MOUNT EREBUS 215 



The walls of the crater itself were of special interest. They were formed, as 

 far as superficial appearance went, of belts of dark pumiceous lava and bands of 

 white snow. The latter were not necessarily interbedded, though it is quite possible 

 that some of them were so, as for a considerable distance before reaching the edge 

 of the crater we had observed, as already stated, that the floor of the older crater 

 had been levelled up by alternate beds of snow and pumice with felspar crystals. 

 The two last had obviously been produced from the present active crater, and had 

 been deposited in their present position by the action of strong winds coming from 

 a southerly direction. A specially thick bed of dark-brown pumiceous lava occurred 

 at perhaps about 300 feet below the lip of the crater, and when the main steam 

 cloud was blown aside we noticed many scores of small steam jets rising from the 

 line of contact of its upper surface with the snow. It is unlikely that these were 

 all fumaroles, and the phenomenon seems to suggest that this thick brown layer of 

 rock possibly marks the highest flood-level of the latest eruption of lava within the 

 crater. On this view this incrustation of lava within the crater still retains 

 sufiicient of its original volcanic heat to vaporise the snow in contact with it. 



As regards the height of Mount Erebus, our aneroid levels alone made it about 

 13,270 feet. This result combined with that of the hypsometer gave the height as 

 13,330 feet. Sir James Clark Ross determined its altitude in 1841 to be 12,400 feet ; 

 Captain Scott in the National Antarctic Expedition of 1901-4 originally esti- 

 mates its height at 12,922 feet. This last estimate was based on trigonometrical 

 measurements, which of course should be more accurate than measurements 

 dependent on atmospheric pressui'e, as are those made with aneroids or hypso- 

 meters. 



These sections below show the four craters of Erebus, together with the order 

 of superposition of the various lavas and tuff's and material infilling the second 

 crater. 



These sections show that the bottom of the oldest crater of Erebus must have been 

 close to sea-level. It also shows the progressive shifting of the volcanic chimney 

 from north to south. The active fumaroles on the south side of the crater suggest 

 that this shifting is still in progress. 



We observed that the eruptions of Erebus, like those of Stromboli, were most 

 frequent during a low barometer. The chief eruption of Erebus seen by us was 

 that which took place on] June 14, 1908. On that morning, about 8.45, just as 

 the small blizzard of the preceding night was subsiding, we noticed that Erebus 

 was more than usually active. The steam cloud over its summit was exception- 

 ally broad and tall, and there were frequent strong outbursts of steam. At 11.30 A.M. 

 it became obvious that an eruption of altogether unprecedented vigour, so far as 

 our experience of Erebus went, was now in progi-ess. Immense masses of steam 

 rushed upwards to at least 2000 feet about the summit of the volcano in about half 

 a minute, and then spread out to form a vast mushroom-shaped cloud. It was 



