38 ESKAR EXCAVATION IN NOVA SCOTIA. PREST. 



the melting ice added to the accumulation and formed a 

 permanent eskar. I think all will agree that where the 

 slope is so slight as in Maine and Nova Scotia, no advance 

 was possible after the mass and moving power of the ice had 

 dwindled to a certain point. When this stage was reached 

 its dissolution began. Only then began that re-erosion and 

 redeposition of stratified eskar material that is so noticeable 

 a feature of these deposits. 



It has been objected bj' some, that hills and other local 



irregularities would mark the icefields with a system of 



radiating cracks. I admit this where the ice 



Objections was thin or the elevations were increased to 



mountains. But I cannot think that a 300 or 400 



foot hill would be noticeable under an ice sheet 



Plasticity 5,000 to 10,000 feet thick. And besides, the well- 



ofice known plasticity of ice enables it to accommodate 



itself to extreme irregularities of surface. This 



fact is attested to by the testimony of many 



explorers and investigators. For this reason small and local 



cracks not enlarged by running water would certainly close, 



freeze up and disappear in winter. But the immense cracks 



formed along the slopes of a continental glacier are too wide 



and deep to be thus easily disposed of. That 



Permanent they were not thus disposed of is evident to all 



crevc^ses who have read the account given of them by 



Arctic and Antarctic explorers. Only in great 



icefields could such deep and lasting crevasses be formed. 



Even there the smaller cracks would close or refill with ice 



before they could gather enough material to keep them open 



until a higher temperature and a flow of water made them 



permanent. The size of the larger cracks must have made 



them permanent from the first. 



I have made the claim that the edges of the cracks thus 



formed may be used as an eroding tool. But it has been 



objected that on account of the plasticity of ice 



Erosion 3,11 cracks may close before being used in the 



ice cracks work of erosion or as a place for the deposition 



of debris. That all cracks do not do so we have 



these facts to the contrary, viz. : Shackleton, Nansen, and 



