Patterned ground near Dundas (Thule Air Force Base), Greenland

Abstract

Near Dundas in northwest Greenland is an area of 150 square miles (380 square km.) known as Nunatarssuaq. Drift covers most of the region and shows various forms of patterned ground that have developed by repeated thawing and intense freezing.

Stone-rimmed polygons form the prevailing pattern on nearly level till surfaces. These grade into elongate or stretched polygons and stone stripes on sloping ground. On many of the steeper slopes, stone-banked solifluction lobes have developed. All these forms reflect the prevailing stony character of the drift.

In outwash deposits, only a large-scale fracture pattern is common, and limited areas of water-sorted drift (outwash) can by this characteristic be identified readily from a helicopter. No frost-sorted stone borders have developed around outwash polygons. The primary patterns in both till and outwash show a hexagonal motif and are believed to have developed by contraction resulting from extreme low temperatures. The subsequent frost-sorting process which has given rise to the stone borders is not definitely known. The chief factors governing development of patterned ground in the drift are believed to be: 1, slope; 2, composition of the material; 3, moisture content; 4, drainage; and 5, depth of thaw.