U4512 CORNELL UNIVERSITY LIBRARY GIFT OF THE PUBLISHER i jjll '7'taf^o "2 !25!2 n o 8^- 1 T T i + + ++++,' 1 V ' Figure 2. Seasonal and daily temperature distribution in Irkutsk, Siberia, in isopleths. Lat 52°16'N, Long 104°19'E. Elev 491 m. 1887-97. 1 sUl b I §1 al |l sUl 2l |Iil^ 200 1- PRECIPITATION (MM) Figure 3. Seasonal and daily temperature distribution in Quito, Ecuador, in isopleths. LatO°14'S, Long 78°32'W. Elev. 2850 m. 1906-7. 12 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Spitsbergen ( Green Harbor) Lat 78°2'N, Long M-M'E Elev 7 m DAYS 3 o o c 1 1 1 1 1 'Ai ••'.'*■ I' •''■"■^'■iV " J LI l>.l hi Itl < < < 3 £ -> S S -J CO Sagastyr (Lena River) Lat 73°23'N, Long 126°35'E Elev 5 m o < z -» (O 20- ?■■•/•• < = 1 is Vblftl * < < 3 Uj l> Iz o < Sonnblick (Alps) Lat47°03'N, Longl2°57'E Elev 3106 m 30 Zugspitzfe (Alps) Lat 47°25'N, Long 10°59'E Elev 2964 m Yakutsk (Siberia) Lat 62°01'N, Long 129°43'E Elev 108 m 30 -rsT^ « 20- >- < o 10 ■I97;;:0si I ui ivi liiiti r>n: iz < Schneekoppe (Rieson Gebir.ge) Lat 50°44'N, Long 15°44'E Elev 1602 m 01;ekminsk (Siberia) Lat 60°22'N, Long 120°26'E Elev 202 m Berlin-Dahlem Lat 52°27'N, Long ISMS'E Elev 57 m Table I. Frost alternation frequency and its annual distribution in different frost climates of the world. III. CLIMATIC PREREQUISITES FOR STRUCTURE SOILS 13 El Misti - Summit station (South Peru) Lat Ib^ie'S, Long 71°25'W. Elev 5850 m SO- a Itl l>l"i; Alto de los Huesos (South Peru) Latl6°l6'S, Long71°25'W. Elev 4137 m 30 El Misti Mont Blanc Station Lat 16''16'S, Long 71''25'W Elev 4760 m 30- Kerguelen Island Lat 49°25'S, Long 69°53'E Elev 16 m 30 «»20-; FROST FREE ICE DAYS FROST ALTERNATION OATS DAYS Table I. (cont) . [Frost-free days — temperature remains above freezing; ice days — temperature remains below freezing; frost alternation days — both freezing and thawing tempera- tures occur]. column for different altitudes of central Europe, in the third and fourth foT different altitudes of the southern Peruvian Andes and for the sub-Antarctic island group of Kerguelen. In the higher latitudes the number of frost alternation days is generally small, e.g. Schneekoppe in the Riesen Gebirge, 81; Zugspitze, 81; Spitsbergen, 59; Sagastyr' at the mouth of the Lena River, 42.5; Yakutsk, 42. Moreover, with the exception of the high mountains above the timberline, they occur in seasons when there is a heavy snow blanket, so that the frost alternation of the air can affect the soil only very weakly. The situation is quite different in the tropical high mountains. There, as in the lowland tropics, seasonal fluctuations are either lacking or are very small, but we come rapidly, on climbing into the tropical high mountains, to a clirjiate zone where a double fluctuation about the freezing point occurs almost everyday. In the southern Peruvian Andes at 4000-5000 m elevation there are more than 300 frost-alternation days (Fig. 4, Table I). Moreover, the seasonal snow cover either plays a small part or is lacking entirely in the tropical mountains (Troll, 1942) , so that the fluctuation of the air temperature cani effect the soil surface cbnside-rably more powerfully, the change from incoming to outgoing radiation being much stronger. Practically speaking, at suitable elevations all days of the year have frost alternation of the soil. It follows from these climatic facts that there must be a basic difference in the dynamics of soil freezing and structure-soil formation among the several subnival climates. The contrast is greatest between the polar subnival climate, as in Spitsbergen or the Siberian tundra and the mountain climate of the interior tropics. The simplest way to recognize the dynamics of structure-soil formation is by contrasting these two types. Observation has taught me that the structure soils in the tropical subnival zone, such as stone nets, stone stripes, and cellular soils, exhibit principally the same ground pattern as those described from the arctic, but several notable differences are conspicuous: 14 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES EL MISTI S8S0 (SUMMIT) EL MISTI^4760 (MONT BLANCT VINC0CAYA-»-4377 ALTO DE LOS HUES0S-»4I37 3437 CUZCO->^33eO ARE0UIPA«236O 1000 Ll FROST FREE DAYS 6000 < > 2000 1000 50 100 ISO ZOO DAYS 250 300 350 365 Figure 4. Vertical distribution of frost days, ice days, frost-alternation days, and frost-free days in a profile of the southern Peruvian Andes. Stations on the west slope of the Andes and on El Misti Observations fEl Misti El Misti Alto de h Arequipa Oct. 1893 - Dec. 1895 Jan. 1894 - Dec. 1895 Mar. 1894 - Dec. 1895 Jan. 1892 - Dec. 1895 ,E1 Misti - summit - Mont Blanc los Hueses jquipa Stations on the Altiplano ^fVincocayo ICuzco Dotted line shows boundary of frost-free days in the abnormal period Nov. 1888 - June 1890. Nov. 1888 - Apr. 1890 July 1894 - Dec. 1895 1) Tropical structure soils are more regular and homogeneous in the sorting of materials than the polar. 2) The inner measure of the forms (the cross section of polygons, width of stripes) is quite generally very snnall (10-25 cm). 3) They are either completely without vegetation, or at most are covered with certain fruticose lichens, which do not cling to the soil or stones, but lie completely loose on top. 4) They are more closely associated with cohesive, argillaceous, wateT-retaihitig rock than in polar regions. III. CLIMATIC PREREQUISITES FOR STRUCTURE SOILS 15 All these differences can be explained without difficulty by the soil-climate relations. In the subnival zone of the tropical high mountains there is no permafrost. Freezing of the ground takes place with a daily rhythm — every night the ground freezes, and every morning it thaws again. Ice formation reaches only a few centimeters into the soil. It is understandable that, with such a slight penetration of frost, only structure soils of limited dimension can exist. The frequency of freezing likewise causes a frequent movement of soil particles. The pronounced regularity of the forms will be clear without further comment. Apparently a very short time is sufficient to develop such a daily structure. The absence of vegetation is thus explained, for the daily agitation of the upper soil layers precludes the seeding of the higher plants and also of the clinging cryptogams*. Lastly, it is easily understandable that in such a process, affecting only the uppermost layers of the ground, the water- retaining ability of the soil and its capillary absorptive capacity are prime prerequisites for structure-soil formation. Other soils dry out too easily on the surface, hindering ice formation. It is to be expected on climatic grounds that, between the extreme cases of polar and tropical structure soils, transitional and intermediate forms would be found in the middle latitudes, in the mountains of the subtropics, and in the temperate and sub- polar latitudes. Moreover, the contrast in the oceanic and continental climates of higher latitudes should provide important differences in frost-soil forms. Indeed, we shall find that, in the special conditions of an extreme oceanic condition, structure - soils found in subpolar regions strongly resemble in appearance and dynamics those of the tropics. Before we go on to an analysis of the different climatic types, it is necessary to review past results and the state of structure-soil research, which previously was almost entirely restricted to polar relations. We also want to utilize this review to contribute viewpoints on essential questions, using material developed in subsequent chapters. 6. The suggestion that paucity of vegetation on structure soils may be due to a lack of plant nutrients, as Steche (1933) believes, is certainly in error. 16 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES IV. THE PROBLEM OF FROST-SOIL FORMATION IN THE LIGHT OF PREVIOUS RESEARCH 1. Convection hypothesis and the frost-thrust theory About 10 years ago in the German literature, an energetic dispute, with after- effects even today, raged on the structure -soil problem. It concerned a hypothesis which may be termed the convection hypothesis or soil-flow hypothesis. The theory suggested that, in a strongly water-saturated soil, vertical convection currents between the surface and the substratum could be set up by temperature differences just as in a viscous fluid. It was first proposed by O. NordenskjQ.Id (1907) in connection with the investigations of the French physicist Benard ( 1900) , who produced a polygonal cell system of convection flow in the thin stratum of a viscous liquid by warming the lower layer. The hypothesis was abandoned by NordenskjOld himself (1911), and played no further role until it was presented anew 18 years later by Low (1925) and Brunt (1925), merely on the basis of photographs by Elton (1927) of stone nets from Spitsbergen. Hudino (1933) in Japan made similar convection studies with sugar beet syrup and rice suspension in an attempt to explain the polygonal ground observed by Fujiwhara (1928) in the same manner as Brunt. Most recently convection research has been carried out by Romanovsky (1939). H. Gripp adopted this concept (after 1926), after he observed the many evidences of solifluction soils and structure soils in Spitsbergen in 1925, and especially the water-saturated soil islands of the tundra. Such loam islands from northern Sweden had also been described by the names gSrlehm (jaslera) and gSrlehm boils [Garlehmbeulen] (A. G. HOgbom, 1905; Bergstrfim, 1912; FrSdin, 1918). Gripp extended the picture of the "loam effervescing by w^ater absorption" to the water "bubbling up" because of heat, and introduced the all-inclusive concept of bubble-soil [ "Brodelboden" ] for soil spots, stone nets, cellular soils, and stone stripes. The expression soon enjoyed a gro^ving popularity, and the hypothesis soon became kno>vn as the "Brodel hypothesis". Most important, the irregular beds contorted into the shapes of pockets, streaks, and knots, which were increasingly observed in the older Pleistocene deposits of Germany, Holland, northern France, England, etc. , began to be known as "Brodel soils" after 1927. Steeger (1926) had already recognized them as formations of periglacial climate. But after 1927 well-known research workers began to define them in the special Gripp frame of reference and to describe them as Brodel soils (Keilhack, 1927; Wolff, 1927; Firbas and Grahmann, 1928). Pleistocene frost-soil phenomena are undoubtedly involved, but, in contrast to the recent frost-soil patterns which Gripp designated as Brodel soils, they are for the most part formations of amorphous solifluction. However, a purely descriptive term like "strangle soils" [Wiirgebaden] (W. Wolff, 1930) or pocket soils [ Taschenboden] (Dewers,1934) or a generally explanatory term like cryoturbate deposits (Edelmann, Florshvitz, and Jeswiet, 1936) is to be preferred in any case. Dticker (1933b and c) has gone still further, and has coined the name "Brodel pavement" [ Brodelpflaster] for those Pleistocene solifluction soils in which there is a concentration of stones on the surface due to contemporaneous deflation, in distinction to the general "stone pavement" [ "Steinsohle" J , which originates by deflation only. The convection and Brodel hypotheses, however, soon came into conflict with the so-called frost-thrust theory, which goes back originally to G. de Geer (1899, 1903), was thoroughly treated by B. Hogbom, and later adopted in modified form by a majority of structure-soil investigators and by Poser (1931, 1934) in preference to Gripp's theory. The frost-thrust theory explains the sorting of rock materials by an unequal displacement of large and small particles by ice formation in the soil. HOgbom assumed that, in polygonal soils, a radial frost pressure was exerted from the beginning, resulting from a chance orientation of the finer debris (Orvin, 1942, was of the same opinion) . But Eakin (1916) sharply differentiated between a vertical frost heave, and a horizontal frost thrust. Beskow (1935) in fact pointed out that, in Sweden, frost heave and frost thrust had been distinguished 170 years ago by Runeberg (1765). Frost heaving was a subject of detailed investigations in highway construction, first in the U. S. A. by Taber (1916, 1918) and Wyckoff (1918) and by Taber's thorough frost experiments (1929, 1930); in Sweden by Beskow for the Swedish Highway Institute ( 1930, 1935) ; and in Germany by Ducker ( 1939-1942) in the course of work for the Reichsautobahn. Poser also would distinguish sharply between frost heave and frost IV. THE PROBLEM OF FROST-SOIL FORMATION 17 thrust, but used the term frost thrust not only for lateral frost pressure in the ground, which may produce a tilted orientation of the stones ( 1931) , but also for lateral displacements of stones on the domed surface ( 1 934) , for which I would prefer a term like lateral frost displacement (in analogy with the well-known displacement on beaches). Perhaps one can say now that neither theory is entirely right or wrong. Both Low and Gripp assumed that convection movements could take place with a gradient from OC (at the lower boundary of the thawed soil^ to +4C (at the surface). H. Mortenson (1932) was able to show, however, that Gripp in his calculations had made an error in the value of the water densities, and that the forces involved do not reach sufficient strength to move a stable layer of sedinnents. On the other hand, Gripp and Simon (1933, 1934) experimentally produced convection movements in a thick paste of quicksand in Thouletsch solution by heating. Steche came to the conclusion analytically that convection is only possible in a soil with over 60% water. Gripp assumed for the basis of his Brodel hypothesis that a type of quicksand or suspension exists in the movements in thawed frost soils for which the laws of static friction do not apply, but rather the hydrodynamic laws. The convection theories are also contradicted by the temperature measurements of Poser in Spitsbergen (1931) and those of Mohaupt (1932) in the Alps. In any case, it is difficult to account for the existence of structure soils on the basis of density differences of water between and 4C. It would nevertheless be just as remiss to exclude convection entirely in favor of unilateral frost thrust. Frost is indeed absolutely essential and exerts effective forces, but the viscous condition of the thawed ground (saturated flow-earth) , is an important prerequisite, at least for the polar structure soils. Both phenomena are intimately connected, as the frost provides for the adsorption of water in the upper soil layers and thereby creates the first requirements for flow-earth formation. The concentration of -water in frost soil may be so great, as Beskow has also shown, that frozen soil samples may become a liquid suspension after thawing and agitation. J. G. Andersson and Frodin considered the flow of thawed ground of primary importance and underrated the action of frost pressure. They even considered polygon formation as due to flow movement alone. The same applies even nriore strongly to Gripp. Conversely, HQgbom has over- emphasized frost pressure and underrated flow movement. The role of each process in each type of structure-soil formation cannot always be determined. It depends on type of rock, climate, ground-water occurrence, and land forms. On sloping ground and in water-saturated soil, flow movement due to gravity can cause large-scale solifluction ( slope -solifluction ; macro- solifluction ) . But this movement is conditioned by previous frost heaving and water adsorption. Johansson (1914) had already clearly recognized that the key to soil-flow problems is the adsorption by the freezing portion of the ground from the adjacent, still unfrozen mass. On the other hand, stone nets on level ground cannot be explained by frost heave and frost thrust alone. .Miniature soil flow can occur inside the individual polygons — at least a surface migration of particles from the center of the polygon toward the periphery, a type of "microsolifluction". Poser (1934) would ascribe this surficial stone movement to frost thrust, while Beskow (1930) calls it "miniature earth flow". However, we should not insist upon one universal explanation. We shall see that, in some cases of stone-net formation, the soil particles are raised obliquely to the surface of the stone net in the daily cycle of needle -ice formation and thawing, and thenjust settle back due to gravity, and so are displaced laterally. But there are also cases in which the viscosity of the seasonally thawed polygonal ground causes more flow. Nature offers an interesting experimental situation when structure soils exist immediately next to one another on level and sloping ground with a similar soil 'composition. Here one can easily see the gradual transition: on level ground stone nets develop through radial movements (frost-heaving and micros,olifluction) ; on slopes, with increasing angle, because of additional slope-solifluction (macrosolifluction) stripe patterns develop (see Fig. 29, 30) . Similarly, soil mounds [Erdhugel; 18 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES BultenbOden] gradually give way to garland and terrace forms. H. Kaufmann (I929)i in his treatise on rhythmic phenomena, called the two types "stationary rhythm" and "translation rhythm". In the striped ground, the radial and downslope displacements cause diagonal movements from the middle of the fine -soil stripes on both sides towards the stone stripes. H. Gripp, who has assumed continuous convection streams around the "Brodel-focus" for polygonal ground, proposes a "spiral movement" for the striped ground, as he very clearly shows in his schematic presentation of the Brodel hypothesis (a modification of Orvin's presentation in terms of the frost-thrust theory) . The contrast of stationary and translation rhythms concerns only the influence of the landforms. Other differences are yielded by climate. In a review of the different subnival climatic types, many different opinions come forth, e. g. the dispute over the meaning of regelation. It is clear that a frequent alternation of freezing and thawing can offer greater mechanical action than a single cycle. Surely in the structure soils of the high mountains of low latitudes, with their small seasonal variations, their strong daily temperature variations, and their high frequency of frost-alternation, regelation is the critical factor in the formation of frost soils. Here ice formation penetrates every night from above to a shallow depth in the soil, and disappears completely in the daytime. It is quite different in the high latitudes, at least in the winter-cold areas, where Soil is frozen for a large part of the year in thi deeper layers, and where thaw is a seasonal occurrence. In this case the frequency of regelation is much less important. Although de Geer (1903) believed that regelation is the decisive factor which sets the flew soil on the surface in motion over a glide- base of the "tjale", and HOgbom (1909 and 1914) differentiated between saturation solifluction and regelation solifluction, FrOdin (1914) demonstrated by temperature measurements in the nnountains of northern Sweden that regelation is without importance there and may even have a negative effect under some circumstances. 2. Permafrost and seasonal frost. "Solifluction" The role of permafrost in the formation of structure soils is similar.' Where permafrost is present in the substratum, it hinders the percolation of the -water from the thawed ground in summer, and thus creates the conditions for saturated flow-earth during the warm season. It is, however, associated with the very winter-cold climate of the polar and high-continental subpolar zones (Shostakovich, 1927, Sumgin 1929- 1933). In Figure 61 the extent of permafrost in northern Eurasia is reproduced from official Russian sources (Great Soviet World Atlas, 1937). In a few continental subpolar climates, such as northern Scandinavia, the seasonal tjale works in a similar manner. But there is structure-soil formation in climates which show no trace of tjale, such as the high oceanic subpolar climates of Kerguelen, southern Georgia, and southern Iceland, or in the high mountains of low latitudes. In those places there is only a short-lived ice formation in the uppermost soil layers, but this ice nevertheless has the ability to draw up water from the deeper soil horizons, and thereby to produce a considerable concentration of water in the uppermost layers, providing a basis ,for surficial flow. At this point we are faced with the question of how we should deal with the concept of "solifluction" (soil flow). J. G. Andersson, who initiated the idea, knew only polar conditions. He understood it to be only the flow of water-saturated soil over frozen ground. Salomon (1929) likewise confined it to "soil m^ovements over a tjfile" (commonly perennial tjale) , and other authors follow this usage, e. g. Poser. 7. R. Pohle (1924) has proposed abandoning the expressions ground ice [Bodeneis] and ice soil [Eisboden], not used clearly previously, for ground and soil which has a lasting freezing temperature, year in and year out, summer and winter, and to speak instead of frozen ground [Frostboden] . The term "Gefrornis", on the other hand, should designate the lasting condition of frost (Swedish "tjale", Russian "merzlota") . Later authors like Shostakovich (1927) and Meinardus (1930) have followed him correctly. It is strongly recommended, however, that "permafrost [Dauerf rostbttden, Dauergefrornis, ewiger Gefrornis]" be used if the permanent frost is meant. There is also the long-lasting annual frost to which one must apply the terms frozen ground [Frostboden] and frost [Gefrornis]. Also the word "tjale" designates a permanent condition only in the association "perennial tjale". IV. THE PROBLEM OF FROST-SOIL FORMATION 19 As the processes concerned with a long-lasting seasonal frost are so closely similar to the frost extending into the summer that it is not possible to make a distinction m the effects, and as the decision whether perennial or merely seasonal frost is present can be very difficult, we shall have to extend solifluction, as it mostly occurs, to soil flow over seasonally frozen soil. The concept is usually limited to fluid movements which occur on sloping terrain under the influence of gravity. However, Serensen (1935), for example, includes the structure soils of level land as well, such as stone nets, stone rings, and cratered ground as forms of solifluction. But here we shall make a sharp distinction between "slope-solifluction" , which moves in a direction determined by gravity, and "micro-solifluction", for soil flow from the center to the borders of the individual frost-soil forms. Should we ascribe to solifluction, however, those movements in the uppermost soil layers which are produced by short-lived, perhaps only nightly, soil freezing? In this case it would no longer be a matter of actual flow, or fluid movements in the strict sense, or a water concentration above a frozen substratum. The structure forms produced in this manner are miniature forms. The miniature stone nets and stone stripes are so similar to the larger forms originating over frozen subsoil that previous investigations have not made a distinction. Serensen, for example, includes the miniature stone nets in solifluction forms. Other authors are divided on this matter. Scaetta used the term "solifluction" for the slope movements due to the nightly surficial frost of tropical mountains. Others, such as Fluckiger, avoid such a designation. To define a precise boundary will not be easy here. In this type of frost also, there is certainly water concentration through ice formation and there is fluid movement in the uppermost soil layer, even though it be of very short duration between each freezing. It is clear to us that such a wide concept of the idea would extend considerably its original definition by Anderssen. But one can then make a distinction with regard to the tinne factor. In the solifluction of higher latitudes, where the frost of the subsoil is permanent or lasts for several months, one may refer to seasonal solifluction , and in the other case to diurnal solifluction or at least to short-period solifluction . In an earlier publication 1 have spoken of a tjale solifluction , which would correspond to seasonal solifluction (Troll, 1941), and contrasted with it " needle-ice solifluction" . But since needle-ice formation is only one characteristic of diurnal solifluction, and since a generic name for the diurnal or short-period surface freezing of the ground surface has not been introduced, it seems to me that the distinction according to the time factor is better because it is more generally applicable. It should be explicitly noted, however, that the concept of "seasonal solifluction" of higher latitudes does not imply that short-period frosts play no role there. But they are only a portion of the large contrast of winter frost and summer thaw, while in the diurnal solifluction of tropical mountains the daily regelation prevails alone, and seasonal subsurface frost is entirely lacking. In the mountains of middle latitudes and in oceanic subpolar areas, both processes may operate and are intermingled according to the climatic character, locality, nnicroclimate, year, and weather. 