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Antarctic peat: Formation of vertical edges

3. Vertical edges

A characteristic of many Antarctic moss peat banks is that one side has a vertical edge. A metre rule for scale is visible in many pictures.

Pictures 1-7: Signy Island, S.Orkneys.

Pictures 8-9: Moe Island, S Orkneys.

Picture 10: Walker Point, Elephant Island – the tallest known vertical edge at 3 metres (picture from 1976-7 Joint Services Expedition to Elephant Is).

All pictures, except 10, taken 1975.

4. Vertical edge formation

The vertical edges are not erosion features – note absence of eroded peat at their base. The pictures here demonstrate their formation.

Picture 4 is a key one, showing how moss shoots at the edge of the moss bank break off and hang down. This can happen at periodic intervals, as illustrated in picture 5. The whole structure is supported by the permanently frozen undecomposed moss peat (permafrost).

For a description of how they form see: Fenton, J. 1982.  The formation of vertical edges on Antarctic moss peat banks. Arctic & Alpine Research Vol. 14.

All pictures taken on Signy Island, 1975.