46 DISCOVERY REPORTS 



abruptly in sheer and inaccessible cliffs from 50 to 100 ft. higii which continue round the coast to the eastern side 

 of the island. The rock is lava, at a distance dark in colour, and much broken with cracks and fissures. . . .The island 

 is remarkably free of snow and ice, and although snow may lie thinly on it after a heavy fall it does not remain for 

 long. [This fact strongly suggests that there is still much residual heat in the cone, and that it may only be dormant.] 



Penguin Island is a volcanic cone in the shaping of which three, and perhaps four, periods of activity seem to 

 have been involved. What seems to have been the earliest and biggest eruption is represented now by the concave 

 section of a very large, but almost entirely cut away crater which occupies nearly the whole of the western face of 

 the cone, from the shingle beach up to the summit. The degree of concavity is not very high, yet it is unmistakable. 

 The sides of the interior of this now almost destroyed cone are composed of rather finely divided volcanic clinker 

 of a rich brick-red colour which gives this side of the island its characteristic tint. The clinker fragments have the 

 even consistency of a coarse gravel. Projecting out of this eroded crater, its base on a level with the beach, is a huge 

 plug [? dike] of lava from three to five feet in width and rising vertically like a wall for nearly a hundred feet. Similar 

 though less conspicuous plugs [dikes] occur elsewhere in this crater. 



Main summit crater. A later eruption is perhaps represented by this crater, a third of a mile across and about 

 200-300 ft. deep, which occupies the summit of the cone. Evidently the rim of this crater has crumbled away 

 considerably, for it is highest to the north, but slopes downward towards the south (see sketch, Fig. 2). The bottom 

 is rather damp and shows signs of there having been water lying about. On the east side of the interior of the bowl 

 a gigantic plug of lava sticks up vertically for about 100 ft., the top, however, not projecting beyond the rim of the 

 crater. There is some quite deep snow, which is possibly permanent, inside the bowl on its north-east side. 





Fig. 2. Penguin Island. 



Another eruption, subsequent to that which produced the main summit crater, is represented by the small secondary 

 cone which rises concentrically from the bottom of the former. The secondary cone is about 100 ft. high and has 

 a crater less than 80 yards across at the rim, and about 20 ft. deep. 



Ash beds. Much of the lower part of the cone, and a large part of the 100 ft. plateau to the south-east and east 

 of it, seem to be composed of horizontally stratified ash beds of a light colour. 



The coastal cliffs throughout are composed of lava often broken by cracks and fissures. On the eastern side of 

 the island the crests of the cliffs are extremely rugged and often twisted into grotesque sliapes, evidently the result 

 of cooling in the surface of an ancient lava flow. At the south-west corner of the island a certain warmth was felt 

 on the lava and inside a fissure. The heat experienced was very slight, but we were of the opinion at the time that 

 it was unlikely to have been due to absorption from the sun. 



Crater on east side. On the east side of the island, some 60-80 yards from the coast, another old crater occurs in 

 the 100 ft. plateau. Its rim is flush with the general level of the plateau, and it is rather a remarkable sight, strongly 

 resembling an old quarry. It is a perfect circle and about 150-200 yards across at the rim. The sides are steep, 

 descending for at least 50 ft. There is deep water at the bottom in which a few penguins were swimming; the water 

 was not icy cold. On its west side the crater cuts through horizontally stratified, light-coloured beds of volcanic 

 ash at least 30 ft. in thickness. On the eastern rim of the crater there is much glassy lava, obsidian, of various hues. 



All specimens of the lavas collected from the volcanic cone of Penguin Island represent textural 

 variants of a typical olivine-basalt. The most fully crystallized type comes from the plug in the 

 summit crater. In thin section it is found to be highly porphyritic with numerous phenocrysts of 

 fresh olivine and pale brown augite, sometimes aggregated into clots, and very numerous micro- 



