PERMAFROST — BLACK 281 



is generally much slower. Permafrost is one of the most important 

 agents in keeping the soils supersaturated (containing more water than 

 pore space — a suspension) and in keeping many rock fragments wet. 



It is less widely known that mass-wasting processes in the Arctic 

 and sub- Arctic are instrumental in the transport of tremendous vol- 

 umes of material. With the exception of unbroken bedrock, the ma- 

 terials on the surface of slopes greater than 1° to 3° are on the move 

 everywhere in summer. The amount of material involved and the 

 rapidity of such movements impress all who have studied them (Wash- 

 burn, 1947, and others) . 



Permafrost, on thawing slightly in summer, supplies a lubricated 

 surface and additional water to materials probably already saturated. 

 Hence solifluction (pi. 6, fig. 1), mud flows (pi. 6, fig. 2), and other 

 gravity movements take place with ease and, in favorable locations, 

 even supply material to streams faster than the streams can remove it 

 (Wahrhaftig, 1949, and others). Bryan (1949) has coined the term 

 "cryoplanation" to cover such processes, including also frost-heaving 

 normal to slopes and settling vertically, which in the Arctic are instru- 

 mental in reducing the landscape to long, smooth slopes and gently 

 rounded forms. Such physiographic processes are only partly under- 

 stood and their effects only qualitatively known (Bryan, 1949). 



Permafrost, by aiding in maintaining saturated or supersaturated 

 conditions in surficial materials, indirectly aids in frost-stirring (con- 

 geliturbation), frost-splitting, and mass- wasting processes so that, in 

 places, bedrock is disintegrated, reduced in size, thoroughly mixed, 

 and rapidly transported. The result is a silt-sized sediment that is 

 widespread in the Arctic. Various authors (Bryan, 1949; Hopkins, 

 1949; P. S. Smith, unpublished manuscript; Zeuner, 1945; Taber, 

 1943a; Tuck, 1940) disagree as to whether some of the material is 

 derived from eolian, lacustrine, or local frost-splitting and mass- 

 wasting processes. Size-grade-distribution curves, mineral compari- 

 sons, chemical analyses, comparisons with glacial materials and with 

 organic materials, etc., have been used by various investigators to prove 

 their point, but the differences of opinion have by no means been re- 

 solved. 



Frost action (frost-heaving, frost-stirring, and frost-splitting) and 

 gravity movements result in many surface forms that are found most 

 abundantly in areas of permafrost, i. e., strukturhoden^ involutions, 

 frost boils, hummocks, altiplanation terraces, terrecettes, and soil 

 stripes (Judson, 1949; Richmond, 1949; Schafer, 1949; H. T, U. 

 Smith, 1949 ; Cailleux, 1948; Troll, 1948, 1947, 1944; Washburn, 1947, 

 Conrad, 1946 ; Zeuner, 1945 ; Taber, 1943a ; Sharp, 1942b ; Gatty et al., 

 1942; Steche, 1933; Hogbom, 1914; and others). Annual freezing in 

 permafrost areas also forces changes in surface- and ground-water 



