212 GENERAL GEOLOGY 



last being still active. Its central portion is filled largely with bands of felspar 

 crystals with pumice and a little sulphur alternating with bands of drifted snow. All 

 around the northern, western, and eastern portions of the inner wall of the crater 

 there runs a deep fosse, the appearance of which is shown on the accompanying 

 sketch. This fosse is formed in two ways. In the first place, the absorption of solar 

 heat by the black rocks so warms them that the snow and ice in contact with them 

 melts away, often for some distance back from the rock face. In the second place, the 

 blizzard winds are blowing here from the S.S.E. or S.E., and impinging against the 

 sharp summit of the crater rim produce a very violent back eddy. This helps to further 

 excavate the snow filling the old crater, leaving a clean vertical wall of snow with an 

 overhanging snow cornice. We were at a loss for some time to find a crossing place 

 over the fosse, until at last we reached the snow-drift shown on the sketch (Fig. 2). 



This second crater is formed of kenyte lava, like the third and fourth craters. Its 

 altitude as determined by aneroid is about 11,300 feet. The extraordinary ice 

 structures due to the freezing of the vapour from numerous fumaroles and solfataras 

 are illustrated in the photo by Dr. Mawson (Plate LXIII. Fig. 1). It may be 

 mentioned that for about a couple of miles before reaching the foot of the slope of 

 the great cone, to which this crater belongs, we observed several fragments of very 

 fresh and somewhat glassy kenyte lava. This occurred in the form of lapilli and 

 bombs, varying in size from that of a hazel nut to that of a man's head. These had 

 an extremely fresh appearance, which makes it probable that Erebus has been in a 

 state of eruption in very recent time. These bombs were met with at a distance of 

 about 4 J to 5 miles from the present active crater. They must have been carried 

 to between W.N.W. and N.W. from the active crater by a strong south-easterly 

 blizzard. That such blizzards actually crossed right over the summit of Mount 

 Erebus on occasions was proved by us as the result of our experience in the terrific 

 blizzard of March 8-9, 1908, which we encountered when at an altitude of 9000 feet 

 on the north-west slope of Erebus. The floor of the second crater, deeply filled with 

 snow and ice, was very strongly grooved by the blizzard wind in a general south-east 

 and north-west direction, leaving hard sastrugi in high relief The angle of slope 

 of this second great cone of Erebus is gentle at first, but rapidly increases until it 

 reaches an angle of 34°. Its sides are formed of aretes of jagged lava, with smooth, 

 hard marble-like neve slopes between. 



In regard to the fumaroles on the floor of this crater we observed that approxi- 

 mately one hundred were visible, out of which some twenty were sufliciently near for 

 us to observe them carefully, and we saw that nearly all were emitting vapour from 

 chimney-like openings at their sides or summits. These openings were mostly 

 situated to leeward of the prevalent winds. The fumaroles appear to be joined 

 together underground by tortuous channels and irregular crevasse-like openings in 

 the ice. The temperature of the vapour, though obviously above that of the 

 surrounding air, was not sensibly warm. It must be explamed that none of these 



