Nonsorted Stripes Research Articles

Patterned ground above the alpine timberline in the High Sudetes, Central Europe

ABSTRACT Patterned ground in mountainous areas has a high palaeogeographic significance as it is associated with cold environments and frequently with permafrost conditions. Most patterned ground (i.e. sorted polygons, sorted nets, sorted stripes) in the High Sudetes is overgrown by vegetation and is relict. However, wind-blown summit areas with low snow cover allow for the activity of sorted circles, earth and peat hummocks, and some non-sorted stripes. The extent of patterned ground above the alpine timberline in the High Sudetes presented here is based on detailed field geomorphologic mapping. Patterned ground occurs on summit planation surfaces and surrounding gently sloping terrain, and covers 5.23 km2. Sorted polygons are the highest-elevated patterned-ground type. The spatial distribution of patterned ground is shown in the map, which could be helpful for future research of the Quaternary geomorphologic evolution of the mountain landscape and for nature protection planning in the High Sudetes.

Spatial and temporal distribution of soil organic carbon in nonsorted striped patterned ground of the High Arctic

The role of periglacial processes on soil carbon distribution is examined at a High Arctic site in northwest Greenland. A 16‐m trench dug across a series of nonsorted stripes at Thule Air Base revealed sand‐rich wedges underlying striped, vegetated troughs, and organic‐rich soil horizons buried at depth. The site has sparse prostrate vegetation and is estimated to contain 9.4 kg/m2 of soil organic carbon (SOC) in the active layer. The distribution of carbon is variable with nearly half (49%) stored in the sand wedges, which only account for 10% of the trench area. Additionally, 62% of the total SOC was found below 25 cm, highlighting the significant role of cryoturbation and physical redistribution of carbon in permafrost‐affected soils. Carbon in the active sand‐rich wedges dates from modern at the surface (65 ± 35 radiocarbon years) to 2695 ± 40 radiocarbon years at depth, and carbon turnover time appears to be ∼450 years. Buried organic horizons found at 50–70 cm depth have radiocarbon ages of 27,480–31,900 BP. A conceptual model is proposed in which the active sand wedges have developed in an approximately 30 ka surface containing buried soils preserved in permafrost or under a cold‐based glacier. As the ice retreated and soils warmed, soil development and active cryoturbation resumed forming nonsorted stripes in the modern surface.

Glaciation and Periglacial Morphology in the Northwestern Venezuelan Andes

Abstract. Evidences of previous glaciation in the northwestern Venezuelan Andes, mainly in Páramo de Piedras Biancas, include a main morainic level at 3400 to 3700 m, and minor moraines at higher elevations up to about 4300. Glaciated valleys, hanging valleys, rock, steps, glacial channels, cirques, arêtes, horns, striae and grooves on polished rock, roche mountonnés, and whaleback forms, are the main evidence of glacial sculpture and erosion. The main morainic level probably represents a Late Wisconsin glacial advance, and the higher moraines are either neo-glacial or due to minor readvances during the main postglacial retreat. The main morainic level, 400 m higher than that in the southeastern Venezuelan Andes, indicates that the glacial climate was drier in the northwestern part than in the southeastern part of this mountain range. Present-day periglacial features include micro-terrassettes, turf exfoliation, talus, and striated ground, above 3500 m; and nonsorted stripes, sorted polygons or sorted circles, and sorted nets, above 4000 m. The present-day periglacial zone is located between approximately 3600 and 4700 m. During glacial times it probably readied down to 2400 m in the southeastern, and 2900 m in the northwestern parts of the Venezuelan Andes.

Mass-Wasting at Sachs Harbour, Banks Island, N. W. T., Canada

Rates of movement of nonsorted stripes on slopes of very low angle (2 to 4°) were measured over a 3-year period, 1969 to 1972, at Sachs Harbour in southern Banks Island. Average annual subsurface m...