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Ground (subsurface) ice
Shumskii, P. A.; National Research Council of Canada. Division of Building
Research
CHAPTER IX, GROUND (SUBSURFACE) ICE. P. 274 - 327
NATIONAL RESEARCH COUNCIL OF CANADA
TECHNICAL TRANSLATION 1130
PRINCIPLES OF GEOCRYOLOGY
(PERMAFROST STUDIES)
PART 1, GENERAL GEOCRYOLOGY
BY
P. A. SHUMSKII
FROM
ACADEMY OF SCIENCES OF THE U. S. S. R.
V. A. OBRUCHEV INSTITUTE OF PERMAFROST STUDIES MOSCOW 1959
TRANSLATED BY
C. DE LEUCHTENBERG
THIS IS THE ONE HUNDRED AND NINETEENTH OF THE SERrES OF TRANSLATIONS
PREPARED FOR THE DIVISiON OF BUILDING RESEARCH
OTTAWA
•
This translation is the fourth arranged by the Permafrost SUbcommittee of the Associate ｃｯｲｲｾｩｴｴ･･ on Soil and Snow Mechanics of the National Research Council of the Russian permafrost publi-cation "Principles of Geocryologyll. The first translation in this group was of Chapter VI entitled IIHeat and Moisture Transfer in Freezing and Thawing Soils ll by G.A. Martynov (TT-I065). The second vias Chapter IV II General Mechanisms of the Formation and Development of Permafrost" by P.F. Shvetsov (TT-1117) and the third was Chapter VII IIGeographical Distribution of Seasonally Frozen Ground and Permafrost" by LYa. Baranov (TT-1121).
This translation of Chapter IX by P.A. Shumskii reviews the highlights in the history of ground ice investigations which were
initiated in the eighteenth century. The main body of the text
consists of a discussion of each of the types of ground ice
encoun-tered in permafrost rq;ions. These include segregated ice, injected
ice, ice veins, multiple ice veins, cave ice, thermokarst cave ice,
karst cave ice, and buried ice. The modes of origin,
characteris-tics, properties and geographical distribution of each of these types of ice are discussed in detail.
The Division is grateful to the Geological Survey of Canada for arranging the translation of this chapter in response to the request of the Permafrost ｓｵ｢｣ｯｮｾｩｴｴ･･Ｎ
Ottawa
J1.me 1961+
R.F. Legget Director
..
•
Title: Author: Reference: Translator: Technical Translation 1130Ground (subsurfacc) ice (Poazcl:mye l 'dy)
P.A. Shumskil
Principles of :::;eocryolo::?;y (permafrost studies), Part I, General
geoc r-yoLcgy , Chapter IX. Academy of Sciences of the U.S.S.R. HoscOi'! 1959. ｰＮＲＷ［ｾＭ［ＱＲＷ
(Osnovy geokr1oloGii (merzlotovedeniya), ChastI pervaya,
ObshchayCl c;eokrioloe;iya, Glava IX. Akademiya Nauk SSSR. Moskva
1959. s.274-327)
C. de Leuchtenberc;, Translation Bureau, Department of the Secretary of State
Introduction
Ice, in the broad sense of the \'1orc1*, refers to all solid phases of
water (H20 )** ; nine phases are known today, one amorphous and eiGht crystalline .. (Shumskii, 1991-2 ; 19552)' The wor-d ice, however-, usually refers to only one,
common ice or ice I, inasmuch as this crystalline modification of ice can
• exist under thermodynamic conditions characteristic of the terrestrial
cryo-sphere***. Ice does not form isomorphic mixtures vlith other substances and therefore all natural ice phases belong by their chemical composition to one mineral type. Fr-eshwater-, saline wate r and brine ice types, containing salts as mechanical admixtures, are varieties of that mineral.
All ice located in the earth's crust, irrespective of its origin or form of occurrence, is called ground ice (Vernadskii, 1934,; Kim, Pavlov, 1911-3;
Grave, 1951).
O\'Jing to its physico-chemical properties, ice is the lightest, the coldest and because of that the most surficial of all the minerals forming
the earth's crust. The main masses of ice are concentrated on the earth's
surface where, as well as in the atmosphere and hydrosphere, they represent the most \'Jidespread solid substance. In the lithosphere, ice occurs only in
the uppermost horizons and in a significantly lesser quantity. According to
the approximate data available to us the total ｶｯｬｬｬｩｾ･ of ground ice amounts to 0.5 million lcm3, or to about 2% of the total volume of ice on the globe.
Nevertheless in parts of the lithosphere ice is the main component. There are
*
**
***
In the narrOH sense the term ice refers to solid ice (icc I), free of interconnecting air pores, in contrast to such porous substances as snow, firn, ri1l1e, etc.
The concentration of heavy isotopes of hydrogen and oxygen, H2 (deuterium),
H3 (tritiwn), 0'7 and 0'8 is insignificant in nature and exerts no per-ceptible influence on the physico-chemical properties of water and ice. Other artificially obtained modifications of ice cannot exist as bodies of macroscopic dimensions under the combinations of temperature and pressure existing in the earth's crust and on its surface. This howeve r does not exclude the possibility of their existence as thin films on the surface of
solid bodies. It is probable that the internal part of the films of bound
water, vrhf.ch plays a great part in soils, is a modification of ice exist-ing under high pressure (Vernadskii, ＱＹＳＮＧｾ 1; Parkhomenko, 1956). At least the binding energy (deterl:1ined by the heat of wetting) and the physical properties of adsorbed or hycroscopic water are in agreement with the heat of cr¥stallization and the properties of the "hot " ice VIII (Shumskii,
of the soil stratum 10 - 30 m in thickness, consists of 50 -
80%
(by volwne)of ice. However, when the reserves of ice in the earth's crust are compared
with those in the world's ocean* and in the atmosphere, it comes out that the first are several times larger despite their much smaller spatial
concentra-• tion. Thus the part of the terrestrial cryosphere represented by the
litho-sphere, i.e. the cryolithozone, occupies by its ice quantity a second place
• with respect to the ice that is being accumulated on the surface of the
con-tinents, although that zone has a much smaller surface than the latter. The significance of ice in nature and for human economic activity is stipulated not only by its widespread occurrence but also by its position amid
the series of minerals. Ice is the solid phase of a substance which takes an
exclusive part in the chemical and biochemical processes, and which in its
liquid phase is the indispensable condition for organic life. Yet in the
thermal succession of mineral formation, ice belongs to the last and coldest stage, which is separated from all other ones by the stage of formation of
organic substances. With this, as well as with the specific physical
proper-ties of ice, is connected its specific role in the biosphere, where it dis-turbs by its appearance in any significant quantity the normal course of organic, chemical as well as all other geological and geographical processes. All features of nature and economic utilization of a region with a continuously frozen subsoil are, in the end, stipulated by the phase-changes of water in the earth's crust - the appearance, existence and disappearance of the ground ice.
By cementing SOil, which is friable in its thawed state, ice radically
changes its mechanical properties. The thermal properties and water
perme-ability of soil containing icc are likewise significantly changed. The
forma-tion of certain types of ground ice causes frost-heaving of the ground, and the melting of that ice causes flow of the ground, its subsidence and
destruc-tive thermokarst processes. Because of this, the presence, formation and
disappearance of ground ice types determine the main features of relief of a region with frozen ground, its hydrogeological regime, conditions for building houses, etc. and all human economic activity.
Inasmuch as all ground ice types are accumulations of one and the same mineral - ice I, the majority of their most important physical properties are generally uniform, and at constant temperature they vary comparatively little
with difference in structure and content of admixtures. However, the
*
Shelf-ice of the Antarctic is excluded as it is a continental type of for-mation."
