1. The Moss peat banks of Signy & Moe Islands, South Orkney IslandsThe peat is formed by two species of moss: Polytrichum strictum and Chorisodontium aciphyllum. It is underlain by permafrost at a depth of c.15-20 cm, and is up to two metres thick and 5,000 years old.
Signy Island:Deep moss peat banks on level or gently sloping ground at the northwest end of the island.Note that a metre rule is visible as a scale marker in some photos.
Signy Island:A turf on a steep slope dominated by Polytrichum strictum below Observation Bluff.
2. Vertical edges of Antarctic moss peat banksA characteristic of many Antarctic moss peat banks is that one side has a vertical edge. These are visible in many of the photographs above taken on the South Orkney Islands. However the tallest such edge, at 3m height, is at Walker Point, Elephant Island (see picture below).The vertical edges are not erosion features – note the absence of eroded peat at their base. The pictures here demonstrate their formation. All the pictures were taken on Signy Island in 1975.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..
3. Erosion of moss peat banksAlthough the vertical edges are not erosion features, erosion can sometimes be observed on Antarctic moss peat. This illustrates the point that peat erosion can ba a natural phenomenon, occurring in the absence of grazing, burning or human impact.These pictures all taken in 1975.
5. Other moss peat banks in Antarctica & South Georgia1 & 2: Moss turf dominated by Chorisodontium aciphyllum at Shingle Cove, Coronation Island (South Orkneys). Pictures taken 1999.3-8: Moss turf dominated by Polytrichum strictum on steep ground above the penguin colony on Cuverville Island (Antarctic Peninsula). Note that the moss is slowly sliding downhill over the permafrost, with picture 8 showing moss peat which has slid down and accumulated at the bottom of slope. Pictures taken 1988/9.9: Moss turf dominated by Polytrichum strictum at Galindez Island, Argentine Islands (Antarctic Peninsula). See also the two pictures of Galindez Island under ‘Ice Retreat’ above. Pictures taken 1975.10: The deepest moss peat bank found: c.3m deep, at Walker Point on Elephant Island (picture from 1976-7 Joint Services Expedition).11: Turf of Polytrichum strictum at Maiviken, on South Georgia, with the grass Festuca contracta. Picture taken 1975.
1A collapsed vertical edge: perhaps the underlying permafrost which holds the whole bank together, has thawed. Signy Island.2The active layer (unfrozen moss & peat) has slid down over the permafrost (permanently frozen peat). Moe Island.
3-7 Erosion of the surface of the peat bank, possibly caused by exposure to wind as the peat has become deeper. Pictures 3-5 Signy Is, 6-7 Moe Island.
8Wind has here blown away a section of Polytrichum turf.
Antarctic-type peat formed by Polytrichum strictum has recently been found by the author outside Antarctica in both the Falkland Islands and Scotland. See pictures below.
The surface 5cm of an Antarctic moss turf of Polytrichum strictum showing the tightly-bound moss shoots. In this species the shoots are held together by rhizoids, small root-like outgrowth similar to roots in higher plants. In this picture two-year’s growth of rhizoids are visible growing out of the cut surface of the turf.