Key sites
Lounders Fea, a glacially-disturbed sandstone blockfield with extensive deflation surfaces
Erected pebbles and cracked clasts associated with former ground ice
Periglacial landscapes
Defintion: any area with a tundra climate, such as mountainous areas in mid-latitudes, or where frost processes are active or permafrost occurs in some form.
Two generations of periglacial feature exist on Orkney:
- features active today or earlier in the Holocene
- features formed under intensely cold conditions during the Loch Lomond Stadial and the early phases of deglaciation
Active periglacial features are confined to the
hill tops of Hoy and reflect a prevailing environment of high wind speeds,
heavy but now short-lived snowfalls, high ground moisture levels, and frequent
freeze thaw cycles in winter. The relict forms reflect, at least in part, more
severe periglacial conditions when permafrost may have been widespread. The
former presence of ground ice allowed heave processes to move much bigger
blocks than is currently possible and enhanced frost weathering generated
large volumes of scree and other angular rubble.