"
properties and behaviour of the entire mass of frozen ground depends essen-tially on the form and quantity of the ice contained in it, and the conditions
and mode of its (the ice) occurrence. The latter are indissolubly connected
with the origin of the ground ice. Therefore, the central question of the
entire and long history of ground ice investigations was the problem of its origin, forms and conditions of its occurrence.
Highlights in the History of Ground Ice Investigations
Early period. Emergence of the theory of vein ice formation and
observa-tions on the burial of surface ice. Russian and Soviet sciences have the
priority and leading role in the study of ground ice. The first information
on ground ice was gathered in Siberia by P. Lassinius during the Great Northern
Expedition in 1753 (Baer, 1842) and H.P. Laptev in 1739 (1851). Already
investigations in the 18th century had shown that ground ice is widespread in
northern and eastern Siberia (Pallas, 1773-1778; Georgi, 1775; Sauer, 1802). Ground ice attracted general attention at the beginning of the 19th century because of a discovery in the Lena delta of a mammoth corpse amid "ice floes" and the discovery on the west coast of Alaska of a "mountain of pure ice" which likewise contained mammoth bones (Adams, 1807; Kotsebu, Chamisso, 1821-1823) .
The problem of the origin of large masses of ground ice was solved at the very time of its birth by A.E. Figurin, who had correctly described the condi-tions for the occurrence of the chief type of ground ice and had indicated its forrmtion in the frost fissures from "the ancient time" to these days (Figurin, 18231 , 18232)'
K.M. Baer pointed out in the first general, theoretical work on ground ice, that it is formed by the burial of naleds - taryns, river and sea ice and glaciers beneath overburden, by the freezing of water that penetrates beneath
the turf floating on it, or water that fills fissures in soils. K.M. Baer
conceived the idea on the vein origin of ice right at the site of the mammoth
discovery in the Lena delta and on the coast of Alaska. He attributed great
significance to the frost-generated formation of fissures and postUlated that there was a gradual wedging of soil by veins of ice arising in it (Baer, 1842, 1866) .
I.A. Lopatin described the various types of ground ice on the lower
Yenisei, Sakhalin and in Transbaika1ia; he was the first to observe the burial of firn at the foot of slopes, of bottom ice in rivers, and ice floes on
marine beaches. He recorded and gave the correct explanation of ice veins
that are being formed amid the "tundraic layers" in the frost-generated clefts (Lopatin, 1876, 1897).
II
At the end of the 19th century, A.A. Bunge had described the vein ice of the Lena delta and Bol'shoi Lyakhovskii Island, and had carried out observa-tions on the contemporary processes of vein ice formation in the
frost-generated fissures. He had established the genetic relation of the polygonal
ndcrorelief with the formation of vein ice and the occurrence of ice vein grids on vast spaces of tundra (Bunge, 1884, 1885, 1887, 1903).
History of the firn-c;lacial hypothesis of ground ice formation. While A. Bunge was conducting his investigation there was a sudden change in opinion on the nature of large masses of ground ice that arrested for a long time the development of the theory on the vein formation of ice in Russia, and deter-mined the fundamental trend of scientific thought in that problem up to the
present time. That trend had been prepared by the triumph of the continental
glaciation theory over the drift ｨｾｔｯｴｨ･ｳｩｳ and by the widespread occurrence of ground ice in the Siberian lowlands, and it had been natural to connect this with the events of the glacial period.
The firn-glacial ｨｾｯｴｨ･ｳｩｳ on the origin of ground ice had been offered
for the first time by E.V. Toll, viho used as his argument the vast extent of fossil ice on Bol'shoi Lyakhovskii Island, the granular and vesicular struc-ture of ice and discoveries of moraine beneath the ice in Anabar Bay. However, distinctions between fossil ice and glacial ice had forced E. Toll to assume the existence of a special ｴｾ･ of glaciation for northern Siberia siHlilar "to the continental ice or to the very thick firn field" whLch remained under-developed due to the fall of temperature and was converted into a "dead fossil glacier" under the cover of "earthy and lacustrine formations" (Toll, 1887,
1892, 1894, 1895, 1897). Also of great influence was the work of I.P.
Tolmachev, who, haVing studied under the microscope the texture (size, shape and orientation of crystals) and composition (quantity of mineral and gaseous admixtures) of ice specimens, taken from the site of the mammoth discovery on the Berezovka River, had come to the conclusion that deposits of ground ice are accumulations of snow in river valleys covered by mud (Tolmachev, 1903).
Having personally investigated the coast of the Arctic Ocean,
LP.
Tolmachev,was convinced of the \videspread occurrence of vein ground ice (Tolmachev,
1907; Tolmachoff, 1929); but this conclusion did not get wLde pUblicity and in the question of the ice texture and its genetic significance Tolmachev
ren:aincd an authority because of his first work asserting the snow ｨｾｯｴｨ･ｳｩｳ of ice ｦｯｲｮｾｴｩｯｮＮ
Instead of going to the bott om of the matter further investigations of large r:;round ice masses consisted maLn Ly in ac curnuLatLng data on their spread, and the discussions of principles revolved mainly around the problem of the anow or Glacier origin of r:;round ice, or on the type and number of glaciations on the plains of northern Siberia.
•
K.A. Vollosovich was developing opinions on the existence of two horizons of ground ice on the New Siberian Islands and coastal Low Lands between the Lena and ｋｯｬｾｮ｡ Rivers, and, accordingly, on two glaciations in that region, which were mandt'e s t.ed by the development of continuous firn fields whLch formed true glaciers wher-e the topography was favourable (Vollosovich, 19091, 19092, 1915; Wollosowitsch, 1909).
A. A. Grigor' ev, who connected the ground ice of central Yakutia with the thermokarst relief forms, added to the hypothesis of Tolmachev-Vollosovich by supplementing it with the lake hypothesis of A.J. Haddren (Haddren, 1905), and proposed to call the asswned glaciation in the form
"or
stationary ac cumul a-tions of firn snow in company with lakes frozen to the bottomllas glaciation
of the eastern Siberian or embryonic type. In A.A. Grigor'ev's opinion,
central Yakutia was glaciated three or four times (Grigor'ev, 1926, 1927, 1930 2, 1932).
Later the hypothesis on the snow-glacial origin of the large ground ice masses in its various forms was shared by V.A. Obruchev (1930, 1931), H.M. Ermolaev (193211 193221 1933), N.I. Sumgin (1937,194°2,194°3, 19J+04 , 1947), A. I. Gusev (19381 , 191W), ｖＮｾＱＮ Ponornarev (19!.tO, 19511 , 19512 , 1952), I.P.
Geras irnov and K. K. Markov (1939),
v.
N. Saks (1936, 19 45 1, 191+52 , 19 461 , 191+6 2,191+8, 1951) and others.
The difference be twe en fossil ice and snow ice as well as general climatological considerotions gave rise to a series of hypotheses on the
peculiar characteristics and time of development of glaciation in Siberia. In
addition to the above-mentioned hypotheses the following ones should be kept
in mind: V.V. Lamansky is on glaciation at high latitudes due to the
modera-tion of climate (Lamansky, 1914), K.K. Markov on the metachronism (reverse development in time) of glaciation in Siberia and Europe (Markov, 1938;
Gerasimov, Harkov, 19)9), D.M. Kolosov on the discordant development of glaci-ation of plains and mountains of the U.S. S .R. ' s northeast (Kolosov, ＱＹＩＭｾＷＩＬ
V.A. Zubakov (1951) on the four types of lithe passive surficial glaciationll of Siberia and Alaska, B.N. Gorodkovand I.P. Gerasimov on the possibility of extending the conclusions relative to the character lIof the postglacialll land-scape in the region of fossil ice development to periglacial regions of the old continental glaciation (Gorodkov, 1948; Gerasimov, 1952), and N.A.
