Aerial view of low, pingo, or palsa-like featuresLocation: Maguse River delta, Nunavut, Canada; NTS 55E Eskimo Point; approx. 61° 15' N, 94° 00' W
Aerial view from about 300 m altitude of low, pingo, or palsa-like features near the mouth of the Maguse River, on its delta. These 4- to 8-m-diameter, 1- to 2-m-high mounds are surrounded by seasonally flooded, vegetation-free stony mud and seem to be largely composed of medium-grained sand, which is vegetated, as I recall, by grasses and caribou moss. The mounds are thought to be uplifted by the formation of ice lenses just below the surface, but no segregated ice was observed in the upper 75 cm of the mounds. The features are typically ornamented by prominent cracks radiating from their centers as a result of expansion of the sediment surface caused by the doming. The mounds seem to degenerate landward on this very flat coastal plain (see image 0049), and they occur just above the tidal zone. They have been observed only on the south side of the Maguse River delta and appear to be unique periglacial features. On the ground, these mounds are honeycombed with burrows dug, it appears, by arctic foxes, and the ground around them is littered with the remains of animals, mainly birds. As we walked through this landscape, we could hear hollow-sounding barking noises coming from the burrows. This ecosystem is truly unique, and the vegetation is particularly lush on the mounds, presumably as a result of fertilization by scat and animal remains. See also images 0049, 0048, 0109, and 0131.
Updated 04/07/2010 AW