146 GLACIOLOGY 



past the Dogger Bank against the eastern shores of Northumbria, and thrust and 

 glaciated and over-rode part of that coast at a distance of 400 to 500 miles from the 

 Norwegian glaciers, just as to-day the Ross Barrier is thrusting and over-riding and 

 glaciating Cape Crozier at a distance of some 300 miles from the contributing 

 glaciers ; in spite of the stemming action of Ross Island which leads to the develop- 

 ment of great pressure ridges and shear planes along the zone of contact between 

 land and ice. It must be remembered too that some of the ice at the Ross Barrier 

 edge has advanced fully 500 miles north of where the soles of the Heiberg and 

 Devil's Glaciers leave the shore-line, and that formerly, during the maximum 

 glaciation, that edge was even 700 miles north of where those glaciers left the 

 shore, and that, though aground for tliis entire distance, the piedmont still could 

 move forward and grind and heavily glaciate the hard volcanic rocks high up on 

 the shoulders of Ross Island. 



The individual glacier ribs or ice jetties of the North Sea Piedmont may be 

 compared to the runners of a sledge, while the bay ice between represents the 

 sledge decking. The friction of this superstructure (carrying its load of old snow- 

 largely granulated into ice) on the sea floor would be reduced to a minimum by 

 the glacier runners, the bay ice between these "runners" being afloat. (See actual 

 section in this report of the Drygalski-Reeves Piedmont in Koss Sea.) But such 

 runners should scoop out grooves in the sea floor. Do the soundings of the North 

 Sea reveal the presence of such grooves ? It is doubtful whether such can 

 now be traced, but it must be remembered that if again we judge by the analogue 

 of the Drygalski-Reeves Piedmont there is a distinct tendency after the grooving 

 effected by a glacier "runner" during a maximum glaciation for the "runner," as it 

 gradually floats up out of its groove during deglaciation, to aggrade that groove, at 

 all events for a distance of many scores of miles to the seaward of the coast-line, 

 and tidal scour and other marine currents should help this work of aggrading. In 

 the case of surface-carried moraine material, which as Antarctic experience shows 

 would soon become englacial, there is no limit to the distance out to sea to which 

 aggradation may take place, other than the length of the extension seaward of the 

 glacier, and the limit of the drift of its icebergs. 



It is possible that detailed soundings of the North Sea will yet reveal traces of 

 the grooves of the glacier "ruiniers" under the North Sea Piedmont during the 

 Great Ice Age. 