Naginskii on the development in western Siberia at first of an lIe mbr yon i c " glaciation that was later overlapped by moving ice descending from the mountains (Nacinskii, 1953).
All this created a great confusion in the problems of ancient glaciation and the history of the Quaternary Period in regions of development of laree ground ice masses.
-8-..
DcvclQ1?lJlcnt of the theory of vein-ice formation. During the period of domination of the sn01'l-ice hypothesis nobody denied other possibilities of gr-ound ice f'or-matLon . Only the possibility of explaining in that vJay the
formation of large ground ice masses Has denied. The vein origin of the major
mass of ground ice in Alaska and Siberia \-JaS advocated after A.A. Bunge, only
by K. Leffing":ell, who observed the contemporary formation of ice veins and described in more detail than his predecessors the rnechan:i..sm of their formatlon and gr-adua l growth (Leffingi';ell, 1915, 1919).
Since investigators of the Quaternary Period became acquainted with the processes of formation of IIice wedge sI I , fossil pseudomorphs from ice veins
were discovered during the last three decades almost ･ｶ･ｲｊｾｬｨ･ｲ･ along the edge of the Quaternary ice sheets in Europe and North America and they were
inter-preted as evidence of the past distribution of frozen ground. Vein ice was
described by 3.G. Par-khomenlco (1929), P.K. Khmyznikov (1934), P.P. Shvetsov (1938), A.I. Gusev (19381 ) , A.N. Tolstov (19Ln ) and P.N. Kapterev (Bykov and
Kapterev, 191W).
Objections to the vein origin of the large masses of ground ice, repeat-edly raised by the supporters of the snow-ice hypothesis, boiled down nlainly to the impossibility of imagining how the veins of ice could penetrate to a significant depth and "wher-e all that huge mass of earth that should have been forced out by the ice is gonell
(Ermolaev, 19321 ) , The answer to that question is that the great vertical extent and the depth of penetration of ice veins
are ･ａｾｬ｡ｩｮ･､ by the syngenetic growth of the latter simultaneously with the
accumulation of sediments surrounding them; the basis for this conclusion vias
prepared by G. Steche (1933),
w.
Soergel (1936, 1942) and definitively formu-lated by G. GalhJitz (191i9) and A.I. Popov (1952, 19531 , 1953:;». G. Ga11witz
and B.N. Dostovalov analyzed the relation between the accumulation of sedi-ments and the form and structure of ice veins formed in them (Galhlitz, ＱＹＱｾＹ［
Dostova10v, 1952).
The vein origin of ground ice in central Yakutia has been ascertained by P.A. ｓｨｾｾｳｫｩｩ (1950, 1952) with the aid of petrographic analysis, and the e1ectrometric works of R.I. Korkina have exposed the occurrence of ice in the
form of a grid of vertical veins (Korkina, 1952). Subsequent studies at the
V.A. Obruchev L'1stitute of Permafrost Studies, U.S.S.R. Academy of Sciences, have proved the vein nature of the main mass of eround ice of the
Yana-Indigirka coastal lowland, Bol'shoi Lyakhovskii Island, Lena delta, the mouth of the Anadyr River, the north coast of Chwchotskii Peninsula, the Aldan River area and elsewhere, (Vtyurin, 19511 , 19512 ; Grigor'ev, 1952); Efimov, Shumskii,
1952; Shumskii, Vtyurin, Katasanov, 1953 and others). Some supporters of the
•
adnutt.co the vein origin of icc in the ｩｮｶ｣ｮｴｬ｛ｾＨＩｴ･ｃｬ rC[:;lons (Solov'ev, 1951).
I!wL'stiC:.::ltion of ice fOl'li;Qtion dur:L12.C;. the frcczinc; of' moint soil. The problem of icc f'o.ri.iatLon in the freezinG of the soil in intimntely connected with the pr-ob Lc:» of moLs t.ur-e lili;::ration in it and the natur-e of forces whLch a1101': the icc to be seGreGated in the sround as bodies wnos e d.irnenoLone exceed the cava tics oriGinal1y exis tine; in the gr-ound , and this is evidently the result of expanding the soil skeleton.
Early investigators attached ｾｉｾｯｲｴ｡ｮ｣｣ only to water infiltration from the surface to the frozen layer (Beechey, 1831; Baer, 181(2). Later there wer-e
developed in many versions two more fundamental theories of viat e r- migration in freezinG grow1d, namely: the theory of migration under pressure, due in par-ticular to the increase of volume during the freeZing in closed systems, and the theory of dra'l'ling the capillary or film water to the f'r-e czLng plane. The main role in de veLoptrig the first-naraed theory belonc;s to: S.A. Pod'yakonov
(1903), V.N. Suka che v (1911), K. Ni1ciforov (1912), R.I. Abolin (1913), D.A. Dranitsyn (191h) and E.I. Swngin (1929, 1931, 1940" 191(02 , ＱＹｾＰＳＩＧ The
second theory vas developed by V. I. Shtu1ceneberg (1885, 189if), A.F. Lebedev
(1930), G.Y. Bouyoucos (1923)*, S. Taber (1929, 1930), G. Be skow (1935) and recently by many other investiGators. As it was stated repeatedly in the literature, the movement, of wat er' vapour does not have any essential signifi-cance for the formation of ice due already to the gas impermeability of strata whLch sec;ree;ate ice in the course of freezing.
Hater misratine; uncleI' pressure freezes in the voids created by i t at the boundary of the wat.er--fmper-meabLe , frozen layer. En contrast to this the mechanism of ice segrer.;ation in every other type of mic;ration requires an ad-ditional explanation. T\'IO such explanations are known . According to the
first of thew, ice in freeZing, thinly disperse stratn is secregated on frac-tures which arise due to the reduction of volwne on coagulation of the col-loids. Hater is squeezed out into the fractures, and the crystals of ice grow-ing there assist the squeeZgrow-ing of water by exertgrow-ing pressure upon the fracture
'\'1aLls . Such an explanation was given by LA. Lopatin (1873), P. I. Holmquist (1898), G. Hesselman (1907), R.I. Abolin - for peat (1913), G. Given (1915),
A.E. Fedosov (1935) and others. The second explanation attributes the main importance to the pressure of grOi'linc; ice crystals in the direction of the gr-owt.h (independent of the V01W,lC expansion of wat er- freezing in a closed
space). The gr-owarig crystals push apart the soil surroundine; them. This
*
G.Y. Bouyoucos. Movement of soil ｾｾｩｳｴｵｲ･ from small capillaries to the large capillaries of the soil upon freezine;.J.
Ac;r. Res. Ｒｌｾ (5), 1923.assumption stated by B. H8cboIil (1910, 191)+) has been experimentally proved by S. Taber (1916, 1917, 1918" 19182), and the explanation of the physical nature "of the force of crystallization" resulting from surface tension has been given by C.W. Correns (1926).
