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Thermokarst in Siberia and its influence on the development of lowland relief
QUATERNARY
RESEARCH
Thermokarst
1,
103-120 (1970)
in Siberia
and
Its Influence
of Lowland
TADEAS
CZUDEK
on the Development
Relief
1 AND
JAROMI’R
DEMEK
1
Received January 2,197O “Thermokarst” as a process is the melting of ground ice and the consequent formation of depressions. Thermokarst landforms depend on the tectonic regime of a region, the ground ice content, and the degree to which the permafrost equilibrium is disturbed. Thermokarst forms are especially prominent in the lowlands of the subnival region with permafrost. The authors distinguish two modes of thermokarst developmentpermafrost back-wearing and down-wearing-based on their investigations in Siberia. The first mode is characteristic of a more dissected relief. In this case permafrost back-wearing takes place and the process is characterized by development of gullies, thermocirques, and parallel retreat of steep walls with ice veins, resulting in a lower lowland level. The second mode of thermokarst development is due to permafrost melting from above and is typical of a flat undissected relief, mainly that of watershed regions. Characteristic forms are depressions with steep slopes and flat floors (alases). Thermokarst valleys develop through coalescence of alases. Thermokarst processes destroy the lowland relief of large areas and create characteristic forms resulting in a lower lowland level. Thus thermokarst represents a special type of lowland development in permafrost conditions. I. INTRODUCTION Thermokarst is the process of melting of the ground ice accompanied by local collapse of the ground surface and the formation of
depressions. In thermokarst regions, underground and subaerial forms develop such as funnel-shaped pits, larger basins with flat bottoms and steep slopes, dry valleys, caves, etc. The term “thermokarst” was introduced by M. 11. Yermolayev in the USSR in 1932, and in the English language by S.W. Muller in 1944, and is now widely used in textbooks of geology and geomorphology (for instance, Shchukin, 1964 ; Tricart, 1967 ; Hamelin and Cook, 1967; Embleton and King, 1968). 1 Institute of Geography, Czechoslovak Academy of Sciences, Brno, Mendlovo n&m. 1, Czechoslovakia.
Thermokarst occurs in regions having a considerable ice content in the soil. This is why the most intensive development of thermokarst occurs in lowlands. The development of thermokarst is due to the disruption of the thermal equilibrium of the permafrost and the increase in the depth of the active layer. The reasons for the disequilibrium and permafrost degradation can be various. Roughly, they can be divided into two groups : climatic and local. Among climatic reasons for permafrost degradation are changes such as general increase of temperature or humidity (e.g. snowfall), or increase of continentality leading to warmer summers. Local causes can again be subdivided into two groups : natural causes and the influence of man. For instance, a natural cause is the 103
104
CZUDEK
AND
development of polygonal ground-a characteristic process of subnival regions. Accumulation of water takes place where ice veins cross or in low centered polygons (Hussey and Michelson, 1966, p. 152). The water temperature in these pools is always higher than the temperature of the adjacent ground. In the Jano-Indigirskaja Nizmennost (Lowland) the thickness of the active layer is twice as great beneath 20-25 cm of water than in the adjacent ground (Table 1) . Due to thermal and chemical effects of the water, the ice vein starts thawing and the thermokarst process begins. Such thermokarst development takes place even in severe Arctic conditions, as in the case cited where the permafrost temperature is -9 to -11°C (Mushkin, 1960, p. 41). Other local causes can be vegetation changes caused, for instance , by forest fires due to lightning. :\mong the influences of man belong clearing of forests, ploughing of grassy slopes, damage of vegetation due to vehicles, and construction activity. For instance, PCwC (1954) described excellent examples in the surroundings of Fairbanks, Alaska, where forest areas were changed into fields. The thermokarst process can manifest itself in the relief in different ways. The extent of the geomorphic changes depends on (1) the tectonic regime of the region, (2) the ice content in the soil, and (3) the degree and rate of equilibrium disturbance, i.e., the increase in depth of the active layer. The
DEPTH
OF THE
.&CTIVE
LAYEK
IN
DEMEK
thermokarst can manifest itself only in the relief of stable or rising lowlands. In the regime of a subsiding lowland the developing forms are quickly filled with deposits. The deposits of lowland areas in the subnival zone with permafrost often involve numerous thick masses of ground ice. The quantity of ground ice in fluvial. lacustrine. and eolian deposits is frequently SO-90%, of the total volume of deposits. It usually occurs in two basic forms : ( 1) segregated ice dispersed in the soil and (2) ice veins and ice wedges (Fig. 1). The ice wedges and ice veins may occupy 30-60s of the surface in some regions of the Central Jakutian Idowland of Siberia. The distribution of ground ice is also important in thermokarst development. Three general types can be distinguished. The first type comprises ground ice in deposits of stable regions where permafrost developed after deposition (epigenetic type‘). In such deposits most ground ice occurs in the upper part because of water migration toward the freezing front; downward the ground ice content decreases. The second type comprises deposits in subsiding regions where deposition was simultaneous with freezing (syngenetic type). In the deposits the ground ice is distributed throughout the whole profile. Enormous syngenetic ice veins developed in this way in some lowlands (e.g., Kolymskaja Nizmennost in Siberia) (Popov, 1953). For in-
THE POLYC;ONAL GROUND OF THE (LOWLAND) (MURHIN, 1960, p. 501
JANO-IKDIGIRSRAJA
Depth Humidity
in central
part
of polygon
Relatively dry polygon centers Moist polygon centers IVater layer 7-10 cm deep in polygon center Water layer 20-25 cm deep in polygon center Lake 30 X 10 m with deoth 25 cm and more
of acti\-e
NIZUEKNOST
layer
(cm)
polygons Lat 70”37’N
polygons I,at 71”30’N
30-31 38-41 52-56 62-69 >75
23-25 31-33 39-42 51-53
THERMOKARST
IN
SIBERIA
AND
stance, the ice wedges in the exposures at the Indigirka River near the village of Sypnyj Jar are 40-50 m thick. The third and less important type comprises the ice cores of pingos and palsas. From the geomorphic point of view, the origin of thermokarst forms can be ascribed to lateral permafrost degradation (,backwearing and to permafrost degradation from above ( down-wearing j as described below. 11. BACK-WEARING THERMOKARST PROCESS Lateral permafrost degradation or backwearing takes place mainly as a result of lateral and vertical river erosion or marine and lacustrine abrasion. During spring, floodwaters undercut river banks. The river water is warmer than the soil, and thermo-
FIG.
Photo
1. Ice vein J. Demek
in the Lena (August
1966).
River
DEVELOPMENT
OF
LOU’T,A4iXD
105
RELIEF
erosion can act in the frozen soil and develop deep tl~ermoerosional niches at river level (Fig. 2). For instance. the undercutting of sandy terrace deposits by the Lena River may extend inwartl as much as 10 m (Yefimov. 1964. 1). 99 ) The frozen deposits that are exposed due to lateral river erosion or collapse of undercut l~locl~sthaw later in summer. Thennonbrasiotl niches 3 m high and 20 m deep occur at the foot of cliffs on the coast of the More Laptevych (Sea) and the Vostok-no-Sibirskoje More (Grigoryev, 1966, p. 77).
Several stages of thermokarst development can be found on the river scarps of the Central Jakutian Lowland (Fig. 3). The first stage is the thawing of ice veins and ice wedges, leading to thaw gullies that display a
terrace on Pegcanaja
Gora,
north
of
the
town
of
Jakutsk.
106
CZUDEK
.\ND
DEMEK
FIG. 2. Examples of lateral and thermal erosion by rivers. (A) Lena River terrace in the the town of Jakutsk; (B) Deputitko River bank, Chrebet Cerskogo in NE Siberia; (C) River bank, Chrebet Cerskogo in NE Siberia; (D) Aldan River, lower course; sliding due effects of the river. 1, Ice veins ; 2, frozen fluvial sand ; 3, frozen loams ; 4, humus and peat; upper permafrost limit.
mocirque consists of a vertical or overhanging slope at the head and an uneven floor. Longitudinal and cross sections of ice veins usually appear in these slopes (Fig. 6). The ice thaws and the vertical slope retreats parallel to itself. Disintegrated baydjarakhs can be found on the cirque floor so that the bottom is uneven with conical elevations. Aq thaw-water gully usually drains the thermocirque. Landslides and mud flows occur in places on the gully banks in the mushy material. The development of gullies takes place
strikingly regular distribution on slopes. The distance between gullies corresponds to the diameters of the ice-wedge macropolygons in the terrace deposits of the rivers (Fig. 4). Due to the continuing development of gullies, the vegetation is damaged and domelike relief features develop. As ice veins parallel to the river bank thaw, the polygon centers become isolated and form conical hills called “baydjarakhs” in Jakutia. During further development the baydjarakhs are successively destroyed and an amphitheatrical hollow (thermocirque) forms (Fig. 5). The ther-
I
:
:
:
0
IO
20
30
FIG. 3. Thermocirque development on a river frozen fluvial sand; 4, active layer; 5, landslides veins and ice wedges.
vicinity of DeputPtka to thermal 5, river; 6,
,
LO M
bank. 1, Ice veins and ice wedges; 2, frozen loams; 3. and mud flows ; 6, colluvium; 7, pseudomorphs of ice
TIIERMOKARST
IX
FIG. 4. Gullies and baydjarakhs Photo J. Demek (August 1966).
even in the high Arctic (Fig. gullies in the baydjarakh Tajmyr Peninsula opposite increased years (1937-1946)
SIRERTA
Ai-iD
DEVELOPMENT
created by lateral
7). One of the region of the Dickson, in 9 in depth from
permafrost
OF
l.O\VT.hIiD
degradation.
