effects of wind

Key sites

Channerwick

Clettnadal

Fugla Ness

Ronas Hill

Sel Ayre

 

Periglacial landscapes

Summit of Ronas Hill, a glacially-disturbed granite blockfield with extensive deflation surfaces

 

 

 

 

 

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.

Three generations of periglacial feature exist on the Shetland:

  • 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
  • features inherited from phases of periglacial activity prior to the last ice sheet

Permafrost conditions are absent from Shetland today and the active forms 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. Both the Sel Ayre and Fugla Ness SSSIs show good examples of periglacial slope deposits that predate the last ice sheet.