110 THE ICE AGE IN CANADA. 



among the islands, from which every particle of sea-weed 

 has been removed by pan ice. 



"During a period of subsidence, the blocks of stone, 

 boulders, mud, and sand, pushed to and fro on the shallow 

 sea-bottom by pan ice, ultimately accumulate in hollows 

 and ravines below its action ; and when the debris is 

 pushed into profound submarine valleys, such as exist on 

 the Labrador coast, the mass will resemble boulder-clays, 

 and in a sinking marine area it will accumulate to a 

 great thickness ; in a rising area it would be liable to be 

 remodelled by the action of the waves, except in the case 

 of very deep valleys. There are not many known narrow 

 and profound submarine valleys on the north-eastern 

 coast of Labrador, but those which are known offer 

 precisely the conditions required for the accumulation of 

 boulder-clays or drift by the action of pan ice. 



" The seaward extension of Uksuktak fiord, which lies a 

 little to the south of Hopedale, affords an apt illustration. 

 Commander Maxwell's soundings show a profound sub- 

 marine ravine between clusters of islands for upwards of 

 eight miles, in which the depth reaches 124, 126, 123, 

 106, and 130 fathoms. Between the islands of Niatak 

 and Paul, near Kain, the lead shows 71 fathoms. It is 

 evident that the material torn from the surrounding 

 islands by pan ice, and pushed along the bottom of the 

 sea into these profound submarine valleys during a period 

 of general submergence, will be protected from the action 

 of the waves, and the loose blocks and boulders will have 

 a forced arrangement in the mud, as if they had been 

 pushed over a bank, and thus produce the irregular dis- 

 position so frequently seen in boulder-clay deposits. In 

 such narrow and profound valleys as those instanced, the 

 accumulation of boulder-drift probably goes on at the 



