THE HEART OF THE ANTARCTIC 



In this case the Ross Sea subsidence area (if such it 

 be) would have approximately the same relation to the 

 Andean trend-lines in the Antarctic that the Gulf of 

 Mexico and the Ajitillean and West Indian fracture zones 

 bear to the trend-lines of the tropical Andes. It must, 

 nevertheless, be admitted that the Great South Polar 

 Shield of ancient and practically incompressible crystalline 

 rock, intensely folded in the past, would be incapable of 

 being further folded now, and if the Andean zone of 

 disturbance traversed this shield it would be likely to 

 traverse it as a zone of fractures with local lava eiFusions, 

 rather than as a fold range of the Pacific type. This 

 important matter will be discussed by us in detail in the 

 Geological Memoir of this Expedition. 



Summary. — The following inferences are tentatively 

 suggested in regard to the geology of Antarctica: 



(1) The majority of the tabular bergs of this region 

 are largely, in some cases wholly, snowbergs, not icebergs. 



(2) True icebergs are also found. 



(3) Glaciers in the Antarctic push out in some cases 

 thirty miles from the coast, and must be afloat, as argued 

 by Ferrar, for the greater part of this length. 



(4) The Great Ice Barrier is formed of true glacier 

 ice at its sides and inland extremity, but the centre and 

 seaward portion is formed, in its upper part, chiefly of 

 snow. We agree with Captain Scott's conclusions that 

 the Great Barrier except at its edges and perhaps at some 

 distance inland must be afloat. At its eastern side it has 

 been moving seawards at the average rate of about five 

 hundred yards a year for the past seven years. 



(5) Throughout the whole of the region of Antarctica 

 examined by us, for 16° of latitude, there is evidence of 

 a recent great diminution in the glaciation. In McMurdo 

 Sound this arm of the sea now free from land ice was 



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