Permafrost as a Natural Phenomenon: Encyclopedia Arctica 2a: Permafrost-Engineering

Author Stefansson, Vilhjalmur, 1879-1962

Permafrost as a Natural Phenomenon

EA-I. (Robert F. Black)



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Introduction 1
Constitution and Properties of Permafrost 2
Extent 2
Thickness 3
Temperature 4
Character 5
Relation to Terrain Features 6
Origin 7
Geologic Ramifications 8
Engineering Significance 12
Biologic Significance 13
Factors Affecting Permafrost 14
Practical Applications 17
Recognition and Prediction 19
Construction 20
Water Supply 22
Sewage Disposal 23
Agriculture 24
Mining 24
Refrigeration and Storage 26
Trafficability 26
Military 27
Future Research Needed 28
Bibliography 30

EA-I. Black: Permafrost as a Natural Phenomenon


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Fig. 1 Areal distribution of permafrost in the Northern Hemisphere 2-a
Fig. 2 Representative cross section of permafrost areas in Alaska and Asia 4-a
Fig. 3 Representative temperature profiles in areas of continuous, discontinuous and sporadic permafrost 4-b

EA-I. (Robert F. Black)

Permafrost (perennially frozen ground) is a widespread geologic phenomenon whose importance and ramif ac ^ ica^ tions are rapidly becoming better ^^ known and more clearly understood. For many decades European scientists have been describing surficial features produced by frost action and permafrost, but for the most part they have given only passing reference to perennially frozen ground. The current problem is to understand perma– frost so as to be able to evaluate it in the light of any particular endeavor, whether practical or academic. To understand permafrost we need a precise standardized terminology, a comprehensive classification of forms, a systemization of available data, and coordination of effort by geologists, engineers, physicists, botanists, climatologists, and other scientists in broad research programs. These objectives are only gradually being realized.
This article is largely a compilation of or reference to recent available literature. Its purpose is to acquaint geologists, engineers, and other scientists with some of the many ramifications and practical applications of permafrost. New data from unpublished manuscripts of the U.S. Geological Survey are included where appropriate for clarity or completeness. References in this paper generally are only to the later American or German works, as

EA-I. Black: Permafrost as a Natural Phenomenon

most contain accounts of the earlier literature. Unfortunately, the bulk of the literature is in Russian and unavailable to the average reader; some of it has been summarized by Muller (41). A list of 190 Russian articles that deal with permafrost is given by Weinberg (97). The Arctic Institute of North America (82) is currently preparing an annotated bibliograph ^ y^ of all ^^ arctic literature, including permafrost.
The multitude of problems associated with frost action appropriately should accompany any discussion of permafrost. However, lack of space permits only passing reference to the relationship between permafrost and frost action. An annotated bibliography on frost action has been prepared by the Highway Research Board (43).
The term permafrost was proposed and defined by Muller (41). A longer, but more correct phrase, is “perennially frozen ground” (77). The difficulties of the present terminology have been discussed by Bryan (4; 6) who proposed a new set of terms. These are discussed by representative geologists and engineers (7). Such terms as cryopedology, congeliturbation, congelifratcion, and cryoplanation have been accepted by some geologists (9; 17; 35; 85) in order to attempt standardization of the terms referring to perennially frozen ground and frost action. The term permafrost has been widely adopted by agencies of the United States Government, by private organizations, and by scientists and laymen alike. Its use is continued in this article as it is simple, euphonious, and easily understood by all.
Extent . Much of northern Asia and northern North America contains perennially ^ Fig. 1^ frozen ground (Fig. 1) (14; 41; 46; 72; 77; 84).
Figure 1

EA-I. Black: Permafrost as a Natural Phenomenon

The areal subdivision of permafrost into continuous, discontinuous, and sporadic zones is already possible on a small scale for much of Asia but, as yet, only for part of North America. Refinements in delineation of these zones are being made each year. The southern margin of permafrost is known only approximately, and additional isolated bodies are being discovered as more detailed work is undertaken. The southern margin of permafrost has receded northward within the last century (47).
Permafrost is absent or thin under some of the existing glaciers, and it may be absent in areas recently exhumed from ice-cover. A greater extent of permafrost in the recent geologic past is inferred from phenomena associated with permafrost (9; 30; 53; 54; 58; 60; 66; 83; 84; 98; 106). Some of the more important phenomena are fossil ground-ice wedges, solifluction deposits, block fields and related features, involutions in unconsolidated sediments, stone rings, stone stripes and related features, and asymmetric valleys (66). The presence of permafrost in earlier geologic periods can be inferred from the known facts of former periods of glaciation and from fossil periglacial forms.
In the Southern Hemisphere, permafrost is extensive in Antarctica. It probably occurs logically in some of the higher mountains elsewhere, but its actual extent is unknown.
Thickness . Permafrost attains its greatest known thickness of about 2,000 feet (620 meters) at Nordvik in northern Siberia (I. V. Poir e ^ é^ , oral ^ accout ✓^ communication). Werenskiold (99) reports a thickness of 1,050 feet ^ (^ 320 meters ^ )^ ^^ in the Sveagru n van coal mine in Lowe Sound, Spit z ^ s^ bergen. In Alaska its ^^ ^^ greatest known thickness is about 1,000 feet, south of Barrow.

EA-I. Black: Permafrost as a Natural Phenomenon

Generally, the permafrost thins abruptly to the north under the Arctic Sea. It is discontinuous and sporadic as it gradually thins to the south ^ Fig. 2^ (Fig. 2) (14; 41; 77).
In areas of comparable climatic conditions today, permafrost is much thinner in glaciated areas than in nonglaciated areas (77; 78).
Unfrozen zones within perennially frozen ground are common near the surface (41) and are reported to occur at depth (14; 77). They have been interpreted as indicators of climatic fluctuations (14; 41), or as permeable water-bearing horizons (77).
Temperature . Below the depth of seasonal change, the temperature of perennially frozen ground ranges from slightly less than 0°C. to about −12°C. (I. V. Poir e ^ é^ , oral communication). In Alaska the minimum temperature recorded ^ accout ✓^ to date is −9.6°C. at a depth of 100-200 feet in a well about 40 miles south– west of Barrow (J. H. Swartz, 1948, written communication). Representative temperature profiles in areas of continuous permafrost are shown in Figure 3A; in areas of discontinuous permafrost, in Figure 3B; and in areas of sporadic ^ Fig. 3^ permafrost, in Figure 3C.
Temperature gradients from the base of permafrost up to the depth of minimum temperature vary from place to place and from time to time. In 1947-48, four wells in northern Alaska had gradients between 120 and 215 feet per degree centigrade (data of J. H. Swartz, G. R. MacCarthy, and R. F. Black).
The shape of a temperature curve indicates pergelation or depergelation– aggradation or degradation of permafrost (41; 77). Some deep temperature profiles have been considered by Russian workers to reflect climatic fluctua– tions in the recent geologic past. No known comprehensive mathematical approach has been attempted to interpret past climates from these profiles,
Figure 2 []
Figure 3

EA-I. Black: Permafrost as a Natural Phenomenon

although it seems feasible. Some of the effects of Pleistocene climatic variations upon geothermal gradients have been discussed by Birch (2) and Ingersoll and Zobell (32).
Character . Permafrost is defined on the basis of temperature, and it may encompass any type of natural or artificial material, whether organic or inorganic. Generally, permafrost consists of variable thicknesses of perennially frozen surficial, unconsolidated materials; bedrock; and ice. Physical, chemical, or organic composition, degree of induration, texture, structure, water conte c ^ n^ t, etc., very widely and are limited only by the ^^ extremes of nature o f ^ r^ the caprice of mankind. For example, perennially ^^ frozen mammals, bacteria, artifacts, beds of sand and silt, lenses of ice, and beds of peat can collectively be lumped under the term permafrost. Ground perennially below freezing but containing no ice has been called “dry per– mafrost” (41).
Permafrost composed largely of ice is abundant, particularly in poorly drained, fine-grained materials. The ice occurs as thin films, grains, fillings, veinlets, large horizontal sheets, large vertical wedge-shaped masses, and irregular masses of all sizes. Many masses of clear ice are arranged in geometric patterns near the surface, i.e., polygonal ground and honeycomb structure. The ice may be clear, colorless, yellow, or brown. In many places it contains numerous oriented or unoriented air bubbles, silt, clay, or organic materials. Size, shape, and orientation of the ice crystals differ widely. Discordant structures in sediments around large masses of ice are evidence of growth (38; 77; 78).

