282 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



migration and commonly results in pingos, frost blisters, ice mounds, 

 icings, aufeis, and other related forms (MuUer, 1945; Troll, 1944; 

 Sharp, 1942a; Mullis, 1930). (PI. 7 and pi. 8, fig. 2). Many of the 

 forms produced by frost action and seasonal freezing are closely 

 related in character and origin; however, the lack of a standardized 

 terminology for these features produces a perplexing picture. 



Little can be said quantitatively regarding the importance of frost 

 action (and indirectly permafrost) in ancient sediments and soils 

 (Zeuner, 1945). Throughout the world, deposits of former glaciers 

 have been found in the stratigraphic column. They indicate many 

 periods of glaciation and, hence, cold climates. Undoubtedly perma- 

 frost was present during those times. Fossil forms derived from frost 

 and permafrost are known (Horberg, 1949 ; Judson, 1949 ; Richmond, 

 1949; Schafer, 1949; H. T. U. Smith, 1949b; Wahrhaftig, 1949; Zeu- 

 ner, 1946, 1945 ; Troll, 1944 ; and others) . These forms provide data on 

 the processes producing the surficial materials and on the environment 

 of deposition. These features are only now being recognized and 

 studied in the detail that is wan-anted (Bryan, 1949) . 



Permafrost throughout the world has provided an outstanding 

 wealth of material for paleontologists and archeologists (Hibben, 

 1941). In perennially frozen Alaskan placers alone, investigators 

 have found more than 27 different plants (Chaney and Mason, 1936), 

 including whole forests of buried stumps (Giddings, 1938) ; nmner- 

 ous iron and other bacteria; algae; 87 species of diatoms (Taber, 

 1943a) ; bones of at least 20 species of large mammals, represented 

 by tens of thousands of specimens (Taber, 1943a; Wilkerson, 1932) ; 

 numerous species of rodents ; and a few species of mollusks, sponges, 

 and insects (Taber, 1943a). Permafrost in Siberia has been a store- 

 house for Pleistocene mammals (Tolmachoff, 1929). 



Permafrost upsets many readings taken by geophysicists in deter- 

 mining the internal constitution of the earth. Velocities of seismic 

 waves, for instance, are materially increased by frozen ground con- 

 taining much ice and may result in considerable errors in determina- 

 tions of depths. Although the actual increases are not definitely 

 known, they probably fall within the range of 1,000 to 8,000 feet per 

 second (J. H. Swartz, oral communication). Unfortunately, the 

 lower contact of permafrost causes, with present equipment, no satis- 

 factory reflections or refractions. Seismic methods cannot be used to 

 determine the thickness or variability of the zone distorting the seis- 

 mic waves. DifFiculties in drilling, preparing, the explosive charges, 

 checking the ground waves, and getting interpretable effects are aug- 

 mented in permafrost areas. 



Electrical methods, particularly the resistivity methods, have given 

 promise of solving some of the difficulties in determining the extent 