3. The forces causing frost-soil formation. The swelling theory . In the phenomena of frost-heave, frost thrust, and soil flow considered thus far, the motivating forces come from four processes: 1) from simple temperature changes, producing a change of the specific gravity (convection); 2) from volume changes of the soil as a result of changes in the condition of the aggregate (freezing and thawing of soil water); 3) from cohesion of freezing soil water (high attraction of water from deeper, unfrozen soil layers); 4) from gravity, which seeks to equalize the displacements created by volume changes and cohesion. To these forces, Steche (1933) added a fifth force, which he made the basis of a new theory, namely the swelling which occurs in all colloidal soil constituents , particularly 20 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES clay and humus. Structure-soil formation is certainly strongly associated, especially in tropical areas, with cohesive colloid-bearing soils, and it was explained heretofore, of course, by the water-retaining properties of such soils. The colloidal substances react to the ion content. The presence of free ions (salts) leads to coagulation, i. e. , the flocculation of particles in the size range of l-lOOiJ-ji into larger particles, producing a coarser, looser, more crumbly structure. With the lack of salts, on the other hand, the soil disperses, becomes filled in with fine material, and hardens. In climates with alternating freezing and thawing, the ionic content of the soil also varies considerably. During the freezing of the soil water, the salt content of the unfrozen water becomes enriched, and produces coagulation and crumbly structure. In addition, however, the colloids themselves can swell. The clay greedily absorbs water and thus develops considerable pressure, like swelling peas breaking a flask. The colloids grow at the expense of the water which has filled the pores. Steche considers this swelling process during alternate freezing and thawing to be the chief mainspring of structure-soil formation. He emphasizes especially the primary swelling in polygon fields and at the "Brodel centers" resulting from the saturation of the soil in the spring. For further development, he also refers to in-filling, which may lead to fissuring, frost-thrusting especially in autumn, and microsolifluction (C. Troll) of domed ground. The swelling theory certainly signifies a valuable extension of our knowledge of frost-soil processes. For mineral structure soils it is very possible that the effect of frost pressures, and notably frost heaving, may have been greatly underestimated. Even in the vegetation-covered forms (turf hummocks and ridges, peat hummocks) which exhibit few outward signs of frost pressure, it seems to me that the swelling theory, which takes special account of the unusual behavior of humus colloids, has particular application. 4. Sorting of material The greatest difference of opinion in the whole frost-soil question centers upon the process of sorting in stone-net and stone-stripe ground. In 1927 Elton listed 21 theories suggested up to that time. Since then they have increased by several. Today it is not a question of establishing any one of these theories as valid alone or in general. We realize that there are different forces which can be operative, and that these forces can work together in different types of process. It was unquestionably a disadvantage that the discussion was originally based rather one-sidedly on an example of structure soils from Spitsbergen. Observations in different climates would have allowed different genetic types to be distinguished from the first. The most important contributions from Spitsbergen have been furnished by B. HOgbom, Meinardus (1912), F. Nansen (1921), Huxley and Odell (1924, 1925), Gripp, Eltori (1927), and Orvin (1942). To these maybe added interpretations gained from observations in other polar ranges, by Eakin in Alaska, Leffingwell in Alaska, Steche in Iceland, and Beskow in northern Sweden. Today all theories which do not concern frost or consider it as subsidiary must be completely rejected, such as those of Philippi (earth- quakes, cf. von Drygalski, 1904) , Miethe (mud eruptions) , Trevor-Battye (1921, ice-floe effects), Behlen (1930, mineral heat). The fact remains that, if there is enough water and enough fine material, "diakinetic minor movements" will be released in a soil mass of different unsorted grain sizes by temperature fluctuations in accordance with the "tendency toward a minimum of internal friction" (Kaufmann,1929) . It has long been known that stones will be heaved upward by frequent freezing of soil, and eventually become "frozen out". This phenomenon is related to the fact, which Hamberg (1905, 1915) had already recognized in principle, that steeply inclined ice layers arise under a stone, whereby forces are released which are directed concentrically against the stone and upward. Of course, with thawing, the stone will settle, but because of the rearrangement of the flow-earth surrounding the stone, it will not fall back into its old position. "In freezing, the upper end of the stone, is stuck fast into the frozen crust, while in melting the lower part is still gripped by the ice when the outer shell is already thawed material. The movements of the stone thus do not coincide with those of the masses of mud which lie around the middle of the stone. During freezing the upper end of the stone follows the movement of the mud; on thawing, the lower end. The stone on freezing thus makes a centrifugal nnovement ■which is greater than the centripetal movement at the thaw" (Hamberg, 1915) . Beskow has diagrammed this IV. THE PROBLEM OF FROST -SOIL FORMATION 21 process graphically with exceptional clarity (Beskow, 1930). Orvin stated: "When water-saturated soil freezes it expands slightly less than the freezing water. The enclosed stones, however, retain their size. The effect is that they are thrus out of the underlying unfrozen ground. . . " In southern Finland P. Kokkonen (1930} experimentally investigated the freezing-out of solid objects from the soil by burying wooden blocks in the ground at depths of 5 to 60 cm. The heaving of the blocks was from 2 to 5 times greater than that of the ground surface, providing they did not extend significantly below the frozen soil layer. Inequalities in the surface ( differential frost-heaving") result from uparching and contraction. If these are present the separation of larger constituents of the ground is not only vertical, but also lateral. For the final result it does not greatly matter whether the relative displacement of the stones first occurred upwards and then sideways on the arched surface, as Beskow assumes, or whether the displacement occurs obliquely upwards, radial to the borders, as HOgbom (1914), Klute (1927) and most recently, Orvin (1942) believed. In the polygonalgroundandturf mounds of the Swedish mountains, according to Beskow, the layers of ice lie parallel to the surface, so that they slant outward and downward along the edges of the polygons and mounds, producing an oblique pressure against the polygons and turf mounds, which causes differential heaving. Sorting itself is thus no longer puzzling; the only question is how do the several forces act singly and together, for the different conditions of soil composition, water content, frost duration, frost depth, and frequency of freezing and thawing. 5. Experimental frost-soil research The greatest advances have been achieved by experiments, especially by Taber, Beskow, and DUcker, in the past 20 years. These were preceded by the experimental investigations of Atterberg (1911, 1912), and Johansson ( 1 914) , on the water- absorbing capacity, the stability, and the fluidity of the soil types. Atterberg studied different soil types, mixed with enough water to form a paste, for their water content; the limits at which the mixture had certain properties of plasticity; and finally the difference in water content between the two limits. He designated as the most important degree of plasticity the liquid limit , at which the soil ceased to be fluid. Johansson went further; he determined the stability or coherence at different water contents between the limits, set up stability curves and measured viscosity (ease of movement of particles at different water-contents). He designated as the shrinkage limit that point on the plasticity scale which indicates that, with further drying, the soil can no longer shrink and begins to fill its pores with air. The liquid loams — designated in Sweden as "garlehm" or "jaslera" (A. G. HOgbom, 1905), in Norway as "krabb" or "koppjord" (Bjorlykke, 1896) — are the center of interest in these investigations. For clays the liquid limit is reached at a very high water content; between it and the shrinkage limit clay is of a plastic nature. This is not the case in the liquid loams. Here the liquid limit and shrinkage limit fall practically together, and the plastic stage is lacking. With higher water content than that of the shrinkage limit, the soils immediately pass into the viscous state. The tendency of soils to flow is in inverse proportion to their plasticity, but in direct proportion to their water-capacity. This tendency is greatest in grain sizes of 0.05 to 0.0006 nnm, or a size not in the clay range, but rather in the grade size designated as fine sand ( Swedish "Mo") and coarse silt [Schluff]. Johansson was the first to recognize that at freezing a strong flow of water is drawn from beneath to the level of ice formation, and that a supersaturation of the frozen layers can be brought about if the necessary capillary force is present. At this point, Taber's (1949) tests led to the recognition of the so-called excessive frost heave . This means that the expansion of the soil by ice formation results not only from the volume increase of the water of the freezing layer, but that a very much greater expansion takes place through the drawing up of water from deeper layers. The rise depends on molecular cohesion during gro'wth of ice crystals. The main factors of excessive frost heave are: the size of the soil particles, the amount of available water, the size and percent of capillary space, and the amount of cooling. The intensity of frost heave was determined primarily by differences in soil texture and the amount of available water. In laboratory tests Taber was able to attain heaving which amounted to 60% of the depth of the frost. 22 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES If one places moist clay in an upright glass cylinder, covers it with a layer of porous sand, and permits freezing from above, a layer of pure ice is formed at the boundary between the clay and the sand in the form of acicular prisms ("ice filaments", needle ice) which push up the sand layer above. The forces produced by frost heaving are considerable. Taber was able to attain pressures of 14 kg/cm^, corresponding to a water column of 140 m in height. The limit of ice formation was reached not because no more crystals could be formed under high pressure, but because the forces of attraction were not sufficient to raise more water. In the substratum robbed of its water, desiccation cracks could form in a polygonal fracture pattern (Terzaghi, 1925) . Water separation is difficult in very porous soils and also in very fine-grained colloidal soils; best is an opening of less than one micron. Under the most favorable circumstances, ice layers can still be formed with a grain size of 0.07 mm. If alternating thawing and refreezing take place, frost heaving is especially strong, because then melt water is available in plenty. Especially important is the direction of frost heaving. It is normally directed upward in soils, not because of least resistance in this direction, but because it operates in the direction of crystal growth, which is normal to the cooling surface. Beskow (1930) continued Taber 's work, and correlated it with observations of structure soils and solifluction forms in northern Sweden. He later (1935) applied improved experimental procedures, in order to eliminate previous sources of error. He also thoroughly examined the hydrodynamic laws which control the capillary rise of water, as well as the thermodynamic laws of soil freezing. In Sweden he found extreme frost heave of several decimeters per meter, and as much as Vz m/m in northern Sweden. Thawing of such soils often produces in part subsidence of the soil cover ( "tjSlskjott") , in part seepage of the liquid subsoil; in either case strong deformation which makes ground-ice research of great practical importance in programs of highway construction. The studies of Taber and Beskow, which have made clear the dependence of "differential frost heaving" on soil texture, water content, vegetation cover, etc. , have generally given us a deeper understanding of the dissimilar frost movements in natural soils which lead to certain structures. For modern road building, the reaction to frost heaving of the different soil types which will be encountered is especially significant. Besides Beskow (1933), similar investigations have been made by others, especially Casagrande (1934) , Morton ( 1936) , and DUcker ( 1939a-e, 1940, 1942). The frost susceptibility of a soil can be ascertained sufficiently by examination of the grain size. Assuming the possibility of water replenishment from the subsoil, an inhomogeneous soil, according to Casagrande, may be designated as susceptible if it has more than 3% of a grain size under 0.02 mm. In very uniform material, this limit is 10%' of the 0.02 mm size ("frost-criterion" of Casagrande) . An experimentally determined curve gives limits for different constituents and grain sizes, and fixes the limits of the range of frost-susceptible and non-frost-susceptible soils (Fig. 5). SAND ^EHLSANOl SILT |CLAY| COARSE MED. RNE coVrseIfme MARSE FINE _90 S^SO (-70 160 S2 50 ^40 *30 20 10 ^. \V \N. S S ^EAV NG6-9 S, \ , ^ \ V IK^l__ s |5.l -•^ 0?. — ^^ ^EAVING^^T^ ■ ^^ ^ 2,0 GRAIN SIZE(MM) 0,5 0.2 0,1 05 .02 .006 GRAIN SIZE (MM) ,002 2t. .001 Figure 5. Frost criterionfor homogeneous and inhomogeneous soils, after A. Casagrande (1934) (from Backer, 1939) Figure 6. Frost criterion for soil types found in the state of New Hampshire according to Morton (1936) (from Dtlcker, 1939). The curves of Beskow and Morton (Fig. 6) are essentially similar to those of Casagrande. Backer investigated the degree of frost susceptibility for different size fractions and mixtures of size fractions. The greater the water supply from the subsoil, and thereby the greater the heaving, the greater is the degree of frost danger. IV. THE PROBLEM OF FROST-SOIL FORMATION 23 On the other hand, the smaller the rate of frost penetration, the greater the water supply. The quotient of the heaving and the rate of frost penetration thus shows the frost susceptibility. The practicability of the Casagrande frost criterion has been repeatedly affirmed. Only the highly porous pyroclastic rocks (pumice gravel and pumice sand) form an exception, for in spite of their gravelly character they are very frost susceptible, because of their porosity,, which reaches a fineness of 0.05-0.02 mm. (Dttcker, 1939b). On the other hand, the effect of frost is very different in the case of cohesive clay soils, according to the content of kaalinite or montmorillonite; the boundary of frost danger is reached when a content of 25-15% montmorillonite is attained (Dttcker, 1940). 6. Grain size in the fine-grained frost soil. Frost soils as source material for loess formation . The experimental studies on frost danger in natural frost soils are very important, such as those carried out by Beskow (1930) on Lapland soils and by Diicker (1937) on fine-grained structure soils from the Riesen Gebirge. The fines of the stone-net soils of the Riesen Gebirge contained about 50% of 0.1-0.2 mm grain size ( "Mehlsand") and the rest was about equal parts coarser sand and finer silt. When the fraction below 0.02 mm amounts to more than 20%, these soils would be considered as dangerous, as the investigations confirm (excessive frost heaving of 25%). Beskow has also established the predominance of the 0.1-0.2 (O.Ol) mm grain size over the entire profile of the fine-soil terrain of the Lapland structure soils. There is no gradual transition to the coarse constituents of the stone nets and stone rings, which is not explained by sorting alone. Beskow and Ducker also assume that the grain size in question occurs not only by separation from a primary matrix, but arose through frost- splitting of finer particles. Frost splitting must, therefore, reach a natural limit sonnewhere below the size in question, probably because of the lowering of the freezing point in very small cracks. This was lately shown also by Fedosov (1938) through freezing experiments with soil samples. In contrast to the mechanical disintegration, chemical weathering in cold clirhates stays within narrow limits because of the very slight hydrolysis, as Ramann recognized and as was recently confirmed by the investigations of E. Blanck(l919, 1928) in Spitsbergen. Soil frost therefore has still another critical action on the soil besides the water storage, structural change, and sorting; namely, it produces a mechanical disintegration with a dominant fine fraction of 0.1-0.01 mm. If this phenomenon should be confirmed by grain-size analyses of numerous fine soils from frost features, it could have far- reaching significance for the problems of Pleistocene soil formation and sedimentation (DUcker, 1937), for the corresponding grain sizes are the same as those we know from fine eolian deposits of glacial climates. By far the dominant grain sizes of eolian sand lie between 0.2 and 0.01 mm; those of loess between 0.05 and 0.01 mm. According to the general conception, the distinction between loess and eolian sand goes back to segregation by wind transport, with which the extent of the loess and eolian sand in northern Gremany agrees, insofar as the loess is carried farther than eolian sand. Both, however, must have been derived from sediments rich in the grain size 0.2 to 0.01 mm. Moraines and glacial deposits therefore do not come into consideration, as Keilhack recognized, but the fluvio-glacial deposits in which a separation by water has taken place and the finer constituents (glacial flour) concentrated. For many loess deposits of central Europe an origin from- gravel fields, sand plains, and stream valleys has been established (cf. Dewers, 1941, p. 204) . The new concept opens the question, whether Pleistocene frost-soil formation in a completely barren periglacial climatic region did not cause a disintegration of" fine -grained soil to the grain size suitable for deflation of eolian sand and loess. Although lam not of the opinion that loess "for the greatest part can be considered as the deflation material of Pleistocene frost soils" (Dflcker, 1937), such frost soils can be recognized as a second supplier of loess material. For both cases of loess, formation in a glacial climate was absolutely a prerequisite. Only thus can we understand the distribution of the loess on the earth, especially the fact that it is found nowhere on the edge of the dry regions opposite the tropics. Without frost, no loess' 24 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES 7. Structure of ground ice Concerning the structure of ground ice itself — foreshadowed by the extensive studies of the Russians on permafrost and ground ice in Siberia (see below) — precise observations have been made, particularly in northern Europe, by Holmquist (1897), Hamberg ( 1905, 1915), Hesselman (1907), Hellaakoskx ( 1912) , uppermost soil laye.- -- , proper, a hard-frozen soil layer with a structure dependent on the water content of the ground and on the texture of the soil. Frozen ground itself occurs in three forms: (1) Porous frozen ground is possible only with very porous earth; the walls of the soil pores are surrounded by an ice layer 1-14 mm thick, needle-like and arrow-like to begin with, in massive form after regelation. (2) Massive frozen ground of uniform almost homogeneous structure occurs only in "single-grained soil" (sand, very fine sand, clay) with small water content. (3) Layered frozen ground containing uniform, pure, almost horizontal ice layers 0.1-20 mm thick, is found in all mineral soils which have a granular or uniform crumb structure providing that the water present in the soil is more than the specific water content ("soil-frost water content") of the soil type. The soil structure and the water content determine the structure of the ground ice — a conclusion which Poser (1932) also reached on the basis of an especially instructive ground-ice profile in permafrost in Greenland. That the rate of cooling is not without importance for the structure of soil frost is shown by the experimental work of Gwen (1925) and Jung ( 1931 , 1933). According to them, with slow cooling, only a few large ice crystals will form, because of the decrease in rate of formation of crystal centers, but with rapid freezing at low temperatures many very small crystals will form. In the former case the soil particles are thrust out and soil gathers into large aggregates; in the latter case homogeneous soil frost originates. V. NEEDLE ICE (PIPKRAKE) 1 ■ Methods and history of investigation By our own observations, it Avas discovered that the so-called needle ice [Kammeis] plays a significant role in the middle latitudes as well as in the high mountains of the lower latitudes. Needle ice is known by very different names in the literature ( Haarfrost, Haareis, Nadeleis, Stengeleis, Eisfilamente, Effloreszenzeis, or Barfrost, in English as needle ice or ice filaments, in the USA as mush frost, in Swedish as pipkrake, in Finnish as rouste and in Japanese as shimobashira) . In the international terminology, the Swedish term "pipkrake" has taken preference. Needle ice is ground ice which takes the form of fine needle -like ice crystals in compact clusters beneath the ground surface, with the ice needles standing upright perpendicular to the cooling surface. One could compare the layers of ice with the fasciculate bristles of a brush and accordingly speak of it as brush ice. Also the comparison with asbestos is evident. Needle ice is formed in fine-grained bare or sparsely vegetated soils (clay, loess, marl, shale, and peat) with no snow cover or at most a slight covering of snow, by the abrupt freezing on the surface of the ground, most frequently by night freezing due to radiation loss. Usually one sees the ice bristles covered superficially by a thin layer of soil or pebbles, but one can find heavy stones pushed up by layers of needle ice. The base of the ice needles forms a smooth, moist, barely frozen surface. Needle ice originates at the contact of a superficially dried soil layer with moist under-soil. Water is sucked up from the pores of the moist soil to form the long ice needles. If the needle ice can reform for several days and weeks without being melted again by the warmth of the day, the ice formation of a single day can be recognized by a distinct stratification parallel to the undersurface. The stratification usually decreases in intensity with depth, since the frost action through the growing ice gradually decreases and the water supply is used up. The earliest observations of needle ice were made on plaster (S. T. Rigaud) and on dead plant fragments (Herschel, 1833) , and only later on moist earth V. NEEDLE ICE (PIPKRAKE) 25 (Le Conte, 1850) in England. The phenomenon was introduced into German literature by G. A. Koch (1877), who saw it in Tirol and Vorarlberg, and by B. Schwalbe, (1885) who had become acquainted