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Development and decay of a lithalsa in Northern Québec: A geomorphological history
Authors:Fabrice Calmels  Michel Allard  Georg Delisle
Institution:aCentre d'Études Nordiques, Université Laval, pav. Abitibi-Price, Québec, Qc, Canada G1K 7P4;bBundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hannover, Germany
Abstract:The complete life cycle of a permafrost mound is reconstructed from its growth until its degradation. The study site is a lithalsa, which is the subject of a long-term monitoring that includes geocryological observations, measurements of permafrost properties on cores, ground temperature measurements, and observations of landform changes. The landform likely grew as a palsa under cold climatic conditions in the past. The peat cover was subsequently eroded. Early stages of degradation are witnessed since 2003 as a new thermokarst pond is starting to form though mound collapse. Settlement of the structure has been observed, and a rim ridge has begun to form. Ultimately, the lithalsa shall disappear and be replaced by a circular thermokarst pond surrounded by a rampart, similar to many other ones in the study area. The monitoring of the thermal regime of the lithalsa illustrates the pattern of internal warming and points to the causes of its degradation.
Keywords:Palsas  Lithalsas  Permafrost  Thermal regime  Thermokarst  Landform processes
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