PERMAFROST — BLACK 287 



A knowledge of whether permafrost is actively expanding, or the 

 cold reserve is increasing, is stabilized, or is being destroyed is essen- 

 tial in any engineering problem. Past experience has amply demon- 

 strated that low cost or high cost, success or failure, is commonly based 

 en a complete understanding of the problems to be encountered. Once 

 the conditions are evaluated, proper precautions can be taken with 

 some assurance of success. 



Muller (1945) and Liverovsky and Morosov (1941) give compre- 

 hensive outlines of general and detailed permafrost surveys as adapted 

 to various engineering projects. These outlines include instructions 

 for the planning of the surveys, method of operation, and data to be 

 collected. Karely does the geologist or engineer on a job encounter 

 "cut and dried" situations, and it is obvious that discretion must be 

 exercised in modifying the outlines to meet the situation at hand. 



In reconnaissance or preliminary survey to select the best site for 

 construction in an unknown area, it is recommended that the approach 

 be one of unraveling the natural histoiy of the area. Basically the 

 procedure is to identify each land form or terrain unit and deter- 

 mine its geologic history in detail. Topography, character and dis- 

 tribution of materials, permafrost, vegetation, hydrology, and climate 

 are studied and compared with known areas. Then inferences, deduc- 

 tions, extrapolations, or interpretations can be made with reliability 

 commensurate with the type, quality, and quantity of original data. 



Thus the solution of the problems depends primarily on a complete 

 understanding of the thermal regime of the permafrost and active 

 layer. No factor can be eliminated, but all must be considered in a 

 quantitative way. It is understandable that disagreement exists on 

 the mean annual air temperature needed to produce permafrost. Few, 

 if any, areas actually have identical conditions of climate, geology, 

 a,nd vegetation; hence, how can they be compared directly on the 

 basis of climate alone? Without doubt the mean annual temperature 

 required to produce permafrost depends on many factors and varies at 

 least several degrees with variations in these factors. For practical 

 purposes, however, units (terrain units) in the same climate or in 

 similar climates may be separated on the basis of geology and vegeta- 

 tion. Thus there is a basis for extrapolating known conditions into 

 unknown areas. 



The advantages of aerial reconnaissance and study of aerial photo- 

 graphs for preliminary site selection are manifold. Aerial photo- 

 graphs in the hands of experienced geologists, soils engineers, and 

 botanists can supply sufficient data to determine the best routes for 

 roads and railroads, the best airfield sites, and data on water supply, 

 construction materials, permafrost, trafficability conditions, camou- 

 flage, and other problems. Such an approach has been used with 