Hummocks of "pr-easur-c -eweLlang'' Hi th ice cores were recorded for the first time by G. Radde in 1958 (Radde, 1958). S.G. Parkhornenko (1929) called
them ice laccoliths, and NoI. Tolstikhin (1932) - hydrolaccoliths. At the
present time such humnrocks with ice or icy cores are known in almost all permafrost regions. There is a hypothesis that perennial hUlTllllocks due to heaving occur simultaneously with the beginning of deep freezing of the litho-sphere (Leffingwell, 1919, or later Porsild, 1938; Baranov, 19L+O, Sachs, 1940). Their confinement to the narrow geographical or climatic zone, or to the
region of recent subsidences has been pointed out by V.N. Andreev (1936), V.N. Sachs (19452), V.N. Ponomarev (1951), A.I. Popov (1953 2), and G.V. Gorbatskii
(1952). V.G. Zol'nikov offered an hypothesis, concurrent with K. ｌ･ｦｦｩｮｾｬ･ｬＱＧｳ
opinions, on the pressure sweLl Lng during the formation of the perennial cryolithozone (permafrost zone), but ascribing this mode of formation not to the icy cores of the swelling ｨｵｮｾｯ｣ｫｳ but to the main mass of ground ice in central Yakutia (1949, 1950).
The processes of formation of ice-inclusions at the expense of water which has infiltrated and been drawn to the zone of crystallization, as well as the type of structure of frozen ground which arose in that way, have been described by I.A. Lopatin (1873), P. HoLmqudst (1898), P. Kokkonen (1926), S. Taber (1929, 1930" 19302 ) , Eo Jung (1932), V.I. Moroshkin (1933), G. Beskow
(1935), S. Erikssen (1941), A.M. Pchelintsev (1948,), A.I. Popov (1953,), F.G. Bakulin (1958), and others.
Attempts were 1ike\'lise made to ascribe a similar origin to the large
masses of ground ice. The infiltration hypothesis of G. Holmsen (1912) and
the closely related hypotheses of S.P. Kachurin (1946, 1950, 1952), M.I.
Sumgin, S.P. Kachurin et a1. (19LW) and A.A. Grigor'ev (19Lt6), as well as the
segregation hypotheses of G. Beskow (1935), S. Taber (1943) and P.S. Vadil0 (1951), belong here.
Hypotheses on the origin of ground water and ice by condensation were offered by A.F. Lebedev (1913, 1930) and F. Nansen (1915); finally P.I.
Koloskov combined these hypotheses v11th the segregation hypothesis by assuming that the migration of moisture from below proceeds in the vapour state, that the water vapour is being condensed and afterwards upon the freezing of water
there begins the segregation and growth of ice layers in the frozen ground (1946, ＱＹＱｾＷＩＪＮ
C1nssification of Ground Ice
The variety of opinions on the nature of ground ice is explained to a
•
great extent by the superficial approach to its study by some investigators, carried out, as a rule, by imperfect methods incidental to other wor-ks .
Poorly substantiated extrapolations, \'lhich aim to ascribe a universal significance to a particular phenomenon are typical of many investigators, who became acquainted in one way or another with a limited range of processes of
ice formation. To counterbalance these groundless generalizations, there
appeared in the literature widespread emphasis on the great variety of condi-tions for the formation and type of ground ice, which to some extent resulted
in many classifications, usually of a speculative character. Although correct
in principle, this approach in practice began to negate the validity of the generalizations, and this led to uncertainty in determining the nature of ground ice in any specific case.
Many classifications of ground ice exist at the present time; they include factual material of varying completeness, are constructed according to diverse principles, and generalize variously justified opinions on the nature of ground ice (Baer, 1842; Toll, 1895; Abolin, 1913; Leffingwell, 1919; A.A. Grigor'ev, 1930,; Satow, 1930; Vernadskii, ＱＹＳｌｾＱ［ Tolstikhin, 1936, 1941; Sumgin, 191W; Solov lev, 1947; Suslov, 1950; N.F. GrigorIev, 1952; Solov lev, 1952; Grave, 1951; Zubakov, 1951; Shumskii, 1950).
Ground ice occurrences are divided most frequently into groups of atmo-genic and hydroatmo-genic, syngenetic and epigenetic, contemporaneous and fossil, but all these subdivisions are inadequate for classification.
The atmogenic and hydrogenic, or more precisely sublimation and congela-tion modes of ｦｯｲｲｲｾｴｩｯｮ (by means of crystallization of vapour and water, respectively) do not typify the whole complex of processes and conditions of
formation of a given type of ice. Some of the most widely-spread types of
ground ice are of mixed origin, their composition includes both sublimated and congelated mat.er-LaL, uh Lch have been metamorphosed to varying degrees.
To set off the synGenetic ice, which formed at the same time as the
ground which surrounds and covers it, against the epigenetic ice, which formed within the ground after the latter was formed, is also of no conclusive
*
A more detailed review of the history of investigation of ground ice is gi ven by Shumakf.I , 19533'significance. There are variations in ground ice fonned in sedimentary soil
during their simultaneous accumulation and freezing. He shall call these
variations syngenetic ice, side by side with buried surface ice. From this
point of view a number of varieties of ground ice can be syngenetic and epi-genetic, depending on whether they formed in the stratum of soil or whLLe the
• soil was being deposited.
The dating of ice by dividing it into the ｣ｯｮｴ･ｮｾｯｲ｡ｮ･ｯｵｳ and ancient, fossil, as well as by the lTIOre precise geological and absolute chronolgy, is of great interest, but does not pertain to the genetic classification of ice. The influence "of the time factor" to which some investigators ascribed great
significance, is adequately studied today. It can be asserted that the
processes of ice recrystallization, occurring without external influences, i.e. having as their source the free energy of crystal aggregates, do not lead to the changes which are so essential in order to speak of the diverse types of
ice in relation to its age. Any of the existing ground ice types could and
can arise in certain regions both in the distant past and at the present time, and consequently ice can be represented by fossil and contemporary forms.
Of essential significance for the systematization of ground ice is its relation to the other ｣ｯｮｾｯｮ･ｮｴｳ of the frozen ground mass or the relative
role of ice in the composition of that mass. From this point of view the
three following types of ground ice can be distinguished.
1. Ice as an independent, monomineral substance occurring in other mineral matter as more or less large bodies, their formation being the result of a specific geological process that has brought about their composition, struc-ture and mode of occurrence.
2. Ice which is a soil-forming mineral, being part of polymineral soil, occurs usually as the cement of frozen soil between grains of other minerals. Small lens-like formations, veins and nests of ice belong to this type too; all of them can be regarded as a composite part of a polymineral frozen SOil, and cause the latter to acquire a certain structure.
3.
Ice which is not a soil-forming mineral. Loose accumulations ofsublimated ice crystals in subsurface voids, fractures and caves, representing the subsurface homologue of rime.
Despite the great significance of the above morphological division it cannot serve as a basis for a genetic classification, because in a number of cases the distinctions between ice of the first and second type are only
qualitative in character, and are not accompanied by variations in the mode of formation.
Amid the processes of ground ice formation we should distinguish three fundamental c;roups to \'lhich the three types of ice correspond:
(1)
(2)
the f'r-eczLnrtIJ of moist soil creates constituted ice;
the filling of cavities in frozen soil by ice causes the formation of cave-vein ice;
(3) the burial of surface ice produces buried ice (Fig. 57).
The ice ｣･ｴｾｮｴ of frozen strata, segregated, injected and vein ice belong
• to the constituted ice. The ice cement is I'oruned during the freezing of moist
disperse ground at the expense of wate r- freezing in pores be twe en particles of the solid skeleton ,'J1thout disturbing the mutual distribution of these
parti-cles. If the freezing of a primary sedimentary soil is combined with
crystal-lizational differentiation "lith attraction of wat er- and formation of ice whd.ch
pushes the soil skeleton apart, segregation ice is formed. If the freezing is
accompanied by the squeezing of water or obstruction of ground wate r flow, by migration under a head, by penetration and freeZing of water in the voids created by it, then injection (intrusive) ice will be f'o rmed . Finally, if fissured 'vJater-bearing soil freezes - which applies mainly to rather compact in situ soil - then vein ice will be formed in those fissures.
