Hummocky moraine

Definition: A strongly undulating surface of ground moraine, with a relative relief of up to 10 m, and showing steep slopes, deep, enclosed depressions and meltwater channels. It results from the down wasting (i.e. thinning) of ice which may be stagnant or active. Blocks of ice may squeeze debris released from the ice into crevasses between the blocks.

A belt of hummocks 1.6 km long runs across Papa Stour. The mounds run N-S and represent a still stand or readvance during the later stages of glacier retreat.

On the Sandness Hill plateau there is a series of morainic mounds and meltwater channels which terminate in small eskers. The depositional forms contain only local debris and must relate to a final phase of local glaciation.

Hummocky moraine, Burn of Mail (HU 426286). Note the boulders on the surface of the mounds. Photo by Hamish Ross