with it in the Harz. In the 21st ( 1879^ 80) , 29th ' (1884), and 3 1st ( 1884-85) annual volumes of the English journal "Nature", very diverse observers occupied themselves in most spirited manner with ice filaments, mostly under the title "Peculiar Ice Forms" (Duke of Argyll, R. Mendola, O. Fisher, H. King, D. "Wetterhan, B. Schwalbe, R. Woodd Smith, J. Rae, F. Pollock, C. C. Collier, J. D. Paul). They observed needle ice on dead twigs, on mortar, and on moist ground in Switzerland, in the Black Forest, in the Harz, and on Dartmoor. H. King spoke for the first time of its formation by capillary attraction, and B. Schwalbe was able to show that needle ice, which he skillfully grew on the surface of dead twigs in the lecture room, had resulted from the sucking of water out of the wood fibers. The first systematic observations of needle ice in nature nnay have been made by the Swedish forester H. Hesselman (1907). He recognized the essential processes of the formation of needle ice (absorption of water from the soil capillaries of the unfrozen layer beneath the needle ice, origin on bare or sparsely vegetated ground). He showed the significance of needle-ice formation to forestry and agriculture, namely that the roots of young trees and especially of young seeds were torn up and destroyed by the frequent freezing. The "winter kill" is largely an effect of frost heaving and needle -ice formation, as it is also in central Europe. Kokkonen (1927), in connection with frost studies in Finland, has also investigated the relation of the hardiness of rye in winter to the flexibility and tensile strength of its roots. The needle ice continues to grow, according to Hesselman, only as long as the subsoil remains unfrozen. If the ground is frozen, the "dead needle ice" remains lying on the surface. Hlgbom (1914), Johansson (1916), Hamberg (1916), and later Beskow (1935) extended the studies for Sweden to include geological aspects, yet HOgbom would attribute no geological significance to them. For Sweden, with its strong ground-ice effects, this decision may be understandable even if not accepted. Beskow pursued especially the connections of needle ice and related ground-ice formation and transitions between them in their relationship to soil type and the water table in nature. In fine clay soils there are all transitions between needle ice and stratified ground^frost, and in coarser soils the distinctions are sharp. In the same soil needle ice can form near the ■water table (i. e. on the lower part of a ditch •wall) , and stratified ground frost can form farther from the water table. Valuable studies on needle ice were performed in the course of a Frankfurt thesis by O. Krumme (1935) in the Hochtaunus in the winters 1932-33 and 1933-34. For months, he traced the origin and disappearance of needle ice simultaneously with weather conditions fromi the Taunus Observatory. During the middle of the winter the needle ice built up and lasted, in some cases forming large projections (40 cm high) during the longer frost periods, but in March it was formed and destroyed on particularly bare places in the cycle of nightly outgoing radiation and daily incoming radiation of the sun. That needle ice has great geomorphic importance has already been shown by von Richthofen (leader in research expedition 1901, p. 95) . Especially when ice occurs on inclined slopes and scarps, the raised stones and soil particles sink back to a lower position if they do not roll completely down the steep slopes. Deckert (1913) describes in the clearest manner the general effects created in the southern Appalachians by the extensive "ice meadows" of needle ice on the loamy weathering soil under the influence of the frequent temperature variations. "Each of the little ice columns bears on its top a loam or stone fragment which it raised up by its growth; when the column breaks the fragment falls and rolls down the slope. The total effect is a very significant mass movement, sometimes amounting to many cubic meters over a distance of a kilometer. At no time of the year are the Allegheny waters so turbidly muddy as when the strong rains set in after extensive formation of efflorescent ice. Efflorescent ice is the most important contributor to the winter break-up and impassability of North Carolina highways, and its unpoetic popular name (mush-frost) finds here its justification". 26 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Krumme investigated the morphological effects of needle ice in the lateral movement of stones on the convex surface of polygons and in the exfoliation of turf by the undermining effect of needle-ice erosion. Stone-net construction by needle-ice formation occurs, as we have shown by unequivocal observations in South Africa, not in the "tundra region", as Krumme believed, but only in the mountains of low and middle latitudes. Turf exfoliation [Rasenabschalung] , on the other hand, which one can observe in connection with the formation of needle ice everywhere in the German Mittelgebirge may have significance in all frost climates, as is shown by observa- tions on Iceland and by our own observations in the Alps and in the mountains of the tropics and subtropics. The effect of needle ice can thus be combined with the effect of the wind, since fine crunribly soil lifted by the needle ice is well prepared for wind erosion, especially that which is protected from rain by the overhanging turf roofs. In such places, an arid microclimate actually prevails, similar to that in the hollows of solution and honeycomb weathering in vertical sandstone walls, where even salt efflorescence occurs, even in the present humid microclimate. I could apply observations of turf exfoliation by needle ice and wind in the high Alps, for example, to the eolian sands of Gamsgrube in the Pasterze. Stiny reported the same from the Reisseck group in Carinthia (KSrnten) . In the turf exfoliation recently described by Iwan (1937) on the loess and eolian sand of Iceland, needle ice as well as wind must play an important role. In the case of turf exfoliation over cohesive soils (Fig. 7), wind is certainly only subordinate if active at all. Also the frost heaving of turf hummocks, where they become completely bare of vegetation on the surface (see Fig. 8) , is produced in the high Alps by needle ice. The crumbly humus soil in such places is not swelling loam as in the north but is a loosened needle-ice frost soil. Mohaupt (1932) has also shown the great importance of needle ice in slope erosion by Figure 7. Turf shells [Rasenschalen] formed by needle ice in the high Alps ( small castle stable above the Pasterze, Hohe Tauern, 2700 m) . The old surface on the right is covered with a turf mat (Curvuletum) . the bare soil on the left (with carpet of pioneer vegetation) is frost- heaved soil. Needle ice is most effective in the scarp; the lower surface advances under the turf in humus soil 30 cm thick, and undermines the turf cover which re- mains stationary. Photographs by C. Troll, 27 August 1941. Figures. Turf hummocks (soil hummocks"thufui") on a surface bare and frost-heaved by needle ice (crumbly frost soil) on Delorette_road above the Hochjochhospiz (OtztalAlps, 2740 m). Photograph by C. Troll, 31 July 1941. V. NEEDLE ICE (PIPKRAKE) 27 excellent observations in the high Alps. Moreover, he was able to establish that, in stony soils deficient in fines, the freezing of needle ice produced little columns and mounds of soil which appeared swelled up or pressed up between the stones and are not unlike the excrement of earth worms. We shall see that these forms are very common in the rnountains of the lower latitudes. Th. Hay (1936) has described extensive needle- ice formation in the Lake District of northern England. He was able to show that thicker stratified needle ice was fornned during the frosts of successive nights. If he exposed a patch of unfrozen subsoil on a surface covered with needle ice, on the following night a new layer of needle ice was formed here, while the crystals grew to double length above the undisturbed part. Between the two ice layers, a raised layer of soil could be found, proof that meanwhile the frost limit had moved somewhat deeper. This would be expected theoretically because the dehydration by ice formation drys out the underlying layer of soil so that the new ice formation must be established somewhat deeper. Most important. Hay traced to needle ice the origin of true sorted structure soils, particularly the 30-40 cm wide stone stripes. Soil stripes and stone stripes form a level surface in summer, but the soil stripes are raised after heavy frosts in the fall. Under the domed soil stripes, at the boundary with the unfrozen subsoil, a layer of needle ice 5j cm thick developed; under the stone stripes, a much thinner layer developed. Stones were raised high by needle ice.* They must therefore be raised in the deeper channels of the stone stripes. When the needle ice thaws, the water concentration results in a mass of muddy soil, a kind of saturated flow soil , in the soil stripes. The interdependence of ice formation and solifluction in the origin of structure soils is seen to be especially clear and significant. With the needle-ice denudation of slopes, we thus have all transitions from down- ward movement in homogeneous soil materials to regular structure soil with sorting of particles. Needle-ice denudation is also a form of solifluction, although it only affects the uppermost soil layers. The most important process is the frost heaving of stones and of the uppermost layer of soil, but the formation of a surface layer of soil over- saturated with water due to the thawing of needle ice also plays a recognized role. Deckert (1913) describes this very adequately: "The little ice columns melt together in the forenoon for the most part into a formless ice mush, from which the popular name "mush frost" is taken. " However, this solifluction and flow- soil formation are significantly distinguishable from that of polar latitudes. They do not occur over a deeply frozen subsoil or over perennial or seasonal tjM.le, but in a very thin surficial layer of frost soil over unfrozen subsoil. They do not develop in long seasonal cycles but in short alternation of frost and thaw, in the alternation of separate weather situations and also in the diurnal alternation of nightly frost and solar heating. It is therefore suggested that this special form of solifluction be distinguished by the term "needle-ice solifluction" (pipkrake solifluction) . 2. Geographical distribution of needle ice Needle ice is a phenomenon of soil frost typical of short-period or daily frosts, and occurs on or directly below the surface of the ground. In every respect it is the full counterpart of permafrost, which results from long-period effects of frost. While the geographical distribution of permafrost has been thoroughly studied for a long time, no evaluation of the geographical distribution of needle ice has been under- taken heretofore in scientific literature. However, the study of needle-ice geography is rightly of increased significance for the mechanics of soil erosion in different frost climates of the earth. Basically one can expect the formation of needle ice in all frost climates. The frequency and regularity of its occurrence must be subject to laws which go back to the relation of seasonal and daily variations of temperature and to the relation of the times of frost variations to the times of snow covering. Here only a preliminary imperfect attempt can be made, based upon sparse data from the literature and on personal experiences and oral inquiries. 8. According to Krumme (1935), there is no strong heave of the stones in relation to the fine earth, no actual "freezing out" of the stones as with true soil ice. However, the earth masses around and overlying the large stones are lifted and removed by the stratified ice needles, so that the stones gradually come to the surface. Only when they just rest on the surface of the ground are they lifted by ice needles. 28 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES a) P olar zones and temperate latitudes. Needle ice is least common in the high polar climates. I have recognized no mention of it anywhere in the literature on these areas. To be sure, W. Bierther believes that he has seen needle-ice formation of great extent in East Greenland, during the break in the cold at the time of snow nnelt, but it occurs only on the ice and not on the ground (personal communication). But is this real needle ice, whose formation on glacier ice is difficult to imagine physically, or is it hoarfrost? Hoarfrost certainly plays a significant role in northern climates for the miaintenance of glaciers, according to H.W:son Ahlmann. In comparison, needle ice is very widespread in the oceanic subpolar climate of Iceland. Steche (1933) observed two cases of needle ice which had formed in cold nights and disappeared again after the sun came up, and W. Iwan confirmed that needle ice is very frequent (personal communication). He also attempted to trace the origin of loess in Iceland to ablation of frozen needle-ice soil. The great frequency of frost alternation (100-120 frost-alternation days) and the formation of structure soils (see below) would be very suitable for this observation. In the strongly oceanic subpolar climates, needle ice appears to be the chief form of ground freezing. On Kerguelen, where there are 238 frost-alternation days at the ground surface, but generally no freezing can be measured at a depth of 5 cm, one can scarcely explain the ice formation in any other way (Meinardus, 1923). Although needle ice as such is not described from here, the loose frost-heaved soil and the miniature structure soils speak significantly for it. For the strongly continental subpolar climates of northern Sweden and Finland, there are accurate descriptions of needle ice by Sv/edish and Finnish workers. But here needle ice is already an inferior form of ground-ice formation, and it is not recognized as a builder of structure soils ( cf . Hesselman, H8gbom, Kokkonen) . On the oceanic mountains of the British Isles, on the other hand, even the formation of structure soils appears to be traced back to needle ice, according to the observations of Hay. In the German Mittelgebirge, with their much higher limits of structure soils, the effect of needle ice is especially extensive in the hill and mountain regions. This holds for the cohesive soil types which are suitable for it. In the search for suitable non-heaving soils for dam sites in the winter 1939-40, the German military geologists in western Germany could make very useful distinctions from the appearance of needle ice during snow-free freezing weather. Soils from clay shales, graywacke, clayey variegated sandstone, and marly shell limestone at altitudes of 300-400 m showed needle-ice formation everywhere (naturally not in the meadowlands but only on bare places such as road cuts, molehills, and stream gullies), and proved therefore unsuitable (personal communication from R. Bickerich) . Needle ice from the Alps was described by Mohaupt (1932) and Metzler (1933). The formation of needle ice during the winter in the Alpine forests corresponds to that of the German Mittelgebirge. In the high mountain regions, on the other hand, where the time of frost-alternation is in the warm season (Table I), the frost heaving of ground by needle ice is found to occur especially after the melting of snow in the late summer and fall. The formation of needle ice varies in the Alps from the valleys to the sub-nival slopes as the result of snow melting from winter until late summer. In the high Alps, it has the greatest morphological effects on soil of suitable water content for it forms on all bare places and causes solifluction. These bare places are therefore not only the prerequisite but also the result of needle -ice formation. If needle -ice denudation has begun at some naturally or artifically created bare spots (animal trails, roads), it induces the destruction of vegetation by undermining the turf (Mohaupt 1932). I was able to make corresponding observations in the mid-summer of 1941 in the Otztal Alps at altitudes of 2500 to 2700 m (Fig. 9-10) . At these altitudes, sorting and structure soils can be produced, especially in the form of soil-stripe groundlErdstreifenbOden] (see Figs. 42, 43) , although only a small part of alpine structure soils nnay be explained by needle ice. b) Subtropics of the Northern Hemisphere . In the subtropics there is a natural lower limit for needle-ice formation. But there, as in the Alps, it must naturally recede into the high mountains during the summer. In Greece in 1940 I observed V. NEEDLE ICE (PIPKRAKE) 29 &?»ajfe-«r^imi^ Figure 10. Stones heaved by needle ice. The underside of the upright stone in the center is noticeably covered with needle ice. Place and time as in Figure 9. Figure 9. Niche -like bare spots covered with needle ice, in an area of marked needle -ice solifluction, under- mining the turf edge. On Delorette road over the Hochjochhospiz (Otztal Alps, 2600 m) Photograph by C. Troll, 7 July extended needle-ice formation in April on Parnes Mountain near Athens at 920 m altitude on red karst loam. It was found very abundantly on the loamy weathering mantle of the high limestone ridges of the Appennines (personal communication from H. Lembke) . In the Sierra de Guadarrama of Spain, Llarena saw it at 1900 m (personal communication) . In the High Taurus of Asia Minor (Ala Dag) , which have a heavy snow cover in winter that remains in high places until June, the sunnmer is absolutely dry. Due to the strong radiation in the high regions in September, nightly freezing occurs with strong warming during the day. During this time, according to Spreitzer (personal communication) needle ice is formed in the high mountains. However, the frequency of occurrence and the nnorphological activity is certainly different in the subtropics in relation to the times of frost and the times of precipitation. In the Appalachian Mountains, the strong needle -ice denudation described by Deckert in its imposing perfection is "a special phenomenon of the southern Appalachians". It occurs especially in the autumn months, which already have strong frosts in the nnountains but relatively little precipitation and slight snow cover. These observations from the Appalachians are matched by Schmitthenner 's (1932) from the East China monsoon regions. There we have the opposite to the Taurus, a very cold, 30 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES dry winter and hot, wet summer. Snow falls in the winter, particularly towards the end of January and in February, but it is frequently melted by the midday sun. It occurs similarly to hoarfrost, which can incrust trees and bushes in a fantastic manner in those mountains. Melted snow and hoarfrost produce muddy, water-soaked soil. Under the influence of the dry winter winds, ground layers of needle ice measuring 20-30 cm grow out of this wet soil. "The needle ice layer pushes up soil and stones, which on melting are transported down the slopes. . . Needle ice appears to have considerable morphological activity in an almost subtropical climate." Schmitthenner traces the origin of the angular, squared rock forms of the eastern China and Korean mountains to the intensive winter frost-splitting and needle-ice solifluction. He traced its lower border from the Lao Shan Mountains south of the middle Yangtze River (29 "North Latitude) at an altitude of 1500 nn through the Hwai Mountains, where on the north it sinks down to the base of the mountains, thence toward the mountains of Shantung, the Liaotung Peninsula, and to the Diamond Mountains of Korea. The contrast of the Mediteranean and monsoon climates is also thus beautifully expressed in the different seasonal occurrence and the different altitudes of needle-ice soils. In the province of Kwantung, W. Credner (personal communication) saw the winter formation of needle ice at 900 m. In Japan, needle ice is a very widespread phenomenon, so that as in Sweden it has attained a popular name ( "Shimobashira") . In writings it was described long ago (Wagener, 1877). It appears there everywhere at sea level, for example on the shore of Tokyo towards Kyoto, and especially from the end of December until the beginning of March. M. Schwind gave me the following brief description: "The mass of columns is underground, that is, it raises the overlying ground surface high. If one steps upon it, he sinks down deeply. With thawing weather there is a damp smear, which makes gardening troubles for the Tokyo resident. It is very important for soil mixing. Moist soil layers "s'weat" and one might say "freeze out" more ice than other layers. In the Canton Plain the frequent alternation of firm clays and volcanic ash beds shows a similar alternation in the strength of the ice formations: with warming, the ice- bearing layer "flows"; thereby fine projecting ridges originate on the cut. Shimobashira is ^x^idespread in Japan, especially the fine specinnens I saw at Shizuoka on the Nippon Taira". c) Structure-soil formation by needle ice on the Drakensberg . In a cold-winter and moist-summer climate similar to that of eastern China, everywhere at much greater altitudes, I observed beautiful needle-ice formation in the Drakensberg of South Africa at the end of winter in June, 1934. The high plateau around Mount aux Sources at 3000-3300 m bore a discontinuous, patchy snow cover, which was exposed in the dry air to a very strong radiation ablation by evaporation, with penitentes formation. In the moist debris soil over the basalt slabs, icy v/ind grew beautiful needle ice each night, which raised the fine soil high and gave it a crumbly structure when unfrozen. The fine soils were in nnany places completely vegetationless as a result of thorough freezing by needle ice. In the early morning, one could see a layer of very pure needle ice about 5 cm in height under a very thin layer of soil. The asbestos -like ice layer rested on a completely level, smooth unfrozen soil layer and was raised up in segments frozen together completely loose from the soil. The bottom surface was also smooth, so that a knife could be pushed under it without disturbing it (Fig. 11-12). In the night during which the needle ice described originated, an ice layer 2-| cm thick formed in water puddles nearby. The morning rise in temperature, with the dominant radiation conditions, allows the entire ice formation to disappear again. We are thus concerned with the typical needle-ice frost-heaved soil as it is known throughout so much of the world. However, two kinds of observations are new and significant for our problem. The crumbly fine soil in many places was arranged not irregularly but showed a distinct parallel arrangement of stripes 2-3 cm broad (Fig. 13). The ice bundles were also arranged in parallel ridges corresponding to the ridges of the crumbly surface. Generally the ice needles under the soil crumbs appeared thickly concentrated, but in the intervening areas they were scattered or completely lacking. An alternating striped arrangement of needle-ice bundles is given by the soil stripes (Fig. 14) . This striping, however, has nothing to do with the stripes caused by slope solifluction such as stone stripes; it has no relation to the V. NEEDLE ICE (PIPKRAKE) 31 Figure 11. Fine soil frost-heaved by needle ice on the high surface of the Drakensberg (South Africa, 3100 m) . To show the 5 cm high layer of ice needles under the crumbly frost-heaved soil, the needle ice in front is removed to the unfrozen underlayer. Photograph by C. Troll, 28 July 1934. Figure 12. Needle-ice frost heaving of Fig. 11 shown schematically. A -- unfrozen loamy soil, compact, without any structure, with flat upper surface. B -- 5 -cm high layer of ice needles, free of soil, with individual needles about 1 mm thick and frozen together in bundles, densely placed beneath the earth crumbs. C -- raised earth crumbs. Figure 14. Arrangement of ice -needle bundles (ground plan) in wind- striped frost-heaved soil of Figure 13. \ Figure 13. Wind-striped frost-heaved soil. Stripes in the direction of the cold winds. Place and time as in Figure 11. 