EA-I. Black: Permafrost as a Natural Phenomenon

Relation to Terrain Features . In the continuous zone of permafrost, the upper limit (permafrost table, 41) is generally within a few inches to 2 feet of the surface. Large lakes and a few large rivers lie in thawed areas slightly larger than the basins they occupy (3; 41). Well-drained, coarse– grained materials may thaw annually to a depth of 6 feet. Poorly drained, fine-grained materials protected from solar radiation and insulated with m i ^ o^ ss and other vegetation may thaw annually to a depth of only 4 inches. ^^
In the discontinuous zone permafrost is absent under most major rivers and lakes. Permafrost may be absent in the tops of some well-drained low hills. Seasonal thaw (active layer, 41) penetrates 1 to 10 feet depending upon insulation, amount of energy absorbed from solar radiation, drainage, and type of material.
Sporadic bodies of permafrost may be relics below the active layer or may be forming in favorable situations in poorly drained, fine-grained materials on north-facing slopes. In the zone of sporadic permafrost, the active layer may or may not reach the permafrost table, and ranges between 2 and 14 feet in thickness.
Generally, the depth of thaw is at a minimum in northern latitudes and increases to the south. It is at a minimum in peat or highly organic sediments and increase successively in clay, silt, and sand to a maximum in gravelly ground or exposed bedrock. It is less at high altitudes than at low altitudes and less in poorly drained ground than in dry, well-drained ground. It is at a minimum under certain types of tundra and increases successively under areas of bog shrubs, black spruce, larch, white spruce, birch, aspen, and poplar to a maximum under tall pines. It is less in areas of heavy snowfall, in regions having cloudy summers, and on north-facing slopes (41; 77; 78; 84).

EA-I. Black: Permafrost as a Natural Phenomenon

Works of man commonly upset the natural thermal equilibrium and may tend to destroy permafrost or to aid in its formation. Most roads, runways, and other structures on the surface of or in the ground generally have s lower ^ [: S]^ permafrost tables than undisturbed natural areas adjacent to them. Structures above the ground and insulated from the ground partially protect the surface from solar radiation and commonly produce higher permafrost tables.
Origin . The origin of perennially frozen ground is discussed by Muller (41), Zeuner (106), Taber (77), Cressey (14), Nikiforoff (44), Leffingwell (38), and others. In general, it can be stated that most sporadic bodies of permafrost are relics of colder climates. Discontinuous bodies of permafrost are largely relics but under favorable conditions may grow in size, and pergelation (4), of new deposits may take place. In areas of continuous permafrost, heat is being dissipated actively from the surface of the earth to the atmosphere, and new deltas, bars, landslides, mine tailings, and other deposits are being per– gelated (incorporated in the permafrost).
Local surface evidence indicates that in places heat is being absorbed into the base of permafrost faster than it is being dissipated at the surface (29; 104). Hence, the cold reserve is being lessened and the thickness of permafrost is decreasing from the base upward.
The mean annual air temperature required to produce permafrost undoubtedly varies many degrees because of local conditions. Generally, it is given as 30° to 24°F. Theoretically permafrost can form above 32°F. (80), and apparently is doing so locally in parts of southwest Alaska that have poor drainage, abundant vegetation, cloudy summers, and relatively slight absorption of solar radiation (S. Abrahamson, oral communication).

EA-I. Black: Permafrost as a Natural Phenomenon

The relative effects of past climates have been inferred qualitatively through a study of present temperature profiles, ancient deposits, pollen analysis, changes in floras, the regimen of plants, soil structures, block fields, etc.
The origin of large clear ice masses in the permafrost is a special problem in itself. Numerous theories are extant and one or more may apply to a particular mass of ice (38; 77).
Throughout the Arctic and Subarctic the role of permafrost is extremely important. As an impervious layer in zones of continuous permafrost, it exerts a drastic influence on surface waters, completely prevents precipita– tion from entering the natural ground-water reservoirs, and commonly causes a concentration of organic acids and mineral salts in suprapermafrost water. In zones of discontinuous permafrost, and less so in areas of sporadic perma– frost, ground-water movement are interrupted or channelized. The quality of water, too, can be materially affected by storage for centuries, and subsequent release by thawing of organic and inorganic materials (36). In fact, our present concepts of ground-water reservoirs, ground-and surface– water movements, infiltration, quality of water, and so on, must be modified in considering permafrost as a new geologic formation, generally not uniform in composition or distribution, that transcends all rock and soil formations. Furthermore, it must be considered as much in regard to past as to present conditions.
In cold climates, physical disintegration (frost splitting, congeli– fraction) plays a more important role than chemical weathering. The repeated

EA-I. Permafrost as a Natural Phenomenon

freezing of water- w ^ s^ aturated materials and the growth of ice crystals in ^^ numerous small pores, cracks, joints, cleavage planes, or partings is by far the most effective disruptive proces . ^ s.^ Taber (77) has shown that, ^^ without water, disintegration is generally much slower. Permafrost is one of the most important agents in keeping soils supersaturated (containing more water than pore space; a suspension) and in keeping rock fragments wet.
Mass-wasting processes in the Arctic and subarctic are instrumental in the transport of tremendous volumes of material. With the exception of unbroken bedrock, the materials on the surface of slopes greater than 1° to 3° are everywhere on the move in summer. The amount of material involved and the rapidity of such movements impress all who have studied them (96).
Permafrost, on thawing slightly in summer, supplies a lubricated surface and additional water to materials probably already saturated. Hence, solifluction, mud flows, and other gravity movements take place with ease and in favorable locations even supply material to streams faster than the streams can remove it (94). Bryan (5) has coined the term “cryoplanation” to cover such processes (including also frost heaving normal to slopes and settling vertically), which in the Arctic are instrumental in reducing the landscape to long smooth slopes and gently rounded forms. Such physiographic processes are only partly understood and their effects only quali ^ ta^ tively ^^ known (5).
Permafrost, by aiding in maintaining saturated conditions in surficial materials, indirectly aids in frost-stirring (congeliturbation), frost-splitting, and mass-wasting processes in such a way that, in places, bedrock is disinter– grated, reduced in size, thoroughly mixed, and rapidly transported. The result is a silt-sized sediment that is widespread in the Arctic. Various authors

EA-I. Permafrost as a Natural Phenomenon

(5; 29; 67; 77; 87; 106) disagree as to whether some of the material is derived from aeolian, lacustrine, or local frost-splitting and mass-wasting processes. Size-grade distribution curves, mineral comparisons, 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 opinions have by no means been resolved.
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., strukturb o ^ ö^ den , involutions, frost boils, hummocks, ^^ altiplanation terraces, terr e ^ a^ cettes , and soil stripes (9; 13; 25; 28; 35; 58; 60; 63; 65; 70; 77; 83; 84; 85; 96; 106). Annual freezing in permafrost areas also forces changes in surface- and ground-water migration and commonly results in pingos, frost blisters, ice mounts, icings, Aufeis ^ Aufeis ^ , and other related ^^ forms (41; 42; 62; 84). 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 quantitively regarding the importance of frost action (and indirectly permafrost) in ancient sediments and soils (106). Throughout the world, deposits of former glaciers have been found in the stratigraphic sequence. Undoubtedly permafrost was present during those times of glaciations, as fossil forms derived from frost action and permafrost are known (30; 35; 58; 60; 65; 84; 94; 105; 106). These forms provide data on the processes that produced the surficial materials and on the environment of deposition. These features are only now being recognized and studied in the detail that is warranted (5).

