Significance: a series of moraines and channels that may relate to the final development of small glaciers on Shetland in a brief period of intense cold at the close of the last glaciation

Deposits in this valley comprise ridges and moraines which show clear parallel alignments along the lower slopes. The deposits have long been interpreted as moraines that represent a former ice limit and subsequent ice retreat. Parallels may be drawn with the patterns of hummocky moraine elsewhere in Scotland. Flinn (1977) observed that the deposits near HU 424291 were distinct from the hummocky moraine and formed part of a landslide which had broken up into blocks. The landforms have been mapped by Ross (1996) who identified a number of asymmetric moraines and meltwater channels. He also noted the abundance of vein quartz on moraines, derived from a source up-valley.

How old are these moraines? A reconstruction of the equilibrium line altitude for an independent valley glacier by Ross suggests this was less than 200 metres at its lowest. This is low relative to altitudes in western Scotland for other small Loch Lomond Stadial glaciers. On Hoy, however, there are a number of undated moraines related to corrie glaciers with even lower equilibrium line altitudes. It is possible therefore that the Burn of Mail moraines also relate to a glacier of Loch Lomond Stadial age. Ross offers the alternative explanation that these are retreat moraines from an ice lobe moving from an ice shed lying west of the hills. The site has been sampled for dating using cosmogenic radionuclides.