CHAPTER XI 

 VULGARISM 



The chief volcanic trend lines have already been described in Chapter I., dealing with 

 the physiogi'aphy of the region. In this chapter it has been explained that the chief 

 volcanic centres are situated at the ends of a network of faults running partly parallel 

 to the great horst, partly more or less rectangular to it, as shown on the accompany- 

 ing Plate LX. The volcanoes may probably be grouped in two main zones. 



Firstly, the zone to the east of the horst ; secondly, that which lies to the 

 west. The latter has not yet been definitely proved to be volcanic, but the shape 

 of many of the hills on the western side of this horst, such as Mount Judd, Mount 

 Bowen, Mount Priestley, Mount Mackintosh, suggest that tliey are probably volcanic, 

 and the rocks of which they are composed appear to be very black. The existence 

 of this western zone may be looked upon at present as problematical, and our 

 attention may now be directed to describing the volcanoes on this belt to the 

 east of the gi'eat horst. This zone, having a general north and south trend, is 

 crossed by strong tectonic lines running either due east and west, or from about 

 E.S.E. to W.N.W. One of the strongest of these cross lines is that upon which 

 Mounts Terror, Terra Nova, and Erebus are situated. This great fracture zone 

 runs through Cape Royds, and, according to the discovery just reported by Mr. F. 

 Debenham, undoubted traces of it are met with at New Harbour in the form of 

 very recent craters of basic lava.* These occur near New Harbour. Thus this 

 strong transverse line has a length of nearly 100 miles in an east and west direc- 

 tion measured from Cape Crozier to Dry Valley. 



Our description will commence with Erebus and its parasitic cones, touching 

 next on Cape Royds, the Dellbridge Islands, Hut Point, and finally Mount Bird, 

 aU these localities being situated on Ross Island, which is itself entirely composed 

 of lavas and tuffs of Cainozoic age, except for some insignificant inclosures of what 

 appears to be Beacon Sandstone in the lavas. 



Mount Erebus. The general appearance of Mount Erebus is well shown in the 

 photograph by Dr. D. Mawson forming the frontispiece to this Memoir, as well as 

 in Plate II. It wiU be noticed that, if one looks across the ice in the foreground at 

 Backdoor Bay, one sees a wide belt of mounds of moraine gravel, amongst which 

 occur at intervals patches of raised marine muds, together with shallow ice-filled 

 * Press account of scientific results of the Scott Expedition. 



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