The origin of pingos in regions of thick permafrost, Western Canadian Arctic

The presence of pingos in regions of thick and continuous permafrost is often explained by the freezing of a talik previously developed be¬neath a standing water body, usually a lake. These pingos are generally referred to as “Mackenzie Delta” or closed system type pingos. A number of pingos studied in the islands of the Western Cana¬dian Arctic indicate that the conditions for fav¬ourable closed system pingo growth are much more varied. For example, pingos situated on low terra¬ces of the Thomsen River in north central Banks Island (73° N) probably developed following the lateral migration of the river and the freezing of a talik which had formed beneath the channel (Fig. 2). Two near parallel pingo-like ridges deve¬loped on the lower part of the gentler slope of an asymmetrical valley in southern Banks Island (71° N) are thought also to have formed by the freezing of sub-channel taliks at times when the stream migrated laterally to produce the valley asymmetry (Fig. 6). On Prince Patrick Island, elon¬gate pingos located near the coast at Satellite Bay (77° N), formed following fluctuations of sea level and the inundation of river valleys (Fig. 7). Other pingos, located in the central parts of Prince Partie Island (76° N), appear related to the presence of deep faults in the underlying bedrock at a time when permafrost was aggrading (Fig. 9). Those pingos thought related to the evolution of streams often exhibit an elongate, ridge-like form.