EA-I. Black: Permafrost as a Natural Phenomenon

Permafrost throughout the world has provided a wealth of material for paleontologists and archeologists. In perennially frozen Alaskan placers, investigators have found more than 27 different plants (11), including whole forests of buried stumps (26); numerous iron and other bacteria; algae; 87 species of diatoms (77); bones of at least 20 species of large mammals, represented by tens of thousands of speciments (77; 100); and a few species of mollusk a ^ s^ , sponges, and insects (77). Permafrost in Siberia has been a ^^ storehouse for Pleistocene mammals (81).
Permafrost upsets many readin ^ g^ s taken by geophysicists in determining ^^ the internal constitution of the earth. Velocities of seismic waves, for example, are materially increased by frozen ground containing much ice and may result in considerable errors in determinations of depths. Although the actual increases are not definitely known, they probably range within 1,000 to 8,000 feet per second. Unfortunately, the base of permafrost causes, with present equipment, no satisfactory reflections or refractions, and seismic methods cannot be used to determine the thickness or variability of the zone distorting the seismic waves. Difficulties in drilling, preparing explosive charges, checking ground waves, and obtaining interpretable effects are augmented in permafrost areas.
Electrical methods, especially resistivity methods, give promise of solving some of the difficulties in determining the extent and thickness of permafrost (20; 34; 41; 74). Generally, resistivities of frozen silt and gravel are several thousand ohms higher than those of comparable unfrozen materials and may be 20 to 120 times as high (34; 74). However, as is well known, the type of material is less important than the amount of unfrozen ground water and dissolved salts within the material. Even in frozen ground these factors are

EA-I. Black: Permafrost as a Natural Phenomenon

so variable that resistivity data can be interpreted with reliability only by experienced men and generally only for areas where some positive checks can be made through drilling.
Sumgin and Petrovsky (73) discuss a new radio-wave technique, used where permafrost is below −5°C.
In Alaska during World War II, difficulties encountered by the Armed Forces in obtaining permanent water supplies, and in constructing runways, roads, and buildings in permafrost areas focused attention on permafrost as nothing else could (1; 33; 78; 101). O^n^ly then did most people realize ^^ that in Russia similar difficulties with railroads, roads, bridges, houses, and factories had impeded colonization and development of the North for decades. Now, with the recent progress in aviation and because of the strategic importance of the North, active construction and settlement for military and civilian personnel must increase, and the problems of permafrost must be solved.
Fortunately we can draw on the vast experience of the Soviet Union. Their engineers have shown that it is “…a losing battle to fight the forces of frozen ground simply by using stronger materials or by resorting to more rigid designs. On the other hand, the same experience has demonstrated that satisfactory results can be achieved and are allowed for in the design in such a manner that they appreciably minimize or completely neutralize and eliminate the destructive effect of frost action… Once the frozen ground

EA-I. Black: Permafrost as a Natural Phenomenon

problems are understood and correctly evaluated, their successful solution is for the most part, a matter of common sense wher ^ e^ by the frost forces are ^^ utilized to play the hand of the engineer and not against it.” Hence, “…it is worth noting that in Soviet Russia since about 1938 all governmental organizations, municipalities, and cooperative societies are required to make a thorough survey of the permafrost conditions according to a prescribed plan before any structure may be erected in the permafrost region….” (41, pp. 1-2, 85-86).
Specifically, permafrost must be considered in construction of buildings, roads, bridges, runways, railroads, dams, and reservoirs; in problems of water supply, sewage disposal, telephone lines, drainage, excavation, ground storage, and in many other ways. Permafrost can be used as a construction material or as a base for construction, but steps must be taken to insure its stability, Otherwise, it must be destroyed and appropriate steps taken to prevent its formation.
Permafrost, because of its low temperature and ability to prevent runoff, is a potent factor that aids in controlling vegetation in the Arctic and Subarctic (40). Many places have semiarid climate, yet have luxuriant growths of vegetation because permafrost prevents the loss of precipitation through underground drainage (low evaporation possibly as important). Such conditions are natural breeding environments for mosquitoes and other insects.
Conversely, luxuriant growths of vegetation, by insulating the permafrost in summer, prevent deep thawing and augment cold soil temperatures. Hence, those plants with deep root systems, such as certain trees, are dwarfed or absent, and nourishment available to smaller plants is limited.

EA-I. Black: Permafrost as a Natural Phenomenon

Raup (56; 57) points out that much arctic soil is unstable because of fro son ^ st^ action (commonly associated with permafrost), and that standard ^^ biological methods of describing plant communities do not apply. The normal associations have been greatly disturbed, special communities for different frost forms can be identified, and above all the plant communities must be described on the basis of their physical habitat.
Permafrost probably controls the distribution of some animal species, such as the frogs or toads, that require thawed ground into which they can burrow for the winter. The fox can have dens only in dry elevated places where the depth of thaw is 2 feet or more. Similarly, permafrost affects worms, burrowing insects, and other animals that live in the ground.
Indirectly, permafrost, by exercising some control on types of vegetation, i.e., tundra vs. forest, also exercises some control on the distribution of animals such as the reindeer and porcupine.
Most major factors affecting permafrost are recognized qualit ^ at^ ively, but ^^ none is well known quantit ^ at^ ively. These factors are easily visualized by ^^ turning to the original definition of the term permafrost. As permafrost is fundamentally a temperature phenomenon, we may think of it as a negative temperature produced by climate in material generally of heterogeneous composition. Permafrost is produced because, through a combination of many variables, more heat is removed from a portion of the earth during a period of 2 or more years than is replaced. Hence, a cold reserve is established.
Basically, the process can be reduced to one of heat exchange between the sun, the atmosphere, and the earth. The sun, through solar radiation

EA-I. Black: Permafrost as a Natural Phenomenon

(insolation), and the interior of the earth, largely through conduction, supply practically all primary heat to the surface of the earth (biological processes, natural or artific ^ i^ al fires, chemical reactions, comic or other ^^ rad uatnibs ^ iations^ excepted). This primary heat is dissipated to the atmosphere ^^ and to outer space by conduction, radiation, conve n ^ c^ tion, and evaporation. ^^ The atmosphere by warm winds and precipitation distributes the secondary heat to the surface of smaller areas.
We know that earth temperatures at the depth of seasonal change are in most places within a few degrees of the mean annual air temperature, and a geothermal gradient is established from the surface to the interior of the earth. The geothermal gradient at any one place is relatively fixed from year to year, although it varies from place to place and has changed markedly during geologic time. It is generally considered to be 1°F. for each 60-110 feet of depth in sedimentary rock in the United States (93); possibly 0.1 or 0.2 calorie per square centimeter per day is transmitted to the surface from the interior (80). In contrast, the sun supplies possibly as much as several hundred calories per square centimeter per day to the surface, depending primarily on the season and secondarily on cloudiness, humidity, altitude, latitude, and other factors. This period of rapid heating, however, is very short in the Arctic, and for many months heat is dissipated to the atmosphere and outer space. When dissipation of heat outweighs intake, a cold reserve is produced. If the ground remains below freezing for more than 2 years, it is called permafrost.
Although the fundamental thesis of the problem is simple, its quanti– tative solution is exceedingly complex. In only a few isolated areas in the Arctic have we any information on the geothermal gradients in and below

EA-I. Black: Permafrost as a Natural Phenomenon

permafrost. The climate (including insolation) is so incompletely known that a present it is not possible to evaluate climatic factors except in a general way as they effect primary or secondary heat or in dissipation of heat (37). Thus, the following conditions tend to produce permafrost: ( 1 ) long cold winters and short cool summers; ( 2 ) low precipitation the year around and especially low snowfall; ( 3 ) clear winters and cloudy summers; ( 4 ) rapid evaporation the year around; ( 5 ) strong cold winds in summer and winter; and ( 6 ) low insolation.
The materials involved have different specific heats and different heat conductivities (41; 61; 68; 69). Chemical and physical properties vary widely, yet are of primary importance (69; 75; 76). Water transmits heat about 25 times as fast as air, and ice 4 times as fast as water. Thus, poorly drained silt and muck are much more easily frozen than dry, coarse-grained gravel. Smith (69) points out the marked effect of soil structures and of architecture of pore space on thermal resistance in natural soils.
The dissipating surface of the earth is even more complex and more changeable. Water-saturated, frozen vegetation and soil (bare of snow) serve as active conductors in winter, whereas lush, dry vegetation and dry porous soil act as excellent insulators in summer. Black-top pavements are good conductors and heat absorbers in summer and can destroy permafrost. An elevated and insulated building with circulating air beneath may unbalance the thermal regime of the ground toward pergelation. Heat conductivities of some earth materials are known under fixed laboratory conditions, but the quantitative effect in nature of variable moisture conditions and of changing vegetation is not. Changes in the volume, composition, or tempera– ture of ground water or surface runoff have effects as yet little known qualitatively or quantitatively.