32 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES ground slope but has a uniform compass orientation, toward the very strong and bitter- cold winds which during this season blew from the South African continent toward the east coast. The striping originates from the ice formation, not from direct wind- shaping of the soil by the blowing of sand or deflation. It should be described as " wind- striping of needle ice " or preferably as " wind-striped frost-heaved soil " in contrast to structure soils striped according to slope. Unfortunately it was not possible to follow the formation of these stripes by observation, but it would be possible with electric illumination in the course of a frost night. Here the physical experiment must be caught at the right moment. But it is not difficult to imagine that with a uniform wind direction the ice formation at the surface of the ground and especially beneath the surficial soil crumbs would accomplish a certain adjustment to the cooling wind, since certainly the slight movements of air between the projecting soil particles will have a certain orientation. The second very important observation was an especially clear sorting and structure-soil formation by needle ice. Where thin layers of mixed granular debris are lying on the basalt slabs of the plateau, one could see again and again a sorting of this debris, as is photographed in Figures 15 and 16 and repeated schematically in Figure 17. The debris islands are fringed by a ■wreath of stones, the largest stones being toward the outer edges and the smaller always towards the center. The dry large stones appear in pictures as white wreaths around the debris islands. Towards the center, there is moister unfrozen granular nnate rial which always shows a crumb structure, suggesting that it has been frozen by severe frost or when thoroughly wet, after a rain or snowfall. Farther inwards, needle ice is formed in still finer and moister debris, in a crowded layer 3-4 cm thick bet'ween the upper layer of soil crumbs and the unfrozen soil beneath. In the center of the debris island, where the debris is still coarser and more Avater is often available, single needle -ice bundles grow so that they can be distinctly recognized in the photograph as white flakes on the undisturbed upper surface (Fig. 16). The cross -section (Fig. 17) shows without further comment that we are dealing with sorting by frost heaving. With each nightly raising and each daily sinking, the stones raised the most by needle ice migrate somewhat to the side, on the arched, hourglass -shaped surface of the debris island ("needle-ice displacement") , so that in a very short time they are apparently pushed to the margin. •X. ^-^^ ^''-^ '*j&v Figure 3 6. Miniature stone nets on Mount Kenya at 4000 m. On very gently sloping ground, the stone polygons are somewhat deformed longitudinally. Faint wind striping of the fine earth is seen in the left foreground. Photograph by C. Troll, 1 May 1934. 8 -IS cm Figure 37. Cross section through polygonal "cake soils" (stone-net soils with sharply separated fine-soil areas). Diagonal lines: hard, frozen, fine-soil cakes of vesicular structure. Perpendicular lines: unfrozen, soft, moist subsoil somewhat elevated under the stone bands. The stone bands are either built up to the height of the cakes or form (only at the surface) shallow channels. A plateau near the Hall tarn on Mount Kenya, East Africa, about 4250 m. VII. STRUCTURE SOILS OF THE TROPICAL HIGH MOUNTAINS 51 c .— . ^ S 2 A 'i to „ s CO t:( r^ ^ * U ao S;^ ix' ? r— * ' * Tj 0- rt < m "— ' 7 a, >- J .Sri rt ni o,y 4-> . ni cs a '^ s I- ?„ W) 0, rt.2 S c " 60 O .-H 43 g O — 0) o a o S d m o S ■ tn > ,Q ■ 'O .— I !h C 1) C > rt O X o o ' C C C! di ^ " Mt3 o " 4-. <" (D J3 2 ni X ■" O ^1 •" C C ^ 0) t3 "i S '» rt (U M ni 1- ST C OJ rt- a SB'S "a. ^ri <" -J^ -H wi m ^ ? oj - c r-l "H -M CO «i,~. m .i:; ye o . in 00 (M D r; ^^0 ro ^ (!) . ^^£ ^■■« . ■r4 -M S S ni (0 en j3 52 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES I found stone-stripe ground to be very sparse higher on the debris slope of Mount Kenya. They were primarily the usual type of broad soil stripes separated by narrow stone stripes, circunnventing the larger stones (Fig. 41). One variation was found on the steep slope of the large lateral moraine north of the Hall tarn. Between the gravel (from millet-seed size to dove-egg size) and individual larger stones were small heaps of earth (resembling "worm earth") which were crumbly and moist, thus dark compared to the light gravel. These were loosely arranged in stripes that extended downslope in the direction of strongest declivity. The crumbly stripes project 1-2 cm above the gravel surface and look as if they have been pressed out from between the stones. Digging showed that the gravel layer was only a few centimeters thick, underlain by a mixed wet subsoil with no size-separation of particles. The surface of the subsoil 'was some'what higher below the crumbly stripes than below the gravel layer (Figs. 42, 43) . This is a special type of structure soil, which can originate only in debris with a very little fine earth. The fine- soil crumbs are evidently raised by nocturnal freezing, but unfortunately I could not observe this directly. The type has already been described as "soil stripes" by Mohaupt (1932, p. 23 ff. ) from South Tirol dolomite. He speaks of earth boils [Erdbeulen] which break through the debris like buds. At one other place, in the Figure 41. Miniature striped ground on the debris slope of Mount Kenya at 4300 m. The larger unsorted stones are circumvented by the stone stripes. Photograph by C. Troll, 2 May 1934. Figure 42. Soil-stripe ground at 4400 m near the Hall tarn on morainic gravel poor in fines. The fine -soil crumbs which swell up between the gravel particles like buds are arranged in stripes down the slope and appear dark because of their moisture. Photograph by C. Troll, 9 May 1934. VII. STRUCTURE SOILS OF THE TROPICAL HIGH MOUNTAINS 53 Grodener Valley, Mohaupt (1932, p. 31) observed them on level ground, but with- out the row-forming pattern. "Many stones are present, and the soil Figure 43. Diagrammatic cross section between them appears swelled or forced through the miniature soil -stripe out, not unlike earthworm excretions. ^^^^^ ^^ p. ^^ Diagonal lines indicate Small columns and heaps of soil have unsorted subsoil. then been formed. The dark soil contrasts well with the light stones. The soil heaps lie on the ground loosely and can be cleared away easily. " At dawn Mohaupt could observe the development caused by needle ice. A thick layer of needle ice had formed under the surficial stone and soil layer. When the ice melted, the clumps of soil raised by needle ice remained clamped in the interstices and thus canne to the surface. In our cases, the same has surely happened, but in connbination with slope solifluction and stripe-like sorting. The moist subsoil under the cover of gravel and fine-soil stripes marks the lower limit of nightly freezing, the base level of needle-ice formation, and thus the lower limit of pebble sorting. For neither Kilimanjaro nor Kenya ar^ there continuous meteorological records to enable us to compare the elevation of the structure soils with the frequency of frost alternation. According to the findings from the tropical Andes, there is no doubt that here also the zone of structure soils coincides with the altitude zone of maximum frost alternation. It is surely permissible in this case to draw conclusions about the temperature conditions of both nnountains from the observable effects of frost. On Kilimanjaro this altitude range would be between 4300 and 5000 m, on Kenya between 4000 and 6000 m, in agreement with the higher sno'w line of Kilimanjaro. Commonly all structure soils of the tropical high mountains are due to daily alternation of freezing and thawing operative throughout the year, and to the very shallow freezing, extending only a few centinneters into the soil, which understandably permits only soil structures of small dimension (miniature polygons and narro'w striped soils) . The daily regelation and the constant movement of the ground surface by the ice explain the very regular development as well as the generally complete lack of vegetation on the tropical structure soils. From this one may conclude that the tropical structure soils could form in a very short time, perhaps in a fraction of a year or even in a few weeks. The manner of nightly ice formation is not uniform. Needle ice is only one form of surficial soil freezing, but it plays an important role. Above all, needle ice is the cause of the extensive completely vegetationless surface of frozen soils which was observed in the tropical high nnountains on frost-sensitive soil types. Daily solifluction and especially needle-ice solifluction are very effective in surficial erosion of slopes. VIII. THE HIGH-POLAR STRUCTURE SOILS (ESPECIALLY OF SPITSBERGEN AND GREENLAND). It seems appropriate to discuss next the high-polar conditions, the complete antithesis of the purely tropical conditions. They are to be found in Spitsbergen, the classic land of structure -research, and in Greenland (where I have made no observations of my own). SOrensen (1935), the expert on conditions in eastern Greenland, has already emphasized the very great similarity of the structure soils there to those described from Spitsbergen, which is to be expected from the similarity of climatic elements. (Compare the thermo-isopleth diagram for Danmarks Havn, Fig. 44, with the diagram for Green Harbor, Fig. 1) . The same conditions appear to exist in Novaya Zemlya also, from where only a few recent observations are accessible to me, and in antarctic Graham Land (Nordenskjfild, 1911). The most important original observations on the various fornns of the Spitsbergen structure soil are given in the following: Wulff, 1902; Resvoll-Holmsen, 1909; Dubois, 1911; Meinardus, 1912a-b; Miethe, 1912; Sapper, 1912; 1914; Hftgbom, 1914; Nansen, 1921; Huxley and Ode U, 1924; Elton, 1927;Gripp, 1927; 1929; Poser, 193 1; Ahlmann, 1936; 54 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES and Mattick, 1941. For Greenland, we rely particularly on the descriptions of Nieland (1930), Poser (1932), and Sorensen (1935). Dege,for Spitsbergen (1938, 1941, 1943), and Seidenfaden, for Greenland (1931), deal less with structure soils than with amorphous solifluction. In contrast to the tropical high mountains, the large proportions of the high-polar structural forms are most striking. The large stone nets and stone rings, with diameters from one to several meters, and stone stripes from one-half to several meters wide (Fig. 45, 46, 47) are by far the predominant forms. Diameters from 0.5 to 3.0 m are given also for the loam, islands amid the larger stone -rubble areas. Miniature forms of stone stripes and stone nets, similar in size to those of the tropical mountains, are by no means completely absent and are being given more consideration in more recent literature, in attempts at a morphological classification, particularly by Poser (1931). Special conditions prevail in regard to the size and arrangement of the fracture nets [Spaltennetze] or cellular soils [ Zellenbbden] . On the other hand, the immense tetragonal frost fractures ("Taimyr polygons" or tundra polygons ), which are typical of the entire winter-cold continental tundra regions of Siberia and Alaska, have been observed as a rarity by two authors, Holmsen (1912-13) and K. Gripp (1929, 1939) in Spitsbergen and by Poser (1932) in East Greenland (with sides from 8-12 up to 15-20 m long, even up to 100 m) . From Nordaustlandet (Northeastland) Figure 44. Seasonal and daily course of temperature in the high-polar climate of East Greenland (Danmarks Havn) , expressed in thermo-isopleths. Figure 45. Polar stone rings (large forms), Ny-Aalesund, King's Bay, Spitsbergen. Vegetation zones: Inside adjoining the stone ring, a ring of fruticose lichens ( Centraria delisei , among others) and a little Salix polaris . Soft, fine earth in the center only with a crust of lichens. Photograph by F. Mattick. VIII. THE HIGH-POLAR STRUCTURE SOILS 55 Figure 46. Stone net's (large forms), near Ny-Aalesund (King's Bay, Spitsbergen). Vegetation similar to Fig. 45. Photograph by F. Mattick. Figure 47. Stone-stripe ground(large forms — polar type) north- west of Ny-Aalesund (King's Bay, Spitsbergen) . At large intervals the stone stripes have an irregular sinuous course. Photograph by H. Rieche. 56 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES stone nets with diameters up to 7 m and nnore are described by Ahlmann, and stone nets, distorted by solifluction, from 3-5 m in breadth and up to 1 6 m in length, are described by Poser from King's Bay. Within these gigantic forms there are, however, secondary structures, namely stone rings and stone ellipses of moderate size down to small ones of 20 cm diameter, which are also built up of small stony material. Such combinations of large, small, and miniature stone nets with corresponding gradation of stone sizes ("primary, secondary, and tertiary polygons") have been described also by Huxley and Odell. Likewise, there are combinations of cellular soils (Fig. 48). Poser differentiates a "floating" and an "anchored" stone network, according to vertical structure. The stone borders of the first type penetrate only slightly into the ground; below these is found largely sorted soil, finer than in the polygon area; and then, only a few decimeters deeper, the rocky, unsorted, parent soil. In the anchored network, however, the stone borders reach down to the stony unsorted soil. The anchored stone polygons form no tightly closed nets but are more dispersed, representing a transition to scattered soil islands. Miniature stone nets were found by Poser at King's Bay, in addition to those found as secondary forms in larger polygons. The irregular size of the feature (between 2 and 30 cm) is noticeable in contrast to the regular stone nets of the tropical mountains which appear to be placed by an artist's hand. Such small stone nets were observed in Graham Land also (Nordenskjald, 1911, p. 192). The large stone stripes in Spitsbergen and in the Antarctic are distinguished by a slightly sinuous or tortuous course. This fact and the transition to elongated stone nets suggest that they are derived by soil flow (macrosolifluction) from the large s.tone nets. On the other hand, because of their parallel course, which is diverted only for larger stones, and because of their size, the miniature stone stripes of 4-8 cm width resemble the forms familiar to us from the tropics. Poser and earlier authors (Ule, 1911; Salomon, 1929; Mortensen 1930) assumed that these forms originated in rain rills. But the many miniature stone stripes which are definitely not in rills make this hard to accept. Undoubtedly they are explained by combination of micro- and slope -solifluction. Figure 48. Combination cellular soil, Claas Billen Bay, Spitsbergen. The large fracture nets are emphasized by the overgrowth ("Vegetation-nets"); the arched-up areas between show a secondary division into small polygons. Photograph by F. Nusser, August 1937. VIII. THE HIGH-POLAR STRUCTURE SOILS 57 It is now generally accepted that the fracture nets of high-arctic regions are due to frost action also and are not simply desiccation cracks. Transitions toward sorted stone nets (Nieland, 1930), as well as transitions toward pure desiccation cracks are recognized, for instance, wherever small fracture nets have formed in a summer without frost (Elton) . Unfortunately, the distinction between desiccation cracks arid fracture polygons is not so simple as is imagined by some authors, accord- ing to whom frost-split soils have convex surfaces while pure desiccation cracks always have concave surfaces. In any case, drying-out and frost can work together in various ways. Miniature forms evidently predominate in the fracture nets in the far north also. Diameters from 0.2 to 2.0 m have been reported, although Huxley and Odell also mention gigantic forms ■with diameters of 1 5 to 20 m, and in northern Siberia even with 30 m diameter (according to Middendorf) . The large forms from 1-3 m in diameter are very characteristically subdivided into secondary or even tertiary polygons, as shown by the excellent pictures of ResvoU-Holmsen (1909) , Hagbom (1914), Huxley and Odell ( 1924) , Elton (1927), and Poser ( 193 1) . Here the large forms are older than the secondary fractures, as proved by the plant growth (Mattick 1941) as well as by the fact that the secondary nets first occur along the large fractures. One has the strong impression that the small cellular soils represent only desiccation cracks or at least transitions to them, while the larger and older connections are typical high-polar structure soils. However, critical observations on this subject are lacking. The high-arctic structure soils occur over permanently frozen ground, that is in the overlying ground which alternately freezes and thaws. Saturated flow soil in summer is an essential prerequisite for them according to the proponents of the frost-thrust theory. The depth of nnovement of the flow soil is moderate in the high-arctic region because of the shallow thaw depths, but the permafrost causes the flow to continue during a large part of the year, in any case during the whole summer. The intensity of flow is therefore very great, and solifluctionforms widely dominate the surface. In contrast to the tropical high mountains, where all the frost variations are controlled by daily regelation, the frost alternations play only a subordinate role in the high-polar frost soils. The climate of Spitsbergen records fewer frost alternation days (59) than Berlin (67) (Table I); and most of them occur in the spring when the snow cover hinders the penetration of the temperature change into the ground, as Mortensen (1928) has already emphasized. In July and August, when the ground is bare, they are almost entirely absent. The greatest distinction between frost soils of high-polar regions and tropical high mountains therefore lies in the significance of regelation and soil flow. Solifluction formation is a seasonal phenomenon. There- fore, the dynamics of the high-polar structure soils are essentially based on seasonal changes, while those of the tropical structure soils are exclusively based on daily changes^ " ' The depth of thawing in Spitsbergen and eastern Greenland is generally less than one meter. Largely dependent on the heat of the summer, these values fluctuate between 0.3 and 1.0 m according to exposure, bedrock, weathering soil, and so forth, and average | m (Poser, 1932). It is evident that larger structure-soil forms can be formed in a thaw soil of such depth than in the tropical high-mountain soils where the depth of freezing is only a few centimeters. However, it is quite possible that the small structures, which need only a few centimeters depth, can form in deeper flow soil in addition to the larger forms. In general, there appears to be a definite relationship between the depth of soil sorting and the horizontal dimension of the corresponding forms. That does not exclude the other statement, made by earlier authors, that a definite relationship also exists between the size of the structure forms and the grain-size of the stones in the borders (Meinardus, 1912; Huxley and Odell, 1924; Ivanov, 1931; Poser, 1933). In deeper thaw soils, large stones can be raised ' and transplanted, but a boulder in the stone-striped soil of Kilimanjaro, for example, will not move independently. The derivation of the miniature structure soils found in the high-polar regions remains a problem. It is clear that they are not the result of solifluction occurring 58 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES in the whole thaw layer, as are the large forms. Sbrensen, who attempted (1935) a genetic classification of high-arctic solifluction forms, groups the miniature stripes, miniature stone nets, and cellular soils together and believes that they are caused by limited water supply and early desiccation. The explanation, however, cannot be sought simply in the alteration of only one edaphic ground factor. This is particularly indicated by the combination of large and small forms and by the occurrence of secondary miniature forms within the large primary forms. These perhaps can best lead us to an understanding of the small forms in polar regions. For instance, let us take a fracture-net soil (Fig. 48) with large meshes several meters wide and miniature polygons emanating from the fractures. The large fractures are related to the permafrost and the depth of summer thaw, as is indicated by their depth and greater age. The miniature polygons, however, must be subject to conditions which operate only in the uppermost soil layers. It is suggested — and FrSdin (1914) has observed evidence of it — that cellular soils originate as desiccation cracks due to superficial drying, and then are changed secondarily by melt water and night frosts. In some cases, miniature stone nets could conceivably be due to flow movements restricted to a thin surface layer, perhaps because bedrock lies at a shallow depth. However, this does not prove true for the described patterns. Another possibility is frost effects of shorter duration, perhaps frequent regelation in the spring months. Here one could consider especially local climatic influences; for instance, frost alternation in the spring may have a more severe effect in some places because of early blowing away of the snow. Thus the large forms would be subject to the seasonal course of soil freezing and thawing; the small forms, on the other hand, would be subject more to short-period, daily, and weather-controlled changes of temperature around the freezing point. Theoretically, other different possibilities of microclimatic and edaphic prerequisites can be devised to explain miniature patterns in the polar climate. But there will still be exceptions. Future observation on the spot will have to clarify the special conditions of such cases. The same is true also for the other special case, the gigantic fracture nets (tundra polygons). They probably need a rather deep thawing, but they are also fundamentally different from the stone-net ground. Their formation requires a very deep frost penetration of the ground before the winter snowfalls begin, a condition which is normally not present in the high-polar climate of Spitzbergen and Greenland (See page 638) . SSrensen (1935, p. 64-65) attempted to give a summary of all the solifluction forms occurring in the high-polar climate (structure soils and forms of amorphous solifluction) . But the tetragonal fracture nets and tundra polygons are omitted, and the combination structure soils are not considered. However, it is too early for a genetic classification such as he attempted. Undoubtedly the two most important funda.mental conditions are the initial material (grain size, homogeneous or mixed material) and the slope of the terrain. At present, we can reliably evaluate their influence on the soil forms. The third fundannental condition, water supply (duration of the snow cover, depth of thaw and the time of thawing) is very important, but comparative observations concerning it are still lacking. A final clarification could probably be achieved by a large scale mapping of solifluction forms. Only a survey of the continuous spatial configuration of the different solifluction forms would give an insight into the interplay of the ecologic factors. Such a survey could be conveniently made today by using aerial photographs. The aerial photographs, however, must be supplemented by accurate terrestrial stereoscopic photographs and by proper excavation. The techniques used should be the same as those used for studies of vegetation. Indeed, in a sense subnival soil movements are also manifesta- tions of the life of the soil. The edaphic, local-climatic, microclimatic, and soil- climatic conditions change on a small scale from place to place. The habitats or ecotypes of the soil correspond to the living conditions (biotope) of living matter. To comprehend these regionally by selected examples must be the next objective of arctic soil investigation. IX. THE FROST-SOIL FORMS OF SUBPOLAR CLIMATES 59 1. Scandinavian mountains Most closely related to the high polar climates are the Scandinavian Highlands in the subpolar zone, the Fjeld region or "regio alpina," which grades northward with decreasing altitude into the arctic tundra. The similarity is seen not only in the lower temperatures but also in the entire nature of the temperature regime. The smaller daily temperature fluctuations in the highlands compared to the plains result in a seasonal climate very similar to the high polar climate. This has a direct effect on the soil, so that the permafrost has a great extent in regions above the limit of trees and bushes. H. Reusch (1901) and G. Anderson (1903) have already described the tjale in Norway and northern Sweden. More recently B. Hflgbom (1914) has compiled the few observations about it, and Thienemann (1938) has shown the great significance of the pernnafrost in the ecology of the animal life in Lapland, by supplying breeding places for the myriads of mosquitos, which nourish themselves on the blood of the lemmings and are nourishment for nnany insect-eaters. In some places, permafrost has been found in lower areas in the birch forest region and even in the coniferous forest region. At any rate, seasonal frozen ground can be considered as affecting the entire highland zone of Scandinavia. The observed structure soils and solifluctionforms especially resemble those of high-polar regions . According to basic studies by Frodin (1914, 1918), the true structure soils are the large forms — stone nets, stone rings, and "vegetation-nets" (polygonal vegetation patterns measuring 3 m in diameter on flat ground in homogeneous soil), and also loam boils, soil islands, and small fracture polygons. The structural soils studied by Hogbom (1914), Ule (1914, 1922), Bluthgen (1942), Dege (1941), and by Rathjens and von Wissman (1929) are of the same type. Even in southern Norway the stone polygons have a diameter of 1.5-2.0 m. The last-named authors also described ho'w debris -striped soils (" of the width of a good highway") develop from stone nets on slopes. The very common solifluctionforms, e.g., solifluction ridges, terraces, and streams, stone fields, debris garlands or "gravel terraces" [Kiesterrassen] , and debris spots, correspond to the formation of a distinct summer flow-soil layer. In the descriptions of Scandinavian structure soils I have found no examples of miniature stone nets and stone stripes, with the exception of the extrazonal forms of Oland and Gotland. The cellular soils, which represent special conditions, are an exception to this as in the high Arctic. Like Sbrensen (1935) for arctic solifluctionforms.Beskow (1930) has attempted to establish a genetic system of existing structure soils and solifluction soils on the basis of the Scandinavian findings. He also considered the soil composition and slope as the most important factors. He also took into account the vegetation cover but not the water relations, for which Sorensen rightly criticised him. Significantly, in the Beskow system, the miniature stone nets and stone stripes are omitted, and generally even stone nets. Therefore it seems to me that the formation of structure soils in the Scandinavian highlands, even more than in the Arctic, depends on the seasonal cycle, in connection with the heavy snowfall of the mountains. For a complete understanding of this relation, it would be necessary to know the seasonal distribution of frost alternation for different elevation zones, and to relate it to the snow conditions. However, the preliminary work has not yet been done. The comparison with high-oceanic sub-polar regions, in which the structure soil formation reaches down to sea level, is instructive. 