RELIEF
Aldan
River
107
terrace.
3 to 10 m, and in width from 0.5 to 20 m (KOSOV, 1959, p. 128). In large thermocirques water acumulates on the floor and forms a small pool. The
5
FIG.
(August
5. Thermocirque 1969).
created by lateral thawing
of ice veins. Alden
River
terrace.
Photo J. Demek
108
CZUDER
FIG.
6. Thermocirque
slope in the Aldan
AND
River terrace.
of water accelerates considerably the development of the thermokarst. Steep slopes with thick ice veins have been described, for instance, in the Kolymskaja Nizmennost and Primorskaja Nizmennost in northeastern Siberia (Fig. 8). An estensive lowland occurred here in the Pleistocene, probably extending far into the Arctic Ocean and including the present Lachovskije Ostrova (Islands), and Ayon and Vrangel Islands. In the Upper Pleistocene stratified loams with peat beds were deposited in the lowland during continuous subsidence. Ice veins 30-50 m thick and 10 m wide occur in the loams. The ice veins form a polygonal pattern, the loams being but separated columns among them. Due to the thermokarst. even scarps 25 m high retreat parallel to themselves on a section several kilometers long at an annual rate of 15-18 m. Lakes develop at the base, and the erosional activity of the lakes and undercutting of the scarps accelerate scarp retreat. The lakes are deepest at the foot of the scarps. On the opposite side of the lake there is shallow water, which increases in width by 10-S m per year (Tomirdiaro. 1966. lx 32). Thus a lower
presence
DEMEK
Photo J. Demek
(August
1969).
lowland develops at the level of the lake. The relief of the Primorskaja Nizmennost (LOWland ) has been changed considerably by this process. Small remnants are preserved above the level of the lower lowland and are bordered by scarps with thick ice veins. On the lower level, permafrost aggradation takes place after shifting of the lakes or their desiccation, and even epigenetic ice wedges develop, their dimensions being smaller than those of the Pleistocene ice wedges of the original higher level. Their thickness does not surpass 5-6 m and their width in their upper section ranges from 3 to 4 m. The dimensions of these polygons are 16 X 20 m (Tomirdiaro. 1969, p. 18). 111. DOWN-WEARING THERMOKARST PROCESS Permafrost degradation from above or down-wearing occurs in flat undissected terrain mainly on watersheds. The forms developed depend on the amount of ground ice and on its type. \J’here the amount is small or in places with segregated ice, or both, their
flat shallow depressions develop and area is usually of small extent, as
TITERMOKARST
FIG. Demek
7. Gully (August
created 1966).
by
ice
1K
SIBERlA
vein
thawing
FIG. 8. Schematic cross profile showing lowland. 1, Humus and peat; 2, syngenetic fluvial sand; 5, alas deposits; 6, epigenetic limits.
.\A-D
in
slope
DE\‘ELOI’MEKT
deposits
of
OF
I.O\VI..\h-D
RELIEF
Kular,
northern
Jakutia.
109
Photo
headwall of the upper lowland and the developing lower ice veins and ice wedges; 3, frozen loams; 4, frozen ice veins and ice wedges; 7, water; 8, upper permafrost
J.
110
CZUDEK
AND
illustrated by the results of a forest fire in the lowland along the Jana River July 2.5-27, 1953. Measurements in August 1965 showed that the thickness of the active layer below the unburned forest was 40-15 cm whereas it amounted to SOcm where the fire occurred. Due to the thermokarst process the fire had lowered the surface by 20 cm (Vebernikov, 1966, p. 39). Thermokarst forms are more distinct where there is considerable ground ice and where a polygonal network of ice veins, mainly syngenetic. is developed. The authors studied the development of thermokarst phenomena under these conditions on the middle terraces of the Lena and Aldan Rivers in the Central Jakutian Lowlands. The thermokarst phenomena created by the permafrost degradation from above are found mainly on the Tjungjulju and Abalach terraces. The Abalach terrace forms an extensive surface with an altitude of 116134 m. It is built of sandy river deposits, 20-30 m thick, covered with a loam layer 40-60 m thick. The Tjungjulju terrace consists of 60-80 m of fluvial sands covered with 610 m of loamy deposits (Soloviev, 1962, p. 3940). The mantle loams are of complex origin, probably involving eolian, lacustrine, and fluvial processes in a subsiding lowland. There is much ground ice mainly in the upper loam layer (20-40 m thick) ; thick ice veins occupy 30-60% of the terrain surface. In addition, the loams have a segregated ice content of 40-80%. When the thermal equilibrium of the 1)ermafrost is disturbed thermokarst phenomena develop in several main stages (cf. Soloviev, 1962, p. 45 ff .) In the first stage (Fig. 9) the polygonal system of ice veins begins to thaw. Highcentered polygons develop with troughlike depressions above the ice veins (Fig. 10). The terrain surface undulates but the vegetation cover is not yet destroyed (Fig. 9, Ia). As the depression above the ice veins grows successively deeper, the humus layer splits
DEMEK
and slides into the depressions. The polygon cores ‘keep their height and their flat top. However, as soon as the trough-shaped depressions reach the depth of l-l.5 m, slumping starts and the polygon cores change into conical baydjarakhs. The moss and grass cover is already completely destroyed and the polygon cores exhibit loamy surfaces. Jn places even ice veins crop out (Fig. 9. lb ) In the second stage (Fig. 9, II) the baydjarakhs successively slide and disintegrate, and a depression develops in the center of the baydjarakh field similar to sinkholes in karst regions. Below the sinkholes, there may be subsurface hollows of a tunnel type. P&w& (1953) described a sinkhole with an area of 2.4 X 4.5 m and a depth of 6 m which had horizontal galleries 1 m wide and 0.6 m high with traces of running water. Through successive linkages continuous depressions with steep slopes and uneven bottoms form, which are called dujodas in Jakutia. The water in the depressions promotes the clevelopment of the thermokarst. As soon as a small pool appears that holds water for the greater part of the year, thermokarst development proceeds very quickly. Water is of enormous importance in this process, since it stores the heat that thaws the adjacent permafrost. The water has also simultaneous chemical effects. As the result of the heat storage, thermokarst can form in even the severe conditions of the high Arctic and Antarctic. In case no water accumulates, thermokarst development slows down and even stops, to revive only in more humid years. On steep slopes of dujodas there are baydjarakhs. Slumping is active and ice veins thaw. If the dujoda develops in the taiga, the trees on the slopes lean toward the center of the depression or fall down (Fig. 11). The depression starts developing an asymmetric profile, with the south-facing slope being commonly the steeper and drier. Although the slope exposed to the north is gentler and the thawing on it is rather slow,
THERMOKARST
Ii-i
SIBERIA
AND
DEVELOPMENT
OF
LO\\‘LAND
RELIEF
111
IV a
FIG. 9. Main development stages of alases. Ia, Original lowland surface with syngenetic ice wedges; Ib, initial thermokarst stage-baydjarakhs ; II, dujoda; IIIa, young alas; IIIb, mature alas; IIIc, old alas ; IVa, Khonu with pingo; IVb, Khonu with depression at site of thawed pingo. 1, Syngenetic ice wedges ; 2, larches and grass ; 3, water ; 4, landslides ; 5, alas deposits ; 6, epigenetic ice veins ; 7, pingo ; 8, upper permafrost limit.
it takes place over the whole summer season. In the third stage (Fig. 9, IIIa) a distinct depression with steep sides and a flat bottom develops, called an alas in Jakutia (Fig. 12). In the Jakutian language this term denotes a circular or oval depression with steep sides and a flat floor overgrown with green grass around a thaw lake. In the taiga the lake is usually more or less circular. In the tundra, or in the case of a large alas, the lake is commonly oval, the short axis being commonly parallel to the prevailing direction of summer winds (Rex, 1961, p. 1021). Upon
attaining a certain depth, the lake does not freeze to the bottom in winter and a talik begins to develop below the lake (Fig. 9, IIIa). As the ground ice thaws, the deposits below the lake sag and the thaw lake deepens (Fig. 9, IIIb). In northeastern Siberia, a freshwater lake 1.4-1.6 m deep does not freeze to the bottom (Tomirdiaro, 1966, p. 29). Exploratory borings in the Mackenzie River region have shown that thaw lakes having a diameter greater than 800 m (half a mile) and a depth of at least 2.1 m (7 feet) have a talik roughly 65 m (200 feet) thick (Johnson and Brown, 1964, p. 164). The
112
of
CZUDEK
Fr G. 10. Start of thermokarst F ‘ok .rovsk, Jakutia. Photo
alas fl oor usually dept -ession center. tent , a.n irregular duri “t?: thawing,
FIG.
the
town
11. of
Transitional Pokrovsk,
IZXD
by thawing of ice vein J. Demek (August 1966).
slopes down toward the Due to irregular ice consagging of deposits occurs and a rolling topography
stage Jakutia.
DEMEIi
between Photo
dujoda J. Demek
system
(high-centered
polygons)
near
the
usually develops as a result. Vert ,ical differences of the alas floor can thus arrlount to 2-6 m. The thawing influence of the lake exi Lends
and young (August
alas. 1966).
Slopes
slide,
trees
fall.
Vicinity
of
THERMOKARST
IN
SIBERIA
AND
--I;G. Jakutia.
12. Mature alas Photo J. Demek
with steep slopes (August 1966).