Cave-vein ice is differentiated 'vlith respect to conditions of occurrence,
｣ｯｮｾｯｳｩｴｩｯｮ and structure, depending first of all on the origin of voids in
the surrounding soil. The group of vein-ice types filling the fissures can be
separated from the group of cave-ice types, filling hollows created by the
removal of a portion of the soil material. Strictly speaking, the vein ice of
the group examined differs from the constituted vein ice in that its formation is associated with the influx of at least a portion of the material into the fissures of frozen soil from outSide, or else fronl the earth's surface. If a fracture appears periodically at the same place and the formation of ice is repeated there, then recurring vein ice \'Jill be formed.
ｾＱＰ basic ｧｲｯｾｰｳ can be distinguished within the cave-ice type -
thermo-karst-cave and thermo-karst-cave ice. Thermokarst cave ice originates in hollows
produced by melting of other types of ground ice, especially of recurring
vein ice. Karst-cave ice is formed mainly outside the permafrost region
associated "lith the so-called "cave-T'r-ost " and is represented mainly by deep rime and sinter ice inconwletely filling out a hollow.
Finally, llithin the buried ice type, one can distinGuish the group of chiefly congelated ice, formed by the freezine; of wate r-, and the group of
sedimentary-metamorphic ice - the product of metamorphosed snow, To the first
group belong the autochthonous (buried at the place of formation) ice or hydrocffusions (surface naleds), frozen llater reservoir and bottom ice, as weLl. as allochthonous (sub ject to transport) river, lake and sea ice, and to the second group - snow infiltration ice 01' firn ice (immobile accumulations
•
In this way the genetic classification of ground ice as known at present
is shown in Fig.
57.
The mutual transitions between the various genetictypes of ice are indicated by the horizontal two-way arrows in the upper part of the diagram (between ice types 1 to
5),
and the lower part of the diagram shows how these ice types belong to the nlorphological types listed above. Injection ice (3) and the vein ice proper (4) in the majority of cases, and cave ice (6,7) are always epigenetic, buried ice (8-11) is only syngenetic, and ice cement (1), segregated (2) and recurrent vein ice can be epigenetic aswell as syngenetic in the above indicated sense of that word. Any of the
enumerated types of ice can be contemporary or fossil of varying age.
A review is given below of the basic types of ground ice distinguished in
the present classification. The detail examination of each type has been
determined by the degree to which it was studied and by the relative part that it plays in the freezing of the earth's crust and affects the economic
activity of a country. However, this review does not cover the most
wide-spread and important type of ground ice - the ice cement of frozen ground (No.1 on the scheme), inasmuch as information pertaining to it is given in Chapter VI.
Segregated Ice
Segregated ice is the product of differentiation through crystallization during freezing of moist disperse soil, this freezing being acconwanied by the
attraction of water to the sections where ice is formed. After ice cement it
is the second most important and common type of ground ice and its presence is
characteristic of frozen ground possessing a high ice content. The
distribu-tion of segregated ice practically coincides with the distribudistribu-tion of silty,
clayey and phytogenic frozen strata. Ice of this type is important mainly
because its formation causes significant swelling of the ground and frequent disruption of plant roots, and its melting causes large ground settlements.
Since the mechanism of ice formation has been examine previously (Chapter V), only the forms of occurrence of segregated ice, its composition, texture and structure are described here.
Forms of occurrence. Segregated ice can be formed in freezing ground and
on its surface. In the last case it is represented by ice blooms, arising
from the freezing of ground water pulled up to the surface; these blooms have been repeatedly described since 1821 and are known by us under the names of "ice stalks", "rod-fibrous ice", "soil-needle ice", "ice grass", "ice druses", etc. (Dobrowolski, 1923; Bonstedt, 1921; Chirvinskii, 1936; Gladtsin, 1936; Barnov, 1949; Zamorskii, 1949).
•
Bodies of segregated ice are genetically regarded as constituted inclu-sions (streaks); they commonLy have the form of lenses, or lens-like layers, but those which stopped gr-owfng at the initial stage of their development have
the form of irregular inclusions. Lens-like inclusions can be oriented in
diverse ways. Often the ground is pierced by a network of variously oriented
ice inclusions, with all possible intermediate stages - from a completely disordered orientation, to a more or less rectangular grid or the prevalence
of the horizontal direction with slanting cross-pieces. However, in the
majority of cases the horizontal orientation is prevalent, or a general
orien-tation parallel to the freezing plane. Sometimes only vertical or inclined
inclusions are encountered. The dimensions, shape and arrangement of ice
inclusions determine the character of the cryogenic structure of the frozen
ground containing them. (The description of structures and their formation
in relation to the peculiar conditions of freezing of the ground is presented
in Chapter V. )
Composition and texture. In the majority of cases segregated ice does
not contain admixtures, is very clean and transparent, and its unit weight is
very near the specific weight of the clean ice. However, all transitions from
pure ice to frozen ground with ice cement are encountered; they are the pro-duct of the freezing of individual particles and more or less large xenoliths
of the surrounding ground into the ice inclusions during crystallization. In
the case of large xenoliths, it is difficult to establish the boundary between the ice inclusions and ground with reticulate structuce, l,e. ground pierced by a network of ice inclusions, which from its outer appearance resembles a breccia with an ice cement.
F.G. BalDllin has investigated segregated ice in the VorlDlta region, containing colloidal particles, much thinner than the main mass of particles
of the surrounding soil as impurities. In his opinion the colloidal particles
were brought in by migrating water. This explanation is apparently admissible
for that part of the ice which is formed during the filling of fractures in the freezing soil and is essentially a formation transitional to vein ice.
Small amounts of gases are included in segregation ice and the thinner
the ice, the less gas. Small lenses of ice occasionally contain small
spheri-cal inclusions of air. In larger ice strata fine cylindrical, thread-like
inclusions occur, which are normal to the plane of the ice stratum, indicating
the direction of crystallization. Commonly they appear at a certain distance
from the upper contact and form where the crystallization began; their number increases somewhat in the central part of the incluions, but below it remains constant. Some ice inclusions are likewise pierced by a multitude of vertical,
cylindrical inclusions of air and distinguished because of that by their white
colour. It must be noted that the vertical elongation of gaseous inclusions
in the surface layer of rocks
4 - 5
m thick can appear as the result of secondary processes not associated with segregation occurring during ground freezing*.Structure. The structure of segregated ice varies as does its formation,
and it is apparently regularly associated with the character of structure of
the frozen ground mass. Hypidiomorphic granular texture with orientation of
the main crystal axes usually normal to the plant of inclusions are most
frequently encountered (Fig.
58).
At the same time the crystals have aplate-like form in the thinner inclusions, and columnar in the thicker ones. Allotrionlorphic granular structure with approximately isometric disorderly oriented crystals of varying orientation is much rarer.
The formation of ice inclusions as the majority of other processes of crystallization conles about in two stages: (1) the stage of protocrystalliza-tion - the initiaprotocrystalliza-tion and growth of plate-like ice crystals up to their
amalgamation into one ice body, and (2) the stage of orthotropic crystalliza-tion - the mutually constrained growth of amalgamated crystals normal to the
plane of inclusions (Shunlskii,
1955).
The fewer the individual centres ofcrystallization, the larger the individual crystals in thin inclusions and the
more pronounced is their plate-like form.
