l.»l I. '. RUSSKL1 1 III \< i: GEOLOGY OF \LASKA. 



A- previously stated, the freshm I aciated surfaces in the region occu- 

 pied by th<- Cordilleran glacier i- Buch as to indicate thai the great ice-field 

 of the northwest coast of this continent was of more recent date than ihc 

 Labrador ice-sheet. A study of the junction of those two great areas of 

 glaciation would I"- instructive, and might Bhow whether the ice records of 

 area overlap those of the otl 



It" it ran In- > 1 1 . i w 11 that the various aria- of former glaciatian in the 

 northern hemisphere were not ■»<•*- 1 1 1 »i< -r l by ice at the same time, but had in- 

 dependenl histories, it is evident that the much-discussed question of the 

 cause "t - the glacial epoch would be greatly simplified. This is a difficult 

 proposition to demonstrate, but it seems to be the direction in which glacial 

 Btudies are leading 



In Alaska there is a glacial area of the continental type in which the 

 maximum of ice occupation has passed, and the ice-sheet is fast retreating. 

 In Greenland there is another vast ana occupied by a glacier of the same 

 type which is apparently still increasing. In the northeastern states and 

 the adjacent portion of Canada, in northwestern Europe, and probably in 

 central Asia, continental glaciers existed at a recent date, but have dis- 

 appeared. A Btudy of what may be considered local conditions in th< 

 various areas Bhould show whether variations in ocean currents and land 

 elevation are capable of producing glaciers of the continental type. At 

 pi' -.'Hi tl bservations are insufficient for such comparative study. 



The hypothesis thai continental glaciers, like those of the Alpine type, 

 are individually dependent on local climatic and geographic CMii.liii.in-, if 

 -ii -t a i he. 1, can be used in explaining the presence of glacial records in ancient 

 formations without invoking great revolutions in the earth or changes in its 



smic relations. It' the extinct continental glaciers of the northern hemi- 

 sphere were not contemporaneous, it is apparent that we are now Living in 

 glacial epoch" as truly as was Pleistocene man. The [ce Vgi still 

 r- in Ala-ka, ami has not vet reached its maximum in Greenland. 



W lshinoton, I » < '.. January 12, 1890. 