DEVELOPXENT
OF
LOb~LtZND
113
RELIEF
-and
a small
to its shores i Johnson and Brown, 1964, p. 173), and waves and currents erode the thawed deposits and, in large alases, result in terraces. In Central Jakutia, erosion is most effective on south-facing slopes, which are thawed to a greater depth and are commonly steeper than other slopes, are overgrown with grass, and very often have baydjarakhs. In contrast, the north-facing slope is humid, gentler, and covered with bent trees ( drunken forest). The depth of alases in the Central Jakutian Lowland is usually 3-40 m, and their diameter ranges from 100 m to 15 km (Soloviev, 1962, p. 48). Due to wind action, alas lakes and the alases shift (Fig. 9. 111~). Alas deposits accumulating on the alas floors consist of the loams that have lost their ice content and include material supplied by slumping and solifluction from the alas slopes and the material supplied by lacustrine abrasion. The deposits may have a considerable content of organic matter. The rate of the alas development varies
lake.
17icinity
of
the
town
of
Pokrovsk,
considerably. Some alases have formed within a human generation; others are several thousand years old. Many alases developed during the Holocene climatic optimum, some 4000-5000 years ago (Grigoryev, 1966, p. 65). The latest phase of intensive alas development began some 100 years ago (Kononov, 1965, p. 58). The large alases in the Jano-Indigirskaja Nizmennost (Lowland) developed over a period of several thousand years according to measurements reported by Tolstov (1966, p. 141). Soloviev gives the following survey for the surroundings of the town of Jakutsk : % of the terrain surface
1. Flat watershed without thermokarst 2. Young thermokarst 3. Mature thermokarst and alases 4. Mature thermokarst without lakes 5. Old thermokrast
60.5 1.5 3.0 4.0 31.0
114
CZUDEK
AND
The alas development proceeds to the complete thawing of the ground ice, or to the formation of a stable talik if the width of the lake is considerably less than the thickness of the permafrost. In the fourth stage (Fig. 9, IVa) the alas lake disappears. There are various ways in which this occurs; for instance, the lake can disappear by filling with alas deposits or by draining to a lower alas level or to a river valley. With the extinction of the lake, permafrost aggradation takes place. Baydjarakhs still form on slopes, and as a result. the marginal slopes become flatter and permafrost appears on the alas floor. A special cryogene structure develops in these epigenetically freezing alas deposits. Due to the segregated ice in the upper part of the deposits? the alas floor rises and new ice veins develop. In the Central Jakatian 120wland, these ice wedges are much smaller than those on the Pleistocene surface. The talik freezes from all sides and the developing pressures cause pingos and palsas to form. Conical hills with an ice core, or
FIG. 13. Khonu stage with epigenetic ice veins. Vicinity
permafrost of the town
DEMEK
a core rich in ice, can be found in many alases of the Central Jakutian Lowland. As the ice cores of the palsas and pingos thaw, oval depressions develop that are bordered by a rim (cf. Svensson, 1969). The result of the fourth stage of alas development is thus a flat depression with gentle slopes and an undulating bottom with pingo relics or postpingo hollows, called khonu in Jakutia (Fig. 9, IVb ; Fig. 13). The formation of thermokarst has considerably changed the aspect of the lowlands. In the Central Jakutian Lowland, 40-50s of the initial surface has been destroyed by the formation of alases (Fig. 14). In the north the lowland on the right Jana River bank has almost completely lost its original appearance and has changed into a system of alas depressions mostly filled by thaw lakes. Remnants of the initial surface rise as conical hills and narrow ridges above the alases. The lakes cover areas of 31F km ?. Complicated thaw lakes developed by the coalescence of several alases cover areas of some 25 km 2. The thermokarst process from above created the lower level of the lowland,
aggradation, of Pokrovsk,
and undulating Jakutia. Photo
bottom due to the J. Demek (August
growth 1966).
of
THERMOKARST
IN
SIBERIA
AND
DEVELOPMENT
OF
LOWLAND
FIG. 14. Map of thermokarst relief east of the town of Jakutsk in the Central (following P.A. Soloviev). 1, Original lowland level with syngenetic ice wedges lakes in alases ; 4, recently desiccated lakes in alases ; 5, old alases.
which is situated lo-15 m below the original surface (Protasyeva, 1965. pp. 97-95). IV.
THERMOKARST
VALLEYS
The coalescence of alases results in thermoknrst valleys. In regions where alases develop near each other the ridges separating them are often destroyed. The ice melts and the elementary alases join into a complex alas. By successive addition of othe; alases, an elongated depression develops consisting of wide sections-alas basinsand narrow connecting sections where former narrow watersheds have been eliminated. The ground plan of the alas valleys differs considerably from that of the river valleys in displaying unexpected turns, blind spurs, and in places a trend against the general inclination of the relief. Initially, thermokarst valleys have a steplike longitudinal profile due to irregular ice content and irregular settling of thawed deposits, so that alas floors occur at various heights. However, the dif-
RELIEF
Jakutian ; 2, young
115
Lowland lakes ; 3,
ferences in height become successively graded. The deepest alases are filled and the higher floors are lowered as erosion progresses along thermokarst gullies originating on epigenetic ice veins ( Fig. 15). In the Central Jakutian Lowland a thermokarst valley comes to have a wide grassy bottom and flat slopes covered with taiga (Fig. 16), but even in a mature thermokarst valley the typical basinlike character is preserved. Tn the longitudinal profile the depression for the most part is already well graded. Only the lateral-usually young valleys--lead into the main valley with a rather low step. The alas lake usually has not reached this far and therefore thawing and sagging of the ground are less important here, and even relic ice veins are preserved (Soloviev. 1963. p. SSi. In the main valley, a small stream usually appears, but it has only an indistinct shallow bed and does not erode. The greatest part of the valley is dry for almost the entire year, Only during the spring snowmelt does water
116
CZUDEK
AND
DEMEK
4 3
2
1
-
0
20
70 I
0
5
t 10
120 ,
10 I 14 M
watershed west of FIG. 15. Cross profile of a gully developed by thawing of ice veins. Lena-Viljuj the town of Jakutsk. 1, Humus and peat; 2, frozen brown sandy loam; 3, ice vein; 4, upper permafrost limit; 5, water. Leveled by T. Czudek and J. Demek, May 19, 1969.
rush down the whole grassy valley bottom. In May 1969 the authors watched the snowmelt in the Aat thermokarst valleys of the Lena-Viljuj watershed where long but
FIG.
shallow valleys are incised into the flat surface of the plateau. A water layer 30-50 cm high was rushing down the grassy bottom of these valleys for several days. The water
16. Alas valley on a river terrace west of the town of Jakutsk. Photo J. Demek (August
I9661
THERMOKARST
IN
SIBERIA
AND
was pure and transported only vegetation detritus. The streams did not erode, since the substratum was still frozen. After some days the water level had fallen and the valleys were mostly quite dry.
DEVELOPMENT
OF
LOWLAND
RELIEF
117
b~rz~isl4blllatutt, Poa pvatcnsis, 17icin uncca, and Potcntilla answpina are characteristic here. In large alases the zone is usually divided into ( 1) a subzone, nearer the lake, used as a meadow for hay farming ; and (2) a subzone, farther from the lake, used for V. THERMOKARST AND spring crops-barley and oats for silage AGRICULTURE (Kononov. 1965, p. 59). The outer third zone are dry meadows Clearing of permafrost areas for cultivation usually results in the disturbance of the used as pasture. The density of grass varies thermal equilibrium of the permafrost. De- considerably in different years, depending on the annual precipitation. The soils are pending on the degree of the equilibrium disturbance and the quantity of ground ice frequently saline. On solonchaks, Purrindia tcnuiflora prevails, and on less saline soils, in the soil, the development of thermokarst YepCnS and HO&MIX hcvimay lead to a variety of forms. T. L. PCwO Agropyon dominate (Kononov, 1965. pp. (1966, p. 26) writes that baydjarakhs begin sztb1dat~4m 60-61). to appear in fields within 2-3 years after The gradual development of the nlases clearing. Successively sink holes, tunnels, caves, etc. develop in the fields. Fields and desiccation of the lakes has led to strongly affected by thermokarst occur, for changes in the location of villages, an d instance, in the Kolyma River valley in remnants of abandoned villages can now be found in many alases. northeastern Siberia and in the watershed region of the Lena and Amga Rivers east of VI. THERMOKARST the town of Jakutsk. AND ENGTNEERING On the other hand, the flat alas floors are most important agricultural areas in the The development of thermokarst enCentral Jakutian Lowland. The Jakuts dangers construction in permafrost environarrived in this region with their herds from ments (Fig. 17, 18). In Siberia. buildings on the steppes of southern Siberia. The grass- deposits with a high ice content are comland in the vicinity of the lakes in the taiga monly constructed on timber or concrete was natural pasture for their herds. The piles, with preservation of the permafrost. lakes which do not freeze to the bottom in This technique allows construction of multiwinter, are presently the only water resource storied buildings in northern regions without for the villages. In 1960 the alases supplied danger of thermokarst development. Ther63.3%, of the total hay production in Jakutia mokarst may also affect road construction. (Kononov, 1965, p. 57). Highway embankments in Siberia are usually In the alases with lakes in their centers built of material bulldozed from the immedithree more or less concentric zones can be ately adjacent area. The bulldozers can rake distinguished from the viewpoint of agriup only the active layer, the thickness of culture. The size of the different zones de- which is usually slight (e.g., from 0.4 m in pends on the degree of soil development and the north up to 1.5 m in Central Jakutia). on the age of the alas. A zone with aquatic Thus a relatively large area is denuded on vegetation and peat-bogs occurs closest to both sides of the road, and the thermal the lake. This zone is usually not utilized for equilibrium of the permafrost is disturbed. farming. The adjacent second zone is For instance, construction of the road in the characterized by young humid soils with a settlement of Deputatskij in northern Jakutia high humus content. Plants such as Hordc~z led to thawing of the ice veins and develop-
118
FIG. Photo
CZUDEK
17. Thermokarst J. Demek (51ay
due to bad 1969).
insulation
AND
of a house
ment of a ravine 2.1 m deep. The thaw water created a tunnel in the ice veins below the road and engulfed the road margin in June 1969. Along the shores of northern Siberia
FIG.