2. Oceanic islands of the subantarctic Basically different conditions concerning soil freezing prevail in the high-oceanic climate of the subpolar islands. We had best start with the subantarctic, with Kerguelen, where the structure soils reach down to the beach and for which we have accurate climatologic and soil-climatic data gathered by the German South Polar Expedition (1901-1903) under E. vonDrygalski (1901-1903) and published by Meinardus ( 1923) . Both the yearly temperature fluctuations (because of the highly oceanic climate) and the daily fluctuations (characteristic for the latitude) are very small, so that a singularly even, uniformly cool climate exists, as the thermo-isopleth diagram (Fig. 49) shows. With a mean annual temperature of 3.3C, an annual fluctuation of 6. 40 and a mean periodic daily fluctuation of 2.25C, the air temperature can fluctuate around the freezing point in all months except the summer months of December, 60 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES 3 JTo. rj 3 (ij -> < (n .l>lo IzimToj Ul^lgfc ou < Lj< a-< 33 ZQ-3U.Z^A"aS Figure 60. String bog from southern Labrador (region of the great bend in the Romaine River). Photograph by Schmidt-Collinet (German Mingan- Expedition, 1937, leader Prof. Dr. Eidmann) . Nova Scotia, the string bogs are succeeded by true high moorland. Only suggestions of "Strange" and "Flarken" structures are to be found there (Auer, V. — Peat Bogs of southeastern Canada. Handb.d. Moorkunde, edited by K. von Billow, 7, Berlin, 1933) To the north, however, near the forest border in North America the palsen bogs take the place of string bogs (l. Hustich, 1 939) . In Asia, conditions within the boreal coniferous forest belt change east of the Yenesey. To the west, permafrost does not occur below the tundra zone, but here it abruptly extends far to the south, to the Sayan Mountains in the steppe region on the north edge of the Gobi, and beyond in the Amur River basin. Towards the coast of the Sea of Okhotsk it moves back to the north under the influence of the Pacific, so far in fact that most of the Kamchatka Peninsula is outside the permafrost zone (Fig. 6l). Important studies of the permafrost of Siberia had already been made in the first half of the last century. Because of the greater significance for soil science (in Siberia also for agriculture), for the water content of the rivers, for mining, and for technical building of all kinds, these studies have been extended and intensified especially in recent years by Soviet Russia. JO' www M* w w icw He- or w w ibtr iw w «' 75 Prevailing soil temp, at 10-15 m depth. g^ Below -5C (continuous permafrost). ■^^^^^ -5C to -15C (permafrost with thaw- ' soil islands) . ^^ Above -15C (thaw-soil islands in permafrost; in south, permafrost islands in thaw soil. [-jt;j Above -15C (permafrost islands in thaw soil) . mil Modern glaciation in northern USSR. T'.l Isolated permafrost islands. ;.-; Permafrost only in peat mounds (palsen). ~~~ Southern permafrost boundary. Probable permafrost boundary outside USSR. ' .• Permafrost research stations. Figure 61. Distribution of peTmafrosl and soil temperatures in uortter Eurasia (according to the Great Soviet World Atlas, vol. I.Moscow, 1937). Two decades ago Pohle (1924), Shostakovich (1927), and Sumgin (1927, 1929) gave comprehensive reports of the current status of knowledge. The Academy of Sciences of the USSR has published (1930) a review work, Permafrost [Vechnaia merzlotaj, with contributions by Sumgin, Grigor'ev, Petrovskii, Koloskov, and Mal'cenko, and founded a special research commission which publishes an annual report (Trudy Komissii po izucheniiu vechnoi merzloty, vol.1, 1932; vol.8, 1939) These contain exceptionally rich material on the most diverse aspects of permafrost in Siberia and northern Russia, both scientific and practical, i^ i^ the permafrost regions the surficial thaw layer (extending to the thaw depth) is underlain by permafrost. Beneath the lower limit of permafrost the ground is never frozen and ground water can still exist. The depth of permafrost and the thaw depth depend primarily on climate, next on the bedrock and water factors. It has been established that permafrost extends to 150 to over 300 m depths in the high-polar region as on Spitsbergen (Gripp, 1927), and up to 400 m on the arctic Siberian islands In the tundra of north Siberia, depths to 100-120 m are given (Gerasimov and Markov 1939) 12. It is impossible to cite all pertinent works. See Stoltenberg (1935) and the later references in the Neues Jahrbuch f. Mineralogie, Geologic, u. Palaontolgie, Ref. U, especially vol. 1936, 1939, 1940, and 1941. The latest comprehensive summary of ' permafrost, predominantly for practical requirements, is given by Lukashev (1938). To determine the depth of permafrost, geophysical methods have been used in Russia, electro-magnetic waves (Petrovskii 1934) and seismic methods (Koridalin, 1934). Since the annual and long period changes of frozen ground can cause great damage to railroads and highways (Datskii, 1935;Suslov, 1935), geotechnical investigations are important, concerning the compressive strength (Gumenskaya, 1936) and shearing strength (Sheikov, 1936) of frozen ground of different types and at different temperatures. 7 6 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES but it is in general much less in the forest region of Siberia. According to Shostakovich, it is on the average 18.7 m in the region of Irkutsk, 21 m in Yakutsk, 25.7 m in Transbaikal, and 23 m in the Amur region. Single values of course go higher, as at Yakutsk, where the classic Shergin shaft did not reach the bottom at 116 m (13 6 m according to later borings). On the other hand, the thaw depth in the Siberian forest region is greater than in the arctic because of the stronger summer warming. According to Shostakovich, the mean value for the different parts of the Siberian forest region shows only small fluctuations between 6 and 7 m. The upper borde of permafrost can certainly be somewhat deeper locally: in Yakutsk 18.7 m, Irkutsk region 28.2 m, Transbaikal 29.4 m, Amur region 37.4 m. In these cases we are certainly not dealing with "summer thaw depths", but with the permanent thaw depth, ■which is difficult to explain. While Shostakovich attempted to explain the extent of permafrost by the present climatic conditions (especially by the winter temperature and the slight winter snowfall according to the formula Mean air temperature of Dec-Feb < ^ c ^ Mean snow depth in Jan (cm) ' ' ' Sumginand later others presented convincing evidence that the principal mass of Siberian ground ice was a relic of the Pleistocene. However, the two interpretations are less contradictory than they appear. It is certain that permafrost can exist today in young deposits, certainly in the artificial debris of the railroad embankments. The present boundary indicates essentially the line to which the Pleistocene permafrost has retreated under modern climatic conditions. Also the permafrost has undergone gradual climatic fluctuations and consequent changes in thickness ( Berg, 1935). On the Kola Peninsula and in the Pechora region, and also in a large part of Siberia, a significant retreat of permafrost in the lastdecade is established. It corresponds perhaps to the retreat of glaciers over the world and certainly has climatic causes. Permafrost can also be changed through human soil cultivation. Wood cutting, cultivation, grazing, and grass-cutting can cause it to recede (Tumel', 1935; 1939). On the other hand, wood-burning, according to Krasiuk (1927, should lead to boggy conditions and thereby the strengthening of permafrost. Through the construction of the railroad embankments mentioned above (Khrgian, 1936) the upper frozen layer rose about 13 m in 20 years. In Igarka on the Yenisey (67°NLat), one of the northernmost cultivated areas on the earth, recent cultivation of the surface has lowered the permafrost from 1-1.5 m to 5-6 m depth (Cressey, 1939) . In the soil culture and building customs of the nomadic ''Buryaten", such kno'wledge plays a great role (Pisarev, 1935) . In building, they make small depressions by melting the permafrost, and fill them with water. They cover their winter living sites with straw, dung, or rubble to protect them from thaw until the next winter. In dung heaps, hummocks can originate by the formation of ice lenses just as in the peat. The frost-conditioned soil forms of Siberia are very different from the forms described before, because of the great summer thaw depth and the heavy vegetation cover. As far as the vegetation permits it, solifluction processes play a great role. The frozen ground at shallow depths prevents the growth of forest, and grass takes its place. Vegetation can be still further repressed by very strong frost heaving of the soil, as is the case in the clay bogs or "mari" of the Amur region and the Stanovoi Mountains (Shostakovich, 1927). Hummocky ground appears to be widely distributed in the swampy regions of the forest zone (Abolin, 1913). The topographic forms which are obviously produced by ice may be readily classified into two groups, the depression forms and positive topographic forms. Depression forms originate by the reduction and complete nnelting of underground ice masses. Collapse forms are thus built (funnels, kettles, lakes), either as doline- like single features ("suffosion funnels", Glazov, 1939) or in an entire "hummocky kettle-form microrelief" (Pisarev, 1935; Kudriatsev, 1939). In the Russian literature IX, THE FROST -SOIL FORMS OF SUBPOLAR CLIMATES 77 there has been introduced for the entire complex the expressions "permafrost karst", "thermokarst" (Baranov, 1940), and "frost karst" (Kachurin, 1938). Glasov has also thoroughly investigated the hydrologic phenomena which take place with slow melting of ice lenses between the thaw soil [active layer] and the never-frozen soil. In Yakutia thawing of ground ice develops very shallow doline-like sinks called "alias", which are immediately filled with water and dry out after thawing of the entire ice layer. There remain then the meadow valleys which form the basis of the Yakutia animal industry (Anger, 1937, p. 195, Fig. 191). The complex of permafrost karst recalls especially strongly the forms which originate in Alpine and northern glacial debris by melting of fossil ice. In 1937 I introduced the name "fossil-ice karst" [Toteiskarst] for especially beautiful features of this type (Geol. Rundschau, 1937, p. 601). The similarity is very great, which is not surprising since the Siberian ground ice is certainly also largely relic ice from the Pleistocene. However, it is yet to be established how much the extensive fossil ice forms, like those of the late Pleistocene region of northern Germany, may be traced back to actual fossil ice from glaciers, and how much they may be traced back to permafrost formed during late-glacial times in terrain freed of ice. Conversely, the positive topographic forms in permafrost regions originate by enlargement of underground ice masses. The enlargement may occur during one winter or over a longer time. It depends on the particular hydrology of the permafrost region in the subpolar climate. The relatively small thickness of frozen ground and the presence of ground water in the never-frozen soil below, plus the greater thaw depth, pernait the great rise of springs or artesian ground water and the formation of the often-described icing mounds in riverbeds (Russian "naledi", Yakut "taryn"). This spring ice produces soil forms like the so-called underground "naledi", lens- shaped accumulations of ice in the subsoil which can push up the soil, even when covered by forest, into circular or oval hummocks to a maximum height of 14 m (Abolin, 1913; Shostakovich, 1927; Tolstikhin,1932; 1934; Dzens -Litovskii, 1938; Baranov, 1938; 1940; Kudriatsev, 1939). They are called "icing mounds, " "swell mounds", "hydrolaccoliths" or "ice laccoliths", in Siberia "kotchi" or "bulgunniakhi" They can attain a diameter of 20-100 m and a height of 1-6 m (Kudriatsev). When the underground flow is eliminated and the mound disappears, a lake usually forms in its place, blending into the karst landscape among the many collapse lakes. Icing mounds can melt away annually, collapse and form again (at the same spots because of the spring icings) or else they may reach great age. In Transbaikal, they grow to 80 m diameter. On thawing, a crater filled with muck or by a spring-fed lake appears at the top of the mound. Sukachev (1911) determined a maximum age of 162 years from the annual rings of bent larch trunks on some of these old mounds. These mounds, which are caused by the pressure of ice and water from below, can also crack open and emit mud or stony debris (Shostakovich, 1927). Sometimes chunks of several cubic meters in size are thrown several meters. The process is explained by air pockets which exist under high pressure in the mounds (Baranov, 1938). Icing mounds are typical of large areas of the Siberian permafrost region, for example for Yakutia, with its mean thickness of 9 m of permafrost. Tolstikhin (1934) has described them for the river area of Indigirka, Kachurin (1938) for the Anadyr' area, Kudriatsev (1939) for the Selemdzha area, a northern tributary of the middle Amur. Outside the regions of permafrost, icing mounds can occur as a seasonal phenomenon in interior Asia where winters are cold. They occur in association with salt lakes in the Baraba steppe around Kulunda Lake (Dzens -Litovskii, 1938). They are also described by Gokoev (1939) from the region of the Kirgiz steppe' as forms 10 m wide and 1 m high. Diminutive hummocks 30-40 cm high have even been observed in the Pamirs at 1400 m elevation, thus within the area of cultivation of vines and walnut trees, also here only as formations of winter frost (Markov, 1934). A.E.Porsild (1925) has described spring-ice domes in Greenland, quite similar to those of Siberia. There, however, clearly because of the much deeper freezing, they are restricted to places where warm springs emerge from depth through the permafrost. The flow of these springs is finally cut off in winter by icings. 78 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES As a whole, the subarctic zone shows the greatest contrasts of frost-soil types, representing several climatic types. The Scandinavian mountain region shows far- reaching similarity with the high-polar zone. The same is true of the interior highland of Iceland. Conversely, the high-oceanic subpolar regions, such as the subantarctic islands, the warm coastal regions of Iceland, and the Faroes with their small structure soils formed primarily in short-period frost cycles, are closely related to the tropical high mountains. The tundras of the northern edge of the Eurasian and North American continent are characterized by large peat mounds or palsen, and also by wide-meshed ice-wedge fracture nets in the continental regions. There is also great contrast in the subarctic coniferous forest regions. The moderately continental boreal climates without permafrost are characterized by string bogs. In the high-continental coniferous forest climates, with permafrost and great thaw depth, hydrologic effects (surface-ice formation) and melting forms (permafrost karst) are characteristic. X. THE MOUNTAINS OF TEMPERATE LATITUDES There remains still the problem of examining the climatic characteristics of the structure soils of the mountains between the tropics and the subpolar zones. Here the relations between climatic factors and structure soils are much more difficult to comprehend because of the scarcity of meteorological data in the high mountains. We can expect that the middle latitudes will not have the clear extreme types of the tropical mountains or of the polar zones but only transitions and mixtures of both. However, as the aspect of climatic differentiation has scarcely been noted in previous texts, an attempt to explain the observations concerning it appears opportune. Conversely, the structure soils can be a guide to a clearer understanding of the climatic characteristics of different high mountains of the earth. For the mountains of the temperate latitudes, v/e must confine ourselves to several regions of the northern hemisphere, because there is too little material on the Chilean Andes, and the works of Marshall in New Zealand are inaccessible at present. 1. The mountain ranges of western, central, and eastern Europe The structure soils of the mountains of the British Isles are most similar geographically and typologically to those of the Faeroe Islands. In Scotland, northern England, and Wales they are already found well below 1000 m elevation, fronn about 700 m — if ^ve consider the especially lovf occurrence at Ben Jadain (560 m) as non-climatic intensification (Simpson, 1932). In the seasonal clinnate of those places (Ben Nevis, 1934 m, annual fluctuation 9.7C) , certainly very severe yet moderated by the highly oceanic character, structure soils form under very different conditions than in the German Mittelgebirge. There is no report of permafrost; soil freezing is active in the cold season; alternate freezing and thawing is especially active in the spring and fall. Hay (1936) in the Lake District of northern England was the first to observe the formation of sorted soils by needle ice outside the Tropics; he observed stone stripes 30-40 cm broad. These structure soils resemble those of southern Iceland and the tropical mountains much more than they resennble those of the Arctic. They cannot all be considered as miniature forms, for, besides the narrow stone rings and snnall stone stripes of about 30 cm diam, there are also larger forms of 80-90 cm (Simpson, 1932, Hollingworth, 1934). But, as Hay revealed from his needle-ice observations, the structure soils originate principally in the short-period fluctuations of shallow soil freezing in the colder season. Hay has confirmed observations made elsewhere that the size of the structures is related to the grain size of the sorted materials. However, there is also at least a general relation between the size of the structure forms and the depth of freezing and sorting. With short-period and shallow freezing no large forms can exist anywhere, and large stones cannot be moved. In the German Mittelgebirge, the only real structure soils known so far are those of the Riesen Gebirge, between 1500 and 1550 m. There are very distinct stone networks and stone rings, stone stripes, and soil islands inside rock debris, generally large forms of high-polar type. The stone rings and stone polygons have X. THE MOUNTAINS OF TEMPERATE LATITUDES 79 diameters of 2-4 m, and the borders are 0.7-1 m broad. As in the Scandinavian high mountains, the seasonal frozen ground persists far into the spring, though there is no permafrost in the Riesen Gebirge (Badel, 1937). The climatic relationship with Scandinavia is also expressed in the fact that debris ridges and terraces very similar to the Scandinavian solifluction ridges and terraces occur near this frost-patterned ground, and that, on the bogs of the Riesen Gebirge, Rudolph and Firbas found "Strang" and "flark" complexes like the pattern of the northern string bogs (see Hueck, 1939). They show that solifluction is still operative on bogs today. Gellert and Schaller ( 1929) decided that the structure soils are fossil formations of the periglacial climate of the late Pleistocene. The structure soils thus must have survived the entire post-glacial period, and particularly the post-glacial warm interval, when the tree line- was 400 m higher than today. But the more recent observations of Schott (1931) and Bttdel (1937) have shown that the movements have not come completely to a standstill. Dtlcker (1937) showed that a typical podsol soil profile has fornned on the fine centers of stone rings, a type of microprofile with a thin layer of bleached sand and hardpan [Ortstein], which would be impossible unless a very considerable time has passed since the formation of the feature. DUcker also assumed that smaller structure forms are being developed in the present climate. Mattick (1941) concluded from the study of the vegetation that the formation of these structure soils was essentially completed. We are here obviously very close to the lower limit of structure-soil formation, as was most clearly worked out by Budel (1937) . The great distinction between the structure -soil forms of the Riesen Gebirge and those of the British Isles and their great similarity with those of Scandinavia and the Arctic is not surprising. Certainly the clinaate of the Schneekoppe, with its annual mean of OC, is sonnewhat milder than inner Lapland (annual mean at Karasuando -2.9C) and substantially warmer than west Spitsbergen (annual mean -8.2C), and the annual fluctuation (15.6C) is substantially smaller than in the high latitudes, so that the lack of permafrost is understandable. But the course of frost alternation is very similar to the polar north. Table 1 shows the close similarity of the frost climates of the Schneekoppe (Riesen Gebirge) and west Spitsbergen. Only the short midsummer is frost-free, and in the long winter below- freezing days are so predominant that a deep freezing of the soil can occur. Frost alternation is predominant only during the short transition period in which the snow cover