Journal of Geocryology, v.1, 2000
A. and Sheshin, Y.
MASSIVE ICE: ORIGIN AND APPROCHES TO CLASSIFICATION
A characteristic feature of Arctic coasts
is the presence of ice formations referred to as massive ice. Their
thickness reaches tens of meters, the extension - hundreds of meters.
The ice formations are located mostly on Yamal and Gidan peninsulas in
Western Siberia, but they are also found in the area stretching from
Kolguev island and Yugorski peninsula on the west and up to Chukotka
peninsula and Alaska on the east. There are gas deposits, settlements,
and communication means in the areas of massive ice. For example, the
town of Amderma on Yugorski peninsula is practically fully located above
a congestion of massive ice. The Bovanenkovo gas field is located on
Yamal peninsula in a zone of distribution of most massive ice deposits (thickness
exceeds 100 meters). Many such examples could be presented. Catastrophic
destruction of earth layers occurs during thawing of massive ice caused
natural reasons and human activity.
The extent of damage is revealed by the numerous lake basins that
extend up to several kilometers in the central part of Yamal peninsula.
Massive ice could still be found in the steep coasts of the basins
towering 20-30 meters above ground. Massive ice origins and distribution
should be extensively questioned in areas of intensive Northern
development on the background of global warming.
History and Approaches to Study
The study of underground massive deposits
of ice is already more than 40 years old. For the first time the term
"massive deposits" was used by P.A. Shumski  for
description of the structural forms of injected ice. Thus given term was
connected with the concrete mechanism of origin from the very beginning.
In the consequence, this term has become broader and now does not carry
a genetic meaning. The term has come to represent all monolithic bodies
of underground ice of a various origin and morphology. As time has shown,
this expansion of meaning caused numerous discussions about the origin
of the underground ice.
The task of the authors consists of
providing a solution for the problem of formation of massive ice based
on definition of the conditions of water accumulation (in various forms)
in local zones of soil mass, and based on definition of genetic
mechanisms. The formation of certain genetic type of deposits and their
freezing are on the foreground of such approach.
In the publication, we consider massive ice
only in marine deposits of Arctic Region. There they are distributed
extensively and have the largest sizes. In the region the major factor
determining sedimentation and permafrost formation is fluctuation of sea
level. The low negative temperatures are also a constant factor. As it
was shown by Y.K.Vasilchuk  and others, "the syngenetic frozen
deposits were created continuously through time including the period of
the Holocene optimum in Northern Eurasia". The massive ice is
basically distributed in areas where marine deposits are dominant. The
freezing of marine deposits is connected to their transition in
subaerial position. We
shall consider change of geocryological conditions at this transition,
and then look at processes of ice formation.
Geocryological Conditions of Massive Ice
The coasts of the Arctic seas are
transitive zones between two basic areas of cryolithozone - sea (subaqueous)
and continental (subaerial) . Shown below are the basic types of
massive ice that correspond to the major zones of the Arctic coasts:
Buried ice: deep-water subaqueous
Injected ice: zone of transition from
subaqueous to subaerial position;
Segregated ice: final phase (freezing of
The first area somewhat depends on the zone
climatic factors; the temperatures of the soils are influenced by depth
of sea, salinity of waters, sea currents, a river drain, etc. The
deposits here are mainly in the cool condition, their temperatures range
from positive to 00C and below to -1,80C.
In the deposits, the ice either occurs as separate crystals and
forms small congestions of ice, or it is included in the structure of
deposits as buried ice. Buried frozen soils are can be encountered in
areas of sea subaqueous cryolithogenesis. Temperature conditions in
these deposits are influenced by the same factors.
On depths exceeding the thickness of fast
ice, temperature of ground deposits is determined by a mineralization of
seawater. Shallow water, as known, has a smaller mineralization factor
and higher temperature gradient due to summer heating. At increase of
depth the mineralization of further down waters is increased, and
temperature is accordingly lowered down to -1,8 [4,13].