Photo
18. Bridge J. Demek
deformed due (May 1969).
to
thermokarst
DEMEK
in the
village
of Bajandaj
in the Irkutsk
region.
thermoabrasion leads to coastal retreat. For instance, it caused the complete destruction of the Vasiljevskij and Semenovskij Islands in the Laptevych Sea (Kachurin, 1961, p. 247). Because of sporadic settlement, ther-
processes
in
the
Tunkin
Basin
in
southern
Siberia.
THERMOKARST
IN
SIBERIA
AND
DEVELOPMENT
moabrasion is presently of no economic importance. However, its significance will increase with the installation of technical equipment on northern coasts, and thermoabrasion should be taken into consideration in the choice of building sites. Thermokarst phenomena must also be considered in relation to bank erosion of water reservoirs in the permafrost region. Thawing of thin permafrost below engineering structures can lead to water from below the permafrost reaching the surface under pressure and creating seepages that freeze. Such icings also endanger engineering projects. On the other hand, thermokarst processes are utilized to accelerate thawing of the overburden of mineral deposits. Artificially accelerated thawing is used, for example, in removing the overburden from gold-bearing gravels of the Kular placer deposit in northern Jakutia. Significantly, alas deposits of the lower lowland level in northern Siberia have a
OF
LOWLAND
119
RELIEF
much lower ground ice content and are less affected by thermokarst phenomena than the higher Pleistocene lowland level. ;Zs a result the alas deposits are preferred construction sites (Tomircliaro, 1969). WT. CONCLUSIONS Thermokarst considerably influences relief development of the lowlands in the subnival zone. It destroys the initial surface of large areas and creates a new lower level of the lowlands, which is initially independent of the main level of erosion. The thermokarst process thus represents a special type of relief development.
The authors are indebted to Professor P. I. Melnikov, Director of the Institut merzlotovedeniya SO AN SSSR in Jakutsk, for making their studies in Siberia possible, and to the scientific workers of the Institute, P. A. Soloviev and M. S. Ivanov, for the demonstrations and discussions in the field. The authors are indehted for redaction and valuable comments to Professor A. L. Washburn and Professor T. I,. PCwP.
REFERENCES V. V., BELOPUKHOVA, E. G. I., and SHMELW, L. M. (1967). cheskiye usloviya Zapadno-Sibirskoy nosti.” Nauka, Moscow.
BAULIN,
B., DUBIKCW, “Geokriologinizmen-
DEMEK,J. (1967). Report on the study of cryogene phenomena in Jakutia (USSR). Sbor&k C’eskoslovercske’ SpoleAosti Zeme’pisne’ (Plaha) 72, 99-l 14. DEMEK, J. (1968). Beschleunigung der geomorphologischen Prozesse durch die Wirkung des Menschen. Geologische Rwdschau 58, 111-121. EMBLETON, C.. and KING, C. A. M. (1968) “Glacial and Periglacial Geomorphology.” Arnold, London. GRIGORYEV. N. I;. (1966). “Mnogoletnemerzlyye porody Primorskoy zony Jakutii.” Nauka, Moscow. HANIELIN, L. E., and COOK, F. A. (1967). “Le PCriglaciaire par I’Image” (Illustrated Glossary of Periglacial Phenomena). Les Presses de I’Universitb Laval, Quebec. HUSSEY, K. M., and MICHELSON, R. W. (1966). Tundra relief features near Point Barrow, Alaska. ‘drctic 19, 162-184. JOHNSON, G. H., and BROWN, R. J. E. (1964). Some observations on permafrost distribution at
a lake Canada.
in the Mackenzie A-lYctic 17, 163-175.
Delta,
N.
W.
T.,
S. P. (1961). “Termokarst na territorii AN SSSR, Moscow. KOXONOV, K. 12. (1965). K. vop,-osu o rezhime vlazhnosti pochy alasov Centralnoj Jakutii. Snklm Gosudarstzw~~ay urziewsifctyt, Uledere (/aknfsk,~ 16, 57-75. KOSOV, H. 1;. (1959). Ovrazhnaya eroziya v zone tundry. ~‘cznch~z~~e Doklndy Fysshey Shkoly, KACIIURIN,
SSSR.”
Ckolop-po.qm
jichcskiyc
123-129. MLTI<~IX, N. I. (1960). form relyefa v razvitii Indigirki. Mnterinly
rtmlrg
(AIOSCOW)
NO.
1. pp.
hero-dylrli
mznlrlz
0 znachcnii termokarsta k osnovant
xm~roy
kovy
polygonalnykh v nizovyakh ucJteGya
o
5, 45-55.
hIUr.IxR, S. W. (1944). Common frontiers in geology and related science in the U.S.S.R. and the U.S.A. IS “Science in Soviet Russia,” Jacques Cattell Press, Lancaster, Penn. pp. 11-17. P6wB, T. L. (1954). Effect of permafrost on cultivated fields, Fairbanks area, Alaska. U.S. Geologicnl Suwey Bdletin 989-F. Plimfi, T. L. 11966). “Permafrost and Its Effect on
120
CZUDEK
Life in the North.” Oregon State University Press, Corvallis. POPOV, A. I. (1953). Osobennosti litogeneza alluvialnykh ravnin v usloviyakh surovogo klimata. Ixlesti_va AN SSSR. seriya geograficheskaya (dloscocv), No. 2, pp. 2941. POPOV, A. I. (1966). Le thermokarst. Bidetyn Prvyglacjahy 4, 319-330. PROTASYEVA, I. V. (1965). Landshaftno-geokriologicheskoye deshifrovaniye v nizovyakh reki Jany. Sakha Gosr4davstzxxna~ wiversitetyt Ulcdere 16, 91-101. REX, R.W. (1961). Hydrodynamic analysis of circulation and orientation of lakes in northern Alaska. In “Geology of the Arctic,” Vol. 2 pp. 1021-1043. (G. 0. Raasch, Ed.) University of Toronto Press, Toronto. SIICHUKIS, I. S. (1964). “Obshchaya Geomorfologiya, II.” Izdatelstvo MGU, Moscow. SOLOVIEV, P. A. (1962). Alasnyy relyef Centralnoj Jakutii i ego proiskhozhdeniye. I?, “MnoholetneSoputstvuyuhchiye yim merzlyye Porody i Yavleniya na territorii JASSR.” Izdatelstvo AN SSSR (Moscow), pp. 3&53. SOLOVIW, P. A. (1963). Alasnyye doliny Yakutii. III “Uslociya i Osobennosti Razvitiya Merzlykh Tolshch v Sibiri i na Severovostoke,” pp. 80-90. Moscow. SVESSSON, H. (1969). A type of circular lakes in northernmost Norway. Gcografiska Anrtalev, 51. l-12.
A.N. (1966). Rasshireniya kotlovin termokarstovykh ozer na Jano-Indigirskoj nizmennosti. Materialy Vsesoyusnogo Mcchdzlvedo?rzstveltllogo
TOLSTOV,
alasnykh territorii VIII. Soviesh-
AND
DEMEK
chani3la Jakufskoje 135-142.
po
Geokriologii knihnoye
(merzlotovedieniyu). izdatelstov (Jakutsk)
6,
S. V. (1966). Ozerno-termokarstovaya pererabotka severnykh nizmennostey i yeye inzhenerno-geologicheskoye znacheniye. Materialy VIII. I,-sesoyzbznogo Mezhduvedo,rnstvenlrogo Soztiesltchaniya po Geokriologii (merzlotovedeniyu). Jakutskoje Knihuoye Izdatelstvo (Jakutsk) 7. 24-34. TOMIRDIARO, S. V. (1969). Inzhenernyye metody ravnin osvoyeniya ozernotermokarstovykh Krajnego Severa. Kolpza (Magadan), Vol. 33, No. 3. pp. 17-20. TRKART, J. (1967). “Le Model6 des Regions Periglaciaires.” SEDES, Paris. VEBERSIKOV, L. E. (1966). Nekotorye osobennosti formirovaniya termokarstovogo relyefa pravoberezhnoy terasy reki Jany. Materialy VIII. l~sr.~ogz~~togo dleckdzfzled~rrtstvennogo Sovie&clcarliya ~0 Geokriologii (Merzlotovedieniyu). Jakutskojc Kni.hop? Izdatelstvo (Jakutsk) 7, 35-32. I&‘.\LKER. H. J., and ARNBORG, L. (1963). Petmafrost and ice-wedge effect on riverbank erosion. In “Proceedings of the Permafrost International Conference, 11-15 November 1963, Lafayette, 164-171. National Academy Indiana,” pp. Sciences-National Research Council, Publ. 1278, Was’hington, D.C. A. I. (1964). Merzlotno-gidrogeologicYEFImX’. heskiye osobennosti pribrezhnogo i ruslovogo uchastkov r. Lenp v rayone goroda Jakutska. “Geokriologicheskiye Usloviya Zapadnoy Ilk Sibiri. Jakutii i Cukotki.” Okhrana nedr., Moscow.
