BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 4, pp. 191-204 March 24, 1893 



COMPARISON OF PLEISTOCENE AND- PRESENT ICE-SHEETS 



BY WAR REX UPHAM 



[Read before the Society December 29, 1892) 

 CONTENTS 



Page 



Existing Ice-sheets and Glaciers 191 



The Antarctic Ice-sheet 192 



The Greenland Ice-sheet 192 



The Malaspina Glacier or Ice-sheet 194 



The Mnir Glacier 196 



Inferences from Comparisons of present and Pleistocene Ice-aheets 198 



Probable surface Slopes and Thickness of the Pleistocene Ice-sheets of 



North America and Europe 19S 



Probable Rates of Er< >si< >n by Pleistocene Ice-sheets 199 



Subglacial and englacial Transportation of Drift 199 



Rapidity of final Ablation of the Ice-sheets 200 



Modes of Deposition of the englacial Drift 201 



Origin of Forest Beds between Deposits of Till 201 



The Ice Age viewed as a continuous and geologically brief Period 202 



General Consideration of the Question 202 



Probable Synchronism of Glaciation in North America and Europe 203 



Relation of the Ice Age to human and geologic History 204 



Existing Ice-sheets and Glaciers. 



The guiding principle of geologic investigation, brought out most clearly 

 by Lyell, requires us to seek the explanation of past changes of the earth 

 by observation and study of agencies which are now in operation, pro- 

 ducing similar changes during the present epoch. From such studies of 

 the Swiss glaciers, Agassiz, Forbes, Tyndall and others have given to us 

 the theory of the formation of the drift by land ice, so that the compara- 

 tively small district of the Alps supplied the clue for deciphering the 

 records of the latest completed chapter of the geologic history of north- 

 western Europe and the northern half of North America. Glaciers of 

 other regions in the eastern hemisphere, notably of the Himalayas and 



XXIX-Bull. Geol. Soc. Am., Vol. 4, 1892. " (191) 



