274 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



tute of North America (Tremayne, 1948) is currently preparing an 

 annotated bibliogi-aphy of all Arctic literature, including permafrost. 



The multitude of problems associated with frost action, as we refer 

 to it in the United States, appropriately should accompany any dis- 

 cussion of permafrost. However, lack of space permits only a passing 

 reference to the relationship of permafrost to frost action. An an- 

 notated bibliography on frost action has been prepared by the High- 

 way Research Board (1948). 



Thanks are due Louis L. Ray, P. S. Smith, Inna V. Poire, Troy L. 

 Pewe, David M. Hopkins, William S. Benninghoff, Joel H. Swartz, 

 and D. J. Cederstrom, of the United States Geological Survey, and 

 to Stephen Taber and Kirk Bryan for critical reading of this manu- 

 script. These and others in the Geological Survey have provided 

 many valuable suggestions for which individual acknowledgment is 

 difficult. The use of unpublished manuscripts and notes of P. S. 

 Smith and C. V. Tlieis is greatly appreciated. 



PERMAFROST 



• 



The term "permafrost" was proposed and defined by Muller (1945) . 

 A longer but more correct phrase is "perenniall}^ frozen ground" 

 (Taber, 1943a). The difficulties of the current terminology are pre- 

 sented by Bryan (1946a, 1946b), who proposed a new set of terms. 

 These are discussed by representative geologists and engineers (Bryan, 

 1948) . Such terms as cryopedology, congeliturbation, congelif raction, 

 and cryoplanation have been accepted by some geologists ( Denny and 

 Sticht, unpublished manuscript; Judson, 1949; Cailleux, 1948; Troll, 

 1948) in order to attempt standardization of the terms regarding 

 perennially frozen ground and frost action. The term permafrost 

 has been widely adopted by agencies of the United States Govern- 

 ment, by private organizations, and by scientists and laymen alike. 

 Its use is continued here because it is simple, euphonious, and easily 

 understood by all. 



Extent. — Much of northern Asia and northern North America con- 

 tains permafrost (fig. 1) (Jenness, 1949; Sumgin, 1947; Muller, 1945; 

 Obruchev, 1945 ; Troll, 1944 ; Taber, 1943a ; Cressey, 1939 ; and others) . 



The areal subdivision of permafrost into continuous, discontinu- 

 ous, and sporadic bodies is already possible on a small scale for nmch 

 of Asia, but as yet for only part of North America. Refinements in 

 delineations of these zones are being made each year. The south- 

 ern margin of permafrost is known only approximately, and addi- 

 tional isolated bodies are being discovered as more detailed work is 

 undertaken. The southern margin of permafrost has receded north- 

 ward within the last century (Obruchev, 1946). 