TOMIRDIARO,
RESEARCH
Thermokarst
1,
103-120 (1970)
in Siberia
and
Its Influence
of Lowland
TADEAS
CZUDEK
on the Development
Relief
1 AND
JAROMI’R
DEMEK
1
Received January 2,197O “Thermokarst” as a process is the melting of ground ice and the consequent formation of depressions. Thermokarst landforms depend on the tectonic regime of a region, the ground ice content, and the degree to which the permafrost equilibrium is disturbed. Thermokarst forms are especially prominent in the lowlands of the subnival region with permafrost. The authors distinguish two modes of thermokarst developmentpermafrost back-wearing and down-wearing-based on their investigations in Siberia. The first mode is characteristic of a more dissected relief. In this case permafrost back-wearing takes place and the process is characterized by development of gullies, thermocirques, and parallel retreat of steep walls with ice veins, resulting in a lower lowland level. The second mode of thermokarst development is due to permafrost melting from above and is typical of a flat undissected relief, mainly that of watershed regions. Characteristic forms are depressions with steep slopes and flat floors (alases). Thermokarst valleys develop through coalescence of alases. Thermokarst processes destroy the lowland relief of large areas and create characteristic forms resulting in a lower lowland level. Thus thermokarst represents a special type of lowland development in permafrost conditions. I. INTRODUCTION Thermokarst is the process of melting of the ground ice accompanied by local collapse of the ground surface and the formation of
depressions. In thermokarst regions, underground and subaerial forms develop such as funnel-shaped pits, larger basins with flat bottoms and steep slopes, dry valleys, caves, etc. The term “thermokarst” was introduced by M. 11. Yermolayev in the USSR in 1932, and in the English language by S.W. Muller in 1944, and is now widely used in textbooks of geology and geomorphology (for instance, Shchukin, 1964 ; Tricart, 1967 ; Hamelin and Cook, 1967; Embleton and King, 1968). 1 Institute of Geography, Czechoslovak Academy of Sciences, Brno, Mendlovo n&m. 1, Czechoslovakia.
Thermokarst occurs in regions having a considerable ice content in the soil. This is why the most intensive development of thermokarst occurs in lowlands. The development of thermokarst is due to the disruption of the thermal equilibrium of the permafrost and the increase in the depth of the active layer. The reasons for the disequilibrium and permafrost degradation can be various. Roughly, they can be divided into two groups : climatic and local. Among climatic reasons for permafrost degradation are changes such as general increase of temperature or humidity (e.g. snowfall), or increase of continentality leading to warmer summers. Local causes can again be subdivided into two groups : natural causes and the influence of man. For instance, a natural cause is the 103
104
CZUDEK
AND
development of polygonal ground-a characteristic process of subnival regions. Accumulation of water takes place where ice veins cross or in low centered polygons (Hussey and Michelson, 1966, p. 152). The water temperature in these pools is always higher than the temperature of the adjacent ground. In the Jano-Indigirskaja Nizmennost (Lowland) the thickness of the active layer is twice as great beneath 20-25 cm of water than in the adjacent ground (Table 1) . Due to thermal and chemical effects of the water, the ice vein starts thawing and the thermokarst process begins. Such thermokarst development takes place even in severe Arctic conditions, as in the case cited where the permafrost temperature is -9 to -11°C (Mushkin, 1960, p. 41). Other local causes can be vegetation changes caused, for instance , by forest fires due to lightning. :\mong the influences of man belong clearing of forests, ploughing of grassy slopes, damage of vegetation due to vehicles, and construction activity. For instance, PCwC (1954) described excellent examples in the surroundings of Fairbanks, Alaska, where forest areas were changed into fields. The thermokarst process can manifest itself in the relief in different ways. The extent of the geomorphic changes depends on (1) the tectonic regime of the region, (2) the ice content in the soil, and (3) the degree and rate of equilibrium disturbance, i.e., the increase in depth of the active layer. The
DEPTH
OF THE
.&CTIVE
LAYEK
IN
DEMEK
thermokarst can manifest itself only in the relief of stable or rising lowlands. In the regime of a subsiding lowland the developing forms are quickly filled with deposits. The deposits of lowland areas in the subnival zone with permafrost often involve numerous thick masses of ground ice. The quantity of ground ice in fluvial. lacustrine. and eolian deposits is frequently SO-90%, of the total volume of deposits. It usually occurs in two basic forms : ( 1) segregated ice dispersed in the soil and (2) ice veins and ice wedges (Fig. 1). The ice wedges and ice veins may occupy 30-60s of the surface in some regions of the Central Jakutian Idowland of Siberia. The distribution of ground ice is also important in thermokarst development. Three general types can be distinguished. The first type comprises ground ice in deposits of stable regions where permafrost developed after deposition (epigenetic type‘). In such deposits most ground ice occurs in the upper part because of water migration toward the freezing front; downward the ground ice content decreases. The second type comprises deposits in subsiding regions where deposition was simultaneous with freezing (syngenetic type). In the deposits the ground ice is distributed throughout the whole profile. Enormous syngenetic ice veins developed in this way in some lowlands (e.g., Kolymskaja Nizmennost in Siberia) (Popov, 1953). For in-
THE POLYC;ONAL GROUND OF THE (LOWLAND) (MURHIN, 1960, p. 501
JANO-IKDIGIRSRAJA
Depth Humidity
in central
part
of polygon
Relatively dry polygon centers Moist polygon centers IVater layer 7-10 cm deep in polygon center Water layer 20-25 cm deep in polygon center Lake 30 X 10 m with deoth 25 cm and more
of acti\-e
NIZUEKNOST
layer
(cm)
polygons Lat 70”37’N
polygons I,at 71”30’N
30-31 38-41 52-56 62-69 >75
23-25 31-33 39-42 51-53
THERMOKARST
IN
SIBERIA
AND
stance, the ice wedges in the exposures at the Indigirka River near the village of Sypnyj Jar are 40-50 m thick. The third and less important type comprises the ice cores of pingos and palsas. From the geomorphic point of view, the origin of thermokarst forms can be ascribed to lateral permafrost degradation (,backwearing and to permafrost degradation from above ( down-wearing j as described below. 11. BACK-WEARING THERMOKARST PROCESS Lateral permafrost degradation or backwearing takes place mainly as a result of lateral and vertical river erosion or marine and lacustrine abrasion. During spring, floodwaters undercut river banks. The river water is warmer than the soil, and thermo-
FIG.
Photo
1. Ice vein J. Demek
in the Lena (August
1966).
River
DEVELOPMENT
OF
LOU’T,A4iXD
105
RELIEF
erosion can act in the frozen soil and develop deep tl~ermoerosional niches at river level (Fig. 2). For instance. the undercutting of sandy terrace deposits by the Lena River may extend inwartl as much as 10 m (Yefimov. 1964. 1). 99 ) The frozen deposits that are exposed due to lateral river erosion or collapse of undercut l~locl~sthaw later in summer. Thennonbrasiotl niches 3 m high and 20 m deep occur at the foot of cliffs on the coast of the More Laptevych (Sea) and the Vostok-no-Sibirskoje More (Grigoryev, 1966, p. 77).
Several stages of thermokarst development can be found on the river scarps of the Central Jakutian Lowland (Fig. 3). The first stage is the thawing of ice veins and ice wedges, leading to thaw gullies that display a
terrace on Pegcanaja
Gora,
north
of
the
town
of
Jakutsk.
106
CZUDEK
.\ND
DEMEK
FIG. 2. Examples of lateral and thermal erosion by rivers. (A) Lena River terrace in the the town of Jakutsk; (B) Deputitko River bank, Chrebet Cerskogo in NE Siberia; (C) River bank, Chrebet Cerskogo in NE Siberia; (D) Aldan River, lower course; sliding due effects of the river. 1, Ice veins ; 2, frozen fluvial sand ; 3, frozen loams ; 4, humus and peat; upper permafrost limit.
mocirque consists of a vertical or overhanging slope at the head and an uneven floor. Longitudinal and cross sections of ice veins usually appear in these slopes (Fig. 6). The ice thaws and the vertical slope retreats parallel to itself. Disintegrated baydjarakhs can be found on the cirque floor so that the bottom is uneven with conical elevations. Aq thaw-water gully usually drains the thermocirque. Landslides and mud flows occur in places on the gully banks in the mushy material. The development of gullies takes place
strikingly regular distribution on slopes. The distance between gullies corresponds to the diameters of the ice-wedge macropolygons in the terrace deposits of the rivers (Fig. 4). Due to the continuing development of gullies, the vegetation is damaged and domelike relief features develop. As ice veins parallel to the river bank thaw, the polygon centers become isolated and form conical hills called “baydjarakhs” in Jakutia. During further development the baydjarakhs are successively destroyed and an amphitheatrical hollow (thermocirque) forms (Fig. 5). The ther-
I
:
:
:
0
IO
20
30
FIG. 3. Thermocirque development on a river frozen fluvial sand; 4, active layer; 5, landslides veins and ice wedges.
vicinity of DeputPtka to thermal 5, river; 6,
,
LO M
bank. 1, Ice veins and ice wedges; 2, frozen loams; 3. and mud flows ; 6, colluvium; 7, pseudomorphs of ice
TIIERMOKARST
IX
FIG. 4. Gullies and baydjarakhs Photo J. Demek (August 1966).
even in the high Arctic (Fig. gullies in the baydjarakh Tajmyr Peninsula opposite increased years (1937-1946)
SIRERTA
Ai-iD
DEVELOPMENT
created by lateral
7). One of the region of the Dickson, in 9 in depth from
permafrost
OF
l.O\VT.hIiD
degradation.
