HUT POINT 223 



account for the presence of these numerous small erratics in the crater ? The height 

 of Crater Hill above sea-level is a little over 1000 feet. It has been described by 

 H. T. Ferrar {op. cit., p. 12), where he mentions that the hill is formed of black 

 vesicular basalt and red scoriaceous basalt glass. As we have seen from the evidence 

 at Cape Royds, the basalts are amongst the newest of the lavas of Ross Island. 

 The following explanations may be offered of this apparently contradictory 

 phenomena of the unglaciated state of the crater rim combined with the presence 

 of glacial erratics within the crater : — 



1. The crater is post-glacial in the sense of its post-dating a maximum glaciation, 

 and the presence of the glacier erratics in the crater may be explained by the 

 erratics having been brought into their present position by floating ice dm-ing a 

 period of submergence. This would demand a far greater submergence than 

 that which has already been assumed for Ross Island, for obviously in order 

 to carry erratics into this crater a submergence of at least 800 feet would be 

 requii-ed, possibly 1000 feet. It is conceivable that the crater was formed at the 

 edge of the retreating ice sheet, and therefore only just subsequent to the culmination 

 of the glaciation. In this case flood waters during the season of thaw may have 

 washed down erratics into the crater from the retreating ice front. 



2. A second alternative is to suppose that the crater preceded the maximum 

 glaciation. As we have seen, the height of the moraines left by the Great Ice 

 Barrier durinef the maximum glaciation is near about the level of 1000 feet above 

 the sea. Possibly, then, the rim of crater may have been just high enough to 

 have been above the level of the great ice sheet, or if it was ever covered by ice, 

 the ice over it must have been very thin. If this second hypothesis could be 

 adopted, the presence of glacial erratics dropped by the retreating ice sheet into 

 the crater can of course be readily explained. It is noteworthy that all the erratics 

 seen at Hut Point were uniformly small. No single specimen was more than about 

 1 cubic inch in size. These are in marked contrast to the erratics at Cape Royds, 

 many of which are several cubic yards in volume. * 



A point worthy of attention in the vulcanism of this region is the approximately 

 uniform height of the volcanoes in the main volcanic zones. On the American 

 side of the Antarctic the highest volcano yet found is Mount Haddington, which 

 rises about 8000 feet above the sea. We do not know the altitudes of any possible 

 volcanic cones of any considerable dimensions between that and Mount Morning. 

 Mount Morning, according to Scott's determinations, is 5778 feet in height ; Mount 



* As already stated, subsequent to our expedition, Mr. F. Debenham, B.Sc, of the British 

 Antarctic Expedition of 1910-13, has discovered craters of basic lava and tuflf at Dry Valley near 

 New Harbour, which he considers to be pi'obably post-glacial, that is, later than the maximum glaciation 

 in date. If this determination is correct, the east and west fault fracture running from Cape Crozier to 

 Dry Valley must have been active subsequent to the climax of recent Antarctic glaciation, though, for 

 reasons already stated, the Cape Bird to Erebus line may undoubtedly be considei-ed the most recent 

 active volcanic zone. 