In
ground with reticular structure,which is excessively wetted before freezing, there are often found large monocrystalline inclusions, whereas in rock with bedded structure there occur inclusions with a coarse grained texture (crystals 2 - 5 cm and more in size), as well as with fine-grained texture (crystals less than 1 D1nl in size). At the same time apparently, the greater the role of fracturing and initiation of crystals in the fractures (Chapter
V),
the more disorderly the crystallographic orientation; the independent initiation in pores with selection under theinfluence of variations in resistance to the loosening of the ground in various directions, leads to the regUlation of orientation.
If as the result of orthotropic crystallization an 1nclusion reaches a thickness greatly exceeding the diameter of crystals in the plane of that inclusion, then the crystals acquire a columnar form, and in the fine-grained
varieties even an acicular form.
In
the case of the disorderly, initial* The secondary character of vertical elongation of gaseous inclusions in ground ice of various origin and occurrence in the near surface ground layer is definitely established by comparing the types of structure of ice of similar type and age contained in a frozen ground mass that was exposed on
an ancient erosion surface at different depths in neiGhbouring areas. The
physical nature of this phenomenon is obscure; it can be assumed that it is due to the existence of great temperature gradients in the surface layer.
•
,
orientation there proceeds in the course of orthotropic crystallization a geometrical selection, the result of which is a prismatic granular texture with parallel orientation of the main axes of the surviving crystals normal to
the plane of that inclusion (Shumskii,
1955).
In the case where thecrystal-lographic orientation is orderly right from the beginning, the appearance of the prismatic granular texture at the stage of orthotropic crystallization is not connected to the geornetric selection of crystals.
The largest observed dimensions of segregated ice crystals were 20 x
9
CDI (Vtyurin,
1951
1 ) , Most often crystals in the plane of an inclusion arefrom
5
to 10 mm in size.Injected Ice
Injected ice is the product of the freeZing of water which has been intruded under pressure along the impermeable frozen layers of the ground. Its formation, as distinct from that of segregated ice, is due to the migra-tion under pressure and the freeZing of free ground water, and the separamigra-tion of the surrounding rock is accomplished by the pressure of water and not by
the growing ice crystals. This last peculiarity, with which is connected the
occurrence of concordant injections, distinguishes this type of ice from vein-ice types, which are discordant injections*.
Injection ice is widely distributed; it is characteristic of the major portion of the region haVing continuously frozen ground and in some sections
haVing seasonally frozen ground. In the majority of cases it occurs in much
larger masses than segregated ice. Nevertheless, with respect to quantity and
its significance in the glaciation of the earth's crust it occupies a much
more modest position than cement ice and segregated ice. This is explained by
the fact that injected ice is found only sporadically, under certain condi-tions, in the layer of seasonal freezing and thawing or near the upper bound-ary of the pernlafrost, and they are often associated with more or less
pronounced positive fornls of relief, produced by differential heaving, and
therefore they are geologically short-lived. They have been studied very
little up to the present.
* The assignment of injection ice inclusions to the group of constituted ice types may seem contradictory; however, it is justified by the fact that they are also formed from ground ｾｉ｡ｴ･ｲ and not from moisture introduced into the
earth's crust from outside. For the given limited section the ice is of the
injection type, but in a broader sense, it should be regarded as the product of differentiation of a substance during the freeZing of the earth's crust and thus assigned to the constitution ice type.
The mechanism of formation of injections. Injected ice is a Lways formed due to the nligration of free ground water under pressure or slurry, but the causes of the development of pressure and the role of the freezing of the
ground in that case can be different. In these cases the freezing only
dis-turbs the previously existing hydrogeological regime, by reducing the active
• cross-section of the ground water, or by creating on its way a barrier of
ｷ｡ｴ･ｲＭｩｮｾ･ｲｭ･｡｢ｬ･ frozen ground. In these cases the role of freezing is
passive and the source of pressure is the hydraulic head of a ground-water flow. In other cases a closed system can arise during freezing, i.e. a certain volwne of moistened ground confined on all sides by an impermeable shell, in
whf.ch the free space of the pores is inadequate for compensating the increase in vo Lume of water which is being converted into ice. Under these conditions
the head of water or slurry is created directly by the freezing itself. The
pressure, which can be developed during the freezing of water in a closed volwne, for example, reaches 2045 atm at -22°C, and, because of the hysteresis of conversion into ice III, it apparantly reaches 2500 atm (Talmnan, 1922). Therefore it is in fact limited only by the stiff resistance with sufficiently sharp lowering of the temperature.
The pressure migration during freeZing is mainly typical for water-saturated, coarsely disperse soil in which the formation of cement ice in the pores is accompanied by a volwne increase of up to 9.07%, and caused squeezing of the surplus of free water which arises fronl the front of crystallization
towards the side of the least resistance to its movement. If the freezing
layer is underlain by a water-resistant layer or frozen ground, clay, bed rock, etc., then the frozen covering is often detached through lateral migration and
separated from the underlying water-resistant layer by water lenses or sheets, which later likewise freeze. The sarne result can be obtained in the absence of a water-impermeable layer at the bottom of the frozen strata when there is
a flux of water from below. In supersaturated, fine-grained soil a more or
less liquid slurry, rather than water, migTates under pressure and creates
injections in sections with the least solidly frozen covering. The freezing
of this slurry leads to the formation of soil with high ice content or of ice impregnated with mineral admixtures below which there is soil of normal water content.
The shape of the injection depends on the ratio between the strength of the frozen covering and the strength of its adhesion on the sides and bottom,
as well as on the quantity of inflowing water. A flat intrusive sheet will be
formed with high bending strength of the frozen covering and weak cohesion with the underlying r-ock, In the opposite case the covering is more sharply bent and a hwnmock with a plane-convex core arises, resembling a laccolith in
•
shape. Thus, intrusive sheets, steeply upward bulginc; lenses - laccoliths, or various transitional shapes, sometimes with bulges of the most varied dimensions can arise. \'lith a large inflow of water, compared to the area of heaving, the resistance of the cover is broken, the apical part of the cover-ing is dissected with "endogenous" fractures, and water- of slurry pour out to the surface - a laccolith becomes a "hydrovolcanoll
which produces a naled (icing) or "mud volcano". If compressed gases are accumulated inside the hum-mocks, then a rupture of the covering may be followed by an eruption of water spouts or liqUid mud, several metres high, and sometimes by explosions scat-tering fragments of the covering.
Fractures can be rapidly closed by the freezing of water which fills them, but under continuous wat.er- pressure they may be reopened and eruptions
repeat-ed. This process will be stopped, if the water pressure weakens or if the
strength of the covering is increased by freezing. In this case an injection
can be guided to another place where the covering happens to be more yielding. As a result, groups of hummocks will arise.
Such is the general ｳ｣ｨ･ｮｾ of the processes of differential swelling
(heaving) and the formation of injection ice. Under different cryohydrological
conditions these processes do not follow the same course and different results emerge.
Types of ice injections. Injected ice inclusions can arise in the layer
of seasonal freeZing and thawing, or at the bottom of a freeZing or
permanent-ly frozen mass of small thickness. In the first case they are represented by
seasonal short-lived formations, and sometimes pereletoks, whereas in the second case they are perennial formations, although not long-lived as compared
with other types of ground ice. Seasonal, as well as perennial ice injections
are being formed by the freeZing of closed systems or under the action of the
hydraulic head of a ground water flow. Closed systems arise during freeZing
of a seasonally thawing layer above frozen ground, and within the frozen
ground - upon freeZing of taliks under lakes which do not extend to the bottom
of the frozen ground. Thus it is possible to separate the following types of
ice injections and differential heaving associated vlith them according to the condition of formation:
1. Seasonal
(a) at the outlets of ascending springs in the zone of seasonally frozen soils,
(b) on freeZing of closed systems in the seasonally thaWing layer, (c) on f'r-o ez Lng of supr-ape r-maf'r-ost "later;
2. Perennial
..