strongly hinders its penetration into the ground. A slight cooling of the climate of the Schneekoppe would produce almost complete agreement with Spitsbergen with respect to the frost alternation. Thus structure-soil formation in the Riesen Gebirge occurs essentially during the transition from winter freezing and from spring soil saturation, very different from the British Isles and southern Iceland. In the Riesen Gebirge, as in the Arctic, occasional small forms can originate during short- period frost alternation next to the prevailing large forms. The only observation which can be cited is a combined stone net, in which a secondary miniature stone net with a 20-30 cm mesh is formed inside a large stone ring (Mattick, 1941). Such forms have been described frequently from the Arctic (see above) . It appears from the somewhat sketchy accounts of Tiulina (1931) that the structure soils in the southern Urals correspond to the Riesen Gebirge type. In the other German Mittelgebirge which reach above the forest border (Bohmerwald, Schwarzwald, and Vosges Mountains), structure soils have not yet been recognized. In the forest belt, for example in the Oberharz and in Thuringer Forest, there are certainly many suggestions of string bogs. The boulder fields which are extensive over the forested slopes of the German Mittelgebirge are fossil forms of periglacial solifluction of the Pleistocene (Badel, 1937). On the other hand, forms of amorphous solifluction at 1300 m elevation in the Vosges have been carefully examined and described as originating under the present climatic conditions (Rempp and Rothe, 1934; 1935) . There are soil hummocks of the type of Icelandic " thufur", and on the slopes there is terracing of the turf soils which is commonly ascribed to animal trails and is called "Kuhgangeln" (Tirol), "Kuhtreien" (Switzerland), or "Sentiers de vache" (Vosges), The hummocks as in the Alps, are in part of purely biologic origin, such as overgrown stones, anthills, mule droppings, the effects of animal grazing, isolated Sphagnum hummocks ("miniature bogs"), which Issler described in 1909 (see Issler, 1942). But the authors mentioned have come to the conclusion that there are also 80 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES soil-hummock fields or hummock nets ("reseaux de buttes") which depend on soil freezing and frost-heaving phenoniena, and which grade into soil terraces or hummock rows on slopes with the help of solifluction. Although the forms involve only the humus - bearing soil layer, a definite sorting of material occurs; there is a very stone-poor and mobile fine soil under the hummocks, and a much more stable, stone-rich soil in the furrows between. The soil becomes uniform only At 10 or 20 cm beneath the surface of the furrows. The influence of water saturation and of the very common needle ice in the Vosges is an open question. The hummock formation is partly a physical process of frost movement, partly a product of the different vegetation ( Vaccinium shrub-heath on the hummocks, Nardus grass-heath on the furrows. ) "The formation of hummocks goes back in the beginning to both, but the effect of frost is intensified the more the hummocks grow"(l935). In March a stronger ice formation was observed in the hummocks than in the furrows. The growth of hummocks leads finally to a conversion to heather and to removal by water and wind. Also pasturing contributes to their destruction. That the hummock nets are not of biologic origin only is seen from the fact that they usually change into soil terraces on steep slopes, and that they are lacking where patches of snow remain a long time in the spring. In the soil terraces ("sentiers de vache") the authors mentioned differentiate three types: (1) Those at 1300 m, which are associated closely with the hummock nets, bear the same vegetation, and differ from them only in pattern, adapted to the slope. They are due to strong soil-frost action in places regularly stripped of snow by the wind. (2) Similar formations in the old sno'w depressions of cirques. They originate by gliding and settling because of the strong water saturation on the borders of the snow patches (nivation). (3) Those which extend down on steep slopes to lower elevations, to 600 m. Odum (1922), who described them as "terracettes" (Danish "Faarestier") , explains them by a combined effect of soil creep and turf spalling. These formations, like the second type, can no longer be designated as frost soils in the exact sense, although needle -ice formation may play a role in the turf spalling. In all cases, animal trails are not the only cause, but in some cases they contribute to the natural processes. 2. The mountain ranges of the New England states The structure soils which have been described in the last decade from the mountains of New England (Antevs, 1932; Leavitt and Perkins, 1935; Nichols, 1936; Goldthwait, 1939; Denny, 1940), show a rise in the lower limit from the coast of Maine (350 m) to the interior (Mt. Washington 1500 m) , similar to the rise inEurope, but the lower limit also rises from north to south. They occur also throughout on the crests above the forest border. This is not to say, however, that their origin in lower places is prevented solely by the vegetation, as Nichols and Denny assume. In many cases vegetation and structure soils may go back to the same climatic origins. According to the concurring statements of the observers, the structure soils of the mountains are miniature stone nets and stone stripes of 8-35 cm diam with an average of 15-20 cm. This formation is surprising, for the New England states, located on the eastern edge of the continent and affected by cold rain in spite of the southerly position, have an essentially cold continental climate, as in western and central Europe. It may not be compared with the north European climate, for the temperatures of the lowlands correspond in the winter somewhat to those of Finland, in the summer to those of southern France. For an explanation of the frost-soil type, the frost-soil climate of these zones of moderately high mountains must therefore be examined, and this is not possible at present. The forms suggest that short-period frost and very frequent frost-alternation are important. Probably these can occur only during the transitional seasons. But what is the time relation of frost alternation and absence of snow? A short-period origin is supported by the fact that structure soils can be formed rennarkably quickly. Goldthwait stated that on the Presidential Range at 1500 m elevation stone stripes had formed ane^w within a year. They are found there again and again in the neighborhood of the observation tower, which in summer is visited by crowds so that the soil in the vicinity is trampled. But in addition to these recent miniature stone nets there are fossil formations of distinctly larger size, which Denny assigns to the nnuch severer periglacial climate of the Pleistocene. In any case a precise examination of recent and glacial soil-flow phenomena and their lower borders in these mountains is particularly needed. X. THE MOUNTAINS OF TEMPERATE LATITUDES 81 3. Alps and Pyrenees A really extensive field for observation of structure soils exists today in the Alps, especially in the Central Alps, where the lower limit lies at about 2200 m ( see p. 7) . A glance over the material shows that the formations can be divided into two main groups according to locality and form. Most observations come from the debris areas and moraines of active glaciers which have been freed of ice for the first time in the last 100 years, partly since 1900, and which are not at all or only incompletely covered by vegetation. Especially numerous observations of this type were gathered by H. Kinzl (1928) in his studies of old glacier positions in very different parts of the Central Alps. The observations of Salomon (1929), Mattick (1941), and those of Mohaupt (1932) on the Alpein glacier belong predominately to this type. They lie at elevations of 2200-2600 m. There are also structure soils which are not on glacial terrain, but mostly at greater elevations, from 2700 m up to the windblown areas above the snow line at 3400 m. Mohaupt (1932) was the first to make detailed observations of these, well substantiated by pictures and drawings. But the examples described by Gignoux (1931) and the striped soils mentioned by Salomon also belong to this second group. In the structure soils of glacier terrain on level ground we have in general stone rings, stone nets, and soil spots [Erdflecken] , larger although less distinct than the arctic forms (Fig. 62) . They are due to heavy soaking of the glacial deposits by glacial melt water under poor drainage conditions. In the viscous to loose soft soil, not protected by a continuous plant cover, frost can have its full effect. The structure-soil forms are of the polar type and resemble somewhat those of the Riesen Gebirge and the Scandinavian high mountains. The diameter of the stone rings and nets ranges between 0.5 and 2 m. Stones with a platy shape stand on edge. As in those areas, combination stone nets also occur, with an especially coarse border and secondary small stone polygons 1-2 cm in diam (Kinzl). The forms have been observed also on very young soil which was deposited and uncovered by the glacier only 10 years before. In fact Kinzl has even shown that there are connmon structure soils on the morainic cover of active glaciers. Figure 63, published with his kind permission, serves as proof. In connection with the stone rings on the Pasterze Glacier, he notes very correctly that stone rings on glacier ice can originate in a completely different manner, namely by radial slumping of large stones on melting ablation cones, but in the exainple illustrated this definitely does not apply. In another case, where confusion with true structure soils is possible, there are broad stone stripes on fresh debris ^^S^ Figure 62. Indistinct stone net (large form) on the morainic terrain of the Schwarzensteinkees ( Zillertal Alps, 2115m). Photograph by C. Troll, August 1925. Figure 63. Structure soil (fine-soil center with sorted stone ring) on the 2-m thick moraine debris over the active Grabler glacier. Photograph byH. Kinzl, 19 August 1941. 82 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES bared by the glacier. The parts of the stone stripes on sloping ground show definite frost structures. If, on the other hand, they are flat ridges many meters broad in the direction of glacier movement, like the moraine belts in front of the Kannkogel glacier in Stubai, described by Lagally (1926, p. 139)* and compared in form to hunchbacks, then I might, after examination, consider these very indistinctly sorted stripes as formis of ground-moraine accumulation especially if they are on level ground where one could scarcely automatically ascribe the formation of stripes to soil frost. In contrast, the broad, strikingly well sorted stone structures found by Mohaupt (1932, p. 23) in front of the Alpein glacier are certainly true frost soils. Kinzl, after systematic excavations of stone rings, noted that the area of fines was very frequently underlain by large stones at shallow depth (i cm to 3 cm). As the polygon areas are distinctly domed in such cases and the sorting is as distinct as usual, it is certain that stronger frost heaving of the larger boulders is involved. The process is well known and easily understood. But here it demonstrates that these structure soils go back to the seasonal alternation of freezing, for short nightly frosts do not penetrate the ground deeply enough to form ice under the larger still sunken boulders and heave them up. Forms of this type, however, also point to the alternation of winter freezing and summer saturation. Of course similar forms can exist in the Alps away from a glacier, if the debris in an area of snow patches is very thoroughly saturated with water. FrOdin has described such a case from Pic du Midi in the Pyrenees at 2600 m, where he actually found frozen ground at a depth of 20-50 cm in August (1924, p. 39). But on the whole permafrost seems to be uncommon in the high Alps and high Pyrenees. Several authors suggest the possibility (Tarnuzzer, 1911; Waldbauer, 1921; Salomon, 1929; Gignoux, 1931) but actual observations are lacking. It seems that frost in association with structure soils has been found only by Allix (1923) in the French Alps at 3052 m elevation and in a unique form. Ice columns 20-30 cm thick and 75-100 cm deep extrude from flat depressions and around them the stony material is sorted according to size. The highest observed stone nets, from Mont de Lans in Oisans (Allix, 1923), also belong to this structure soil type. Moreover, the so-called "pavement soils", which exhibit no particular structure but show a mosaic-like stone pavement pressed into soft soil, resemble this type. They are formed under a very long-lasting snow cover, extending into the summer, through the continued effect of snow pressure, snow sliding (nivation) , water saturation, and perhaps also frost heave. In the high Alps they are found at lower elevations in front of the glaciers and also on the flattened ridges above 3 000 m. They were first described and named by Waldbauer (1921) from Maloja Pass; mentioned by De Martonne (1923) as "dallage de blocs" and by Stiny (1926) as "Steinplattenboden" in other places in the Alps; and finally considered under structure soils in the works of Kinzl (1928) and Salomon (1929). They are widespread also in the Scandinavian high mountains and in the Arctic, e. g. in Greenland (SOrensen, 1935). Certainly distinguishable from the type more commonly described from the Alps are structure soils which generally occur at great heights on normal debris soils not softened by glacier melt water or firn melt. In by far most cases they are miniature forms, but often show a very distinct sorting and are generally very poor in vegetation. Numerous examples of striped ground which Salomon ( 1929) observed in Engadine between 2500 and 2900 m were "miniature forms with a stripe width of a few decimeters at most. " The fine stone nets which Gignoux (1931) discovered on the south end of the Grand-Motte in the French Alps at 2800 m are definite miniature nets with a diameter of 10-20 cm. Miniature stone nets and stone stripes were reported by Mohaupt (1932) from different places in the East Alps, and from Fotscher valley (Stubai) and from the South Tyrolean Dolomites (Sella plateau and Puez group) at elevations of 2700-2850 m. Those of the Fotscher valley are a special case, since they have been formed under a thin periodic water cover. The most beautiful stone nets are those of Sella plateau with a constant width of 20-25 cm for the fine-soil area and 5-15 cm for the stone bands between. The most beautiful stone stripes are those of Col della Pierres in the Puez group. [♦Complete reference not given. ] X. THE MOUNTAINS OF TEMPERATE LATITUDES 83 These are distinguished by the small amount of fine soil, so that only small fine- soil stripes lie between the much broader stone stripes, and appear to have broken through the stone debris from beneath. They have been sorted out of a debris cover only 8-10 cm thick which lies over bedrock. Mohaupt has called them "soil stripes". Also remarkable here is the constant, 5-6 cm, width of the fine-soil stripes. The stone nets which W. Sander saw on debris 15 cm deep over bedrock on the Great Burgstall in the Pasterze (Hohe Tauern),and the stone nets and stripes which L. Krasser has found in the Silvretta (both above 3000 m) also belong to the miniature forms. All these forinations of the second group are known to us as the normal type in southern Iceland and in the tropical high mountains, and only as a rarity in Spitsbergen. Mohaupt himself has compared his stone nets of the Sella plateau with Poser's miniature stone nets. The soil-stripe groundwe recognize from Mt. Kenya (Fig. 42) ; they have been seen also in oceanic northwest Iceland (see p. 64 ) . There can certainly be no doubt that in the high Alps there are two very different types, the larger polar type predominant at lower elevations above 2200 m, and the tropical miniature type prevailing at greater elevations above 2700 m. How is this proximity to be explained? Wherein do the two types differ genetically? The arctic type, as we have seen, is associated with strong water saturation of the subsurface during time of thaw. The sorting extends more deeply and the frosts which cause it extend more deeply into the soil than seasonal freezing. Large stones intensify the other- wise moderately good sorting. The miniature forms, on the other hand, are formed in a thin surface layer of soil. Their particularly clear forms, the great parallelism of stripes, and the constancy of the inside measurements indicate an origin in short- period, weather-controlled, or daily alternation of freezing, as does the shallow depth. The penetration of fines through the coarser debris in the soil stripes (with the formation of soil buds [Erdknospen] , soil columns [Erdsaulchen] , or "worm-earth" [Wurmerde] is accomplished demonstrably by nightly needle -ice frost heaving. The climatic prerequisites for the two types are also certainly different. Evidently the relation of the time of frost alternation to the time of snow cover is the decisive factor . The diagrams for Schneekoppe, Zugspitze, and Sonnblick in Table I show that, at elevations of 2000-2500 m, the alternation of positive and negative air temperatures occurs in spring and fall, when the snow cover hinders their penetration into the soil. At greater elevations, the time of frost alternation comes during the summer when the ground at these elevations is snow-free and the soil can freeze and thaw frequently. There is also, however, an edaphic relation. The miniature forms of the high Alps, at least those clearly formed, have originated for the most pa.rt over bedrock in only a shallow debris cover. Gignoux assumes a water-bearing layer at slight depth for his miniature nets, in which, strange to say, he did no excavations despite repeated visits. The structure soils of the Sella plateau lie in debris of 0-30 cm thickness over stone flats, those of Col della Pierres in debris 8-10 cm thick over rock. Under such conditions we have even found excellent miniature forms on the Baltic Sea islands of Oland and Gotland, and this "nonclimatic intensification" should play a role in the high-Alpine miniature forms. But frost climate is still a prerequisite also, namely a snow-poor frost-alternation period, which occurs on the Baltic Sea islands when the snow is blown off in winter, in the high Alps in the summer, and in the tropical high mountains over the whole year. Salomon (1929, p. 14) ascribed the stone stripes in the Alps to melt-water rills, as did Poser for the miniature striped soil in Iceland and Spitsbergen. As already shown for Iceland and the tropical mountains, melt-water rills are not necessary and, at best, are probably only an accessory cause in some cases. As there are many occurrences in the tropics in which stones do not lie in furrows but rest loosely on the fine soil , so in the Alpine forms the fine soil frequently occurs so sparsely on the surface that the stone stripes do not form furrows but constitute the fundamental ground layer. But the transition from stone stripes into stone nets especially is against the idea of melt-water rills as cause. The entire picture of miniature forms clearly shows that the regular parallel miniature stripes are a result of interaction of very frequent radial movement (microsolifluction) and general slope movement (slope solifluction) . 84 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Besides the frost texture soils, all the forms of amorphous solifluction, which originate with the help of humus soil and turf soil and under heavy vegetation cover, are in full development in the Alps. The simplest examples on level ground are the soil hummocks (Solch, 1922) or'hummocky ground of the type of Icelandic "thufur' , which have a wide distribution especially in the crystalline Alps. On slopes these "stationary rhythms" are disturbed by solifluction and change into "translation rhythms": ridged ground (stone ridges), debris ridges, turf ridges, migrating stone ridges, terraces, garland soils, cow paths, debris polygons and tongues, stone streams, etc. Such forms are especially well developed in the Styrian border mountains, on the Koralpe, the Stubalpe, and the Gleinalpe with their broad flat ridges and gentle slopes on crystalline bedrock. Their great extent and their significance for general land denudation above the forest limit are shown from the reports of Salch ( 1 922) and Stiny ( 1 93 1 ) . The lower limit of recent soil-flow phenomena there is set at 1850 m, or 350 m higher than in the Riesen Gebirge and 500-600 m higher than in the high Vosges. Solch speaks of "net-like and lattice -like swellings of the soil which occur in sandy brown loam with small stones and are surrounded by rings of plants. " An especially beautiful example of purely mineral soil hummocks was found by von Gallwitz (personal communication) on the 2167 m-high Dobratsch near Villach in Kfirnten [Carinthia] . The little hummocks, about |- m high, consist of stone-free loam, just as the other soil. The net-like furrows running between them have a breadth of a few cm and are overgrown with grass like the hummocks. Such earth swells play a special role if they are built entirely or in part of peat. They were described from Switzerland by Stager (1913) as "hummocky terrain". More recently Gams (1941) has summarized them for the central East Alps. They occur from elevations of 2200 to 2750 m. For the highest "dwarf hummock peat bog", reproduced in Figure 64, the topographic relation to solifluction ridges, stone streams, and pavement ground is shown in a sketch. In the text and with the name "peat hummock bog" Gams shows definitely the relation to the larger mounds produced by cores of permafrost and to the palsen bogs of Lapland. However, if we wish to establish the great importance of peat in the name, then a distinction should be made between "peat mounds" or "palsen" and "dwarf hummock peat ground. " In the Alps we can very frequently observe the cracking open of these hummock soils according to the pattern of the northern crater soil (BergstrOm, 1912). However, this cracking does not occur as swelling-loam eruptions, according to my experience, but through needle -ice frost heaving ( see Fig. 8) . On gentle slopes, small terraces develop from these frozen soils, with arcuate turf ridges and a more or less bare terrace surface; the most suitable designation is "garland soil" ( see Fig. 65) . It is not possible here to describe all forrns of amorphous solifluction in the Alps. Only two especially good examples are presented. Figure 66 shows the the structure of a typical high-Alpine fine-earth garland soil from the Hohe Tauern (2300 m) . Here we have a case of soil flow in an almost stone -free weathering soil in which the relationship of the different horizons of weathering soil is not completely destroyed. The individual soil horizons lie in recumbent folds, and on the face of the terraces the upper soil layers are overturned and thickened. The expression "turf ridges ( Tarnuzzer) is thus thoroughly applicable. The total displacement in such cases, as Beskow (1931) has claimed, is greatest on the surface, as a result of the gliding of the upper soil layers over the (still frozen?) layers. It is known that during such processes large blocks can move rapidly and can buckle up turf ridges in front of them. The vegetation cover differs even where the flat surfaces and the ridges are uniformly covered by turf, which rests only on fine earth: Curvuletum on the flats, herbaceous Salicetum on the ridges. The contrast is much stronger when the terrace surfaces show frost-heaving phenomena ( see Fig. 8) , or vifhere a sharp separation occurs between stone debris and turf-covered soil ridges. The latter case is typical of the garland soils of the Kalkalpe. Figures 67 and 68 show an unusually beautiful example of this type, which G. Wagner observed on the largely dolomitic rubble at the Goppinger Hut in the Lechtal Alps (2300 m) and kindly placed at my disposal. They are similar to the "debris facets" described by Gbtzinger (1913) and Baedecker (1922) in the limestone plateaus of the Raxalpe and the Schneeberg. These also are turf ridges, but in a very different fornn from the earlier example. One has the X. THE MOUNTAINS OF TEMPERATE LATITUDES 85 Figure 64. Dwarf hummock peat bog on the Delorette trail above the Hochjochhospiz at 2740 m. (Otztal Alps) View of the Kreuzspitze. Photograph by C. Troll, 31 July 1941. ,. >*^-. _ / ; — — ^.