318 TECTONIC GEOLOGY 



Alexander I. Land, Charcot Land, &c., represent the structui'e which Suess terms a 

 " panzer-horst." Along the north-western lines of fracture lie the partly active or 

 dormant volcanoes of Bridgman Island and Deception Island. On the other side, 

 that is, on the south-east side of West Antarctica, is another series of powerful fractures 

 that separate the mainland along Crown Prince Gustaf Channel from the James 

 Ross, Snow Hill, Seymour, Vega I. Islands, and the Hope Bay region. J. Gunnar 

 Andersson has already suggested the existence here of powerful faults having a down- 

 throw towards the south-east. Along this line of fractures, where seen, there have 

 been extensive outflows of basaltic lava, and there is evidence of definite points of 

 eruption here, such as Paulet Island, Mount Haddington, and Mount Christensen in 

 Ilobertson Island. We thus see that West Antarctica is in effect a horst flanked 

 by a volcanic zone on either side, with evidence of the heaviest fracturing on the 

 side which faces the Pacific Ocean. 



As regards the probable trend of these Antarctic Andes southwards from 

 Graham Land, if we may judge from experience of trend lines in other parts of the 

 Avorld, we should expect that, after describing the big loop between Weddell Sea and 

 the Falkland Islands, the trends would return to approximately their former bearing, 

 which is nearly meridional. This direction would carry them right into the high 

 ranges recently traversed by Captain Amundsen. If we study the structure of the 

 great horst from near the South Pole up to South Victoria Land we see that tecton- 

 ically it much resembles in its broad features the Antarctic Andes of West Antarctica. 

 The heaviest fracture, amounting in this case to 6000, probably 8000, feet lies on the 

 side nearest to the Pacific. This too is a zone of active or extinct volcanoes, such 

 as Mount Morning, Mount Discovery, Mount Erebus, Mount Terra Nova, Mounts 

 Terror, Bird, Melbourne, Cape Jones, and probably several of the high peaks, such 

 as Mount Herschell, &c., in the Admiralty Range. 



The continuity of the horst is somewhat Interrupted in South Victoria Land by 

 cross faults running approximately east and west, so that it is somewhat uncertain 

 as to whether the Balleny Islands lie on the west or on the east side, respectively, 

 of the horst. The appearance of mountains of very black rock, such as Mount 

 Mackintosh, seen by the Magnetic Pole Party of the Shackleton Expedition on the 

 western side of the horst, suggests that there is probably a volcanic zone in this 

 region corresponding with that of the Paulet and Mount Haddington belt. A study 

 of the bathymetric chart shows that it is very possible that the Tongan Deep, which 

 traced southerly bends eastwards to avoid the New Zealand-Chatham Islands 

 plateau, still farther south trends in the direction of Ross Sea. It seems equally 

 probable that Tasman Sea describes a deep loop southwards towards the Macquarie 

 Islands, and is still farther prolonged southerly by the deep indent in the Antarctic 

 coast between Cape North and Adelie Land. 



If the correlation of these broad tectonic features is correct. New Zealand obviously 

 forms a prolongation equatorwards of the horst of South Victoria Land. It will be 



