Depth of Frost in Circumpolar Regions 33 



IX. Depth of Frost in Circumpolar Regions 



I. statements by RUSSELL 



Russell " says : " The reason for the great thickness of the frozen 

 layer at these localities seems to be that deposition and freezing went 

 on at the same time. These certainly seem to be the conditions 

 under which the great thickness of frozen material beneath the 

 tundra and in the flood plains of the larger rivers of Alaska have 

 accumulated. 



" It seems to me that this must also be the explanation of the 

 origin of all frozen deposits which contain alternating strata of clear 

 ice and of frozen layers of mud and peat like those exposed in the 

 borders of the tundra and along the banks of the Yukon. 



" It is recorded by K. E. von Baer that the ground at Yakutsh, 

 Siberia, is frozen to the depth of 382 feet. It has been assumed by 

 various writers that the great depth of ice (frost?) in this and other 

 similar instances is due directly to surface temperature, the down- 

 ward limit to which the winter's cold can penetrate being limited 

 by the internal heat of the earth. Before accepting this explanation 

 as final it should be ascertained whether the strata at the localities 

 where depth of frozen material has been encountered might not have 

 been frozen progressively as they were laid down." 



In the Pleistocene lacustrine silts and clays as exposed today to 

 depths of at least one hundred and fifty feet we have examples of 

 deposits of homogeneous material without any interstratification of 

 ice or any other material being in a frozen state. These clays could 

 not freeze while being deposited under water. Consequently they 

 have assumed a frozen state since the waters of the lakes have been 

 drained off. And the cold that caused this freezing is the same 

 that has frozen the ice beds now lying conformably on top of the 

 clays. 



On page 130 (op. cit.) Russell gives a mathematical presentation 

 of the subject by R. S. Woodward : 



" The considerable depth below the earth's surface to which frost 

 or the temperature of freezing is known to penetrate in the Arctic 

 regions, raises the interesting question of the relation between the 

 thermal properties of the earth's crust and the time and depth of 

 penetration, etc." 



" The conclusion reached by Mr. Woodward indicates that the 



'= Notes on Surface Geology of Alaska. Bull. Geol. Soc. Am., Vol. I, p. 129. 



