chiefly by the elevation of the "grounding line, " where the peripheral ice cliffs 

 and ice shelves begin to float (Hollin, 1962; Voronov, 1960). During glacial 

 stages of the Northern Hemisphere, the consequent drops in sea level displaced 

 the grounding downward and northward, and allowed the ice sheets to advance to 

 the outer boundaries of the continental shelf (Voronov, 1960) . 



This "grounding line" concept brings out a very important point. It shows 

 that the glacial history of the Antarctic periphery is governed not so much by cli- 

 mate as by sea level changes. Thus, the Antarctic glacial fluctuations were de- 

 pendent on, and more or less in phase with, those of the Northern Hemisphere. 



Corroborating this argument. Hough's age dating (U, lo, Ra) of sediment cores 

 from the Ross Sea and from the South Pacific Ocean strongly indicates an in-phase 

 correlation with the last two glacial advances in the Northern Hemisphere (Hough, 

 1950; 1953). 



According to Voronov (1960) and Hollin (1962), the general surface profile 

 of the Antarctic ice cop is determined, above all, by the viscous and plastic prop- 

 erties of the underlying ice. The remaining factors (sub-glacial relief, quantity 

 and distribution of accumulation, marginal ablation, temperature changes, etc.) 

 which may affect the shape of the ice sheet are of secondary importance and do 

 not materially affect its profile. Hollin found that the parabolic curve 



h= 4.7v^T~ 



(where d is the distance from the edge of the ice sheet In meters and h is the 

 height of the ice sheet from sea level in meters) fits the observed profiles as far 

 as 200 miles from the ice edge . 



If the grounded ice sheet of Edward VII Peninsula were to advance 35 miles 

 seaward to ilvs continental shelf edge from the present ice edge, a consequent 

 vertical increase of about 4,000 feet of ice over the present shoreline would be 

 indicated by the formula . A greater increase in thickness would occur over the 

 southern Edsel Ford Mountains, because they are farther from the shelf edge. 



All of the peaks visited in the Rockefeller Mountains and in the Edsel Ford 

 Range showed conclusive evidence that they had been overridden by an ice sheet 

 (Wade, 1937) . An additional 1,000 feet is believed to be a reasonable minimum 

 figure for the thickness of ice necessary to result in overriding (Wade, personal 

 communication) . 



Hollin (1962) concluded, from the highly positive regime of the Antarctic 

 Ice sheet and from mechanics of the ice, that, once the continental ice sheet was 

 established at the beginning of the Pleistocene, the Ice in the interior did not 



16 