EA-I. Black: Permafrost as a Natural Phenomenon

All these factors must be considered as being in delicate balance between freezing and thawing. It is to be emphasized that the thermal regime is not uniform but changes from hour to hour, day to day, week to week, year to year, and cycle to cycle. Specifically we must think in terms of geographic position, topography, lithology, structure and texture of soils and bedrock, hydrology, geothermal gradients, thermal conductivities, vegetation, climate (temperature, precipitation, cloudiness, wind, insolation, evaporation), and cultural features.
What effect cosmic dust clouds, changes in carbon dioxide content of the atmosphere, inclination of the earth’s axis, eccentricity of the earth’s orbit, sun spots, etc., have on permafrost can only be surmised as they e ^ a^ ffect inso- ^^ lation and dissipation of the earth’s heat
In the area of permafrost, prior to the construction of buildings, towers, roads, bridges, runways, railroads, dams, reservoirs, telephone lines, utilidors, drainage ditches and pipes, facilities for sewage disposal, establishments for ground-water supply, excavations, foundation piles, or other structures, it is imperative that the engineer have complete understanding of the extent, thick– ness, temperature, and character of the permafrost and its relation to its environment. The practical importance of the temperatures of permafrost cannot be overemphasized. Knowledge of whether permafrost is actively expanding, is stabilized, or is being destroyed, is essential in any engineering problem. Experience has amply demonstrated that low cost or high cost, success or failure, commonly is based on the degree of understanding of the problems to be encountered. Once the conditions are evaluated, proper precautions can be taken with some assurances of success.

EA-I. Black: Permafrost as a Natural Phenomenon

Muller (41) and Liverovsky (39) give comprehensive 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. Rarely does the geologist or engineer on a job encounter “cut-and-dried” situations, and it is obvious that discre– tion must be exercised in modifying the outlines to meet the situation at hand.
In reconnaissance or preliminary surveys to select the best site for construction in an area, it is recommended that the approach be one if unravel–ing the natural history of the area. Basically the procedure is to identify each land form or terrain unit and determine its geologic history in detail. Topography, character and distribution of materials, type and distribution of vegetation, hydrology, and climate must be studied as compared with known areas. Then, inferences, deductions, 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 under– standing 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 what mean annual air temperature is needed to produce permafrost. Few, if any, areas actually have identical conditions of climate, geology, and vegetation; hence, they cannot be compared directly on the basis of climate alone. Without doubt the mean annual tempera– ture required to produce permafrost depends upon many factors and varies at least several degrees with variations in these factors. For practical purposes, however, separate units (terrain units) in the same climate or in similar

EA-I. Black: Permafrost as a Natural Phenomenon

climates may be established on the basis of geology and vegetation. Thus a basis exists for extrapolating known conditions into unknown areas.
The advantages of aerial reconnaissance and study of aerial photographs for preliminary site selection are manifold. Aerial photographs in the hands of experienced geologists, soils engineers, and botanists can supply suffi– cient data to determine the best routes for roads and railroads; the best airfield sites; and data on water supply, construction materials, permafrost, trafficability conditions, camouflage, and other problems. Such an approach has been used with success by the Geological Survey and other organizations and individuals (3; 55; 95; 103).
Emphasis is placed on the great need for expansion of long-term applied and basic research projects on permafrost for a clearer understanding and evaluation of the problems (33; 41).
Recognition and prediction of permafrost go hand in hand in a permafrost survey. If natural exposures of permafrost are not available along cut banks of rivers, lakes, or oceans, it is in places necessary to dig test pits or drill holes to obtain undisturbed samples for laboratory tests and to determine the character of the permafrost.
Surface features can be used with a considerable degree of accuracy to predict permafrost conditions if the origin of the surface forms is clearly understood. Vegetation alone is not the solution, but it can be used with other factors to provide data on surficial materials, surface water, character and distribution of the permafrost, and particularly on the depth of the active layer (16; 41; 71; 77).
Cave-in or thermokarst lakes (taw sinks, 29; 3; 41; 95) and ground-ice mounds (62) are particularly good indicators of fine-grained materials containing

EA-I. Black: Permafrost as a Natural Phenomenon

much ground ice. Polygonal ground can be used with remarkable accuracy also if the type of polygonal ground and its origin is clearly known. Numerous types of Strukturb o ^ ö^ den , polygonal ground and related forms have been described ^^ and their origins discussed (9; 28; 58; 63; 96). The type of ice-wedge poly– gon described by Leffingwell (38) can be differentiated from others on the basis of surface expression. The author’s work in northern Alaska (1945-48) revealed that the polygons go through a cycle which can be described as youth, maturity, and old age--from flat surfaces with cracks, to low-centered polygons, and finally to high-centered polygons. Size and shape of polygons, widths and depths of troughs or cracks, presence or absence of ridges adjacent to the troughs, type of vegetation, and other factors all provide clues as to the size-grade of surficial materials and the amount of ice in the ground. Frost mounds, frost blisters, icings, gullies, and many other surficial features can be used with reliability if all factors are considered and carefully weighed by the experienced observer.
Geophysical methods of locating permafrost have given some promise (20; 34; 41; 73; 74). Various temperature-measuring and recording devices are employed. Augers and other mechanical means of exploring the permafrost are used (41).
Construction . Two methods of construction are used in permafrost areas (41). In one, the passive method, the frozen-ground conditions are undisturbed or provided with additional insulation so that heat from the structure will not cause thawing of the underlying ground and weaken its stability. In the second, the active method, the frozen ground is thawed prior to construction, and steps are taken to keep it thawed or to remove it, and to use materials not subject to heaving and settling as a result of frost action. A preliminary

EA-I. Black: Permafrost as a Natural Phenomenon

examination is necessary in order to determine which procedure is more practicable or feasible.
Permafrost can be used as a construction material (if stress or load does not exceed plastic or elastic limit), removed before construction, or controlled outside the actual construction area. Muller (41) has shown that it is best to distinguish: ( 1 ) continuous areas of permafrost, ( 2 ) discontinuous areas, and ( 3 ) sporadic bodies. Russian engineers recom– mend that in ( 1 ) only the passive method of construction be used; in ( 2 ) or ( 3 ) either the passive or active method be used, depending upon thickness and temperature of the permafrost. Detailed information and references on the construction of buildings, roads, bridges, runways, reservoirs, airfields, and other engineering projects are presented by Huttl (31), Hardy and D’Appolonia (27), Zhukov (107), Corps of Engineers (88;89), and others.
Eager and Pryor (18) have shown that road icings are more common in areas of permafrost than elsewhere. They, Tchekotillo (79), and Taber (78) discuss the phenomena of icings, classify them, and describe various methods used to prevent or alleviate icing.
One of the major factors to consider in permafrost is its water content. Methods of predicting by moisture diagrams ( e ^ é^ pures ) the amount of settling of buildings on thawing permafrost are presented by Fedosov (22).
It should again be emphasized that permafrost is a temperature phenomenon that occurs naturally in the earth. If man disturbs the thermal regime know l ingly ^ or unknowingly,^ he must suffer the consequences. Every effort should be made to ^ 2 words missing. Cf. original p. 26 ✓^ control the thermal regime--to promote pergelation or depergelation as desired. Generally, the former is difficult near the southern margin of permafrost. If the existing climate is not cold enough to insure that the permafrost