^ ^.^^^y ^^ ^,i^ v^,.c j.-,..i.aoai.iit^d.i.ion uer Mineralbaden Schwedens (Mechanical analysis and classification of the mineral soils of Sweden ) , Int. Mitt, f. Bodenkunde. vnl.TT. ' ' — ' ~ Auer, VainO (1920) Cber die Entstehung der Strange auf den Torfmo oren (The origin of raised strips in peat bogs ), Acta forestalia fennira (h^1=;^i.;) ..„i ii ^'— p. 1-145 (text in German) . Z ~~ (1923) Moorforschungen in den Wal dgebieten von Kuusamo und KnoloiSrvi ( Investigations of bogs in the forest regions of Kuusamo a nd Knoloiarvi^ — ETit forest, fenn. (Helsinki) , vol. VI. ~ ' [* Where the original title is not available, the English translation only is given in parenthesis. ] ^ & ^ 1-00 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES AueriVainS (1927) Untersuchungen (Iber die Waldgrenzen und Torfbade'n in Lappland ( investigations of the forest boundary and peat soils in Lapland ) , Communciations ex Instituto Quaestionum Forestalium Finlandiae editae (Helsinki), vol. 12. Baedecker, D. (1922) BeitrSge zur Morphologic der Gruppe der Schneebergalpen ( Contribution to the morphology of the Schneeberg Alps ), Geogr. Jahresbericht aus Osterreich, vol. 12. Baranov, I, la. (1938) O metodike sostavleniia merzlotnykh kart (Methodology in permafrost charting ) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, vol.6, p. 107-125 ( text in Russian) . (Referate (Abstracts) Neues Jahrbuch f. Mineralogie, Geologie und Palaeontogie, vol. II, 1940. ) (1938) Nabliudeniia nad zamerzaniem vody (Observations on water freezing ) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, vol. 6, p. 167-171 (text in Russian) . (Ref. N. Jahrbuch f. Min. usw. , vol. II, 1940.) Beechey, F. W. (1831) Narrative of a voyage to the Pacific and Bering Strait . London: H. Colburn and R. Bentley, 742p. Behlen, H. (1930) Eine neue Theorie der Struktur- (Steinring- Steinnetz-oder Brodel-) BSden, unter besonderer Berdcksichtigung von Spitzbergen . . (A nevf theory on structure soils with special reference to Spitsbergen. . . ) . Zeitschrift Deutschen geol. Gesellschaft, vol.82, p. 635-636. Behr, Fritz M. (1918) tjber geologisch wichtige Frosterscheinungen in gemSssigten Klimaten (Geologically important frost phenomena in temperate climates ), Zeitschrift Deutsch. geol. Ges. , vol.70, p. 95-117. 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(1934b) Einige wesentliche Charakterztlge der nordwestdeutschen Diluvialmorphologie (Some essential distinctive characteristics of northwest German Quaternary morphology) , Abhandl. Naturwissenschaftlicher Verein (Bremen), vol.29. 1941) "Das Diluvium. " In Das KSnozoikum in Niedersachsen ("The Quarternary. " In The Cenozoic in lower Saxony) , Geol. u. Lagerstatten Niedersachsens (Oldenburg) , Teil III. Douville, Robert (1917) Sols polygonaux ou reticules (Polygonal or reticulated soils ). La Ge'ographie, anne'e 31, p. 241-251 (text in French) . Dranitsyn, D. A. (1914) O nekotorykh zonal'nykh formakh rel'efa krainego severa ( Some zonal forms of the relief of the far north ) , Pochvovedenie, vol.16, no. 4, p. 21-68 (text in Russian and French) . REFERENCES 103 Dubois, A. (1911) La region du Mont Lusitanla au Spitzberg (The Mount Lusitania region of Spitsbergen ) , Bulletin, Societe neuchateloise de geographic, t. 21 , p. 1 -77 ( text in French) . Dtlcker, A. (1933a) Frostschub und Frosthebung (Frost thrust and heave ), Centralblatt fUr Mineralogie, Geologie und Palaontologie , Abt. B, p. 441-445. (1933b) "Steinsohle" oder "Brodelpflaster" ("Stone floor" or "Brodel pavement" ) , Centralblatt fUr Mineralogie, Geologie und Palaontologie, Abt. B (1933c) Die "Windkanter des norddeutschen Diluviums in ihren Beziehungen zu periglazialen Erscheinungen und zum Decksand (Ventifacts of the north German Quaternary in their relations to the periglacial phenomena and to the cover sand ) , Jahrb. Preuss. Geol. L. -A. , vol. 54. (1937) Ober Strukturbaden im Riesengebirge (Structure soils in the Riesen Gebirge ) , Zeitschrift Deutsch. geol. Ges., vol.89, p. 113-129. (1939a) Neue Erkenntnisse auf dem Gebiete der Frostforschung (New knowledge in the field of frost investigation ) , Die Strasse, (Berlin) , vol. 1 7. (1939b) Die Frostgefahrlichkeit vulkanischer Lockergesteine (The frost susceptibility of porous volcanic rocks ) , Die Strasse, vol. 1 7 1939c) Der Einfluss von SalzlSsungen auf das Gefrieren von Boden ( Influence of salt solutions on soil freezing ) , Die Strasse, vol. 17. (I939d) Untersuchungen tlber die frostgefSlhrlichen Eigenschaften nichtbindiger BSden (Investigations on the frost-susceptible properties of cohesionless soils ) , Forschungsarbeiten aus dem Strassenwesen, vol. 17. Berlin: Volk u. Reich Verlag, 79p. (1939e) Beziehungen zwischen Frosthebung und Gef riertemperatur ( Relations between frost heaving and freezing temperature ) , Die Strasse, vol. 17. (1940) Frosteinwirkung auf bindige BSden (Frost action effects on cohesive soils ) , Strassenbau-Jahrbuch. Berlin: Volk u. Reich Verlag, p. 111-126. 1942) tjber "Bodenkolloide" und ihr Verhalten bei Frost ("Soil colloids' and their behavior when subjected to frost action) , "Der Bauingenieur", vol. 23, p. 235-237. Du Rietz, G. E. (19253.) Die regionale Gliederung der skandinavischen Vegetation ( Regional classification of Scandinavian vegetation ) , Svenska vaxtbiol. sallskapet (Uppsala), Handlingar, vol. VIII. 1925b) GotlS.ndische Vegetationsstudien (Studies of the vegetation of Gotland ) , Svensk^ vaxtsociolog. sallskap. , Handlingar, vol.11. 1921) Vegetationen och det Olandska landskapet (Vegetation and landscape of QJand ) , Svensk turistfSrening (Stockholm), Arsskrift. Dzens-Litovskii, A. I-. (1938) Mineral'nye ozera v usloviiakh vechnoi merzloty ( Mineral lakes under permafrost conditions ) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, vol. 6, p. 79-105 (text in Russian with English summary) (Ref. N. Jahrb. f. Min. usw. , II, 1940). Eakin, Henry M. (1916) The Yukon-Koyukuk Region Alaska , U. S. Geological Survey, Bulletin 631, "Washington. Ebers, Edith (1939) Zur Kultivierung der Buckelwiesen bei Mittenwald (Cultivation of hummock meadows in the Mittenwald ) , Blatter f. Naturschutz (Munich), 22. Jg. .4. Edelman, C. H. ; Florschtttz, F. ; and Jeswiet, J. (1936) tJber spatpleistozane und friihholozane kryoturbate Ablagerungen in den astlichen Niederlanden (Late" Pleistocene and early recent cryoturbate deposits in eastern Netherlands ), Verb. Geol. -Mijnbouwkundig Genoot. v. Nederl. en Kolonien, Geol. -Serie, vol.11, 4. 1-04 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Egorov, S. F. (1931) Rel'ef i nanosy vostochnogo. poberezh'ia Bol'shoi Imandry ( Relief and alluvial"deposits of the eastern shore of Bol'shaya Imandra) ^ Trudy, Geombrfologicheskii institut, Akademiia nauk SSSR, vyp. 1, p. 173-245 ( text in Russian) . Elton, Ch. S. (1927) The nature and origin of soil polygons in Spitsbergen, Quarterly Journal, Geological Society of London, vol. 83, p. 163-194. Ermilov, I. la. (1934) O vliianii vechnoi merzloty na rel'ef (The influence of perma- frost on the relief ), Izvestiia Gosudarstvennogo geograficheskogo obshchestva, vol. 66, no. 3, p. 377-388 (text in Russian) . Fedosov, A. E. (1938) Novyi metod laboraturnogo opredeleniia ob"ema zamerzaiushc h- ego grunta (A new laboratory method for the determination of the volume of ground during freezing ) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, vol. 6, p. 173-176 (text in Russian). (Ref. N. Jahrb. f. Min. , Ref . II, 1940, p. 56/7.) Feilden, H. W. (1896) Notes on the glacial geology of arctic Europe and its islands . Part II, Quarterly Journal of the Geological Society, vol. 52, p. 721-747. Fellman, Jacob (1906) Anteckningar under min vistelse i Lappmarken (Notes on my visit in Lapland ) . Helsinki. Fickeler, P. (1926) Die winterlichen Eisbildungen in Mittelasien (Winter ice formations in central Asia ) , Petermanns geogr. Mitt. , vol. 72, p. 247-253. Firbas, F. ; and Grahmann, R. (1928) tlber jungdiluviale und alluviale Torflager in der Grube Marga bei Senftenberg (Niederlausitz) (Recent diluvial and alluvial peat deposits in the Marga pit at Senftenberg ) , Abhandlungen, SSchsische Akademie der Wissenschaften, Math. -Phys. Kl. , vol.40, 4p. Flohr, E. Fr. (1935) Beobachtungen (Iber die Bahnen der Schneeschmelzwasser im Riesengebirge,Ein Beitrag z. Problem der Blockrinnen ( "Steinstreifen") (Observations on snow melt water channels in the Riesen Gebirge, A contribution concerning the problem of stone stripes ), Zeitschrift Ges. f. Erdkunde, Berlin, p. 353-369. Fltickiger, O. (1934) Schuttstrukturen am Kilimandscharo (Debris structures on Kilimanjaro) , Petermanns geogr. Mitt., vol.80, p. 321-324, 357-359. Fries, Th. C. E. (1913) Botanische Untersuchungen 1910-13 im nOrdlichsten Schweden ( Botanical investigations in northernmost Sweden, 1910-13 ), Akad. Abhandlung, Uppsala. (1917) tjber die regionale Gliederung der alpinen Vegetation der fennoskandischen Hochgebirge (Regional classification of the Alpine vegetation of the Fennoscandian high mountains ) , Vetenskapliga och praktiska undersSkningar i Lappland, Flora och Fauna, vol. IV. Fries, Th. M. (1902) Nigra ord om rutmarken pS. Spetzbergen och Beeren-Eiland ( A few words on the polygonal soils of Spitsbergen and Bear Island ) , Geologiska fSreningens (Stockholm) , FBrhandlingar, vol.24 (text in Swedish) . and Nystrom, C. (1896) Svenska Polarexpeditionen, 1868 (Swedish polar expeditions , 1868). Stockholm. and Bergstram, E. (1910) Nigra jaktagelser Sfver palsar och deras fSrekomst i nordligaste Sverige (Some observations of pingos and their appearance in northern Sweden ), Geol. fbren, , FBrhandl. , vol.32, p. 195-205 (text in" Swedish) . Frttdin, John (1914) Geografiska studier i St. Lule Alvs kallomride (Geographic studies in the source region of the St. Lule River ) . Sveriges geologiska undersSk-oing (Stockholm), Arsbok7, ser. C, nr. 257. • (1915) Slutord angiende frostverkningar i flytjordsnnark (Concluding remarks on frost^action effects in solifluction ground) , Geol. fSren., FSrhandl. .vol. 37. REFERENCES 105 FrOdin, John (1918) tJber das Verhaltnis zwischen Vegetation and Erdfliessen in den alpinen Regionen des schwedischen Lappland (The relation between vegetation and solifluction in the Alpine regions of Swedish Lapland ) , Medd. frin Lunds Univ. Geogr. Institution, Ser. A, Nr. 2 ( Lands Univ. Arsskrift, N. F. Avd. 2, vol. 14, Nr. 24, p. 1-32). Lund u. Leipzig. (1924) Les Associations vegetales des Hauts Paturages Pyreneens . Etude sur leurs affinite''s et sur leurs rapports avec les mouvements du sol dans les Pyre''ne''s (Plant associations in the high pastures of the Pyrenees ). Bull. Soc. d'histoife natur. de Toulouse, t. LII, p. 21-53 (text in French) . Fujiwhara, S. (1928) ( Note on the structure soils on Mt. Norikura (central Japan )), Tirigaku-hyoron, vol. IV Gams, H. (1941) Torfhagelmoore in den Zentralalpen ( Peat-hummock bogs in the central Alps ) , Naturw. Monatsschr. , "Aus der Heimat ", 54. Jg. Garcia-Sainz, Luis (1941) Las fases epiglaciares des Pirineo espanol (Epiglacial aspects of the Spanish Pyrenees ) , Estudios geograficos, vol.11, No. 3, Madrid. Gellert, J. F. , and SchuUer, A. (1929) EiszeitbSden im Riesengebirge (Pleistocene soils on the Riesen Gebirge ) , Zeitschrift Deutsch. geol. Ges., vol.31. (1933) Diluvialer Frostbaden im Oberbaden (Quaternary frost soils in Oberbaden ) , Zeitschrift Deutsch. geol. Ges., vol.85. Gerasimov, I. P., and Markov, K. K. (1939) Lednikovyi period na territorii SSSR ( Glacial period in the territory of the USSR ) , Moscow-Leningrad: Akademiia nauk SSSR, 462p (text in Russian with English summary) . Gignoux, M. (1931) Les sols polygonaux dans les Alpes et la genese des sols polaires ( Polygonal soils inthe Alps and the origin of polar soils ) , Annales de geographie, vol. 40, p. 610-619. Given, G. ( 191 5) KoUoidale Eigenschaften des Tones und ihre Beeinflussung durch Kalksalze (Colloidal properties of clay and their conditioning by calcium salts ) , Diss. GBttingen. Gladtsin, I. N. (1928; 1936) Kamennye mnogougol'niki (Stone polygons) , Izvestiia Gosudarstvennogo geograficheskogo obshchestva, tom 60, p. 305-322; tom 68, p. 811-843 (text in Russian) . Glazov, N. V. (1939) K metodike izucheniia degradatsii vechnoi merzloty (Method of studying the degradation of permafros t) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, p. 155-161 (text in Russian). (Ref. N. Jahrb. f. Min. usw. , II, 1940). Gokoev, A. G. (1939) O bugrakh vspuchivaniia i gidrolakkolitakh v Kazakhskoi stepi ( Frost mounds and hydrolaccoliths in the Kazakh Steppe ) , Izvestiia Vsesoiuznogo geograficheskogo obshchestva, vol.71, p. 541-546 (text in Russian). Goldthwait, R. P. (1939) Glacial geology of the Presidential Range, Doctor's Thesis, Harvard Univ. Gorodkov, B. (1928) Krupnobugristye torfianiki i ikh geograficheskoe rasprostranenie ( Geographical distribution of peat bogs with large mounds ), Priroda, vol. 17, p. 599-601 (text in Russian) . (1930) ( Soils of the tundra plain in the USSR ), II. Int. Congr. of Soil Science. Moscow-Leningrad. Pochvovedenie, vol.25, no. 4, p. 87-104. (1932) Vechnaia merzlota v Severnom Krae (Permafrost in the Far North) Leningrad: Akademiia nauk SSSR. GOtzinger, G. (1913) Zur Entstehung und OberflSchengestalt der Plateaus der Schnee- und Vlitschalm (Formation and surface form of the plateaus of Schnee- und Vlitschalm ) ; Urania, vol. 6, Wien. 106 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Gregory, J. W. (1927) Comment on Elton's report (see Elton, 1927), Quarterly- Journal, Geological Society oif London, vol.83. (1930) Stone polygons beside Loch Lomond, Geographical Journal (London), vol.76, p. 415-418. Grigor'ev, A. A. (1925) Die Typen des Tundra-Mikrorelief s von Polar-Eurasien , ihre geographische Verbreitung und Genesis (The types of tundra microrelief in polar Eurasia, their geographical distribution and genesis ), Geographische Zeitschrift, vol.31, p. 345-359 (text in German) . (1925) Zur Geomorphologie der Bolschemelskaja Tundra (On the geomorphology of the Bol'shezemel skaya Tundra ), Ceitschrift Gesellschaft fttr Erdkunde (text in German). (1930) Vechnaia merzlota i drevnee oledenie (Permafrost and ancient glaciation ) ■ In: Vechnaia merzlota, Sbornik. Materialy Komissii po izucheniiu estestvennykh proizvoditel'hykh sil Soiuza, Akademiia nauk SSSR, no. 80, p. 43-104 (text in Russian) . Gripp, K. (1926) trber Frost und Strukturboden auf Spitzbergen (Frost and structure soil in Spitsbergen) . Zeitschrift Gesellschaft f. Erdkunde (Berlin), p. 351-354. (1927) Beitrage zur Geologie von Spitzbergen (Contributions to the geology of Spitsbergen) , Abhandlungen aus der Gebiete der Naturwissenschaften, Naturwissenschaftlicher Verein (Hamburg), vol.21, nos. 3-4, p. 1-38. (1929) Glaziologische und geologische Ergebnisse der Hamburgischen Spitzbergen-Expedition 1927 ( Glaciological and geological results of Jhe Hamburg Spitsbergen-Expedition 1927 ), Abhandl. Gebiete Naturw. , Naturwiss. Verein, vol. 22. (1930) Gletscher und Bodenfrost, rezent und diluvial (Glaciers and ground frost, recent and diluvia l) , Geolgische Rundschau, Bd. 21 , p. 35 1 -352. (1933) Geologie von Hamburg in seiner nSheren und weiteren Umgebung ( Geology of Hamburg in its nearer and farther environs ) . Hamburg. 1939) Der Oberflachenabtrag im Alt-Diluvium und seine Bedeutung ftlr das Vorkommen palS-olithischer- Funde (Surface erosion in the early Quaternary and its significance for the occurrence of Paleolithic discoveries) , "Offa", no. 4, vol. II. Ber. u. Mitt. d. Mus. vorgeschichtl. Alterttimer in Kiel, Neumtinster o. J. and Simon, V/ilh. Georg (1933) Experimente zum Brodelbodenproblem ( Experiments on the Brodel soil problem ), Centralbl. Mineralogie usw. , Jg. 1 933, Abt. B. p. 433-440. (1934) Die experimentelle Darstellung des Brodelbodens (The experimental representation of Brodel soil) . Die Naturwissen- schaften, vol.22, p. 8-10. (1934) Nochmals zum Problenn des Brodelbodens ( Additional remarks on the problem of Brodel soil ) . (Centralbl. Mineralogie usw. Abt, B, p. 283-286,) GrOnlie, O. T. (1924) Contributions to the Quaternary Geology of Novaya Zemlya , Rept. of Scientific Results, Norske Novaja Zemlia exspedisjon, 1921, Nr.21, Kristiania. Gruner, M. (1914) Die Bodenkultur Islands (Soil cultivation in Iceland ), Arch f. Bionthologie, III, 2. Gumenskaya, O. (1936) ( influence of moisture and temperature on the strength of frozen ground) , Trudy Komissii po izucheniu vechnoi merzloty, Akademiia nauk SSSR, vol. 2. REFERENCES 107 Gusev, A. I. (1938) Tetragonal'nye grunty v articheskoi tundre (Tetragonal ground in the arctic tundra ) , Izvestiia Gosudarstvennogo geograficheskogo obshchestva, vol. 70, p. 377-385 (text in Russian) . Gtlssfeldt, P. (1888) Reise in den Anden von Chile und Argentinien (Journey in the Andes of Chile and Argentina JT Berlin, p. 3 14. Hallen, K. (1913) UndersSkning af en frostknSl (pals) & KaitajSnki myr i Karesuando socken (Investigation of an icing mound in the KaitajSnki marsh in Karesuando country) , Geol. fOren., FSrhandl. , Bd. 35, p. 81-87. Hamberg, Axel (1905) Till fr&gen om forekomsten af alltid frusen mark i Sverige ( On the question of permanently frozen ground in Sweden ), Ymer 1904 (Stockholm) . (1915) Zur Kenntnis der VorgSnge imi Erdboden beim Gefrieren und Auftauen (Soil processes during freezing and thawing) , Geol. fSren., FSrhandl. , Bd.37, p. 583-619. Hartz, N. (1895) "Ostgr^nlands vegetationsforhold (Vegetation of East Greenland )," Medd. om Gr^nland, vol. XVIII (text in Danish) . Hauser, C. (1864) Der vordere Selbsanft (The frontal Selbsanft ) , Jahrb. Schweiz. Alpenclub, vol. 1 . Hawkes, L. (1924) Frost action in superficial deposits, Iceland . Geological Magazine vol. 16, p. 509-513. Hay, Thomas (1936) Stone stripes, Geographical Journal (London), vol.87, p. 47-50. ( 1937) Physiographical notes on the UUswater area , Geogr. Jour. vol. 90. Heim, Arnold (1936) The glaciation and solifluction at Minya Gongkar . Geogr. Jour. vol. 87. Heim, A. , and Gansser, A. (1939) Central Himalaya, Geological Observations of the Swiss Expedition 1936. Denkschr. , Schweiz. naturf orschende Gesellschaft (Zurich) vol. 73, Abh. 1. Hellaakoski, A. R. (1912) Beobachtungen Uber die geomorfologischen Einflttsse der Gefriererscheinungen (Observations on the geomorphological influence of frost phenonnena ) . Helsinki. ( Text in Finnish with German abstract) . Herschel, J. F. W. (1883) Notice of a remarkable deposition of ice round the decaying stems of vegetables during frost . Philosophical Magazine, vol. 2. Hesselman, Henrik (1907) Studier ofver skogsv^xt p& mossar (Studies of tree growth on bogs) , (Medd. frdn Statens Skogsfbrsaksanstalt.vol. 3, 190 6) Skogsv9.rdsfSren. Tidskr. , vol.5, no. 1, p. 25-47 (text in Swedish) . (1908) Vegetationen och skogsvaxten p3. Gotlands hallmarker ( Vegetation and tree growth on the shallow soils of Gotland ) . Skogsv^rdsfaren. Tidskr. (Stockholm). (1915) Om farekomsten af rutmark p& Gotland (The occurrence of polygon fields in Gotland ) , Geol. faren. (Stockholm), Forhandl. , Bd.37, p. 481 -492. Hitchcock, C. H. , ed. (I96I) Geology of Vermont , vol.1, p. 63, Fig. 25. Hobbs, W. E. (1910) Soil stripes in cold humid regions, and a kindred phenomenon , Michigan Acad, of Science (Lansing, Mich.), Report 12, p. 51-53. - (1911) Characteristics of existing glaciers. New York: Macmillan Co. , 301p. Hogbom, A. G. (1905) Om s.k. "jaslera" och om villkoren far dess bildning (On the so-called "jaslera" and the condition for their foundation ), Geologiska fBreningen (Stockholm), FBrhandlingar, Bd. 27. HBgbom, B. (1909) Einige Illustrationen zu den geologischen Wirkungen des Frostes auf Spitzbergen (Some illustrations of geological effects of frost action on Spitsbergen ), Bull. Geol. Inst. Upsala Univ. , vol. 9, 1908-9. 108 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES HOgbom, B. (1914) Uber die geologische Bedeutung des Frostes (The geological significance of frost ) , Bull Geol. Inst. UpsalaUniv. , vol. XIl! (1926) Beobachtungen aus Nordschweden (Iber den Frost als geologischen Faktor (Frost as a geological factor in north Sweden ), Bull. Geol. Inst. Upsala Univ., vol. XX, p. 243-279. Hollingworth, S. E. (1934) Some solifluction phenomena in northern part of Lake District , Geol. Assoc. London, Proceedings, Pt. 2. Holmquist, P. (1897) Mechanische StBrungen und chemische Umsetzungen in dem BSnderton Schwedens (Mechanical disturbances and chemical changes in the banded clay of Sweden} ,Bull. Geol. Inst. UpsalaUniv., vol. III. Holmsen, Gunnar (1913) Spitsbergens jordbundis (Ground ice in Spitsbergen ), Norske geografiske selskabs, Aarbog, vol. XXIV ( 1912-13) , 150p. (text in Norwegian with German summary) . (1915) Om jordlags langsomme glidning, solifluktion (Solifluction, slow slipping of earth layers ), Norske geografiske selskabs, Aarbog, vol. XXV (1913-14) (text in Norwegian) . Howe, E. (1909) Landslides in the San Juan Mountains, Colorado , U. S. Geological Survey Prof. Paper, Nr. 67. Hudino, Yonekiti (1933) Thermal convection of liquid, laden with some powder, Report of the Aeronautical Research Institute, Tokyo Imperial University, vol. VII, no. 15. Hueck, K. (1939) Botanische Wanderungen im Riesengebirge (Botanical trips in the Riesen Gebirge ) , Pflanzensoziologie, vol.3, Jena. Hustich, I. (1939) Notes on the coniferous forest and tree limit on the east coast of Newfoundland-Labrador , Acta geographica (Helsinki) , vol. 7, no. 1 . Huxley, J. S. (1925) Les "sols polygonaux'' et I'evolution des phe^nomenes de denudation dans les pays arctiques (Polygonal soils and the evolution of denudation phenomena in arctic regions ), Annales de geogr. , vol.34, p. 60-62 (text in French). Huxley, J. S. , and Odell, N. E. (1924) Notes on surface markings in Spitsbergen , Geogr. Jour., vol.63, p. 207-229. lanovskii, V. K. (1933) Ekspeditsiia na reku Pechoru po opredeleniiu iuzhnoi granitsy vechnoi merzloty (Expedition along the Pechora River to determine the southern permafrost boundary )] Trudy Komissii po izucheniiu vechnoi merzloty, Akademiia nauk SSSR, vol.2, p. 65-119 ( text in Russian) . Imamura, G. ( ? ) Geomorphology of the Japanese high mountains, Proceedings of the Imperial Academy, vol. 10. Issler, E. (1942) Vegetationskunde der Vogesen (Vegetation in the Vosges) , Pflanzensoziologie, vol. 5, Jena. Ivanov, I. M. (1931) O pochvennykh obrazovaniiakh v Arktike (Soil formation in the Arctic) , Trudy Instituta po izucheniiu severa, vol.49, p. 140-155 (text in Russian ■with German summary) . Iwan, W. (1937) Ober Lttss und Flugsand in Island (Loess and eolian sand in Iceland ) , Zeitschrift Ges. f. Erdkunde, Berlin. Jaeger, Fritz (1909) Forschungen in den Hochregionen des Kilimandscharo (Investiga- tions in the high regions of Kilimanjaro ) , Mitt, aus den Deutsch. Schutzgebieten, vol. 22. Johansson, Simon (1914) Die Festigkeit der Bodenarten bei verschiedenem Wassergehalt, nebst einem Vorschlag zu einer Klassifikation (Strength of soil types at different moisture content, including a proposed classification) , Sver. geol. undersakn. , Arsbok, vol. 7, ser. C. , 256p. REFERENCES 109 Jung, Erhard (1931) Neue Experimentaluntersuchungen Hber die aggregierende Wirkung des Frostes auf dem Erdboden (New experimental Investigations on the aggregating effect of frost on soil ), KoUoidchemische Beihefte, vol.32, p. 320-373. (1932) Weitere Beitrage zur aggregierenden Einwirkung des Frostes auf den Erdboden (Further notes on the aggregating effect of frost on soil ), Zeitschrift fur Pflanzenernahrung, Diingung u. Bodenk. , A., vol.24, p. 1-20. Jugowiz, R. (1908) Wald und Weide in den Alpen (Forest and pasture in the Alps) . Wien. Kachurin, S. P. (1938) Me.rzlotnye i geomorfologicheskie nabliudeniia v ust'e reki Anadyr' v 193 5g (Permafrost and geomorphological observations at the mouth of the Anadyr' River in 1935 ) , Trudy Komiteta po vechnoi merzlote, Akademiia nauk SSSR, vol.6, p. 3-61, (text in Russian). (Ref. N. Jahrb. Min. , vol. U, 1940). Kats, N. la. (1930) Zur Kenntnis der Moore Nordosteuropas (Knowledge of the bogs of Northeast Europe ) , Botanisches Zentralblatt, Beiheft, vol.46. Kaufmann, Henning (1929) Rhythmische Phanomene der ErdoberflSche (Rhythmic phenomena on the earth surface ) . Braunschweig: Friedr. -Vieweg u. Sohn. Keilhack, K. (1927) Uber Brodelboden im Taldiluvium bei Senftenberg und (Iber das Alter der sie begleitenden Torfmull- und Faulschlammablagerungen (Brodel soil i n valley diluvium at Senftenberg and the age of the accompanying deposits of mouldy peat and fetid mud ) , Zeitschrift d. Deutschen geol. Gesellschaft, vol.79. Keranen, J. (1923) ijber den Bodenfrost in Finnland (On frozen ground in Finland) , Mitt. d. MeteoroL Zentralanst. d. finn. Staates, (Helsinki) , Nr. 12, 57p. Kessler, Paul (1925) Das eiszeitliche Klima und seine geologischen Wirkungen im nicht vereisten Gebiet (The Pleistocene climate and its effect on the unfrozen region ) , Stuttgart. Khrgian A. Kh. (1936) O temperature i proiskhozhdenii vechnoi merzloty (On the temperature and origin of permafrost) , Meteorologiia i gidrologiia, vol. 1, no. 5, p. 69-72 (text in Russian). (Ref. N. Jahrb. Min., vol.11, 1937). Kihlman, O. (1890-92) Pflanzenbiologische Studien aus Russisch-Lappland (Study of the plant biology of Russian Lappland ) , Acta, Societas pro fauna et flora fennica (Helsinki), T. 6, no. 3. Kinzl, H. ; Schweizer, H. ; Brecht, W. ; and Schmid, K. (1928) Beobachtungen aber StrukturbOden in den Ostalpen (Observations on structure soils in the eastern Alps ) , Petermanns geogr. Mitt. , vol. 74, p. 261-265. 