CHAPTER VIII 



THE CLIMATE DURING THE RECESSION, AND 

 CLIMATIC PERIODICITY 



The Climate During the Disappearance of the Ice 



The climate during the disappearance of the ice in New Eng- 

 land has been touched upon in the preceding pages. Since, as 

 explained there, the summer temperature seems to have been 

 the chief factor in the melting of the ice, the rate of retreat 

 gives an idea of the temperature. And since the rate of recession 

 varied considerably in the different zones (see pp. 74-84), the 

 temperature also may have undergone great fluctuations. The 

 climate was not arctic, for the melting of the ice, in many zones, 

 was quite rapid. Since, however, a vast amount of heat was 

 used in the melting of the ice and heating of the cold ice water, 

 the temperature remained comparatively low in a belt off the 

 ice front. This arctic to subarctic zone shifted northward as the 

 ice front withdrew. It doubtless accommodated an arctic and 

 subarctic fauna and flora, about which, however, very little is 

 yet known. Although relicts of these northern plants and ani- 

 mals still survive on the highest summits in New England, only 

 a few occurrences in the varve clays seem to have been reported. 

 In the varve clay at Northampton, Mass., particularly at my 

 locality 23, Emerson (1898, p. 718) found remains of the following 

 plants: Viola palustris L., Vaccinium oxy coccus L., Vaccinium 

 uliginosum L., Rhododendron lapponicum Wahl., Arctostaphylos 

 alpina Spr., Arctostaphylos uva ursi Spr., Oxyria digyna Campd., 

 Salix cutleri Tuck., and Lycopodium selago L. Of these, Salix 

 cutleri and Vaccinium oxycoccus are very abundant. The plants 

 indicate an arctic to subarctic climate. They were deposited 

 when the ice border uncovered northernmost Massachusetts. 

 They must have grown in this region or still closer to the ice edge, 

 since any transportation must have been southward. I am 