Freezing of water results in a layer of
water that is saltier and accordingly denser. These waters, when falling
downwards, lower temperature of deposits. In the summer, the thawing of
ice establishes steady stratification of seawaters. Fresh, warm, and
consequently less dense waters are formed in the top layer; more salty,
cold, and therefore more dense waters are formed in the bottom layer.
The self-regulation of natural systems is
interesting to us because "sea water - sea deposits" system is
based on the mechanics of vertical circulation of sea waters that
provide stability of this system and its parameters (temperature,
mineralization, material structure, water content of deposits, etc.).
According to Shpolanskya
, steady negative temperatures in the bottom layer of water could
lead to permafrost formation in the subaqueous position at depths of sea
of 35 - 100 m. Ice could be kept buried in sea deposits at such
The supporters of the glacial hypothesis of
the origin of massive ice consider the possibility of the existence of
widespread glacial coverings in areas of modern Arctic seas. Formation
of massive ice as the result of burying of glacial ice by sea deposits
is not considered in theory, but it follows from the natural conditions
of Arctic Region. An important question is what portion of the deposits
they occupy. From our point
of view, for the explanation of the whereabouts of the origin of the
deposits it is not necessary to involve models of grandiose changes of
palaeogeography. The considered massive ice could still be formed in
modern conditions. Glaciers are widely distributed in the Arctic Region
at the present time. Evidence
of numerous specific landforms suggests that they were widely
distributed in the past. A downfall of summer temperatures by 2-3
degrees would be enough reach it. When
travelling down the Arctic seas, the icebergs are influenced by currents.
When moving in shallow water, the icebergs are processed by seawaters
and buried by deposits. In
our belief, the reasons for the theory of the presented mechanism of
massive ice formation are as follows:
1. The massive ice does not make any
important geological horizon. The formations appear as separate
inclusions in the homogeneous deposits with well-expressed
stratification, marine fauna, and marine type of salinity.
2. The massive ice appears in sediment at
all geomorphological levels.
3. The massive ice is unevenly distributed
within the limits of given geomorphological level. For example, in the
western part of Yamal peninsula the massive ice is found throughout the
deposits more often than in eastern part of the peninsula. One of the
possible reasons for such occurrence could be that the sea currents in
this part of the Arctic Region are directed from west to east;
consequently the ice bodies will be transferred by currents to the
western part of Yamal.
The possibility of existence of massive ice
in the fresh sea deposits poses a problem for the Arctic sea
sedimentogenesis. It is
traditionally believed that the ice formation stops processes of
diagenesis and inhibits life in the sea. In the case considered the
existence of ice formations does not stop diagenesis processes.
The reasons for existence of ice and its
forms differ in subaqueous sea deposits. The ice can be formed as
separate crystals (at negative temperatures the local ice formation
appears even in the saline deposits); deeper down ice is formed in
hashing waters. Ice formation occurs in zones of penetration of fresh
continental waters into the saline sea deposits with a negative
temperature gradient (for example, at mouths of the rivers running into
the Arctic sea). The ice is an authigenic material in sea deposits, so
this problem appears to be more broad and important than the problem of
Massive Ice and Coastal Processes
Origin of coastal permafrost is usually
connected to a regressive cycle of sea sedimentation. The coast is put
out forward into the sea; and a completely new element - coastal bar 
- occurs there. Formation of bars and lagoons is an obligatory stage of
the development of "coastal raisings".
The deposits of clay are found extensively
throughout the lagoons. The salinity of waters and deposits in the
lagoons depends on their closeness to the sea, and also on the gradient
of atmospheric precipitation and evaporation. For the Russian Arctic
coast, the summer evaporation factor is about 10-20 mm, and
precipitation factor is about 100-200 mm. For the most part of year the
reservoirs are covered by ice; fresh thawed water gets into the
reservoirs in spring. Therefore,
the salinity of water in the lagoons is decreased at that time. The
depths of the lagoons vary from several meters up to several tens of
meters up. The lagoons stretch several kilometers in length, commonly
having a width of about a hundred meters and depth of up to 5 m. The
transition from subaqueous to subaerial conditions is accompanied by
significant redistribution of waters and their accumulation in local
zones . These processes are caused by two factors, the first one
being diagenetic processes and the second freezing.
