Miniature stripes on the plateau east of the Lairig Ghru
Large scale stone stripe on the western slopes of Beinn a'Bhuird
Definition: An array of small-scale, geometric features found at the surface of a regolith that has been disturbed by frost action. The group includes circles, polygons, and nets, which normally occur on level or gently sloping surfaces, and steps and stripes which are found on steeper gradients. Both sorted and non-sorted varieties are recognized. The sorted varieties are typically outlined by coarse, stony material, and so are termed 'stone circles', 'stone polygons', 'stone nets', 'stone steps', and 'stone stripes'. The origin of patterned ground involves a complex interaction of several geomorphological processes, including frost sorting, frost heaving, and mass movement.
Patterned ground is perhaps the most striking feature of the periglacial landscape. Small scale patterned ground in the forms of nets and stripes occurs locally on the plateau. It tends to occur on wet sites where granular regolith have been exposed, either by wind stripping or by snow melt. Patterns will reform in a few years on undisturbed sites but the good examples that formerly existed on the floor of Coire Domhain are now disturbed too frequently by walkers to reform.
Large scale patterns occur within block fields or block slopes. King (1971) describes stone nets and polygons over 2 m wide west of the path to the summit of Ben Macdui. Large stone stripes, as well as circles are well displayed on the western summit slopes of Carn Ban Mór (Gordon, 1993). Although there is much debate as to the mechanisms involved in sorting such coarse materials, it is widely agreed that the large scale patterned ground reflects the former existence of permafrost (Ballantyne, 1996). This implies that the large scale patterns were reactivated during the Loch Lomond Stadial, an observation support by the absence of these patterns from inside the former glacier limits. The suggestion that some large scale stripes may have survived beneath a cover of cold-based ice (Gordon, 1993) is supported by the occurrence of the western slopes of Beinn a' Bhuird of boulder stripes that appear to have been truncated downslope by glacial entrainment. More generally, the suggestion that some blockfields may predate the last interglacial implies that large scale patterned ground may also be of considerable age (Gordon, 1993).