EA-I. Black: Permafrost as a Natural Phenomenon

remain frozen, serious consideration should be given to artificial freezing in those places where permafrost must be utilized as a construction material. Techniques similar to those used at Grand Coulee Dam or on Hess Creek (31) can be modified to fit the situation. It should be borne in mind that the refrigerating equipment need only run for a matter of hours during the summer after the ground has been refrozen and vegetation or other means of natural insulation have been employed. Bad slides on roads and railroads, settling under expensive buildings, loosening of the foundations of dams, bridges, towers, etc., probably can be treated by refreezing artificially at less cost than by any other method. If fact the day is probably not far off when air– fields or pykrete (49) or similar material will be built in the Arctic where no construction materials are available.
Where seasonal frost (active layer) is involved in construction, the engineer is referred to the annotated bibliography of the Highway Research Board (43) and to such reports as those of the Corps of Engineers (90; 91).
Water Supply . Throughout permafrost areas one of the major problems is a satisfactory source of large amount of water. Problems encountered in keeping water liquid during storage and distribution or in its purification are outside the scope of this report. Small quantities of water generally can be obtained from melted ice or snow. However, a large, satisfactory, annual water supply in areas of continuous permafrost is to be found only in deep lakes or large rivers that do not freeze to the bottom. Even then the water tends to have considerable hardness and organic content. It is generally not economical to drill through 1,000 to 2,000 feet of permafrost to tap ground– water reservoirs beneath, although artesian supplied have been obtained under 700 feet of permafrost (15) and under 1,500 feet of permafrost (47).

EA-I. Black: Permafrost as a Natural Phenomenon

In areas of discontinuous permafrost, large annual ground-water supplies are more common either in perched zones on top of permafrost or in nonfrozen zones within or below the permafrost (10; 50).
Annual water supply in areas of sporadic permafrost normally is a problem only to individual householders, and presents only a little more difficulty than finding water in comparable areas in temperate zones.
Surface water as an alternate to ground water can be retained by earthen dams in areas of permafrost (31).
Throughout the Arctic, however, the quality of water is commonly poorer than in temperate regions. Hardness largely in the form of calcium and magnesium carbonate and iron or manganese is common. Organic impurities and sulfur are abundant. In many places ground water and surface water have been polluted by man or organisms.
Muller (4) presents a detailed discussion of sources of water and the engineering problems of distributing the water in permafrost areas. Joesting (34) describes a partly successful method of locating water-bearing formations in permafrost with resistivity methods.
Sewage disposal in areas of continuous permafrost is a most difficult problem. Wastes should be dumped into the sea as no safe place exists on land for their disposal in a raw state. As chemical reaction is retarded by low temperatures, natural decomposition and purification through aeration do not take place readily. Large streams that have flowing water throughout the year are few and should not be contaminated. Indiscriminate dumping of sewage will lead within a few years to serious pollution of the few deep lakes and other areas of annual surface water supply. Burning is costly.

EA-I. Black: Permafrost as a Natural Phenomenon

As yet, no satisfactory solution has been found. In discontinuous and sporadic permafrost zones, streams are larger and can handle sewage more easily, but even there sewage disposal still remains in places one of the most important problems.
Agriculture . Permafrost as a cold reserve has a deleterious effect on the growth of plants. However, as an impervious horizon, it tends to hold precipitation in the upper soil horizons, and in thawing provides water from melting ground ice. Both harmful and beneficial effects are negligible after 1 or 2 years of cultivation, as the permafrost table has thawed beyond the reach of roots of most annual plants (24).
Farming in areas of permafrost with much ground ice, however, can lead to a considerable loss in time and money. Subarctic farming can be done only where a sufficient growing season is available for plants to nature during the short summers. Such areas are in the discontinuous or sporadic zones of permafrost. If the land is cleared of its natural insulating cover of vegetation, the permafrost thaws. Over a period of 2 to 3 years, large cave-in lakes have developed in Siberia (I. V. Poir e ^ é^ , oral communication), and pits and mounds are formed in Alaska (50; 51; 52; 59). The best solution is to ^ s^ elect farm lands in those areas free of permafrost or free of large ground-ice ^^ masses (86).
Mining . In Alaska, placer miners particularly and lode miners to a lesser extent have utilized permafrost or destroyed it, as necessary, since it was first encountered. Particularly in placer mining, frozen ground has been the factor that made many operations uneconomic (102) or others economic. In the early part of the century, when gold was being mined so profitably at Dawson, Fairbanks, Nome, and other places in northern North America, it was

EA-I. Black: Permafrost as a Natural Phenomenon

common for miners to sink shafts more than a hundred feet through frozen muck to the gold-bearing gravels. These shafts were sunk by steam jetting or by thawing with fires or hot rocks. If the muck around the shafts or over the gravels thawed, the mines had to be abandoned.
Now, with the advent of dredges, such ground is thawed, generally with cold water, one or more years in advance of operations. In the technique used, holes are drilled through the permafrost at regular intervals of possibly 10 to 30 feet, depending on the material, and cold water is forced through the permafrost into underlying permeable foundations or out to the surface through other holes. Hot water and steam, formerly used, are uneconomi– cal and inefficient. Where thick deposits of overburden cover placers, they are removed commonly by hydraulicking. Summer thaw facilitates the process (48).
Permafrost in lode mining usually is welcomed by the miners as it means dry working conditions. Its effect on mining operations other than maintaining low temperatures in the mine is negligible unless it contains aquifers. Because of low temperatures, sealing aquifers with cement is difficult.
Some well drilling in permafrost requires modifications of existing techniques and more careful planning for possible exigencies (21). Difficulty may be encountered in getting proper foundations for the rig. In rotary drilling difficulty may be experienced in keeping drilling muds at the proper temperature, in finding adequate water supplies, or proper local material for drilling muds. In shallow holes particularly, the tools will freeze-in after a few hours of idleness. Cementing of casings is costly and very difficult as concrete will not set in subfreezing temperatures. (See also “Arctic Alaska Petroleum Exploration and Drilling Operations.”) Deep wells extending

EA-I. Black: Permafrost as a Natural Phenomenon

below the permafrost may encounter high temperatures (100° to 150°F.). Hot drilling muds on returning to the surface thaw the permafrost around the casing and create a settling hazard in the foundation of the rig and also create a disposal problem. In some foundations refrigerating equipment must be used to prevent settling.
Permafrost may act as a tr o ^ a^ p for oil or even contain oil reservoirs. ^^ The low temperature adversely affects asphalt-base types particularly, and cuts down yields; production difficulties and costs increase (21).
Refrigeration and Storage . Excavations are used widely in areas of permafrost for natural cold storage. They are most satisfactory in continuous or discontinuous zones. If permafrost is about 30°F., extreme care in ventila– tion and insulation must be used. Properly constructed and ventilated storerooms will keep meat and other products frozen for years. Detail s ^ ed^ plans and charac- ^^ teristics required for different cold storage rooms are described by Chekotillo (12).
Trafficability . In the Arctic and Subarctic most travel overland is done in winter, as muskegs, swamps, and hummocky tundra make summer travel exceed– ingly difficult (21; 92). Tracked vehicles or sleds are the only practical types. Wheeled vehicles are unsatisfactory as most of the area is without roads. Polygonal ground, frost blisters, pinges, and small, deeply incised thaw streams (commonly called “beaded” streams), rivers, and lakes create natural hazards to travel.
Permafrost aids travel when it is within a few inches of the surface. It permits travel of D-8 Caterpillar tractors and heavier equipment directly on the permafrost. Sleds weighing many tons can be pulled over the permafrost with ease after the vegetal mat has been removed by an angledozer.

