have been obtained for 11 pingos for periods ranging from 20 to 26 years. Most of the 1350 pingos, perhaps one quarter of the world's total, have grown up in the bottoms of drained lakes underlain by sands. Permafrost aggradation on the drained lake bottoms has resulted in pore water expulsion, solute rejection below the freezing front, a freezing point depression, and groundwater flow at below 0° C to one or more residual ponds, the sites of pingo growth. Sub-pingo water lenses underlie many growing pingos.The pure ice which grows by downward freezing in a sub-pingo water lens may be composed of seasonal growth bands which, like tree rings, are of potential use in the study of past climates. Growing pingos underlain by sub-pingo water lenses can often be identified by features such as peripheral pingo rupture, spring flow, frost mound growth, normal faulting, and oscillations in pingo height. Such features, and others, are associated with hydrofracturing and water loss from a sub-pingo water lens. Some of the data derived from the long-term study of pingo growth are relevant to the identification of collapse features, interpreted as paleo pingos, in areas now without permafrost.

The Growth of Pingos, Western Arctic Coast, Canada

1973 ◽  
Vol 10 (6) ◽  
pp. 979-1004 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Growth Rate ◽  
Pore Water ◽  
Closed System ◽  
Water Pressure ◽  
Ice Core ◽  
Growth Stages ◽  
Size And Shape ◽  
Western Arctic ◽  
Arctic Coast ◽  
Strong Control

The growth rates of 11 closed system pingos have been measured, by means of precise levelling of permanent bench marks anchored well down into permafrost, for the 1969–1972 period. As pingo growth decreases from the summit to the base, growth of the ice-core decreases from the center out to the periphery. The pingos have grown up in the bottoms of lakes which have drained rapidly and thus become exposed to permafrost aggradation. The specific site of growth is usually in a small residual pond where permafrost aggradation is retarded. The size and shape of a residual pond exercises a strong control upon the size and shape of the pingo which grows within it. The ice-core thickness equals the sum of the pingo height above the lake flat and the depth of the residual pond in which the pingo grew. Pingos tend to grow higher rather than both higher and wider. Pingos are believed to grow more by means of ice segregation than by the freezing of a pool of water. The water source, and the associated positive pore water pressure, result from permafrost aggradation in sands and silts in the lake bottom under a closed system with expulsion of pore water. The fastest growth rate of an ice-core, for the Western Arctic Coast, is estimated at about 1.5 m/yr, for the first one or two years. After that, the growth rate decreases inversely as the square root of time. The largest pingos may continue to grow for more than 1000 yr. Four growth stages are suggested. At least five pingos have commenced growth since 1935. As an estimate, probably 50 or more pingos are now growing along the coast.

scholarly journals PERFORMANCE OP SAND-FILLED TUBE SHORE PROTECTION TUKTOYAKTUK, NORTH WEST TERRITORIES, CANADA

1982 ◽  
Vol 1 (18) ◽  
pp. 114
Author(s):  
V.K. Shah
Keyword(s):  
Large Majority ◽  
Natural Stone ◽  
Alternative Form ◽  
Shore Protection ◽  
Experimental Basis ◽  
North West ◽  
Western Arctic ◽  
Arctic Coast ◽  
North West Territories ◽  
North Latitude

Seawalls, revetments and groynes designed to protect shorelines require normally timber, natural stone or concrete for their construction. In Tuktoyaktuk, none of these materials is available and to avoid excessive costs, an alternative form of construction, using long sausage shaped tubes filled with sand, was devised on an experimental basis. Tuktoyaktuk is situated on the eastern side of Kugmallit Bay in the Western Arctic at north latitude of 69 deg. 27' and west longitude of 133 deg. 02'. It is approximately 90 miles north of Inuvik and 1450 miles northwest of Edmonton (figure 1). The area is mainly comprised of a long, narrow, boot-shaped peninsula oriented in approximately north-south direction, a complex lagoon, which has been developed as a harbour, east of the peninsula and an island straddling the mouth of the lagoon (figure 2). Certain dwellings exist at the southern and southeasterly shores of Tuktoyaktuk Harbour. A large majority of the inhabitants reside in settlements developed on the peninsula and the southern area linking the peninsula with the mainland. Tuktoyaktuk is used as a transfer point linking the Mackenzie River barge transport with coastwide shipping serving the western arctic seaboard and inland settlements and bases. As a result of this the TCJK settlement has grown to be the largest of the western arctic coast settlements.

Ice wedges on hillslopes and landform evolution in the late Quaternary, western Arctic coast, Canada

1995 ◽  
Vol 32 (8) ◽  
pp. 1093-1105 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Active Layer ◽  
Late Quaternary ◽  
Chronological Age ◽  
Bottom Slope ◽  
Thermally Induced ◽  
Landform Evolution ◽  
Ice Wedge ◽  
Western Arctic ◽  
Arctic Coast ◽  
The Mean

In rolling to hilly areas of the western Arctic coast of Canada, anti-syngenetic wedges, which by definition are those that grow on denudational slopes, are the most abundant type of ice wedge. Through prolonged slope denudation, hilltop epigenetic wedges can evolve into hillslope anti-syngenetic wedges, and some bottom-slope anti-syngenetic wedges, by means of deposition from upslope, can evolve into bottom-slope syngenetic wedges. The axis of a hillslope wedge is oriented perpendicular to the slope, so the wedge foliation varies according to the trend of the wedge with respect to the slope. Because the tops of hillslope wedges are truncated by slope recession, the mean chronological age of anti-syngenetic wedge ice decreases with time, so the growth record for an old wedge is incomplete. Summer and winter measurements show that a thermally induced net movement of the active layer of hillslope polygons tends to transport material from their centres towards their troughs independent of the trends of the troughs relative to the slope. Wedge-ice uplift, probably diapiric, has been measured. Some hillslope polygon patterns may predate the development of the present topography. Many Wisconsinan wedges, truncated and buried during the Hypsithermal period, have been reactivated by upward cracking.

General Solutions for the Statics of Anisotropic, Transversely Inhomogeneous Elastic Plates in Terms of Complex Functions

2006 ◽  
Vol 11 (6) ◽  
pp. 596-628 ◽  
Author(s):  
Kostas P. Soldatos
Keyword(s):  
General Solution ◽  
Elastic Plate ◽  
Plate Theory ◽  
High Order ◽  
Transverse Strain ◽  
Elastic Plates ◽  
General Solutions ◽  
Material Inhomogeneity ◽  
Complex Functions ◽  
Anisotropic Elastic

This paper develops the general solution of high-order partial differential equations (PDEs) that govern the static behavior of transversely inhomogeneous, anisotropic, elastic plates, in terms of complex functions. The basic development deals with the derivation of such a form of general solution for the PDEs associated with the most general, two-dimensional (“equivalent single-layered”), elastic plate theory available in the literature. The theory takes into consideration the effects of bending–stretching coupling due to possible un-symmetric forms of through-thickness material inhomogeneity. Most importantly, it also takes into consideration the effects of both transverse shear and transverse normal deformation in a manner that allows for a posteriori, multiple choices of transverse strain distributions. As a result of this basic and most general development, some interesting specializations yield, as particular cases, relevant general solutions of high-order PDEs associated with all of the conventional, elastic plate theories available in the literature.

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