210 GENERAL GEOLOGY 



lakes or dried-up lakes, the floors of which are strewn with remains of algse and 

 diatoms. These moraines ascend to a height of from 1000 to 1100 feet above sea- 

 level. In the description of the raised marine deposits attention is called to the 

 fact that the one near Cape Barne, at an altitude of about 160 feet above the sea, 

 is actually resting on a foundation of ice. It is very probably the case that there 

 is still a considerable amount of ice, perhaps a relic of the ice of the former Great 

 Ice Barrier, still preserved under this moraine debris. 



A little to the right of the centre of the photograph above the termination of 

 the moraines two parasitic cones are visible. Of these, the one described in detail. 

 Mount Cis, is the one which lies to the right of the other. 



In the centre of the picture, and in the middle distance at the foot of the steep 

 cone jDroper, is a large and very conspicuous black parasitic cone surrounded by 

 a very deep snow fosse. This is probably on the line of fractme trending from 

 the centre of the second crater towards Cape Royds. On the extreme left of 

 the great cone there is just visible the rugged outline of the great cliiF forming 

 part of the first and oldest crater of Erebus. This oldest crater is now largely 

 in ruins, with only small portions of the crater wall preserved at intervals. Its 

 diameter is about 8 miles, as estimated by Mr. H. T. Ferrar,* which agrees closely 

 with our own measurements. 



Unfortunately on our ascent of Mount Erebus in March 1908 we were unable to 

 visit this first and oldest crater. Its general appearance, as viewed from the summit of 

 the active crater, is shown on the accompanying Plate LXI. Fig. 2. The greatest 

 altitude attained by the rim of this oldest crater was not accurately measured, but 

 appears to be of the order of about 8000 feet.f On its inner edge is a stupendous 

 cliff, almost vertical, apparently over 2000 feet in height. Thus the oldest crater 

 was a gigantic explosion crater somewhat analogous to that of Tenerifte. Within 

 this rises the second crater, with its steep outward slope showing that concavo- 

 convex outline so characteristic of cones formed of volcanic ejectamenta. It is 

 buttressed by gigantic aretes of black keny te lava. At the foot of the steep slope of 

 this second crater we observed some smoothed surfaces of ice, evidently representing 

 frozen lakes. These have probably been formed by the thaw-water resulting from 

 the melting of ice and snow in contact with the black kenyte lavas, which in summer 

 absorb so much of the sun's heat that they become quite warm to the touch. This 

 second crater terminates in a magnificent perpendicular — in places overhanging — 

 wall of black kenyte lava. The second crater itself is fully 3 miles in diameter from 

 north to south, and about 2| miles from east to west. The great cliff forming its 

 inner boundary wall is in places at least 80 feet in height. The crater itself is piled up 

 higher towards its southern end by the material of the third and fourth craters, the 



* National Antarctic Expedition, 1901-4, Geology. 



t According to the estimate of a party which examined this old crater in 1912 on their way to the 

 summit of the mountain, it reaches a height of about 10,000 feet (R. E. P.). 



