Contrast between a mudboil-covered till surface and degrading frost polygons

Location: Kaminak Lake Area, Kivalliq, Nunavut, Canada; NTS 55L Kaminak Lake

This image is a closer view of the background of the left side of image 0072, which has an explanation of the scene. Note the large number of active mudboils, which in this region indicate the presence of red clayey till (see image 0091) or marine, fine-grained, offshore sediments. Fine-grained marine sediments (from the post-glacial Tyrrell Sea) undoubtedly underlie, at depth, the lower areas characterized by frost cracks, but the organic peat that develops in these poorly drained sites thaws to less than 50 cm, causing the rigid, perennially frozen, underlying sediments to retain their cracks, which enlarge seasonally. The frost cracks in this image are “degrading” during this particularly hot summer, and the water from the melting ice wedges is pooled over the cracks. Note, also, the strongly developed solifluction stripes that are best developed on areas of active mudboils in this region. The dark part of the stripes is characterized by low, brushy vegetation (dwarf willow, dwarf birch, Dryas integrefolia, etc.) that grows preferentially on the wet depressions between lobes. See detailed discussion for image 0240.

Photo by Dr. A. N. Boydell

Updated 05/06/2010 AW