Studies for Students. 



STRATIFIED DRIFT. 



CONTENTS. 

 Abundance of stratified drift. 



Its origin. 



Glacial drainage. 



Stages in the history of an ice-sheet. 



Deposits made by extraglacial waters during the maximum extension of the ice. 



At the edge of the ice. 



Beyond the edge of the ice, on land. 



Beyond the edge of the ice, in standing water. 

 Deposits made by extraglacial waters during the retreat of the ice. 

 Deposits made by extraglacial waters during the advance of the ice. 

 Deposits made by subglacial streams. 

 Deposits made by superglacial and englacial streams. 

 Relations of stratified to unstratified drift. 



Deposits made by extraglacial waters during the advance of the ice, edge 

 not oscillating. 



Effect of edge oscillation. 



Deposits made by extraglacial waters during the retreat of the ice. 



Deposits made by streams as they issued from the ice. 



Deposits made by subglacial streams. 



Deposits made by superglacial and englacial streams. 

 Deposits classified on the basis of position. 



Its abundance. — The notion is widespread that the drift 

 deposits of the glacial period are unstratified. Lack of stratifi- 

 cation, indeed, is the characteristic which, above all others, is 

 popularly supposed to be the special mark of the formations to 

 which the ice gave rise. 



While it is true that glacier ice does not distinctly stratify the 

 deposits which it makes, it is still true that a very large part of 

 the drift for which the ice of the glacial period was directly or 



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