Solifluction (frost-creep and gelifluction) is an important periglacial process and forms sheets, lobes, terraces, and ploughing boulders. Such landforms are more common in Low Arctic,
subarctic and alpine environments than in High Arctic polar deserts, which are too dry to promote much solifluction. Tongue-like lobes are common in the tundra and forest tundra, where some vegetation patches occur (Plate 11.8). Solifluction lobes tend to form below snow patches. Typically, they are tongued-shaped features, 10 to 100 m long, 5 to 50 m wide, with steep frontal margins or risers, which may stand 1.5 m high. Frostsorting processes often bring about a concentration of clasts around a lobe’s outer margins, which are called stone-banked lobes; lobes lacking marginal clasts are turf-banked lobes. Areas of widespread solifluction lobes are solifluction sheets, which can produce smooth terrain with low slope gradients (1° to 3°) where vegetation is scanty. Terraces are common on lower slopes of valleys (Plate 11.9). Steps are terrace-like landforms that occur on relatively steep slopes. They develop from circles, polygons, and nets, and run either parallel to hillside contours or become elongated downslope to create lobate forms. In unsorted steps, the rise of the step is well vegetated and the tread is bare. In sorted steps, the step is edged with larger stones. The lobate varieties are called stone garlands. No step forms are limited to permafrost environments. Ploughing boulders or ploughing blocks move down slopes through the surrounding soil, leaving a vegetated furrow in their wake and building a lobe in their van
(Plate 11.10).