EA-I. Black: Permafrost as a Natural Phenomenon

In areas of discontinuous and sporadic permafrost, seasonal thaw is commonly 6 to 10 feet deep, and overland travel in summer in many places can be accomplished only with amphibious vehicles such as the “weasel” of LVT. ^ (Landing Vehicle, Track)^ Travel on foot or by horse is very slow and laborious in many places because of swampy land surfaces and the necessity for making numerous detours around slough, rivers, and lakes.
Military . Permafrost alters military operations through its effects on the construction of air bases, roads, railroads, revetments, buildings, and other engineering projects; in its effects on trafficability, water supply, sewage disposal, excavations, underground storage, camouflage, explosives, planting of mines; and in other more indirect ways (19; 92). Military operations commonly require extreme speed in construction, procuring of water supply, or movement of men and materiel. Unfortunately, it is not always possible to exercise such speed (21). Large excavations require that natural thawing, possibly aided by water sprinkling (31), proceed ahead of the earth movers. Conversely, seasonal thaw may be so deep as to prevent the movement of heavy equipment over swampy ground until freeze-up. Similarly, it may be necessary in a heavy building to steam jet piles into permafrost and allow them to freeze in place before loading them. These things take time, and proper planning is a prerequisite for efficient operations.
Camouflage is a problem on the tundra. Little relief or change in vege– tation is available. Tracks of heavy vehicles or paths stand out in marked contrast for years. In aerial photographs it is easy to see foot paths and dogsled trails abandoned 10 years or more ago.
The effects of mortar and shell fire, land mines, shaped charges, and other explosives undoubtedly change as the character of permafrost changes, but no data are available to the author.

EA-I. Black: Permafrost as a Natural Phenomenon

Throughout the foregoing pages brief reference is made to aspects of permafrost or effects of permafrost on engineering, geologic, biologic, and other problems for which few factual data are available. However, in the event that the reader has received the impression that a great deal is known of permafrost, it is pointed out that the study of permafrost is relatively young and immature. It has lacked a coordinated and comprehensive investi– gation by geologists, engineers, physicists, botanists, climatologists, and other scientists. It is barely in the beginning of the descriptive stages, and only now is it receiving the world-wide attention it deserves.
As our civilization presses northward, the practical needs of construc– tion, water supply, sewage disposal, trafficability, and other engineering problems must be solved speedily and economically. Our present knowledge is relatively meager, and trial-and-error methods are being used much too widely. Practical laboratory experiments (75; 76) and controlled experiments at field stations, such as that at Fairbanks, Alaska (33), are needed in various situations in the permafrost areas. From these stations methods and techniques of construction can be standardized and appropriate steps formu– lated to meet a particular situation. Such laboratories must be supplemented with arctic research stations such as are found in the Soviet Union. There, more than 30 natural-science laboratories exist with permanent facilities for pursuing year-round basic studies in all phases of arctic science. The Arctic Research Laboratory at Barrow (64) is a start in the right direction. The academic approach must accompany the practical approach if satisfactory solution of the problem is to be found.

EA-I. Black: Permafrost as a Natural Phenomenon

To name all the specific topics for future research would make this article unduly long as no phase of permafrost is well known. However, the author reiterates that the problems cannot be solved adequately until the phenomenon of heat flows in all natural and artificial materials in the earth is understood and correlated with insolation, atmospheric conditions, geother– mal gradients, and the complex surface of the earth. Then possibly, criteria can be set up to evaluate within practical limits the effect of various structures and materials on the dissipating surface of the earth. The complexities of geology (lithology, structure, and texture of soils and rock), hydrology, vegetation, and climate of the Arctic make the solution a formidable task, but the research is an int i ^ r^ iguing problem for all earth scientists. ^^

EA-I. Black: Permafrost.


1. Barnes, L.C “permafrost, a challenge to engineers,” Milit.Engr . vol.38, no.243, pp.9-11, 1946.

2. Birch, Francis. “The effects of Pleistocene climatic variations upon geo– thermal gradients,” Amer.J.Sci . vol.246, no.12, pp.729-60, 1948.

3. Black, R.F., and Barksdale, W.L. “Oriented lakes of northern Alaska,” J.Geol . vol.57, no.2, pp.105-18, 1949.

^^ 4. Bryan, Kirk. “Cryopedology, the study of frozen ground and intensive frost– action with suggestions on nomenclature,” [: ] ^ A^ mer.J.Sci . vol.224, no.9, pp.622-42, 1946.

5. ----. “The geologic implications of cryopedology,” J.Geol . vol.57, no.2, pp.101-04, 1949.

6. ----. “Permanently frozen ground, “ Milit.Engr. vol. 38, no. 246, p.168, 1946.

7. ----. “The study of permanently frozen ground and intensive frost-action,” Ibid . vol.40, no.273,pp.304-08, 1948. Discussion, pp.305-08.

^^ 8. ----, and Albritten, Jr ^ .^ , C.C. “Soil phenomena as evidence of climatic changes,” Amer.J.Sci . vol.241, no.8, pp.469-90, 1943.

^^ 9. Cailleux, Andr e ^ é^ . “Etudes de cryop e ^ é^ dologie.” Exp e ^ é^ ditions Polaires Fran c ^ ç^ aises. ^^ Exp e ^ é^ dition Arctique (Groenland) 1948-50. Section des Sciences Naturelles, pp.1-67.

10. Cederstrom, D.J. Ground water data for Fairbanks, Alaska . Wash.,D.C., Geo– logical Survey, 1948. MS on open file.

11. Chaney, R.W., and Mason H.L. A Pleistocene Flora from Fairbanks, Alaska . Amer.Mus.Novit . 887. 1936.

12. Chekotillo, A.M. “Podzemnye khranilischa v vechnomerzloi tolshche,” (Underground storage places in permanently frozen ground.) Priroda, Moscow, no.11, pp.27-32, 1946. English translation by E.A. Golomshtok in the Stefansson Library, New York City.

13. Conrad, V. “Polygon nets and their physical development, “ Amer.J.Sci. vo.244, no.4, p.277-96, 1946.

14. Cressey, G.B. “Frozen ground in Siberia,” J.Geol . vol.47, pp.472-88, 1939.

15. Dementiev, A.I., and Tumel, V.F. “Civil engineering in frozen soil, U.S.S.R.,” Canad.Geogr.J . vol.32, no.1, pp.32-33, 1946.

EA-I. Black: Permafrost.

16. Denny C.S., and Raup, H.M. Notes on the Interpretation of Aerial Photo- graphs along the Alaska Military Highway . Unpublished MS.

17. ----, and Stitch, J. Geology of the Alaska Highway . Unpublished MS.

18. Eager, W.L., and Pryor, W.T. “Ice formation on the Alaska Highway,” Public Rds ., Wash. Vol.24, no.3, pp.55-74, 1945.

19. Edwards, N.B. “Combat in the Arctic, “ Infantry J . Jan., 1949, pp.4-8

20. Enenshtein, B.C. “Rezultaty primeneniia elektrorazvedki metodom ^^ postoiannogo to a ^ k^ a v raionakh vechnoi merzloty.” (Results of electro– metric investigations carried out by means of direct current on per– ^^ manently frozen soil d ^ s^ .) Akad.Nauk Inst.Merzlot. Trudy T.5, pp.36-86, 1947. (In Russian with English summary.) Abstracted in U.S.Geol.Surv. Bull .959-B. Wash.,D.C., G.P.O., 1948, pp.126-27. (U.S.Geol.Surv., Geophys.Abstr . 133)

21. Fagin, K.M. “Petroleum development in Alaska, “ Petrol.Engr . 1947, Aug., pp.43-48; Sept., pp.150-64; Dec., pp.57-68.

22. Fedosov, A.E., “Prognoz osadok sooruzhenii na ottaivaiushchei merzlote. ^^ 2 (Metod vlazhnostnyh epiur).” (Forecasting of the settling of build– ings after the thawing of permanently frozen ground, by the method of moisture diagrams.) Akademiia Nauk, Leningrad, USSR. Institut Merzlotovedeniia. Issledovanie Vechnoi Merzloty v Yakutskoi Respublike , no.1, pp.52-85, 1942.

23. ----. “Prognoz osadok sooruzhenii pri ottaivanii gruntov osnovanii.” (The prognosis of the settlement of buildings on the underlying thawing ground.) Akad.Nauk Inst.Merzlot. Trudy T.4, pp.93-124, 1944. (In Russian with English summary.) Abstracted in U.S.Geol.Surv., Bull . 959-C. Wash.,D.C., G.P.O., 1948, p.238. (U.S.Geol.Surv. Geophys. Abstr . 134) Abstract and translation in the Stefansson Library, New York City.