RELIEF
Aldan
River
107
terrace.
3 to 10 m, and in width from 0.5 to 20 m (KOSOV, 1959, p. 128). In large thermocirques water acumulates on the floor and forms a small pool. The
5
FIG.
(August
5. Thermocirque 1969).
created by lateral thawing
of ice veins. Alden
River
terrace.
Photo J. Demek
108
CZUDER
FIG.
6. Thermocirque
slope in the Aldan
AND
River terrace.
of water accelerates considerably the development of the thermokarst. Steep slopes with thick ice veins have been described, for instance, in the Kolymskaja Nizmennost and Primorskaja Nizmennost in northeastern Siberia (Fig. 8). An estensive lowland occurred here in the Pleistocene, probably extending far into the Arctic Ocean and including the present Lachovskije Ostrova (Islands), and Ayon and Vrangel Islands. In the Upper Pleistocene stratified loams with peat beds were deposited in the lowland during continuous subsidence. Ice veins 30-50 m thick and 10 m wide occur in the loams. The ice veins form a polygonal pattern, the loams being but separated columns among them. Due to the thermokarst. even scarps 25 m high retreat parallel to themselves on a section several kilometers long at an annual rate of 15-18 m. Lakes develop at the base, and the erosional activity of the lakes and undercutting of the scarps accelerate scarp retreat. The lakes are deepest at the foot of the scarps. On the opposite side of the lake there is shallow water, which increases in width by 10-S m per year (Tomirdiaro. 1966. lx 32). Thus a lower
presence
DEMEK
Photo J. Demek
(August
1969).
lowland develops at the level of the lake. The relief of the Primorskaja Nizmennost (LOWland ) has been changed considerably by this process. Small remnants are preserved above the level of the lower lowland and are bordered by scarps with thick ice veins. On the lower level, permafrost aggradation takes place after shifting of the lakes or their desiccation, and even epigenetic ice wedges develop, their dimensions being smaller than those of the Pleistocene ice wedges of the original higher level. Their thickness does not surpass 5-6 m and their width in their upper section ranges from 3 to 4 m. The dimensions of these polygons are 16 X 20 m (Tomirdiaro. 1969, p. 18). 111. DOWN-WEARING THERMOKARST PROCESS Permafrost degradation from above or down-wearing occurs in flat undissected terrain mainly on watersheds. The forms developed depend on the amount of ground ice and on its type. \J’here the amount is small or in places with segregated ice, or both, their
flat shallow depressions develop and area is usually of small extent, as
TITERMOKARST
FIG. Demek
7. Gully (August
created 1966).
by
ice
1K
SIBERlA
vein
thawing
FIG. 8. Schematic cross profile showing lowland. 1, Humus and peat; 2, syngenetic fluvial sand; 5, alas deposits; 6, epigenetic limits.
.\A-D
in
slope
DE\‘ELOI’MEKT
deposits
of
OF
I.O\VI..\h-D
RELIEF
Kular,
northern
Jakutia.
109
Photo
headwall of the upper lowland and the developing lower ice veins and ice wedges; 3, frozen loams; 4, frozen ice veins and ice wedges; 7, water; 8, upper permafrost
J.
110
CZUDEK
AND
illustrated by the results of a forest fire in the lowland along the Jana River July 2.5-27, 1953. Measurements in August 1965 showed that the thickness of the active layer below the unburned forest was 40-15 cm whereas it amounted to SOcm where the fire occurred. Due to the thermokarst process the fire had lowered the surface by 20 cm (Vebernikov, 1966, p. 39). Thermokarst forms are more distinct where there is considerable ground ice and where a polygonal network of ice veins, mainly syngenetic. is developed. The authors studied the development of thermokarst phenomena under these conditions on the middle terraces of the Lena and Aldan Rivers in the Central Jakutian Lowlands. The thermokarst phenomena created by the permafrost degradation from above are found mainly on the Tjungjulju and Abalach terraces. The Abalach terrace forms an extensive surface with an altitude of 116134 m. It is built of sandy river deposits, 20-30 m thick, covered with a loam layer 40-60 m thick. The Tjungjulju terrace consists of 60-80 m of fluvial sands covered with 610 m of loamy deposits (Soloviev, 1962, p. 3940). The mantle loams are of complex origin, probably involving eolian, lacustrine, and fluvial processes in a subsiding lowland. There is much ground ice mainly in the upper loam layer (20-40 m thick) ; thick ice veins occupy 30-60% of the terrain surface. In addition, the loams have a segregated ice content of 40-80%. When the thermal equilibrium of the 1)ermafrost is disturbed thermokarst phenomena develop in several main stages (cf. Soloviev, 1962, p. 45 ff .) In the first stage (Fig. 9) the polygonal system of ice veins begins to thaw. Highcentered polygons develop with troughlike depressions above the ice veins (Fig. 10). The terrain surface undulates but the vegetation cover is not yet destroyed (Fig. 9, Ia). As the depression above the ice veins grows successively deeper, the humus layer splits
DEMEK
and slides into the depressions. The polygon cores ‘keep their height and their flat top. However, as soon as the trough-shaped depressions reach the depth of l-l.5 m, slumping starts and the polygon cores change into conical baydjarakhs. The moss and grass cover is already completely destroyed and the polygon cores exhibit loamy surfaces. Jn places even ice veins crop out (Fig. 9. lb ) In the second stage (Fig. 9, II) the baydjarakhs successively slide and disintegrate, and a depression develops in the center of the baydjarakh field similar to sinkholes in karst regions. Below the sinkholes, there may be subsurface hollows of a tunnel type. P&w& (1953) described a sinkhole with an area of 2.4 X 4.5 m and a depth of 6 m which had horizontal galleries 1 m wide and 0.6 m high with traces of running water. Through successive linkages continuous depressions with steep slopes and uneven bottoms form, which are called dujodas in Jakutia. The water in the depressions promotes the clevelopment of the thermokarst. As soon as a small pool appears that holds water for the greater part of the year, thermokarst development proceeds very quickly. Water is of enormous importance in this process, since it stores the heat that thaws the adjacent permafrost. The water has also simultaneous chemical effects. As the result of the heat storage, thermokarst can form in even the severe conditions of the high Arctic and Antarctic. In case no water accumulates, thermokarst development slows down and even stops, to revive only in more humid years. On steep slopes of dujodas there are baydjarakhs. Slumping is active and ice veins thaw. If the dujoda develops in the taiga, the trees on the slopes lean toward the center of the depression or fall down (Fig. 11). The depression starts developing an asymmetric profile, with the south-facing slope being commonly the steeper and drier. Although the slope exposed to the north is gentler and the thawing on it is rather slow,
THERMOKARST
Ii-i
SIBERIA
AND
DEVELOPMENT
OF
LO\\‘LAND
RELIEF
111
IV a
FIG. 9. Main development stages of alases. Ia, Original lowland surface with syngenetic ice wedges; Ib, initial thermokarst stage-baydjarakhs ; II, dujoda; IIIa, young alas; IIIb, mature alas; IIIc, old alas ; IVa, Khonu with pingo; IVb, Khonu with depression at site of thawed pingo. 1, Syngenetic ice wedges ; 2, larches and grass ; 3, water ; 4, landslides ; 5, alas deposits ; 6, epigenetic ice veins ; 7, pingo ; 8, upper permafrost limit.
it takes place over the whole summer season. In the third stage (Fig. 9, IIIa) a distinct depression with steep sides and a flat bottom develops, called an alas in Jakutia (Fig. 12). In the Jakutian language this term denotes a circular or oval depression with steep sides and a flat floor overgrown with green grass around a thaw lake. In the taiga the lake is usually more or less circular. In the tundra, or in the case of a large alas, the lake is commonly oval, the short axis being commonly parallel to the prevailing direction of summer winds (Rex, 1961, p. 1021). Upon
attaining a certain depth, the lake does not freeze to the bottom in winter and a talik begins to develop below the lake (Fig. 9, IIIa). As the ground ice thaws, the deposits below the lake sag and the thaw lake deepens (Fig. 9, IIIb). In northeastern Siberia, a freshwater lake 1.4-1.6 m deep does not freeze to the bottom (Tomirdiaro, 1966, p. 29). Exploratory borings in the Mackenzie River region have shown that thaw lakes having a diameter greater than 800 m (half a mile) and a depth of at least 2.1 m (7 feet) have a talik roughly 65 m (200 feet) thick (Johnson and Brown, 1964, p. 164). The
112
of
CZUDEK
Fr G. 10. Start of thermokarst F ‘ok .rovsk, Jakutia. Photo
alas fl oor usually dept -ession center. tent , a.n irregular duri “t?: thawing,
FIG.
the
town
11. of
Transitional Pokrovsk,
IZXD
by thawing of ice vein J. Demek (August 1966).
slopes down toward the Due to irregular ice consagging of deposits occurs and a rolling topography
stage Jakutia.
DEMEIi
between Photo
dujoda J. Demek
system
(high-centered
polygons)
near
the
usually develops as a result. Vert ,ical differences of the alas floor can thus arrlount to 2-6 m. The thawing influence of the lake exi Lends
and young (August
alas. 1966).
Slopes
slide,
trees
fall.
