Patterned Ground Formation and Description as Suggested by Low Arctic and Subarctic Examples

• Published in: Arctic and alpine research 1976-11, Vol.8 (4), p.329-342
• Main Author: Nicholson, Frank H.
• Format: Article
• Language: English
• Subjects: Chalk; Flint; Freezing; Frost; Ice; Periglacial landforms; Permafrost; Polygons; Stripes; Vegetation
• ISSN: 0004-0851; 2325-5153
• DOI: 10.1080/00040851.1976.12003883

A modified system of patterned-ground field description was developed following observations in eastern England, northwest Alaska, and north Norway. Four major criteria were used: pattern surface form (equiform, elongate, stripe, step); pattern grouping (isolated, semigrouped, contiguous); pattern marking (relief, stone, vegetation); and pattern size. Field evidence of movements in the patterns, mainly from large excavated sections, is presented, which indicates movements downwards and inwards from beneath pattern margins and upwards in the pattern centers. These movements are believed to be mainly due to inclined freezing fronts, the consequent stress pattern and the relative compressional and tensional strengths of frozen ground. The movement towards the center at depth, together with well-known pattern movements, indicates a circulatory model of movement of fines. An approximately radial model of movement for sorting is envisaged. If the two models are combined, the development of many forms of patterned ground can be explained. A tentative hypothesis for pattern initiation suggests that, under critical conditions, pattern centers, which are centers of greater than average heaving, subdue heaving in the margins. These marginal areas of subdued heaving in turn encourage greater heaving a unit distance away, hence triggering new units at regular intervals.