282 POLAR PROBLEMS 



nature have recently been much discussed, ^^ especially the question 

 whether the shelf ice develops through the joining of land-ice tongues 

 or through the thickening of sea ice. Views on this question are 

 tending to converge, to the effect that both processes take place, as 

 Griffith Taylor^* and C. S. Wright^"' have reported concerning the 

 Ross shelf ice, Sir Douglas Mawson^^, together with Frank Wild and 

 J. K. Davis, concerning the Shackleton ice, and P*" concerning the 

 Gaussberg shelf ice (West Ice). According to these reports the 

 masses of shelf ice are complex formations. They develop through the 

 overriding of shallow seas by land ice and through the freezing of sea 

 water itself; this holds true whether these ice masses are developing 

 at present or are survivals of former greater glaciation, which latter 

 is generally the case in the Antarctic. Today the shelf ice forms an 

 outer coast line which lies beyond the inner coast line. The latter is 

 formed by the terminal wall of the inland ice, by solid rock, and some- 

 times by islands.^^ It is an important problem to clarify the relation 

 of these two coasts to each other and to the compact edge of the 

 drift ice farther out. 



Need of Investigation of the Depth of the Shelf Sea 



In this the precise investigation of the depth of the shelf sea is 

 necessary because, as has been said, the shallower seas are the bases 

 on which individual parts of the shelf ice become fixed and thus hold 

 together the floating pieces. From the whole circuit of the Antarctic 

 we now know that the depths of the shelf sea vary greatly and also 

 that quite generally they are considerably greater than they are about 

 the other continents. For around these continents the shelf seas are 

 generally limited outwards by the lOO-fathom line, whereas the shelf 

 seas of the Antarctic go down to looo meters. Explanations have 

 been sought for this. E. Philippi thinks the great depths are due to ice 

 erosion, J. M. Wordie^^ to faults and folds on the sea bottom, Otto 

 Nordenskjold"*" to isostatic sinking under the pressure of continental 

 glaciation. None of these explanations satisfies. To ascribe the 



33 T. W. Edgeworth David: Antarctica and Some of Its Problems, Geogr. Journ., Vol. 43, 1914 

 pp. 605-630; reference on pp. 620 and 629. 



R. F. Scott: The Great Ice Barrier and the Inland Ice, ihid.. Vol. 46, 1915, pp. 436-447; refer- 

 ence on pp. 436 and 441. 



G. C. Simpson: Captain Scott in the Great Ice Barrier, ihid.. Vol. 47, 1916, pp. 226-227. 



C. S. Wright: The Ross Barrier and the Mechanism of Ice Movement, ibid.. Vol. 6s, 1925. PP- 

 198-220; reference on pp. 204 ff. 



3* Taylor, op. cit., p. 378. 



3^ Wright, op. cit., p. 204. 



3' Sir Douglas Mawson: Australasian Antarctic Expedition, 1911-1914, Geogr. Journ., Vol. 44, 

 1914, pp. 257-286; reference on pp. 266-267. 



" Drygalski, Das Eis der Antarktis, pp. 443 ff. 



35 According to Stillwell; see Mawson, op. cit., pp. 270-271. 



33 J. M. Wordie: Shackleton Antarctic Expedition, 1914-1917: Depths and Deposits of the 

 Weddell Sea, Trans. Royal Soc. of Edinburgh, Vol. 52, 1921, pp. 781-793 (= Part IV, No. 30). 



^0 Nordenskjold, op. cit., pp. 7 ff. 