Vicinity
of
THERMOKARST
IN
SIBERIA
AND
--I;G. Jakutia.
12. Mature alas Photo J. Demek
with steep slopes (August 1966).
DEVELOPXENT
OF
LOb~LtZND
113
RELIEF
-and
a small
to its shores i Johnson and Brown, 1964, p. 173), and waves and currents erode the thawed deposits and, in large alases, result in terraces. In Central Jakutia, erosion is most effective on south-facing slopes, which are thawed to a greater depth and are commonly steeper than other slopes, are overgrown with grass, and very often have baydjarakhs. In contrast, the north-facing slope is humid, gentler, and covered with bent trees ( drunken forest). The depth of alases in the Central Jakutian Lowland is usually 3-40 m, and their diameter ranges from 100 m to 15 km (Soloviev, 1962, p. 48). Due to wind action, alas lakes and the alases shift (Fig. 9. 111~). Alas deposits accumulating on the alas floors consist of the loams that have lost their ice content and include material supplied by slumping and solifluction from the alas slopes and the material supplied by lacustrine abrasion. The deposits may have a considerable content of organic matter. The rate of the alas development varies
lake.
17icinity
of
the
town
of
Pokrovsk,
considerably. Some alases have formed within a human generation; others are several thousand years old. Many alases developed during the Holocene climatic optimum, some 4000-5000 years ago (Grigoryev, 1966, p. 65). The latest phase of intensive alas development began some 100 years ago (Kononov, 1965, p. 58). The large alases in the Jano-Indigirskaja Nizmennost (Lowland) developed over a period of several thousand years according to measurements reported by Tolstov (1966, p. 141). Soloviev gives the following survey for the surroundings of the town of Jakutsk : % of the terrain surface
1. Flat watershed without thermokarst 2. Young thermokarst 3. Mature thermokarst and alases 4. Mature thermokarst without lakes 5. Old thermokrast
60.5 1.5 3.0 4.0 31.0
114
CZUDEK
AND
The alas development proceeds to the complete thawing of the ground ice, or to the formation of a stable talik if the width of the lake is considerably less than the thickness of the permafrost. In the fourth stage (Fig. 9, IVa) the alas lake disappears. There are various ways in which this occurs; for instance, the lake can disappear by filling with alas deposits or by draining to a lower alas level or to a river valley. With the extinction of the lake, permafrost aggradation takes place. Baydjarakhs still form on slopes, and as a result. the marginal slopes become flatter and permafrost appears on the alas floor. A special cryogene structure develops in these epigenetically freezing alas deposits. Due to the segregated ice in the upper part of the deposits? the alas floor rises and new ice veins develop. In the Central Jakatian 120wland, these ice wedges are much smaller than those on the Pleistocene surface. The talik freezes from all sides and the developing pressures cause pingos and palsas to form. Conical hills with an ice core, or
FIG. 13. Khonu stage with epigenetic ice veins. Vicinity
permafrost of the town
DEMEK
a core rich in ice, can be found in many alases of the Central Jakutian Lowland. As the ice cores of the palsas and pingos thaw, oval depressions develop that are bordered by a rim (cf. Svensson, 1969). The result of the fourth stage of alas development is thus a flat depression with gentle slopes and an undulating bottom with pingo relics or postpingo hollows, called khonu in Jakutia (Fig. 9, IVb ; Fig. 13). The formation of thermokarst has considerably changed the aspect of the lowlands. In the Central Jakutian Lowland, 40-50s of the initial surface has been destroyed by the formation of alases (Fig. 14). In the north the lowland on the right Jana River bank has almost completely lost its original appearance and has changed into a system of alas depressions mostly filled by thaw lakes. Remnants of the initial surface rise as conical hills and narrow ridges above the alases. The lakes cover areas of 31F km ?. Complicated thaw lakes developed by the coalescence of several alases cover areas of some 25 km 2. The thermokarst process from above created the lower level of the lowland,
aggradation, of Pokrovsk,
and undulating Jakutia. Photo
bottom due to the J. Demek (August
growth 1966).
of
THERMOKARST
IN
SIBERIA
AND
DEVELOPMENT
OF
LOWLAND
FIG. 14. Map of thermokarst relief east of the town of Jakutsk in the Central (following P.A. Soloviev). 1, Original lowland level with syngenetic ice wedges lakes in alases ; 4, recently desiccated lakes in alases ; 5, old alases.
which is situated lo-15 m below the original surface (Protasyeva, 1965. pp. 97-95). IV.
THERMOKARST
VALLEYS
The coalescence of alases results in thermoknrst valleys. In regions where alases develop near each other the ridges separating them are often destroyed. The ice melts and the elementary alases join into a complex alas. By successive addition of othe; alases, an elongated depression develops consisting of wide sections-alas basinsand narrow connecting sections where former narrow watersheds have been eliminated. The ground plan of the alas valleys differs considerably from that of the river valleys in displaying unexpected turns, blind spurs, and in places a trend against the general inclination of the relief. Initially, thermokarst valleys have a steplike longitudinal profile due to irregular ice content and irregular settling of thawed deposits, so that alas floors occur at various heights. However, the dif-
RELIEF
Jakutian ; 2, young
115
Lowland lakes ; 3,
ferences in height become successively graded. The deepest alases are filled and the higher floors are lowered as erosion progresses along thermokarst gullies originating on epigenetic ice veins ( Fig. 15). In the Central Jakutian Lowland a thermokarst valley comes to have a wide grassy bottom and flat slopes covered with taiga (Fig. 16), but even in a mature thermokarst valley the typical basinlike character is preserved. Tn the longitudinal profile the depression for the most part is already well graded. Only the lateral-usually young valleys--lead into the main valley with a rather low step. The alas lake usually has not reached this far and therefore thawing and sagging of the ground are less important here, and even relic ice veins are preserved (Soloviev. 1963. p. SSi. In the main valley, a small stream usually appears, but it has only an indistinct shallow bed and does not erode. The greatest part of the valley is dry for almost the entire year, Only during the spring snowmelt does water
116
CZUDEK
AND
DEMEK
4 3
2
1
-
0
20
70 I
0
5
t 10
120 ,
10 I 14 M
watershed west of FIG. 15. Cross profile of a gully developed by thawing of ice veins. Lena-Viljuj the town of Jakutsk. 1, Humus and peat; 2, frozen brown sandy loam; 3, ice vein; 4, upper permafrost limit; 5, water. Leveled by T. Czudek and J. Demek, May 19, 1969.
rush down the whole grassy valley bottom. In May 1969 the authors watched the snowmelt in the Aat thermokarst valleys of the Lena-Viljuj watershed where long but
FIG.
shallow valleys are incised into the flat surface of the plateau. A water layer 30-50 cm high was rushing down the grassy bottom of these valleys for several days. The water
16. Alas valley on a river terrace west of the town of Jakutsk. Photo J. Demek (August
I9661
THERMOKARST
IN
SIBERIA
AND
was pure and transported only vegetation detritus. The streams did not erode, since the substratum was still frozen. After some days the water level had fallen and the valleys were mostly quite dry.
DEVELOPMENT
OF
LOWLAND
RELIEF
117
b~rz~isl4blllatutt, Poa pvatcnsis, 17icin uncca, and Potcntilla answpina are characteristic here. In large alases the zone is usually divided into ( 1) a subzone, nearer the lake, used as a meadow for hay farming ; and (2) a subzone, farther from the lake, used for V. THERMOKARST AND spring crops-barley and oats for silage AGRICULTURE (Kononov. 1965, p. 59). The outer third zone are dry meadows Clearing of permafrost areas for cultivation usually results in the disturbance of the used as pasture. The density of grass varies thermal equilibrium of the permafrost. De- considerably in different years, depending on the annual precipitation. The soils are pending on the degree of the equilibrium disturbance and the quantity of ground ice frequently saline. On solonchaks, Purrindia tcnuiflora prevails, and on less saline soils, in the soil, the development of thermokarst YepCnS and HO&MIX hcvimay lead to a variety of forms. T. L. PCwO Agropyon dominate (Kononov, 1965. pp. (1966, p. 26) writes that baydjarakhs begin sztb1dat~4m 60-61). to appear in fields within 2-3 years after The gradual development of the nlases clearing. Successively sink holes, tunnels, caves, etc. develop in the fields. Fields and desiccation of the lakes has led to strongly affected by thermokarst occur, for changes in the location of villages, an d instance, in the Kolyma River valley in remnants of abandoned villages can now be found in many alases. northeastern Siberia and in the watershed region of the Lena and Amga Rivers east of VI. THERMOKARST the town of Jakutsk. AND ENGTNEERING On the other hand, the flat alas floors are most important agricultural areas in the The development of thermokarst enCentral Jakutian Lowland. The Jakuts dangers construction in permafrost environarrived in this region with their herds from ments (Fig. 17, 18). In Siberia. buildings on the steppes of southern Siberia. The grass- deposits with a high ice content are comland in the vicinity of the lakes in the taiga monly constructed on timber or concrete was natural pasture for their herds. The piles, with preservation of the permafrost. lakes which do not freeze to the bottom in This technique allows construction of multiwinter, are presently the only water resource storied buildings in northern regions without for the villages. In 1960 the alases supplied danger of thermokarst development. Ther63.3%, of the total hay production in Jakutia mokarst may also affect road construction. (Kononov, 1965, p. 57). Highway embankments in Siberia are usually In the alases with lakes in their centers built of material bulldozed from the immedithree more or less concentric zones can be ately adjacent area. The bulldozers can rake distinguished from the viewpoint of agriup only the active layer, the thickness of culture. The size of the different zones de- which is usually slight (e.g., from 0.4 m in pends on the degree of soil development and the north up to 1.5 m in Central Jakutia). on the age of the alas. A zone with aquatic Thus a relatively large area is denuded on vegetation and peat-bogs occurs closest to both sides of the road, and the thermal the lake. This zone is usually not utilized for equilibrium of the permafrost is disturbed. farming. The adjacent second zone is For instance, construction of the road in the characterized by young humid soils with a settlement of Deputatskij in northern Jakutia high humus content. Plants such as Hordc~z led to thawing of the ice veins and develop-
118
FIG. Photo
CZUDEK
17. Thermokarst J. Demek (51ay
due to bad 1969).
insulation
AND
of a house
ment of a ravine 2.1 m deep. The thaw water created a tunnel in the ice veins below the road and engulfed the road margin in June 1969. Along the shores of northern Siberia
FIG.
