364 DISCOVERY REPORTS 



Delta Island, which is ninety feet in height, could not have been accomplished unless the 

 land had stood at a considerably higher level than it does to-day. 



In discussing the physiographical development of the main outer row of the South 

 Shetland Islands Holtedahl^ states that the marked transverse ridges of Livingstone 

 Island, ridges separated by wide trough valleys, are features that only glacial erosion 

 can produce, while there is no doubt that the sounds which separate the islands were 

 formed by transverse glacial erosion and must therefore have once been filled with 

 glacier ice. For the South Orkneys, a row of islands also separated by sounds and 

 having, in Laurie Island particularly, transverse ridges enclosing deep embayments, he 

 says it may be natural to assume a somewhat similar physiographical development.- Yet 

 there, as in the South Shetlands, the topography cannot be explained without assuming 

 a previous higher stand of the land^ during the time when the present sounds and bays 

 were ice-filled. " The outline of Laurie Island " he writes " reminds one strongly of the 

 outline of the upper part of a mountain where glacial erosion has been at work in a series 

 of folded sediments where rocks of varying hardness are represented. No doubt very 

 recent marine abrasion has done its work, as proved by islands and rocks near the coast, 

 yet the main topographical features have been worked out by glacial erosion." In con- 

 trast to that of Laurie Island the coast of Coronation Island although irregular is not 

 deeply indented by bays; yet as Holtedahl remarks, a further subsidence of Coronation 

 Island, causing the glaciers to retreat, would evidently produce an outline with deep 

 transverse embayments resembling those of its eastern neighbour. 



The major movement associated with the physiographical development of the South 

 Orkneys has thus been one of subsidence ; yet according to Pirie* the latest earth move- 

 ment, in Laurie Island at any rate, has caused elevation to the extent of about fifteen feet, 

 for at that height various raised beaches and sea caves are found around its coast. 



Although the main topographical features as we have seen are the result of an older 

 and more extensive glaciation, it does not follow that the action of the existing glaciers 

 is negligible. On the contrary some of them at least would appear to be responsible for 

 considerable sculpturing of the rocky under- mass. It has already been mentioned that 

 one of the most commonly occurring glacier forms in the Graham Land-South Orkney 

 region is the so-called "ice-foot" glacier of Nordenskjold, a low, and generally narrow, 

 fringing platform, or coastal band of ice, separating the sea from the steep mountain 

 walls behind. It commences typically in an ice-slope curving sharply down from the 

 high land but soon flattens out into the characteristic platform below and terminates in 

 an ice-cliflF which at the South Orkneys is often above 100 feet in height. The front or 



1 Holtedahl, O., 1929, On the Geology and Physiography of some Antarctic atid Subantarctic islands, The 

 Nonvegian Antarctic Expeditions, 1927-8, 1928-9, No. 3, pp. 94-7, text-figs. 38 and 39. 



- Ibid., pp. 101-2. 



3 This would seem to be demonstrated, he says, as far as the South Shetlands are concerned, by the very 

 marked planes of abrasion, indicated by shallow soundings, which characterize the submarine relief to the 

 north of the islands. Compare the shallow soundings which extend for seventy miles south of Laurie Island 

 (see p. 336). 



* Pirie, J. H. Harvey, 1913, loc. cit., p. 852. 