(b) on the freezing of closed taliles under lakes.
Injections at the outlets of ascending springs in the zone of seasonally
frozen soils. Seasonal ice injections of this type do not have much
signifi-cance, but offer a certain theoretical interest. They are known in several
districts of Kazakhstan: from Yuzhnye Mugodzhary in the west to the left
banks of the upper Irtysh River in the east, and to the Golodnaya Steppe in
the south (Gokoev, 1939). The ascending water percolates through a 5 - 10 m
thiclc clay layer and forms a slurry near the surface. In \'linter the frozen layer heaves under pressure from below and creates dome-like hummocks up to
1 metre in height and 1 metre in diameter. Beneath their surface (in July
-August 0.5 m), ice lenses, lasting sometimes until the next winter, occur at shallow depth.
Injections of the seasonally thaWing layer. Ice injections in the
seasonally thawing layer in the permafrost region are conmloner, of much greater dimension and significance and they belong to the second and third types.
During the whole history of investigation of injection ice, there have been numerous opinions on the relative role of the pressure (of water) in the heav-ing process caused by the freezheav-ing of closed systems and descendheav-ing currents in the seasonally thaWing layer. UndOUbtedly both types of injection do exist. Apparently the processes of formation of both of them are interconnected by gradual transitions, that make a precise demaraction rath difficult in many
cases. At the same time the numerous, concrete descriptions, accumulated to
the present time, indicate the prevalence and larger scale of the phenomena of heaving associated "lith the freezing of suprapermafrost water.
Seasonal frost ｨｗｔｨｾｯ｣ｫｳ with ice cores occur mainly in areas of dissected topography, at the bottom of slopes, in valleys of small rivers and in ravines with the run-off of temporary creeks, and they arise from the freeZing of the ground beneath river beds and other ground water occurrences in the seasonally
freezing layer. These hun®ocks reach 2 - 3 m in height. In mountainous
regions with coarse-grained soils, where uat.er- moves easily out of the season-ally freezing layer into rivers, subsurface injections are not as well
developed, and take second place to river naleds (icings). Ice hummocks of
surface naleds or hydroeffusions are replicas of " e a rthyll frost hummocks of the seasonally freeZing layer, the difference being that their coverings
con-sist of ice. On the other hand, in the plains where there are no distinctly
expressed f'Lows of aupr-ape rmat'r-ost "later, differential heaving is poorly developed and in the majority of cases it brings about the formation of only small, intrusive sheets of ice, which alternate with inclusions of segregated ice and are hardly discernible from the latter.
•
The coverinG of icc intrusions in the active layer docs not protect them from thmling and rapid destruction. As a rule, during the first sumrner- the central portion of the hunuaocks collapse and a small thermokarst lake is formed in their place, after uh.Lch the thawing of the remaining peripheral part of the ice inclusion is accelerated. Sometimes, howeve r-, it may last for one or two mor-e war-m seasons (Fig. 59).
Perennial injections. These injections at the outlets of sUbpernmfrost
water are confined to the fringe area of the permafrost region where the perennially frozen ground is thin in areas of complex tectonic structure,
where conditions exist for the ascent of ground water. The covering of this
type of injection may attain a great thickness (up to 15 m) (Baranov, 1940) and sometimes it consists not only of frozen Quaternary deposits but also of
layers of consolidated rock. The height of the hwnmocks at the outlet of
ascending springs reaches 10 - 12 m, sometimes even 15 - 17 m (Loparev, Tolstilchin, 1939).
Of greatest significance are perennial ice injections which form during the freezing of taliks under lakes. They are very \V'1despread, of large size and relatively long duration. The hununocks of this type are known in the literature under the Yakut name of "bulgunnyakh"*. Their height varies mostly
from 2 - 3 to 20 - 25 m, and in northern regions sometimes exceeds 40 m. On
the north coast of Alaska, one such hummock of heaving ground reached a height
of 70 m (230 ft) (Leffingwell, 1919). ｉｾｲｧ･ pingos on the alluvial plains
greatly exceed the highest points of the surrounding country over a vast
expanse. Pingos attain a dialneter of several tens of metres, less often 200 -250 m, and the taliks supplying them reach a diameter of several kilometres. The covering of pingos is 2 - 8 m in thiclcnessj the base of their ice core usually lies 5 - 10 m below the adjacent land surface.
Pingos gr-ow in lake basins vrhLch often freeze through in the middle of lakes which become shallow, and rise gradually over a long period of time, at a rate varying from barely viGible to more than 0.5 rrVyear (Solov'ev, 1952).
Their internal structure has not been studied very mUCh. Data from borings
show that the core does not always consist solely of a continuous ice TIlass. Cores of some pingos consist of soil having very high ice content which are pierced by a multitude of thin ice lenses or by a series of thicker ice sheets. These facts led to the opinion that the suction of water to the cold source rather than pressure heaving plays the main or even the only role in the
for-mation of pingoa, and therefore the pingo ice is not injection but segregated
(Taber, 1943; Vadilo, 1951; Solov'ev, 1952; Popov, 19531 ) ,
It should be noted that heaving humJ:locks at the outlets of sUbpermafrost
likewise have cores not of ice but of soil with high ice content. The
proces-ses of moisture suction and of the segregated ice formation must certainly play a great part in the build up of' perennial hummocks of both types. However, it is impossible to explain the appearance of thick ice lenses in this way.
Large plane-convex ice masses, and less often, irregular ones and series of ice sheets, much thicker than segregated inclusions, are an overly charac-teristic feature of' steep as well as of flat perennial hummocks of heaving, and it is completely alien to the bodies of frozen ground containing ice of
segregated origin. Flat pingos sometimes are similarly composed of thick,
continuous ice lenses. The origin of hunwocks with a series of ice layers in
the core is easy to explain by recurrent injection and high freezing rate, whereas the structure and texture of the ice in the excavated and comparatively well-studied pingos do not admit the possibility of the segregated origin, but indicate the intrusion of large amounts of water masses which froze very
slowly. The intrusion under pressure of slurry and then water on channels
made by the water during formation of the slurry, is possible in some cases
even in clays (Gokoev, 1939). However, in reality almost all water movement
in taliks, to the freeZing of whLch the formation of pingos is connected,
occurs in sands and gravels. Injected ice inclusions occur most often at the
contact of the clay loam to sandy loanl deposits with the underlying sands and
partly within the clay loam or sand. The very fact that the ice cores of
pingos occur in sands excludes the possibility of their segregated origin. P.A. Solov'ev has established the pattern of distribution of pingos for central Yakutia, by the fact that they occur and attain larger dimensions in
areas where sand occurs at shallow depth (Solov'ev, 1952). It can be asserted
that the connection of ice injections with sands and gravels has a general
significance. This follows not only from the mechanism of pressure migration
but also from genetic association with the alluvial deposits of taliks under lakes, the freezing of which leads to the formation of pingos.
The overwhe Inung majority of lakes existing above the permafrost are
either old or of thermokarst origin. In both cases the underlying taliks are
confined mainly to the alluvial stratum, because the large masses of ground ice, the t.haw.Ing of which is the cause of thermokarst hollows, are formed chiefly in fluvial plains (see page 31). However , sands and more coarse-grained strata are the commonest materials in the lower part of a normal pro-file of alluvial strata - the river-bed horizon, cOn1n1only covered by a thinner
clay loam or sandy loam horizon of flood-plain origin. In the majority of
•
•
•
fine-grained flood-plain alluvium, and the pressure migration of water in the taliks between frozen layers is similarly confined to the underlying horizon of the river-bed alluvium.