24. Gasser, G.W. “Agriculture in Alaska ,” Arctic vol.1, no.2, pp.75-83, 1948.

25. Gatty, O., Fleming, W.L.S., and Edmonds, J.M. “Some types of polygonal surface markings in Spitzbergen,” Amer.J.Sci . vol.240, pp.81-92, 1942.

^^ ^^ 26. k Giddings, J. K ^ L^ . “Buried wood from Fairbanks, Alaska,” Tree Ring Bull . 1938, pp.3-6.

27. Hardy, R.M., and D’Appolonia, E. “Permanently frozen ground and founda– tion design. Pts.1 and 2,” Engng.J ., Montreal vol.29, no.1, pp.1-11, Jan., 1946. Reviewed: J.Glaciol . vol.1, no.2, pp.80-82, July, 1947.

28. Högbom, B. “über die geologische Bedeutung des Frostes,” Uppsala Univ. Min.-Geol.Inst. Bull . Vol.12, pp.257-389, 1914.

EA-I. Black: Permafrost.

29. Hopkins, D.M. “Thaw lakes and thaw sinks in the Imuruk Lake area, Seward Peninsula, Alaska,” J.Geol . vol.57, no.2, pp.119-31, 1949.

^^ 30. N ^ H^ orberg, Leland. “A possible fossil ice wedge in Bureau County, Illinois,” Ibid . vol.57, no.2, pp.132-36, 1949.

^^ 31. Huttl, J.B. “Building an earth-fill dam in artic i placer territory,” Engng.Min.J . vol.149, no.7, pp.90-92, 1948.

32. Ingersoll, L.R., Zobel, O.J., and Ingersoll, A. C. Heat Conduction, with Engineering and Geological Applications . N.Y., McGraw-Hill, 1948.

33. Jaillite, W.M. “Permafrost research area,” Milit.Engr . vol.39, no.263, pp.375-79, 1947.

34. Joesting, H.R. “Magnetometer and direct-current resistivity studies in Alaska,” Amer.Inst.Min.Metall.Engrs. Tech.Publ . 1284, Feb., 1941.

^^ 35. Judson, Sheldon. “Rock-fragment slopes caused by past frost acti i ^ o^ n in the Jura Mountains (Ain) France” J.Geol . vol.57, no.2, pp.137-42, 1949.

36. Kaliaev, A.V. “Anabiosis under conditions of frozen ground,” Mikrobiologiia vol.16, no.2, 1947.

37. Lane, A.C. “Northern climatic variations affecting geothermal initial,” Canad.Min.Metall.Bull . 411, 1946, pp.397-402.

38. Leffingwell, E. de K. The Canning River Region, Northern Alaska . Wash., D.C., G.P.O., 1919. U.S.Geol.Surv. Prof.Pap . 109.

39. Liverovsky, A.V., and Morozov, K.D. Construction Under Permafrost Condi- tions . Leningrad, Moscow, 1941. Abstracted: E.A. Golomshtok, the Stefansson Library, New York City.

40. Mozley, A. “Frozen ground in the sub-arctic region and its biological significance,” Scottish Geogr.Mag . vol.53, no.4, pp.266-70, 1937.

41. Muller, S.W. Permafrost of Permanently Frozen Ground and Related Engineer- ing Problems . Ann Arbor, Mich., Edwards, 1947.

42. Mullis, I.B. “Illustrations of frost and ice phenomena,” Public Rds ., Wash. vol.11, no.4, pp.61-68, 1930.

43. National Research Council. Highway Research Board. Bibliography on Frost Action in Soils: Annotated . Wash.,D.C., The Council, 1948. Its Bibliography No.3.

44. Nikiforoff, C. “The perpetually frozen subsoil of Siberia,” Soil Sci . ^^ vol.26, pp.61-78, k 1932.

EA-I. Black: Permafrost.

45. Nordale, A.M. “Valuation of dredging ground in the sub-arctic,” Canad.Inst. ^ ^ Min.Metall. Trans ^ Trans ^ . Vol.50, pp.487-96, 1947. Canad.Min.Metall.Bull . no.425, Sept., 1947.

46. Obruchev, V. “Eternal frost; the frozen soil of northern Russia and Siberia,” Nat.Rev . vol.124, pp.220-27, 1945.

47. Obruchev, V.A. “15-letie Merzlotovedeniia v Akademii Nauk SSSR.” (The 15th Anniversary of Eternal Frost Study in the Academy of Sciences of the USSR.) Priroda , Moscow no.5, pp.92-94, 1946. Translation in the Stefansson Library, New York City.

48. Patty, E.N. “Placer mining in the sub-arctic,” Western Min ., Vancouver, B.C. vo.18, no.4, pp.44-49, April, 1945.

49. Perutz, M.F. “A description of the iceberg aircraft carrier and the bearing of the mechanical properties of frozen wood pulp upon some problems of glacier flow,” J.Glaciol . vol.1, no.3,pp.95-102, 1948.

^^ 50. P e ^ é^ w e ^ é^ , T.L. Groundwater Data for Fairbanks, Alaska . Wash.,D.C., Geological ^^ Survey, 1 [: ] ^ 9^ 48. MS on open file.

51. ----. “Origin of the Mima Mounds” Scientific Mon. , N.Y. vol.66, no.4, pp.293- 96, 1948.

52. ----. Preliminary Report of Permafrost Investigations in the Dunbar Area, Alaska . Wash.,D.C., G.P.O., 1949. U.S.Geol.Surv., Circ . 42.

53. Poser, Hans. “Auftautiefe und Frostzerrung im Boden Mitteleuropas während der Würm-Eiszeit,” Naturwissenschaften Jahrg.34, pp.232-38, 262-67, 1947.

54. ----. “Dauerfrostboden und Temperatur Verhältnisse während der Würm-Eiszeit ^^ im nicht vereisten Mittel--und W o ^ e^ steuropa,” Ibid . Jahrg.34, pp.1-9, 1947.

^^ 55. Pryor, W.T. “Aer o ial surveying on the Alaska Highway, 1942,” Public Rds ., Wash. Vol.24, no.11, pp.275-90, 1947.

^^ 56. Raup, H.M. “Botanical problems in Bo z ^ r^ eal America.” Botanical Rev . vol.7, pp.147-248, 1941.

57. ----. “The botany of southwestern Mackenzie,” Sargentia VI, 1947.

58. Richmond, G.M. “Stone nets, stone stripes, and soil stripes in the Wind River Mountains, Wyoming,” J.Geol . vol.57, no.2, pp.143-53, 1949.

59. Rockie, W.A. “Pitting on Alaskan farm lands, a new erosion problem” Geogr. Rev . vol.32, pp.128-34, 1942.

^^ 60. Schafer, J.P. “Some perig k ^ l^ acial features in central Montana,” J.Geol . vol.57, no.2, pp.154-74, 1949.

EA-I. Black: Permafrost.

61. Shannon, W.L., and Wells, W.A. “Tests for thermal diffusivity of granular materials,” Amer.Soc.Test.Mater. Proc., Committee Reports, Technical Papers, vol.47, 1947. Phil., The Society, 1948, pp.1044-54.

^^ 62. Sharp, R.P. “Ground-ice mounds in tund ar ^ ra^ ,” Geogr.Rev . vol.32, no.3, pp.417-23, 1942.

63. ----. “Soil structures in the St. Elias Range, Yukon Territory,” J. Geomorph . Vol.5, pp.274-301, 1942.

64. Shelesnyak, M.C. “History of the Arctic Research Laboratory, Point Barrow, Alaska,” Arctic vol.1, no.2, pp.97-106, 1948.

65. Smith, H.T.U. “Perioglacial features in the driftless area of southern Wisconsin,” J.Geol . vol.57, no.2, pp.196-215, 1949.