1941) Die Anden-Kundfahrt des Deutschen Alpenvereins nach Peru inn Jahre 1939 (The Andes scientific expedition to Peru in 1939 by the German Alpine Society ), Zeitschrift d. Deutsch. Alpenvereins (Taf. 5 unten. ) . Kjellman, F R. (1879) Om vaxtligheten p^ Sibiriens Nordkust (Vegetation of the northern coast of Siberia ) , Ofversigt af fSrhandlingar, Svenska vetenskapsakademien (Stockholm), arg. 36, no. 9, p. 5-21. (1882) inN.A.E. NordensjSld: Vega-expeditionens vetenskapliga iakttagelser (Scientific observations of the Vega expedition ). Stockholm: F. and G. Beijer, Bd. 1. Klumikov, S. J. (1934) On the phenomena due to the everfrozen soil in the Pamirs , Tadjik Pamir Expedition (Acad, of Science, USSR), vol.54. Klute, F. (1920) Ergebnisse der Forschungen am Kilimandscharo 1912 (Results of investigations on Kilimanjaro, 1912 ). Berlin. (1927) " Die Oberflachenformen der Arktis (Surface forms in the Arctic, " In: DUsseldorfer geogr. Vortrage u. ErSrterungen (Breslau) ), Pt.3, p. 91-100. no STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES ■ Klute, F. (1929) Per Kilimandscharo, ein tropischer Riesenvulkan und seine Vergletscherung einst und jetzt (Kilimanjaro, a tropical volcano, and its present and past glaciation ) , Geol. Charakterbilder, edited by K. Andree, H.36, Berlin, Taf. 6. Knauer, Jos (1943) Die Entstehung der Buckelwiesen (Formation of humped meadows ) , Mitteilungen der geogr. Ges. Mtlnchen, vol. 34, p. 207-220. Koch, G. A. (1877) Uber Eiskrystalle im lockeren Schutte (Ice crystals in loose detritus ) , Neues Jahrb. f. Min. Geol. u. Palaeont. , p. 449-473. Kohl-Larsen, L. (1930) Die deutsche Stidgeorgien-Expedition 1928-29 (The German South Georgian Expedition, 1928-29 ), Zeitschrift Ges. f. Erdkunde, Berlin. Kokkonen, P. (1926) Beobachtungen tlber die Struktur des Bodenfrostes (Observations on the structure of frozen ground) , Acta forestalia fennica (Helsinki), vol. 30, nr. 3 , p. 1 -56. (1927) Uber das Verhaltnis der Winterfestigkeit des Roggens zur Dehnbarkeit und Dehnungsfestigkeit seiner Wurzeln (Relation of the winter hardiness of rye to the flexibility and tensile strength of its roots ) , Acta forestalia fennica, vol. 33. (1930) Beobachtungen Uber die durch den Bodenfrost verursachte Hebung der Erdoberflache und in der Frostschicht befindlichen Gegenstande ( Observations on the frost heaving of the earth's surface and on the conditions found in the frozen layer ) , Maataloustieteellinen Aikakauskirja (Helsinki) , nr. 3. Konovalov, E. (1935) La structure des sols du versant nord-est de I'Elbrouz ( Structure of soils of the northeast slope of the Elburz Mountains) Izvestiia Vsesoiuznogo geograficheskogo obshchestva, vol. 67. KBppen, W. (1920) Die nattirlichen Steinringe und Steinnetze der kalten Zonen (The natural stone rings and stone nets of the cold zones ) , Meteor. Zeitschrift, vol. 37. Koridalin, E. A. (1934) O vozmozhnosti primeneniia seismicheskikh issledovanii k izucheniiu vechnoi merzloty (Possibility of applying seismic investigations to the study of permafros t) , Trudy Komissii po izucheniiu vechnoi merzloty, vol. 3, p. 13-19 (text in Russian) . Krasiuk, A. A. (1927) Pochvy Lensko-Amginskogo vodorazdela (Soils of the Lena- Amga watershed ) , Materialy po izucheniiu Yakutskoi ASSR, vol. 6, p. 176 (text in Russian with French summary). Krebs, N. (1925) Klimatisch bedingte Bodenformen in den Alpen (Climatically conditioned soil formations in the Alps ) . Geogr. Zeitschrift, vol.31, p. 98- 1 08. Krumme, O. (1935) Frost und Schnee in ihrer Wirkung auf den Boden im Hochtaunus ( Effect of frost and snow on the soil in the Hochtaunus Mountains ) , Rhein- Mainische Forsch. , vol. 13. Kudriatsev, V. A. (1939) Dinamika vechnoi merzloty v basseine srednego techeniia reki Selemdzhi i sviazannye s nei usloviia stroitel'stva v etom raione (Dynamics of permafrost in the basin of the middle reaches of the Selemdzha River and construction possibilities in this region ) , Trudy Komiteta po vechnoi merzlote, vol. 8, p. 71-117 (text in Russian with English summary) . Kuhn, Frz. (1913) Aus den Hochkordilleren von San Juan ( Argentinien) (From the High Cordillera of San Juan, Argentina ) , Petermanns geogr. Mitt. , II. Lange, Max. (1912) Eine Kibo-Besteigung (A Kibo ascent ), Zeitschrift, Gesellschaft fUr Erdkunde (Berlin) . Lavrova, M. A. (1934) O nakhozhdenii vechnoi merzloty v raione Volch'ei i Monche- Tun dr na Kol'skom poluostrove (The discovery of permafrost in the region of Volch'ia and Moncha Tundras on the Kola Peninsula ), Trudy Komissii po izucheniiu vechnoi merzloty, vol.3 (text in Russian). (Ref. N. Jahrb. f. Min. usw. , II , 1936). REFERENCES 1 1 1 Lavrova, M. A. (1935) Zametka o nakhozhdenii vechnoi merzloty na iuzhnom beregu Kol'skogo poluostrova~(Note on the presence of permafrost on the southern shores of Kola Peninsula ) , Trudy Komissii po izucheniiu vechnoi merzloty, Akademiia nauk SSSR, vol.4, p. 253-255 (text in Russian) . (Ref. N. Jahrb. f. Min. usw. , II, 1941). Lautensach, H. (1941) Per Hakentozan. Eine vulkanische Landschaft im koreanisch- mandschurischen Grenzbereich (Hakuto-san. A volcanic landscape in the Korea- Manchuria border area ) , Geogr. Zeitschrift, vol.47, 419p, (Taf! II, Bild 4) . Leavitt, H. W. , and Perkins, E. H. (1935) A survey of road materials and glacial geology of. Maine , Maine Tech. Experim. Station, Bull. , vol. 30. Leconte, J. (1850) Observations on a remarkable exudation of ice from the stems of vegetables, and on a singular protrusion of ice columns from certain kinds of earth during frosty weather , Philosophical Magazine, vol.3 6. Leffingwell, E. de K. (1915) Ground-ice wedges, the dominant form of ground-ice on the north coast of Alaska, Journal of Geology, vol.23. (1919) The Canning River region, northern Alaska , U. S. Geological Survey, Prof. Pap. 109p. Leuchs, Kurt (1933) Steinringbildung im oberen Lechtal (Stone-ring formation in the upper Lech Valley ) , Geol. Rundschau, vol.24, p. 222-223. Lopatin, I. A. (1876) Nekotoriia svedeniia o ledianykh sloiakh v vostochnoi Sibiri ( Some information concerning ice strata in eastern Siberia ) , Zapiski, Imp. Akad. nauk (St. Petersburg), tom 29(text in Russian) . Louis, H. (1930) Morphologische Studien in Sddwestbulgarien (Morphological studies in southwest Bulgaria ), Geogr. Abhandl. , 3 Reihe, H. 2, Stuttgart. Low, A. (1925) Instability of viscous fluid motion , Nature, vol.65. Lukashev, K. I. (1938) Oblast' vechnoi merzloty kak osobaia fiziko-geograficheskaia 1 stroitel'naia oblast' (Permafrost region as a separate topographical and construction region ) , Izdanie Leningradskogo gosudarstvennogo universiteta, 187p. (text in Russian). Markov, K. K. (1934) O polygonal' nykh ( iacheistykh) obrazovaniiakh Severnogo Pamira ( Polygonal (honeycomb) formations of North Pamirs) , Izvestiia Gosudarstvennogo geograficheskogo obshchestva, vol.66, no. 3, p. 402-407 (text in Russian). Matthes, Fr. E. (1900) Glacial sculpture of the Bighorn Mountains, Wyoming . U. S. Geological Survey, 21st Ann. Report, Pt. II. Mattick, Fritz (1941) Die "Vegetation frostgeformter Baden der Arktis, der Alpen und des Riesengebirges (Vegetation of the frost-conditioned soil of the Arctic, AlpTj and Reisen Gebirge ) , Beitrage z. System, u. Pflanzengeographie XVIII. Feddes Repertorium spec, novar. regni veget. Beih. Bd. CXXVI, Berlin-Dahlem. Meinardus, W. (1912a) Ober einige charakteristische Bodenformen auf Spitzbergen ( Some characteristic soil structures in Spitsbergen ) , Sitzungsber. Naturhist. Ver. Preuss. Rheinlande u. Westfalens (Bonn), 1912C, p. 1-42. ■(1912b) Beobachtungen tlber Detritussortierung und Strukturboden auf Spitzbergen (Observations on the sorting of debris and structure soils in Spitsbergen ) , Zeitschrift, Gesellschaft fUr Erdkunde (Berlin), p. 250-259 (1923) Meteorologische Ergebnisse der Kerguelenstation 1902-3 ( Meteorological results from the Kerguelen station, 1902-3) , Deutsche Sudpolar- Expedition 1901-1903, E. v. Drygalski, ed. Bd. Ill (Meteorol.), Teilbd. I, 1 Halfte, Berlin u. Leipzig. (1930) Arktische Baden (Arctic soils ) in: Handbuch der Bodenlehre , Blanck, ed. Berlin: Julius Springer, Bd. Ill, p. 27-96 (text in German) . 112 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Metzler, H. K. (1933) Kammeis als Faktor flSchenhafter Abtragung (Needle ice as a factor in surface erosion ) , Geogr. Wochenschrift, vol.1, p. 710-711. Meusel, H. (1939) Die Vegetationsverhaltnisse der Gipsberge im Kyffhauser und im sQdIichen Harzvorland (Conditions of vegetation on the gypsum hills in KyffhSuser and in the southern Harz foreland ) . Hercynia, vol. 2, 154ff. Meyer, H. (1900) Der Kilimandscharo (Kilimanjaro ) . Berlin, p. 149. Miethe, A. (1912) tjber Karreebodenformen auf Spitzbergen (Patterned ground on Spitsbergen ) , Zeitschrift d. Ges. f. Erdkunde (Berlin) , p. 241-244. Mohaupt, "W. (1932) Beobachtungen (Iber Bodenversetzungen und Kammeisbildungen aus dem Stubai und dem GrSdener Tal. ( Observations on soil mixing and needle- ice formation in the Stubai and GrSdener Valley) , Diss. Hamburg. Mortensen, H. (1932) Uber die physikalische MBglichkeit der "Brodel"-Hypothese ( The physical possibility of the "convection" hypothesis ), Centralbl. Mineralogie usw. , Abt. B, nr. 9, p. 417-422. (1928) Ober die klimatischen Verhaltnisse des Eisfjordgebietes ( Climate of the ice fjord region ), Chemie der Erde, vol.3. (1930) Einige Oberflachenformen in Chile und auf Spitzbergen im Rahmen einer vergleichenden Morphologie der Klimazonen (A comparison of surface forms in Chile and Spitsbergen in relation to climate ) , Herm. -Wagner- GedScht- nisschrift. Petermanns geographische Mitt. ( Gotha) , Erg. -H. 209, p. 147-156. Morton, J. O. (1936) The application of mechanics of highway foundation engineering, Proceedings, International Conference on Soil Mechanics and Foundation Engineering, vol.1. Nakajima, Morio (1938) Gravel heaps of lozenge shape of Kikko-ike, Mt. Tadesina , Journal of Geography (Chigaku Zasshi), vol. 50, nr. 588. Nangeroni, G. (1938) Suoli poligonali e suoli a striscie parallele (Polygonal soils and soils with parallel stripes ). Comptes rendue, 15th International Geographical Congress (Amsterdam), Sect. II, p. 298-302. Nansen, Fr. (1921) Spitzbergen . Leipzig. Nichols, R. L. , and Nichols, F. (1936) Polygonboden on Mt. Desert Island, Maine , Science, new. Ser. , vol.83, p. l6l. Nieland, Hans (1930) Uber Erscheinungen des Bodenfrostes und Auftaubodens in WestgrBnland (Phenomena of frozen ground and the active layer in west Greenland ) , Zeitschrift f. Gletscherkunde, vol.18, p. 346-351. Nilsson, Erik (1935) Traces of ancient changes of climate in east Africa , Preliminary Report. Geog. Annaler 1935, 1/2, Stockholm. NordenskjOld, O. (1907) Uber die Natur der Polariander (The nature of Polar regions ) , Geographische Zeitschrift, vol.13, p. 465-478; 557-568; 614-627; 676-687 (text in German) . (1908) On the geology and physical geography of East Greenland , Medd. om Gr^nland, vol. 27, in: Carlsburgfundets expedition til ost-Gr^nland 1898- 1900 (Carlsberg Fund Expedition to east Greenland, 1898-1900 ), by G. C. Amdrup. (1909) Die Polarwelt und ihre Nachbariander (The polar region and neighboring lands ) , Leipzig u. Berlin: [German translation of PolarvSrlden och dess granlander (1907) Stockholm]. (1911) Die Schwedische Sudpolarexpedition und ihre geogra p hische Tatigkeit (The Swedish Antarctic expedition and its geographical activitie s) ,in: Wissenschaftliche Ergebnisse der Schwedischen Sudpolar-Expedition 1901-03 . Stockholm. (Text in German). REFERENCES 113 Norrlin, J. P. (1873) Berattelse i anledning af en till Tornei Lappmark verkstalld naturhistorisk resa (Report on a natural history journey to Tornea Lappmark ) , Notiser ur fOrhandlingar, Societas pro fauna et flora fennica, vol. 13, p. 249-269. Obruchev, S. (1938) Shakhmatnye (ortogonal'nye) formy v oblastiakh vechnoi merzloty (Checkered (orthogonal) forms in permafrost regions) , Izvestiia Gosudarstvennogo geograficheskogo obshchestva, vol.70, p. 737-746 (text in Russian), Odell, N. E. (1925) Observations on the rocks and glaciers of Mount Everest , The Geographical Journal, vol. 66. Odum, H. (1922) Om Faarestiernes Natur (On the nature of sheep paths ), Danm. geol. undersSgelse (Copenhagen), Raekke 1, Nr. 15. Orvin, A. K. (1941) Hvordan opstir jordbunnsis?(Formation of underground ice ) , Norsk geografisk tidsskrift (Oslo), vol.8, H. 8, p. 294-306 (text in Norwegian) . (1942) Om dannelse av strukturmark (Formation of structural ground ) , Norsk geografisk tidsskr. , vol. 9, p. 105-123 (text in Norwegian) . Parkhomenko, S. G. (1932) ( Program for the study of phenomena due to frozen ground and rock ) , In: (Scientific Guide for Agriculture, Tourists, and Forest Rangers) . Moscow (text in Russian). Passarge, S. (1919) Vorzeitformen der deutschen Mittelgebirgslandschaften (Ancient forms of the landscape of the German Mittelgebirg e) , Petermanns geographische Mitteilungen. (1931) Drei Probleme diluvialgeologischer Morphologie (Three problems of Quaternary geomorphology ) , Zeitschrift d. Deutschen geol. Gesellschaft, vol. 83. Penck, A. (1910) Versuch einer Klimaklasslfikation auf physiogeographischer Grundlage (Trial climatic classification on a physiogeographic basis ), Sitzungsber. Pr. Akad. Wiss. , Phys. -Math. Kl. , vol. 12. (1912) iJber Polygonboden in Spitzbergen (Polygonal soils in Spitsbergen) , Zeitschrift Ges. f. Erdkunde (Berlin), p. 244-246 (text in German) . (1941) Die Buckelwiesen von Mittenwald am Karwendel(Hummocky meadows of the Mittenwald at Karwendel) , Mitt. Geogr. Gesellschaft Mtinchen, vol.33. Petrovskii, A. A. (1934) K opredeleniiu niznei granitsy vechnoi merzloty elektrometricheskimi metodami (Determination of the lower limit of permafrost by electrometric methods ) , Trudy Komissii po izucheniiu vechnoi merzloty, Akademiia nauk SSSR, vol.3, p. 5-11 ( text in Russian) . Philippi, E. (1912a) Geologische Beobachtungen auf Kerguelen (Geological observations on the Kerguelen Islands ) , Deutsche Sadpolar-Expedition 1901 -03, E. v. Drygalski, ed. Berlin, Bd. II. (1912b) Geologische Beobachtungen auf der Possession-Insel (Crozet- Gruppe) , (Geological observations on Posse s sion Island (Crozet group ), Deutsche SUdpolar-Expedition 1901-03, E. v. Drygalski, ed. Berlin, Bd. II. Pichi SermoUi, R. (1938) Aspetti del paesaggio vegetale nell' alto Semien (Africa Orientale Italiana) (Aspects of the vegetational terrain in the high Seimien ) , Nuovo Giorn. Bot. Ital. , vol.45. Pisarev, G. F. (1935) Vechniia merzlota v Tunkinskoi kotlovine (Permafrost in the Tunka depression ) , Trudy Komissii po izucheniiu vechnoi merzloty, Akademiia nauk SSSR, vol.4, p. 189-223 (text in Russian) . (Ref. N. Jahrb. Min. usw. ; II, 1941.) Pod'iakonov, S. A. (1903) Naledi Vostochnoi Sibiri i prichiny ikh vozniknoveniia ( Naleds of Eastern Siberia and their origin ) , Izvestiia Vserossiiskogo geografiches- kogo obshchestva, vol.39, p. 305-337 (text in Russian) . Pohle, R. (1903) Pflanzengeographische Studien tlber die Halbinsel Kanin und des angrenzenden Waldgebietes. T. I. (Studies of plant geography on Kanin Peninsula and adjacent forest areas ) , Acta horti Petropol. (St. Petersburg) , T.XXI, fasc. i. 114 STRUCTURE SOILS, SOLIFLUCTION, AND FROST CLIMATES Pohle, R. (1924-25) Frostboden in Asien und Europa (Frozen ground in Asia and Europe ) , Petermanns geographische Mitt. , vol.70, p. 86-88; vol.71, p. 167-169 (text in German) . Porsild, A. E. (1925) lagttagelser over den gr^nlandske kildeis (grl. : Sersineq) og dens virkninger paa vegetationen og jordoverf laden (Observations on Greenland spring ice and its effect on vegetation and soil ) , Geogr. tidsskr. , vol.28, p. 171 - 179 (text in Danish with English sumnnary) . Porsild, M. P. (1902) Bidrag til en skildring af vegetationen paa ^en Disko ( Description of the vegetation of Djsko Island) , Medd. om Greenland, 25 hefte, p. 91-239. Poser, Hans (1931) BeitrSge zur Kenntnis der arktischen Bodenformen (Contribution to the knowledge of arctic soil forms ), Geol. Rundschau, vol.22, p. 200-231 (text in German). (1932) Einige Untersuchungen zur Morphologie OstgrSnlands (Studies on the morphology of East Greenland )~i Medd. om Gr^nland, Bd. 94, nr. 5, p. 1 -55 (text in German) . (1933a) Das Problem des Strukturbodens (The structure soil problem) , Geol. Rundschau, vol. 24, p. 105-121 (text in German) . (1933b) Die Oberflachengestaltung des Meissnergebietes (Surface configuration of the Meissner region) , Jahrb. d. Geogr. ges. Hannover f. 1932 1933. (1934) Bemerkungen zum Strukturbodenproblem (Remarks on the problem of structure soils ), Centralblatt f(ir Mineralogie, Geologie und PalSontogie, Abt. B, p. 39-45. (1936) Talstudien aus Westspitzbergen und OstgrOnland (Valley studies on West Spitsbergen and East Greenland ) , Zeitschrift ftir Gletscherkunde, Bd. 24, p. 43-98. Rathjens, K. , and von Wissmann, H. (1929) Oberflelchenformen und EisbBden in Lappland (Surface forms and frozen ground in Lapland" )"! Petermanns geogr. Mitt. vol.75, p. 120-126. Rempp, G. , and Rothe, J. P. (1934) Sur les phenomenes actuels de nivation et d'accumulation neigeuse dans les Hautes-Vosges (Existing phenomena of nivation and snow accumulation in the Hautes-Vosgos ) , Comptes rendus des se'ances de I'Acad. des Sciences, vol.199, p. 682-684 (text in French) . (1935) Sur certaines formations du sol dans les Hautes- Vosges. Sentiers de vache et reseaux de buttes (Some soil formations in the Hautes-Vosges. "Sentiers de vache" and, "reseaux de buttes"),Bull. Serv. Carte Geol. d'Alsace et de Lorraine, t. II, 2 fasc. ResvoU-Dieset, H. (1909) Lidt om Spitsbergens plantevekst (Concerning Spitsbergen's botany) , Norske geografiske selskabs, Aarbog 20, p. 9-17 (text in Norwegian). Resvoll-Holmsen, H. (1909) Om jordbundsstrukturer i polarlandene og planternes forhold til denn (Contribution on ground structures in polar regions and their plant relation s), Nytt magasin for naturvidenskaberne, vol.47, p. 289-296 (text in Danish) , (1913) "Observations Botanique (Botanical observations)' Exploration du nord-ouest du Spitsberg (Exploration of northwest Spitsbergen) , by G. I. Isachsen et al, pt. 5. Pub. as: Albert I, Prince of Monaco. Resultats des campagnes scientifiques accomplies sur son yacht, Fasc. 44. Reusch, H. (1901) Evig frosen jord i Norge (Permanently frozen ground in Norway ) , Naturen, vol. 25, p 344-346 ( text in Norwegian) . Rieser, A., and Mortensen, H. (1928) Die wissenschaftlichen Ergebnisse einer bodenkundlichen Forschungsreise nach Spitzbergen in Sommer 1926 (Scientific results of a soil science research expedition to Spitsbergen in the summer 1926) . Chemie der Erde, Bd. 3, p. 588-698. REFERENCES 115 Rikhter, G. D. (1934) Nekotorye svedeniia o torfianykh burgrakh v vraione Niudozera-Murmanskii okrug (A few notes on the peat mounds in the region of Nudozero (Lake) , Murmansk distric t) , Trudy Komissii po izucheniiu vechnoi merzloty, Akademiia nauk SSSR, vol.3, p. 121-126 (text in Russian) . Romanovsky, V. (1939) Application de la the'orie convective aux terrains polygonaux, ( Application of the convective theory to polygonal soils ), Revue d. Ge'ogr. phys. et de Ge'ol. dynam. , vol.12, p. 315-327. Rosen, M. F. (1935) Nabliudeniia nad rasprostraneniem vechnoi merzloty v del'te reki Pechory (Observations on the permafrost distribution in the Pechora delta) , Trudy Komissii po izucheniiu vechnoi merzloty, vol.4, p. 151-170 (text in Russian) . Rudolphi, H. (1912) Wanderungen auf den F3.rSer (Travels in the Faeroe Islands) , Deutsch. Rundschau f. Geogr. , 35, Jg. (1913) Die Farogr (The Faeroe Islands ), Zeitschrift d. Ges. f. Erdkunde, Berlin. Runeberg, E. O. (1765) Anmarkningar om n&gra fBrandringar p& jord-ytan i allmanhet, och under de kalla Climat i synnerhet (Observations on some changes in the earth's surface in general, and under cold climate in particular ) , Kungl. Vetensk. Akad. Handl. Salomon, W. (1910) Die Spitzbergenfahrt des Int. Geologenkongresses (The Spitsbergen journe"y"of the International Geological Congress ) , Geol. Rundschau. (1916) Die Bedeutung der Solifluktion ftlr die ErklSrung der deutschen Landschafts- und Bodenformen (The significance of solifluction for under stand.ing German landscape and soil forms ) , Geol. Rundschau, vol. 7. (1924) Felsennneere und Blockstreuungen (Rock fields and scattered boulders) , Sitzungsber. Heidelberg, Akad. Wiss. , Math. -Nat. K. A, vol.3. (1929) Arktische Bodenformen in den Alpen (Arctic soil forms in the Alps ) , Sitzber. Heidelberg. Akad. Wiss., Math, naturw. Klasse, No. 5, p. 1-31. Sapper, K. 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(1936c) Die Kasa-Dake-Kette und die Entdeckung des Rundh5cker- gebietes am Nukedo-Kake (The Kasa-Dake chain and the discovery of the "roche moutonnee" areas at Nukedo-Kake ), Geographical Review of Japan, vol. 12, nr..5 (text in Japanese with German summary) . (1936b) The extension of the diluvial glaciers in the Japanese North- Alps , Journal of Geological Society of Japan, vol.43, nr. 512. (1937a) Beobachtungen auf meinen Reisen durch die Zentral-und Stldalpen im Sommer 1936 (Observations on my journey through the central and southern Alp's, Summer, 1936 ), Geogr. Review of Japan, vol. 13 (text in Japanese with German summary). (1937b) Glazialformen und StrukturbSden in den Japanischen Nordalpen (Glacial forms and structure soils in the northern Alps of Japan ) , Geographische Zeitschrift, vol.43, p. 57-70. Seidenfaden, G. (1931) Moving soil and vegetationin East Greenland , Med. om Gr?5nland, vol.87, no. 2, p. 1-21. Sernander, Rutger (1905) Flytjord i svenska fjalltrakter (Solifluction in Swedish mountain areas ) , Geol. foreningen (Stockholm), Forhandl. , vol.27. Sheikov, M. (1936) ( Shear strength of frozen ground ) , Trudy Komissii po izucheniiu vechnoi merzloty, vol. 2 (text in Russian) . Shostakovich, V. B. (1927) Der ewig gefrorene Boden Sibiriens (The permanently frozen ground of Siberia ) , Zeitschrift Ges. Erdkunde (Berlin), no. 7-8, p. 394-427 (text in German). Simpson, J. G. (1932) Stone polygons on Scottish mountains , Scott. Geogr. Mag., vol.48. Sochava, V. (1930) O piatnistykh tundrakh anadyrskogo kraia (The spotted tundra of the Anadyr' region ) 1 Trudy Poliarnoi komissii, Akademiia nauk SSSR, vol.2, p. 51-68 (text in Russian) : also in Zeitschrift Ges. Erdkunde. SBlch, J. (1922) Die Karbildungen in der Stubalpe (Cirque formation in the Stubai Alps ) , Zeitschrift f. Gletscherkunde, vol.12. Soergel, W. (1932) Diluviale Frostspalten im Deckschichtenprofil von Ehringsdorf ( Quaternary frost cracks in the surface stratum of Ehringsdorf ) , Fortschr. d. Ge ol . u. Palaeontol, vol.11, p. 439-460. REFERENCES ^ 1 'i' Soergel, W. (1936) Diluviale Eiskeile (Quaternary ice wedges ), Zeitschrift d. Deutsch. geol. Gesellschaft, vol. 88. S^rensen, Thorwald (1935) Bodenformen and Pflanzendecke in NordostgrOnland ( Soil forms and vegetation cover in Northeast Greenland ) , Medd. cm GrjSnland, vol. 93. Spethmann, H. (1912) Uber Bodenbewegungen auf Island (Soil movements in Iceland ), Zeitschrift Ges. f. Erdkunde (Berlin). Spreitzer, Hans (1941) Die Eiszeitforschung in der So'wjetunion (Pleistocene research in the Soviet Union ) , Quartar III (Berlin). Stager, R. (1913) Beitrag zur HSckerlandschaft in den Alpen (Hummocky terrain in the Alps ) , Mitt. d. Naturf. Ges. in Bern. Stamm, K. (1911) Schuttbewegungen (Debris movement ), Geol. Rundschau. 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