The dehydration of clay deposits is due to
migration of porous water. Diagenetic waters create pressure on contact
with various layers. The small inclination of sandy layers results in
accumulation of waters and their upward movement .
As it has been previously stated, the
freezing begins in the subaqueous position and under fast ice that is in
contact with the very bottom of the sea. The depth of the sea where
frozen soils occur will vary according to the temperature gradient.
At temperatures of -100C and below the frozen soils
rise to a depth of about 1,5 m. At air temperatures of
and -60C the frozen soils are formed only in the
and -60C the frozen soils are formed only in the
During regression of the sea, the sandy
islands, bars, and sandbanks are formed.
Porous waters are under permafrost pressure. It was observed that
subpermafrost waters were under pressure at the point when freezing of
an underwater bar at meter capacity of a frozen layer occurred .
In the central part of sandy banks, islands,
and bars the freezing of sand protrudes to a large depth. The thickness
of permafrost decreases towards the sea and near the coast; in
subaqueous conditions frozen strata disappears. The pressure of the
subpermafrost waters is proportional to the thickness of permafrost.
Waters are squeezed out from the center of the formatting
As the closeness to the sea decreases and
there are closed lagoons present, the area of permafrost is increased.
At the final stage there are only unfrozen sites in the residual lakes.
At this point the differentiation of porous waters in a strata of
deposits reaches the maximum. On sites that are already frozen and
combined by sand, the water content is minimal, and in unfrozen sites
the water content of deposits is at maximum. Right at the end of the
existence of a lake mode the freezing starts from top. Growing
hydrostatic pressure in strata of freezing deposits reaches the size of
geostatic pressure. At this exact moment a blowout occurs, the layer of
water and all strata above is supported by pressure in this layer.
The accumulation of water in strata of sea
deposits and its allocation as lenses or layers does not contradict a
natural development of the sea coastal zone. The presence of layers of
water of thickness up to 0,5 m is characteristic feature of fresh sea
silts on the depth of about 15 m [10,15]. The pressure of water in
frozen soils of thickness of 12 m is about 1,05 kg /sq. cm, and when
thickness reaches 22 m the pressure increases to 3 - 3,5 kg /sq.cm.
One more group of processes is attributed
to viscous current of generated frozen soils and ice.
The third area of the Arctic sea
cryolithogenesis is an area of freezing of residual lakes.
Gradually losing the connection with the
sea, the lagoons pass into the mode of fresh lakes. After they are
filled by deposits they dry up or break up into the series of fine lakes
or convert to bogs. The probability of formation of massive ice is
increased at the expense of water migration to the front of the freezing
The results of the mechanism are well
presented, but the mechanism itself is not studied in depth. Experience
suggests that the salinization of soils of up to 1% considerably reduces
redistribution of water content at the freezing point of clay soils.
The formation of massive ice is considered
as a consecutive change of processes divided into stages. Our experience
of study of massive ice suggests that the stages could be traced in
There are still different points of view
concerning the origin of massive ice. Such discord could be attributed
to several reasons:
1. In spite of the fact that geocryology as
a science has existed for about a hundred years, the reliable techniques
of a quantitative estimation of growth of ice crystals have not been
2. The problem of reconstruction of changes
in massive ice has not been solved. Under the influence of varying
loadings, the ice changes in structure, morphology, gas, and salt
structure, but quantitatively the character of these changes is not
3. There is lack of precise mechanical and
physical characteristics of deposits containing massive ice.
4. The analysis of change of superficial
conditions is not developed at the point of transition of deposits from
subaqueous conditions to subaerial position.
5. Properties of frozen saline soils
require further study.
The existing classification actually
reduces the large variety of processes carried out in massive ice to
abstract models. It seems to us that it would be more perspective to
consider formation of the ice as a part of sedimentation and freezing of
the certain genetic type of deposit. In conclusion it is necessary to
note that the formation and destruction of massive ice is connected to
cardinal transformation of natural environment.
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