Patterned Ground and Active Layer Phenomena

There has not been much focus on the incidence of patterned ground and active layer phenomena on Disko Island. Ice-wedge polygons associated with thermal contracting cracking are not a widespread landform, but do occur in some areas such as at the northern end of Blresedalen (Figure 7). However, various forms of sorted and unsorted circles (Figure 8) and stripes (Figure 9) are very common and occur from sea-level to high altitudes. Movement in the active layer is also evident in areas with high deposition rates such as on outwash plains, where up to 25 cm high stone heave mounds may form within one or a few years (Figure 10).

Figure 8. Unsorted circles on Pjetursson's moraine, east of Qeqertarsuaq (Godhavn). GPS receiver for scale.
Figure 10. Stone heave mounds formed in glaciofluvial and glacier naled deposits, Kuannersuit Kuussuat (Kuannersuit Valley).

Solifluction is an important process of soil movement in active layers, and solifluction lobes occur on many valley slopes (Humlum et al., 1995). Active layer detachment slides are often observed in connection to solifluction lobes, increasing the rate of down-slope transportation.

Palsas seem to be rare landforms on Disko Island. The author has only observed palsas in peaty wetlands on the eastern shore of the lake in front of Pjetursson's moraine east of Qeqertarsuaq (Godhavn). Thus, it is unknown whether palsas are restricted to the more humid southwestern part of the island.

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