Photo
18. Bridge J. Demek
deformed due (May 1969).
to
thermokarst
DEMEK
in the
village
of Bajandaj
in the Irkutsk
region.
thermoabrasion leads to coastal retreat. For instance, it caused the complete destruction of the Vasiljevskij and Semenovskij Islands in the Laptevych Sea (Kachurin, 1961, p. 247). Because of sporadic settlement, ther-
processes
in
the
Tunkin
Basin
in
southern
Siberia.
THERMOKARST
IN
SIBERIA
AND
DEVELOPMENT
moabrasion is presently of no economic importance. However, its significance will increase with the installation of technical equipment on northern coasts, and thermoabrasion should be taken into consideration in the choice of building sites. Thermokarst phenomena must also be considered in relation to bank erosion of water reservoirs in the permafrost region. Thawing of thin permafrost below engineering structures can lead to water from below the permafrost reaching the surface under pressure and creating seepages that freeze. Such icings also endanger engineering projects. On the other hand, thermokarst processes are utilized to accelerate thawing of the overburden of mineral deposits. Artificially accelerated thawing is used, for example, in removing the overburden from gold-bearing gravels of the Kular placer deposit in northern Jakutia. Significantly, alas deposits of the lower lowland level in northern Siberia have a
OF
LOWLAND
119
RELIEF
much lower ground ice content and are less affected by thermokarst phenomena than the higher Pleistocene lowland level. ;Zs a result the alas deposits are preferred construction sites (Tomircliaro, 1969). WT. CONCLUSIONS Thermokarst considerably influences relief development of the lowlands in the subnival zone. It destroys the initial surface of large areas and creates a new lower level of the lowlands, which is initially independent of the main level of erosion. The thermokarst process thus represents a special type of relief development.
The authors are indebted to Professor P. I. Melnikov, Director of the Institut merzlotovedeniya SO AN SSSR in Jakutsk, for making their studies in Siberia possible, and to the scientific workers of the Institute, P. A. Soloviev and M. S. Ivanov, for the demonstrations and discussions in the field. The authors are indehted for redaction and valuable comments to Professor A. L. Washburn and Professor T. I,. PCwP.
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BAULIN,
B., DUBIKCW, “Geokriologinizmen-
DEMEK,J. (1967). Report on the study of cryogene phenomena in Jakutia (USSR). Sbor&k C’eskoslovercske’ SpoleAosti Zeme’pisne’ (Plaha) 72, 99-l 14. DEMEK, J. (1968). Beschleunigung der geomorphologischen Prozesse durch die Wirkung des Menschen. Geologische Rwdschau 58, 111-121. EMBLETON, C.. and KING, C. A. M. (1968) “Glacial and Periglacial Geomorphology.” Arnold, London. GRIGORYEV. N. I;. (1966). “Mnogoletnemerzlyye porody Primorskoy zony Jakutii.” Nauka, Moscow. HANIELIN, L. E., and COOK, F. A. (1967). “Le PCriglaciaire par I’Image” (Illustrated Glossary of Periglacial Phenomena). Les Presses de I’Universitb Laval, Quebec. HUSSEY, K. M., and MICHELSON, R. W. (1966). Tundra relief features near Point Barrow, Alaska. ‘drctic 19, 162-184. JOHNSON, G. H., and BROWN, R. J. E. (1964). Some observations on permafrost distribution at
a lake Canada.
in the Mackenzie A-lYctic 17, 163-175.
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T.,
S. P. (1961). “Termokarst na territorii AN SSSR, Moscow. KOXONOV, K. 12. (1965). K. vop,-osu o rezhime vlazhnosti pochy alasov Centralnoj Jakutii. Snklm Gosudarstzw~~ay urziewsifctyt, Uledere (/aknfsk,~ 16, 57-75. KOSOV, H. 1;. (1959). Ovrazhnaya eroziya v zone tundry. ~‘cznch~z~~e Doklndy Fysshey Shkoly, KACIIURIN,
SSSR.”
Ckolop-po.qm
jichcskiyc
123-129. MLTI<~IX, N. I. (1960). form relyefa v razvitii Indigirki. Mnterinly
rtmlrg
(AIOSCOW)
NO.
1. pp.
hero-dylrli
mznlrlz
0 znachcnii termokarsta k osnovant
xm~roy
kovy
polygonalnykh v nizovyakh ucJteGya
o
5, 45-55.
hIUr.IxR, S. W. (1944). Common frontiers in geology and related science in the U.S.S.R. and the U.S.A. IS “Science in Soviet Russia,” Jacques Cattell Press, Lancaster, Penn. pp. 11-17. P6wB, T. L. (1954). Effect of permafrost on cultivated fields, Fairbanks area, Alaska. U.S. Geologicnl Suwey Bdletin 989-F. Plimfi, T. L. 11966). “Permafrost and Its Effect on
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CZUDEK
Life in the North.” Oregon State University Press, Corvallis. POPOV, A. I. (1953). Osobennosti litogeneza alluvialnykh ravnin v usloviyakh surovogo klimata. Ixlesti_va AN SSSR. seriya geograficheskaya (dloscocv), No. 2, pp. 2941. POPOV, A. I. (1966). Le thermokarst. Bidetyn Prvyglacjahy 4, 319-330. PROTASYEVA, I. V. (1965). Landshaftno-geokriologicheskoye deshifrovaniye v nizovyakh reki Jany. Sakha Gosr4davstzxxna~ wiversitetyt Ulcdere 16, 91-101. REX, R.W. (1961). Hydrodynamic analysis of circulation and orientation of lakes in northern Alaska. In “Geology of the Arctic,” Vol. 2 pp. 1021-1043. (G. 0. Raasch, Ed.) University of Toronto Press, Toronto. SIICHUKIS, I. S. (1964). “Obshchaya Geomorfologiya, II.” Izdatelstvo MGU, Moscow. SOLOVIEV, P. A. (1962). Alasnyy relyef Centralnoj Jakutii i ego proiskhozhdeniye. I?, “MnoholetneSoputstvuyuhchiye yim merzlyye Porody i Yavleniya na territorii JASSR.” Izdatelstvo AN SSSR (Moscow), pp. 3&53. SOLOVIW, P. A. (1963). Alasnyye doliny Yakutii. III “Uslociya i Osobennosti Razvitiya Merzlykh Tolshch v Sibiri i na Severovostoke,” pp. 80-90. Moscow. SVESSSON, H. (1969). A type of circular lakes in northernmost Norway. Gcografiska Anrtalev, 51. l-12.
A.N. (1966). Rasshireniya kotlovin termokarstovykh ozer na Jano-Indigirskoj nizmennosti. Materialy Vsesoyusnogo Mcchdzlvedo?rzstveltllogo
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chani3la Jakufskoje 135-142.
po
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6,
S. V. (1966). Ozerno-termokarstovaya pererabotka severnykh nizmennostey i yeye inzhenerno-geologicheskoye znacheniye. Materialy VIII. I,-sesoyzbznogo Mezhduvedo,rnstvenlrogo Soztiesltchaniya po Geokriologii (merzlotovedeniyu). Jakutskoje Knihuoye Izdatelstvo (Jakutsk) 7. 24-34. TOMIRDIARO, S. V. (1969). Inzhenernyye metody ravnin osvoyeniya ozernotermokarstovykh Krajnego Severa. Kolpza (Magadan), Vol. 33, No. 3. pp. 17-20. TRKART, J. (1967). “Le Model6 des Regions Periglaciaires.” SEDES, Paris. VEBERSIKOV, L. E. (1966). Nekotorye osobennosti formirovaniya termokarstovogo relyefa pravoberezhnoy terasy reki Jany. Materialy VIII. l~sr.~ogz~~togo dleckdzfzled~rrtstvennogo Sovie&clcarliya ~0 Geokriologii (Merzlotovedieniyu). Jakutskojc Kni.hop? Izdatelstvo (Jakutsk) 7, 35-32. I&‘.\LKER. H. J., and ARNBORG, L. (1963). Petmafrost and ice-wedge effect on riverbank erosion. In “Proceedings of the Permafrost International Conference, 11-15 November 1963, Lafayette, 164-171. National Academy Indiana,” pp. Sciences-National Research Council, Publ. 1278, Was’hington, D.C. A. I. (1964). Merzlotno-gidrogeologicYEFImX’. heskiye osobennosti pribrezhnogo i ruslovogo uchastkov r. Lenp v rayone goroda Jakutska. “Geokriologicheskiye Usloviya Zapadnoy Ilk Sibiri. Jakutii i Cukotki.” Okhrana nedr., Moscow.
TOMIRDIARO,