Pingo Growth and collapse, Tuktoyaktuk Peninsula Area, Western Arctic Coast, Canada: a long-term field study
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...
| Published in: | Géographie physique et Quaternaire |
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| Main Author: | |
| Format: | Text |
| Language: | English |
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Les Presses de l'Université de Montréal
1998
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| Subjects: | |
| Online Access: | http://id.erudit.org/iderudit/004847ar https://doi.org/10.7202/004847ar |
| Summary: | 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. Onze pingos ont fait l'objet d'une étude qui comprend des données de croissance et des relevés détaillés pour des périodes allant de 20 à 26 ans. La majorité des 1350 pingos, qui constituent peut-être le quart du total mondial, se sont développés dans des fonds de lacs asséchés, sous lesquels se trouvent des dépôts de sable. L'expansion du pergélisol dans ces dépressions lacustres asséchées a provoqué l'expulsion de l'eau interstitielle, le rejet des solutés sous le front de gel, une diminution du point de congélation et l'écoulement, à des températures sous 0° C, de l'eau souterraine vers des mares résiduelles, là où croissent les pingos. Sous de nombreux pingos en expansion se trouvent des lentilles d'eau. La glace pure qui se forme lors de la progression du ront de gel dans la lentille d'eau peut ... |
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