66. ----. Physical Effects of iPleistocene Climatic Changes in Unglaciated Areas--Aeolian Phenomena, Frost Action, and Stream Terracing . Wash., D.C., Committee on Interrelations of Pleistocene Research, National Research Council. Preliminary report. In press.

67. Smith, P.S. Permanent Ground Frost in Alaska . Wash.,D.C., U.S. Geological Survey. Unpublished MS.

68. Smith, W.O. “Thermal conductivities in moist soils” Soil Sci.Soc.Amer. Proc . Vol.4, pp.32-40, 1939.

69. ----. “The thermal conductivity of dry soil,” Soil Sci , vol.53, no.6, pp.435-59, 1942.

^^ 70. Steche, Hans. “Beiträge zur Frage der Strukturböden,” Akad.Wiss.Leip z ^ z^ ig, Math.-Phys.Kl. Ber . vol.85, pp.193-272, 1933.

^^ 71. Stone, Kirk. “Aer o ial photographic interpretation of natural vegetation in the Anchorage area, Alaska,” Geogr.Rev . Vol.38, no.3, pp.465-74, 1948.

72. Sumgin, M.I. Vechnaia Merzlota Pochvy v Predelakh SSSR . (Eternal Ground Frost in the U.S.S.R.) 2d ed. Rev. Vladivostok, 1947. (N.K.Z. Dalne– Vostochnaia Geofizicheskaia Observatoriie)

73. ----, and Petrovski, A.A. “Znachenie elektricheskikh metodov dlia izuchenia vechnoi merzloty.” (The impoertance of electrical methods for the study of permanently frozen ground.) Akad.Nauk Inst.Merzlot. Trudy T.5, pp.15-17, 1947. (In Russian with English summary.) Abstracted in U.S. Geol.Surv. Bull . 959-B. Wash.,D.C., G.P.O., 1948, p.130. (U.S. Geol.Surv. Geophys.Abstr . 133)

EA-I. Black: Permafrost.

^^ ^^ 74. Swartz, J.H., and Shepard, E.R. Report i on a Preliminary Investigation s of the Possible Appl e cation of Geophysical Methods to the Studies of Permafrost Problems in Alaska . Wash.,D.C., Bureau of Mines, 1946. Ozalid Report.

75. Taber, Stephen. “Freezing and thawing of soils as factors in the destruct– ^^ tion of road pavements,” Public Rds ., Wash. R vol.11, pp.113-32, 1930.

76. ----. “The mechanics of frost heaving,” J.Geol . vol.38, pp.303-17, 1930.

77. ----. “Perennially frozen ground in Alaska--its origin and history,” Geol.Soc.Amer. Bull . Vol.54, no.10, pp.1433-1548, Oct.1, 1943.

78. ----. “Some problems of road construction and maintenance in Alaska,” Public Rds ., Wash. Vol.23, no.9, pp.247-51, July-Sept., 1943.

79. Tchekotillo, A. “Solving the problem of ‘Nalyeds; in permafrost regions,” Engng.News Rec . vol.137, no.22, pp.62-65, Nov.28, 1946. Trans. by G.P. Tschebotarioff.

^^ 80. Theis, C.V. Ther n ^ m^ al Processes Related to the Formation of Permafrost . Unpublished MS.

81. Tolmachoff, I.P. “The carcasses of the mammoth and rhinoceros found in the frozen ground of Siberia,” Amer.Philol.Soc. Trnas . Vol.23, pt.1, pp.12-14, 1929.

82. Tremayne, Marie. “Bibliography of Arctic research,” Arctic vol.1, no.2, pp.84-86, 1948.

83. Troll, Carl. “Die Formen der Solifluktion und die periglaziale Bodenbtra– gung,” Erdkunde , Bonn B.1, pp.162-75, 1947.

84. ----. “Strukturböden, Solifluktion und Frostklimate der Erde,” Geologische Rundschau B.34, pp.545-694, 1944.

85. ----. “Der subnivale order periglaziale Zyklus der Denudation,” Erdkunde , ^^ Bonn, B.2, pp.1-21, 1 0 ^ 9^ 48.

86. Tsiplenkin, E.I. “Vechnaia merzlota i ee agronomicheskoe znachenie.” (The permanently frozen soils and their agricultural value.) Akad.Nauk Inst. Merzlot. Trudy T.4, pp.230-55, 1944. (In Russian with English summary.

87. Tuck, Ralph. “Origin of the muck-silt deposits at Fairbanks, Alaska,” Geol.Soc.Amer. Bull . Vol.51, no.9, pp.1295-1310, 1940.

88. U.S. Army. Engineering Dept. Airfield Pavement Design--Construction of Airfields on Permanently Frozen Ground . Wash.,D.C.,G.P.O., 1946. U.S. War Dept. Engineering Manual for War Department Construction , pt. 12, chap. 7.

EA-I. Black: Permafrost

^^ 89. ----. Construct t on of Runways, Roads, and Buildings on Permanently Frozen Ground . Wash., D.C., G.P.O., 1945. U.S. War Dept. Tech.Bull .

90. ----. New England Division. Frost Investigation, 1945-1946. Comprehensive Report and Nine Appendices . Boston, 1947. Mimeographed.

91. ----. ----. Report on Frost Investigations, 1944-1945, and 15 Appendices . Boston, 1947. Mimeographed.

92. U.S. Navy. Bureau of Yards and Docks. Cold-Weather Engineering . Wash., D.C., G.P.O., 1948-49. Chap. I-V.

93. Van Orstrand, C.E. “Observed temperatures in the earth’s crust,” National Research Council. Committee on Physics of the Earth. Physics of the Earth. VII. Internal Constitution of the Earth . N.Y., McGraw-Hill, 1939, pp.125-51.

94. Wahrhaftig, Clyde. “The frost-moved rubbles of Jumbo Dome and their sig– nificance in the Pleistocene chronology of Alaska,” J.Geol . vol.57, no.2, pp.216-31, 1949.

95. Wallace, R.E. “Cave-in lakes in the Nebesna, Chisana, and Tanana River valleys, eastern Alaska,” Ibid . vol.56, no.3, pp.171-81.

96. Washburn, A.L. Reconnaissance Geology of Portions of Victoria Island and Adjacent Regions, Arctic Canada . N.Y., 1947. Geol.Soc.Amer. Mem . 22.

97. Weinberg, B.P. “Studies on eternally frozen ground and on freezing of soil,” Amer.Geophys.Un. Trans . vol.21, pp.770-77, 1940.

98. Weinberger, L. “Frostspalten und Froststrukturen in Schottern bei Leipzig,” Geologische Rundschau B.34, pp.539-44, 1944.

99. Werenskiold, W. “Frozen soil in Spitzbergen” Mon.Weath.Rev ., Wash. vol.51, p.210, April, 1923. Excerpt from Geofysiske Publikasjoner vol.2, no.10.

100. Wilkerson, A.S. Some frozen Deposits in the Gold Fields of Interior Alaska. Amer.Mus.Novit . 525. 1932.

101. Wilson, W.K., Jr. “The problem of permafrost,” Milit.Engr . vol.40, no.270, pp.162-64, 1948.

102. Wimmler, N.L. Placer-Mining Methods and Costs in Alaska . Wash.,D.C., G.P.O., 1927. U.S. Bur.Min. Bull .259.

103. Woods, K.B., et al. “Use of aerial photographs in the correlation between permafrost and soils,” Milit.Engr . vol.40, pp.497-99, 1948.

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104. Young, J.W. “Ground frost in Alaska,” Engng.Min.J . vol.105, no.7, pp.338-39, 1918.

105. Zeuner, F.E. Dating the Past . London, Methuen, 1946.

106. ---- The Pleistocene Period, its Climate, Chronology and [: ] Faunal Successions . London, Ray Society, 1945.

^^ 107. Zhukov, V.F. Zemlianye Raboty pri Ustroistv ^ e^ Fundamentov i Osnovanii v Oblasti Vechnoi Merzloty . (Earthworks during the Laying of Foundations in the Permafrost Region.) Moscow, Leningard, Izdatelstvo Akademiia Nauk, SSSR, 1946.

Robert F. Black