82 GLACIOLOGY 



examined by us is concerned, it appears that during the maximum glaciation the 

 whole of the old U-shaped valley, 10 miles in width, was filled with glacier ice to 

 a depth of at least 1500 feet. The upper terrace may have been, no doubt has been, 

 subsequently modified by cirque glaciers, but it was probably not cirque glaciers 

 which originally excavated this gigantic terrace. The evidence of the erratics 

 proves that at Koss Island the whole level of the Ross Barrier in that region was 

 formerly 900 feet higher than at present, the Ferrar Glacier perhaps 3000 feet 

 higher, the Beardmore Glacier 2000 feet higher.* In the face of this evidence, as 

 well as of the complete over-riding with glacier ice during maximum glaciation of 

 the Larsen, Bellinghausen, Crummer, and Priestley Massif, to heights of at least 

 1500 feet above the present surface of the adjacent glaciers, the valley of Granite 

 Harbour must necessarily have been almost completely filled with ice far above the 



Mountain near M' England 

 about 4000 f high. 



M^ England 



4740 f 



SuessSunatak 



M^Marston 



sea level. 



Former mwimujn l^v_^i°f plp£'i''_ ^t maximum g fa elation 

 MackayClacier 



?7 



Trnrr 



' ^Granite wth 

 ) -(/ykes * sii/s 

 ■ \aFdolerite. 



Longitudinal Scale 



Vertical Scale 



1000 2000 3000 4000 500O 



Feet. 



J statute Miles. 



Fig. 40. SECTION ACROSS MACKAY GLACIER, SHOWING WELL-MARKED, 



OVER-DEEPENED VALLEY 



The " trogschulter " to right of the srlacier is about 800 feet above sea^level 



level of the great terrace. The facetting of the rock-spui's which rise considerably 

 above the level of the terrace is also very conspicuous. 



At Cape Roberts, just to the south of the entrance to Granite Harbour, a low 

 headland of gneiss shows evidence of having been lately striated by ice coming from 

 a direction of about W. 10° S. Numerous erratics of kenyte of some size were 

 lying on this headland at about 20 to 30 feet above sea-level. They may have 

 been transported by floating ice from Ross Island during the recent submergence 

 of the coast, of which the raised beaches are evidence. 



Fifteen miles S.S.E. of Cape Roberts is Dunlop Island (Fig. 41). 



The strait which separates Dunlop Island from the mainland, about 1 mile in 

 length and J of a mile in width, is very suggestive of a glacial valley formed by the 



* Suess Nunatak, rising fully 2000 feet above the level of the adjacent Mackay Glacier, has been 

 glaciated over its summit, which indicates a former greater thickness of ice in this valley as compared 

 with its present thickness of about 2000 feet. 



