Ice edge
Beyond the limits of the ice, constant freezing and thawing of water in the ground created many fascinating landforms which can still be seen today. These forms derive from what is technically termed 'periglacial' activity beyond the ice margins and can be seen being formed in arctic and alpine areas today.
On the plateaux
- On many mountain plateaux you can see hummocky ground, where seasonal freezing and thawing has caused the soil surface to bulge in a regular formation.
- There is evidence on these plateaux of the wind having blown sand and gravel, just as it does in coastal sand dunes.
- 'Blockfields' comprising large blocks of stone are common on many mountain tops and plateaux in Scotland. These formed as frost and ground-ice shattered the bedrock.
Steep places
On steeper slopes, the loosened boulders and soil have gradually moved downslope, forming distinctive sheets, terraces and lobes of debris and boulders. Larger boulder lobes in Scotland were last active during the Loch Lomond Readvance (12,900 - 11,500 years ago), but some smaller features have been moving during the last few thousands years.
The trimline
Often on mountain sides there is a distinct lower limit to periglacial landforms formed during the galciation; this 'trimline' marks the upper level of erosion associated with the advance of ice down a valley, trimming off the periglacial forms which were still active above the level of the ice.
Lower ground
On lower ground, examples of periglacial features are more difficult to see. In the gravel terraces of the river valleys, ice-wedge casts can sometimes be found where the permanently frozen ground contracted and cracked. The cracks were filled with material from the surrounding area. At a few sites you can see the rumpling up into folds of the soil layers through repeated freezing and thawing.
Active today
Although smaller than the landforms formed at the end of the last glaciation, modern active features include sorted stone stripes, sorted circles, turf-banked terraces, 'ploughing' boulders, wind-eroded (deflation) surfaces and wind-patterned vegetation.