62 ERNEST DeKOVEN LEFFINGWELL 



doubts its general occurrence. However widespread it may ulti- 

 mately prove to be, it is certainly an interesting feature. Schrader's 

 theory == is that the ground ice is the result of "frozen bays, lagoons, 

 lakelets, or perhaps other coastal bodies of ponded water now raised 

 into low anticlines and cut back by wave action." The locaHties 

 visited by him were Capes Simpson and Halkett, between Point 

 Barrow and the Coville River. Here the ice evidently was not 

 glacial, for boulders are not known to exist on the beach west of 

 Flaxman Island. An inquiry into the presence of air bubbles or 

 granulation would soon settle the question as to whether the ground 

 ice in that region could be accounted for by the freezing of bodies of 

 standing water. 



The writer beheves that he has shown that the ground ice at 

 Flaxman Island is of glacial origin. Its occurrence there is very 

 similar to that of the same formation elsewhere, in that it closely 

 underlies the tundra along the mud cliffs which are such a common 

 feature on the northern shore of Alaska. If future investigation 

 shows that the ice could have resulted from the freezing of bodies of 

 standing water, the explanation given by Schrader seems the most 

 probable one. But if it is granulated, the writer is of the opinion 

 that its history will be found to be connected with that of the region 

 during the glacial period. The following hypothesis is suggested: 



At present the coastal plain is free from snow scarcely three months 

 in the year. During the glacial period the snow did not entirely 

 disappear during the short summer, but accumulated in favorable 

 locahties. As the cKmate grew warmer, silt was brought down by 

 the mountain streams and distributed over the ice by the wind. 

 Moss and grass quickly took root and increased the thickness by the 

 formation of peat. Wherever this covering reached a sufficient depth 

 the ice was prevented from melting and has remained until the present 

 day. Where the thickness was insufficient, the ice melted leaving the 

 depressions which are now occupied by the ponds and lakes which are 

 such a characteristic feature of the tundra.^ 



The temperature of the plain adjacent to the Arctic Ocean is kept 

 in the neighborhood of freezing by the presence of the ice-laden 



1 Op. cit., p. 96. 



2 Schrader, op. cit., p. 46. 