Composition of heaving hummocks. The plane-convex cores of these hwnmocks
are composed of continuous ice lenses, sometimes of layers parallel to the roof - xenoliths of the surrounding frozen ground (Fig. 60), or of more or less thick ice sheets alternating ｾｬｩｴｨ frozen ground. According to data of explora-tion boring, there are also cores composed of strata with high ice content pierced by s,..arms of small layers and lenses of segregated ice; however, hum-mocks opened up by natural erosion or by exploration always contained, as far
as is known, comparatively large ice inclusions. Sometimes an ice lens,
con-tinuous in its central part, is split on the periphery into a number of layers
which thin out and become wedge shaped. Ice veins, piercing the covering and
upper part of the core, are often found in the apical part of the core. Growing hummocks are underlain by thawed water-bearing strata or water
lenses and this water is usually under pressure. In seasonal hwmnocks large
chambers with ice vaults remain after the outflow of water, at the edges of which "narrow black burrows" mouth of a ne twor'k of "ratercarrying channels
-are visible (Nikiforov,
1912).
In the apical parts of such hummocks, airhol-lows are found with an ice vault up to 3.0 m in height (Shvetsov, Sedov,
1941).
ｾｨ･ｮ they are tapped by boring, the compressed air often escapes from the bore-holes with a noise, and when a water lens or a water-bearing horizon is tapped,
fountains may emerge from such boreholes. After the base of a hummock becomes
frozen to a sufficient depth, the influx of water and the swelling cease, because the covering at the given place offers increased resistance.
The basic difference in the formation of hWMlocks with ice cores and with ice-containing cores is, apparently, stipulated by the ratio between the rate of penetration of "later and its rate of freezing. If the former exceeds the latter then a wat.er- lens is found under the frozen layer 'i'lhich gives pure ice
on freezing. ｾｨ･ｮ the ratio of rates of these processes changes with time,
then the freeZing of the water- lens is followed by the freeZing of the water-bearing strata at its base, followed by the intrusion of water and so forth; the result of this is an alternation of injected ice inclusion and ice-bearing strata. The same '1ill happen also because of the periodic ruptures of the frozen covering followed by the outflow of water on the surface, the closing of fractures and the freeZing of the underlying strata until a new intrusion of water.
vlhen the rate of water Lnf'Low has been sufficiently reduced relative to the rate of freeZing, only ice-bearing strata with small inclusions of segre-gated ice will be formed, and the differential heaving will be caused only by
pressure. Thus, e;radual transitions f'r-om injected to segregated ice are
pos-sible. Nevertheless, the predominance of injected ice inclusions, whdch
greatly exceed the segregated inclusions in size, is characteristic generally of heaVing hummocks on closed taliks, on spring outlets and the seasonally t.hawed layer.
ｃｯｭｰｯｳｩｴｩｯｮｾ texture and structure. Dljected ice is very pure and
trans-• parent as a rule because of the almost complete absence of impurities.
Xeno-genic solid impurities occur in it only at the base of inclusions in the form of tongues rising straight up into the ice, or at times bent, and streaks of
small mineral particles, apparently lifted by the movement of water.
Some-times roots, stems and branches of plants \'1i th clwnps of soil are found at the
contacts piercing the ice mass deeply. As an exception it is possible to
observe within the pure, transparent ice, individual pebbles and boulders, the upper parts of which are frozen into the ice; sUbsequent heaVing has lifted them from the underlying pebble-boulder layer.
Air inclusions of various dimensions and shapes occur in the injected ice inclusions; these air inclusions produce an indistinct stratification, paral-lel to the covering, various vertical, oblique and irregular concentrations,
etc.
In
the large injections it is possible to find groups and clusters oflarge vertically stretched and bent bubbles of irregular shapes. Branched
systems, horizontally flattened bubbles, spherical, cylindrical, string-like
bubbles, etc., also occur. The cylindrical and string-like bubbles belong to
the oriented gr-owth type of inclusions wh.Lch arise in the process of
ortho-tropic crystallization and indicate its direction.
In
the ice laccoliths theyare sometimes radially oriented, uhLch is explained by some investigators by the change of the initially vertical position throuBh the distortion of the layers during heaving (Baranov, ＱＹｌｾＰＩＮ Evidently the primary radial
distribu-tion of them is also possible. The apical parts of the ice laccolith
some-• times contain numerous large air inclusions due to the concentration there of
gases expelled during the crystallization of water. An extreme case of such
concentration is the creation of vast air hollows.
The pressure in the cores of the hummocks , and consequently in their gas
inclusions, can be very high. On the other hand, explosions and catastrophic
eruptions of wat.e r and compressed air may apparently lead in some cases to the creation of a vacuum inside the hummocks because of rapid freezing of the supercooled vrater- in the fractures of the covering. This freezing f'Lxes the
reduced pressure after an explosion. Thus, the measured pressure in the air
bubbles, confined to the apical part of a flat ice laccolith near the city of Yakutsk, uas equal to
o.
ｌｾＴ and 0.50 atm (Shuraslcii, 1950).The texture of injected icc :Ls Ii ttle studied. Indications available in the literature, which are based on cursory, visual observations (Baranov,
1940; Sharp, 1942; and others), speak of a vertical prismatic granular texture. The f'cvr crystallo-optical invcstic;ations show that aLl.otr-Lomor-ph Lc c;ranular texture with very larc;e grain sizes, from 1 - 2 to 16 em in diameter, and with
• a chaotic orientation of crystals Ls characteristic of in,jected ice. In some
cases a tendency to linear-vertical and banded horizontal orientation, was
p observed without changing the general character of the texture (Fig. 61).
These facts, as well as the peculiarities of the structure, indicate a slow freeZing, in the majority of cases, of the large volumes of water in the absence of orthotropic crystallization, so characteristic of segregated ice.
In the apical part of the core of the hwnmocks a reduction in thickness and a wedgf.ng out of ice layers were observed, caused by plastic deformation through stretching and rupture on swelling (Shvetsov, Sedov, 1940; Solov'ev,
1952). Optical anomalies do not exist in the ice of flat laccoliths.
The geographical distribution and aGe of injected ice depends on the
features of formation of the various types described above. Seasonal ice
injections occur in seasonally frozen soils; they are Widespread and attain comparatively large sizes in the southern part of the permafrost region where seasonal thawing penetrates to considerable depth; they are less developed to the north and almost ｣ｯｮｾｬ･ｴ･ｬｹ disappear at hieh latitudes, where seasonal
thawing affects only a thin surface layer. Against the background of the
indicated climatic zonality the decree of development of seasonal injected ice depends also on azonal r;eomorphological and hydrogeological factors. Ice injections of the seasonally t.haw.Lng layer are most widespread in regions \'li th dissected topography, less so in mountainous regions with coarse-grained
soils and less so in the plains. In the majority of cases, the duration of
their existence is limited to less than one year, sometimes 2 - 3 years. Only the small, bedded ice intrusions in areas of accumulated flood plain and drift sediments can become syngenetic frozen masses and be preserved for a long time, geologically speaking, amid the smaller segregated ice inclusions.
Perennial injections at the outlet of subpe rrnaf'r-ost wat er-, as mentioned above, occur only in the peripheral zone of the permafrost region Ｌｾｨ･ｲ･ the perennially frozen ground is thin, and in areas with a ｣ｯｲＮｾｬ･ｸ tectonic structure.
At the present time they are known only in the Transbaikal region (Tolstikhin, 1932; Lopa r-ev , Tolstilchin, 1939; Baranov, ＱＹｬｾＰＩＮ
The follO\'Jing three conditions are required for perennial injections to grow in intrapermafrost taliks:
