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Geological cycle of formation of rocks. Methods for studying the earth's interior

Geological cycles

Geological cycles are the largest unit of the established periodicity Kalesnik S.V. General geographical patterns of the earth: a textbook for the geographical faculties of universities / S.V. Kalesnik. - M .: Mysl, 1970. - P. 85 .. They were reflected in the change of sedimentation regimes, volcanism and magmatism, epochs of dissection and leveling of the relief, periods of formation of weathering crusts and eluvial formations, in the alternation of marine transgressions and regressions, glaciers and interglacials, in the climate change of the planet and the content of atmospheric gases.

The entire geological history of the Earth known to us reveals cycles of several hundred million years, serving as a background for shorter (tens of millions, millions, hundreds of thousands of years, etc.) cycles, the nature of which is different. The longest astronomical period is the galactic year - the time between two successive passages of the Sun through the same point in the galactic orbit. This period is 180-200 million years Ibid. P. 86 .. Oscillatory movements of the earth's crust and the resulting changes in the distribution of land and sea determine the geological periodicity with a rhythm of 35-45 million years, which is the basis for the allocation of periods. The indicated periods of time represent a kind of "seasons" of the galactic year, to which various phenomena of the planetary system are confined: large tectonic-magmatic cycles, epochs of transgressions and regressions, land leveling and dismemberment, the emergence of global ice ages, etc.

There is a cycle with a duration of 85-90 million years (the cosmic half-year, or the draconian period for astronomers), due to a change in the position of the ecliptic plane of the solar system relative to the same plane of the universe. When analyzing large deformations of the earth's crust and its surface, a periodicity of 500-570 million years (triple galactic year) is outlined, the reason for which is not yet clear.

The history of the Earth's development over the past 570 million years is divided into three stages: Caledonian (Cambrian, Ordovician, Silurian), lasting about 200 million years, Hercynian (Devonian, Carboniferous, Permian), 150-190 million years long, Alpine (Mesozoic, Cenozoic) , lasting about 240 million years. The latter is often divided into the Early Alpine (Cimmerian) with a duration of about 170 million years and the Late Alpine (Alpine), which began about 70-90 million years ago. Yu.P. Seliverstov. Decree. op. S. 98 ..

With some difference in duration, these stages have common features that make it possible to speak of cyclicality: the beginning of each stage is marked by a general subsidence of the earth's crust, and the end of it by an uplift. In the epoch of subsidence, the sea regime and a monotonous climate dominate; in the epoch of uplifts, land is widespread, powerful folding and mountain-forming movements, and various climates. The average (170-190 million years) duration of these stages roughly corresponds to the duration of the galactic year. There can be no direct reflection in time, since it is necessary to take into account the delay in the reflection of the impact on a specific object. There are assumptions about a possible comparison of the cyclicity of the great glaciations, which were repeated after about 150-160 million years, and the duration of the galactic year (Fig. 1) Seliverstov Yu.P. Decree. op. S. 99 ..

The complexity of the problem of geological cycles consists not only in establishing their causes, but also in the degree of reliability of their existence. In addition, regions distant from each other develop tectonically in different ways. For example, in some areas of Southern Siberia, fold manifestations in the Caledonian era were different in time: the main folding in Tuva was in the Early Ordovician, in the Western Sayan - in the middle of the Silurian, in the Kuznetsk Alatau - on the border of the Middle and Late Cambrian.

The mechanism governing the rhythmic movements of the earth's crust has not yet been clarified and may be associated with the internal features of the development of the Earth or due to the duration of the galactic year.

Figures 2 and 3 show the general picture of the most significant geological rhythms S.V. Kalesnik. Decree. op. S. 86 ..

Geology√ one of the fundamental natural sciences that studies the structure, composition, origin and development of the Earth. She explores the complex phenomena and processes occurring on its surface and in the depths. Modern geology is based on centuries of experience in the knowledge of the Earth and a variety of special research methods. Unlike other geosciences, geology is concerned with the study of its interior. The main tasks of geology are to study the outer rocky shell of the planet - the earth's crust and the outer and inner shells of the Earth interacting with it (outer - atmosphere, hydrosphere, biosphere; inner - mantle and core).

The objects of direct study of geology are minerals, rocks, fossil organic remains, geological processes.

2. Cycle of geological sciences.

Geology is closely related to other earth sciences, for example, astronomy, geodesy, geography, biology. Geology is based on such fundamental sciences as mathematics, physics, chemistry. Geology is a synthetic science, although at the same time it is divided into many interrelated branches, scientific disciplines that study the Earth in different aspects and receive information about individual geological phenomena and processes. So, the study of the composition of the lithosphere is engaged in: petrology, which studies igneous and metamorphic rocks, lithology, which studies sedimentary rocks, mineralogy - the science that studies minerals as natural chemical compounds and geochemistry - the science of the distribution and migration of chemical elements in the bowels of the earth.

Geological processes that form the relief of the earth's surface are studied by dynamic geology, of which geotectonics, seismology and volcanology are a part.

The section of geology dealing with the study of the history of the development of the earth's crust and the Earth as a whole includes stratigraphy, paleontology, regional geology and is called ╚Historical geology.

There are sciences in geology that are of great practical importance. Such as mineral deposits, hydrogeology, engineering geology, geocryology.

In recent decades, science related to the exploration of space (space geology), the bottom of the seas and oceans (marine geology) has appeared and is gaining increasing importance.

Along with this, there are geological sciences that are at the interface with other natural sciences: geophysics, biogeochemistry, crystal chemistry, paleobotany. These include also geochemistry and paleogeography. The closest and most versatile connection between geology and geography. For geographical sciences, such as landscape science, climatology, hydrology, oceanography, geological sciences are most important, studying the processes that affect the formation of the earth's surface relief and the history of the formation of the earth's crust throughout the Earth.

3. Methods for studying the earth's interior.

In geology, direct, indirect, experimental and mathematical methods are used.

Direct√ these are methods of direct ground and remote (from the troposphere, space) studies of the composition and structure of the earth's crust. The main one is geological survey and mapping. The study of the composition and structure of the earth's crust is carried out by studying natural outcrops (river cliffs, ravines, mountain slopes), artificial mine workings (canals, shuffs, quarries, mines) and boreholes (max √ 3.5 √ 4 km. In India and South Africa , Kola well √ more than 12 km., Project 15 km.) In mountainous areas, natural sections can be observed in river valleys, exposing strata of rocks collected in complex folds and raised during mountain building from depths of 16 √ 20 km. Thus, the method of direct observation and study of rock layers is applicable only to a small, uppermost part of the earth's crust. Only in volcanic areas, by the lava erupted from volcanoes and by solid emissions, one can judge the composition of matter at depths of 50 √ 100 km. and more, where volcanic centers are usually located.

Indirect√ geophysical methods, which are based on the study of natural and artificial physical fields of the Earth, allowing to explore significant depths of the bowels.

There are seismic, gravimetric, electrical, magnetometric and other geophysical methods. Of these, the most important is the seismic (“seismism” √ quake) method based on studying the speed of propagation in the Earth of elastic vibrations that occur during earthquakes or artificial explosions. These vibrations are called seismic waves, which diverge from the source of earthquakes. There are 2 types: longitudinal Vp, arising as a reaction of the medium to changes in volume, propagate in solids and liquids and are characterized by the highest speed, and transverse waves Vs, representing the reaction of the medium to a change in shape and propagate only in solids. The speed of movement of seismic waves in different rocks is different and depends on their elastic properties and their density. The more elastic the medium, the faster the waves propagate. The study of the nature of the propagation of seismic waves makes it possible to judge the presence of different shells of the sphere with different elasticity and density.

Experimental research is aimed at modeling various geological processes and artificial production of various minerals and rocks.

Mathematical methods in geology are aimed at increasing the efficiency, reliability and value of geological information.

4. The structure of the Earth.

There are 3 shells of the Earth: the core, the mantle and the earth's crust.

Core√ the most dense shell of the Earth. It is believed that the outer core is in a state approaching liquid. The temperature of the substance reaches 2500 √ 3000 0 С, and the pressure is ~ 300 GPa. The inner core is presumably solid. The composition of the external and internal ~ is the same √ Fe √ Ni, close to the composition of meteorites.

Mantle√ the largest shell of the Earth. Mass √ 2/3 the mass of the planet. The upper mantle is characterized by vertical and horizontal heterogeneity. Its structure differs significantly under continents and oceans. In the oceans at a depth of ~ 50 km., And on the continents - 80 √ 120 km. a layer of low seismic velocities begins, which is called a seismic waveguide or asthenosphere (i.e. geosphere “without strength”) and is characterized by increased plasticity. (The waveguide extends under the oceans up to 300 √ 400 km., Under the continents - 100-150 km.) Most of the earthquake centers are confined to it. It is believed that magma chambers arise in it, as well as a zone of subcrustal convection currents and the origin of the most important endogenous processes.

VV Belousov unites the earth's crust, the upper mantle, including the asthenosphere in the tectonosphere.

The intermediate layer and the lower mantle are characterized by a more homogeneous environment than the upper mantle.

The upper mantle is composed mainly of ferro-magnesian silicates (olivine, pyroxenes, garnets), which corresponds to the peridotite composition of the rocks. In the transitional layer C, the main mineral is olivine.

Chemical composition: oxides Si, Al? Fe (2+, 3+), Ti, Ca, Mg, Na, K, Mn. Si and Mg predominate.

5. Earth's crust.

Earth's crust√ This is the upper shell of the Earth, composed of igneous, metamorphic and sedimentary rocks, with a thickness of 7 to 70 √ 80 km. This is the most active layer of the Earth. It is characterized by magmatism and manifestations of tectonic processes.

The lower boundary of the earth's crust is symmetrical to the surface of the earth. Under the continents, it sinks deep into the mantle, and under the oceans it approaches the surface. The earth's crust with the upper mantle up to the upper boundary of the asthenosphere (i.e., without the asthenosphere) forms the lithosphere.

In the vertical structure of the earth's crust, three layers are distinguished, composed of rocks of different composition, properties and origin.

1 layer√ upper or sedimentary (stratosphere) is composed of sedimentary and volcanic-sedimentary rocks, clays, clay shales, sandy, volcanic and carbonate rocks. The layer covers almost the entire surface of the Earth. The thickness in deep depressions reaches 20 √ 25 km, on average √ 3 km.

The rocks of the sedimentary cover are characterized by weak dislocation, relatively low densities, and small changes corresponding to diagenetic ones.

2nd layer√ medium or granite (granite √ gneiss), the rocks are similar to the properties of granites. Stacked: gneisses, granodiorites, diorites, oxides, as well as gabbros, marbles, silinites, etc.

The rocks of this layer are diverse in composition and degree of their dislocation. They can be unchanged and metamorphosed. The lower boundary of the granite layer is called the Conrad seismic section. The layer thickness is from 6 to 40 km. On some parts of the Earth, this layer is absent.

3 layer√ lower, basaltic, consists of heavier rocks, which are similar in properties to igneous rocks, basalts.

In some places, between the basalt layer and the mantle, the so-called eclogite layer with a higher density than the basalt layer occurs.

The average thickness of the layer in the continental part is ~ 20 km. Under the mountain ranges it reaches 30 √ 40 km, and under the depressions it decreases to 12 √ 13 and 5-7 km.

The average thickness of the earth's crust in the continental part (N. A. Belyavsky) √40.5 km., Min. √ 7 √ 12 km. in the oceans, max. √ 70 √ 80 km. (highlands on the continents).

Geology and the cycle of geological sciences

Geology- one of the fundamental natural sciences that studies the structure, composition, origin and development of the Earth. She explores the complex phenomena and processes occurring on its surface and in the depths. Modern geology is based on centuries of experience in the knowledge of the Earth and a variety of special research methods. Unlike other geosciences, geology is concerned with the study of its interior. The main tasks of geology are to study the outer rocky shell of the planet - the earth's crust and the outer and inner shells of the Earth interacting with it (outer - atmosphere, hydrosphere, biosphere; inner - mantle and core).

The objects of direct study of geology are minerals, rocks, fossil organic remains, geological processes.

Geology is closely related to other earth sciences, such as astronomy, geodesy, geography, biology. Geology is based on such fundamental sciences as mathematics, physics, chemistry. Geology is a synthetic science, although at the same time it breaks down into many interrelated branches, scientific disciplines that study the Earth in different aspects and receive information about individual geological phenomena and processes. So, the study of the composition of the lithosphere is engaged in: petrology, which studies igneous and metamorphic rocks, lithology, which studies sedimentary rocks, mineralogy - the science that studies minerals as natural chemical compounds and geochemistry - the science of the distribution and migration of chemical elements in the bowels of the earth.

The geological processes that form the relief of the earth's surface are studied by dynamic geology, of which geotectonics, seismology and volcanology are a part.

The branch of geology dealing with the study of the history of the development of the earth's crust and the Earth as a whole includes stratigraphy, paleontology, regional geology and is called “Historical geology.

There are sciences in geology that are of great practical importance. Such as mineral deposits, hydrogeology, engineering geology, geocryology.

In recent decades, science related to the exploration of space (space geology), the bottom of the seas and oceans (marine geology) has appeared and is gaining increasing importance.

Absolute and relative age of the earth, geochronological scale.

According to the latest data, the age of the Earth as a planet is estimated to be ~ 4.6 billion years. The study of meteorites and lunar rocks also confirms this figure. However, the oldest rocks of the Earth available for direct study are about 3.8 billion years old. Therefore, the entire more ancient stage in the history of the Earth is called up to the geological stage. The object of geological study is the history of the Earth over the past 3.8 billion years, which stands out in its geological stage.

To clarify the patterns and conditions for the formation of urban settlements it is necessary to know the sequence of their formation and age, i.e. establish their geological chronology.

Distinguish relative age G. p. (relative geochronology) and absolute age G. p. (absolute geochronology).

Establishing the age of the city of the item engaged in science stratigraphy(Latin Stratum - layer).

The absolute age of rocks and methods for determining it.

Absolute geochronology establishes the age of the g.p. in units of time. Determination of the absolute age is necessary for the correlation and comparison of biostratigraphic subdivisions of different parts of the Earth, as well as for establishing the age of the deprived paleontological remains of Phanerozoic and Pre-Cambrian rocks.

Methods for determining the absolute age of rocks include methods of nuclear (or isotope geochronology) and non-radiological methods.

Nuclear geochronology methods in our time are the most accurate for determining the absolute age of gp, which are based on the phenomenon of spontaneous transformation of a radioactive isotope of one element into a stable isotope of another. The essence of the methods is to determine the relationship between the amount of radioactive elements and the amount of stable products of their decay in the rock. According to the rate of decay of the isotope, which for a certain radioactive isotope is a constant value, the amount of radioactive and formed stable isotopes, calculate the time elapsed since the beginning of the formation of the mineral (respectively. And the rock).

A large number of radioactive methods for determining the absolute age have been developed: lead, potassium-argon, rubidium-strontium, radiocarbon, etc. (above the established age of the Earth of 4.6 billion years has not been established using the lead method).

Non-radiological methods are inferior in accuracy to nuclear ones.

Salt method was used to determine the age of the oceans. It is based on the assumption that the ocean waters were originally fresh, then, knowing the modern amount of salts from the continents, it is possible to determine the lifetime of the World Ocean (~ 97 million years).

Sedimentation method based on the study of sedimentary rocks in the seas. Knowing the volume and thickness of marine sediments in the w.c. in individual systems and the volume of mineral matter annually carried to the seas from the continents, it is possible to calculate the duration of their filling.

Biological method is based on the idea of a relatively uniform development of org. the world. The initial parameter is the duration of the Quaternary period, 1.7 - 2 million years.

The method of counting the layers of banded clays, accumulating on the periphery of melting glaciers. Clay sediments are deposited in winter, and sandy in summer and spring, thus. each pair of such layers is the result of an annual accumulation of precipitation (the last glacier on the Baltic Sea stopped moving 12 thousand years ago).

Mineral color

The question of the nature of the color coloration of minerals is very complicated. The nature of the coloration of some minerals has not yet been determined. In the best case, the color of a mineral is determined by the spectral composition of the light radiation reflected by the mineral or is determined by its internal properties, some chemical element that is part of the mineral, finely dispersed inclusions of other minerals, organic matter and other reasons. The coloring pigment is sometimes distributed unevenly, in stripes, giving multi-colored patterns (for example, in agates).

Some transparent minerals change color when incident light reflects off internal surfaces, cracks, or inclusions. These are the phenomena of iridescent color of chalcopyrite, pyrite and iridescence minerals - blue, blue overflows of Labrador.

Some minerals are multicolored (polychrome) and have different colors along the length of the crystal (tourmaline, amethyst, beryl, gypsum, fluorite, etc.).

The color of a mineral can sometimes be diagnostic. For example, aqueous copper salts are green or blue in color. The nature of the color of minerals is determined visually, usually by comparing the observed color with well-known concepts: milky white, light green, cherry red, etc. this feature is not always characteristic of minerals, since the colors of many of them vary greatly.

Line color

A more reliable diagnostic feature than the color of a mineral is the color of its powder, which is left when the test mineral scratches the matte surface of a porcelain plate. In some cases, it coincides with the color of the mineral itself, in others it is completely different. So, in cinnabar, the color of the mineral and powder is red, and in brass-yellow pyrite, the line is greenish-black. The trait is given by soft and medium hard minerals, while hard ones only scratch the plate and leave furrows on it.

Transparency

According to their ability to transmit light, minerals are divided into several groups:

transparent(rock crystal, rock salt) - transmitting light, objects are clearly visible through them;
translucent(chalcedony, opal) - objects, through which objects are poorly visible;
translucent only in very thin plates;
opaque- light is not transmitted even in thin plates (pyrite, magnetite).

Shine

Luster is the ability of a mineral to reflect light. There is no rigorous scientific definition of shine. There are minerals with a metallic luster like polished minerals (pyrite, galena); with semi-metallic (diamond, glass, matte, greasy, wax, mother-of-pearl, with iridescent tints, silky). Many physical properties are important diagnostic features in the determination of minerals.

Cleavage

The phenomenon of cleavage in minerals is determined by the cohesion of particles inside crystals and is due to the properties of their crystal lattices. The cleavage of minerals occurs most easily parallel to the densest networks of crystal lattices. These grids most often and in the best development manifest themselves in the external limitation of the crystal.

The number of cleavage planes for different minerals is not the same, reaching six, and the degree of perfection of different planes may be different. The following types of cleavage are distinguished:

very perfect, when the mineral without much effort splits into separate leaves or plates with smooth shiny surfaces - cleavage planes (gypsum).
perfect, found when lightly hitting the mineral, which crumbles into pieces, limited only by smooth shiny surfaces. Uneven surfaces not along the cleavage plane are obtained very rarely (calcite splits into regular rhombohedrons of different sizes, rock salt - into cubes, sphalerite - into rhombic dodecahedrons).
average, which is expressed in the fact that when a mineral is struck, kinks are formed both along cleavage planes and along uneven surfaces (feldspars - orthoclase, microcline, labrador)
imperfect... Cleavage planes in the mineral are difficult to detect (apatite, olivine).
very imperfect... Cleavage planes in the mineral are absent (quartz, pyrite, magnetite). At the same time, sometimes quartz (rock crystal) is found in well-cut crystals. Therefore, it is necessary to distinguish the natural crystal faces from the cleavage planes that appear during the fracture of the mineral. The planes can be parallel to the edges and have a fresher look and higher gloss.

Break

The nature of the surface formed during the fracture (splitting) of the mineral is different:

1. Smooth break if the mineral is split along cleavage planes, as, for example, in crystals of mica, gypsum, and calcite.

2. Stepped fracture is obtained when there are intersecting cleavage planes in the mineral; it can be observed in feldspars, calcite.

3. Uneven kink characterized by the absence of shiny areas of cleavage, as, for example, in quartz.

4. Grainy fracture observed in minerals with a granular-crystalline structure (magnetite, chromite).

5. Earthy fracture typical for soft and highly porous minerals (limonite, bauxite).

6. Crustaceous- with convex and concave areas like shells (apatite, opal).

7. Splinter(acicular) - an uneven surface with splinters oriented in one direction (selenite, chrysotile-asbestos, hornblende).

8. Hooked- hooked irregularities appear on the surface of the split (native copper, gold, silver). This kind of fracture is typical for malleable metals.

Hardness

Hardness of minerals- this is the degree of resistance of their outer surface to the penetration of another, harder mineral and depends on the type of crystal lattice and the strength of the bonds of atoms (ions). Determine the hardness by scratching the surface of the mineral with a fingernail, knife, glass or minerals with known hardness from the Mohs scale, which includes 10 minerals with gradually increasing hardness (in relative units).

The relative position of minerals in terms of the degree of increase in their hardness is visible when comparing: accurate determinations of the hardness of diamond (hardness on a scale of 10) showed that it is more than 4000 times higher than that of talc (hardness - 1).

Mohs scale

Most of the minerals have a hardness of 2 to 6. The harder minerals are anhydrous oxides and some silicates. When determining a mineral in a rock, make sure that it is the mineral and not the rock that is being tested.

Specific gravity

The specific gravity varies from 0.9 to 23 g / cm 3. For most of the minerals, it is 2 - 3.4 g / cm 3, ore minerals and native metals have the highest specific gravity of 5.5 - 23 g / cm 3. The exact specific gravity is determined in laboratory conditions, and in normal practice - by "weighing" the sample on the hand:

Light (with a specific gravity of up to 2.5 g / cm3) - sulfur, rock salt, gypsum and other minerals;

Medium (2.6 - 4 g / cm3) - calcite, quartz, fluorite, topaz, brown iron ore and other minerals;

With a high specific gravity (more than 4). This is barite (heavy spar) - with a specific gravity of 4.3 - 4.7, sulphurous ores of lead and copper - a specific gravity of 4.1 - 7.6 g / cm 3, native elements - gold, platinum, copper, iron, etc. .d. with a specific gravity of 7 to 23 g / cm 3 (osmous iridium - 22.7 g / cm 3, platinum iridium - 23 g / cm 3).

Magnetic

The property of minerals to be attracted by a magnet or to deflect a magnetic compass needle is one of the diagnostic signs. Magnetite and pyrrhotite are highly magnetic minerals.

Malleability and fragility

Malleable are minerals that change their shape when struck with a hammer, but do not disintegrate (copper, gold, platinum, silver). Fragile - crumble on impact into small pieces.

Electrical conductivity

Electrical conductivity of minerals Is the ability of minerals to conduct electric current under the influence of an electric field. Otherwise, minerals are classified as dielectrics, i.e. non-conductive.

Flammability and odor

Some minerals catch fire from a match and create characteristic odors (sulfur - sulfur dioxide, amber - an aromatic smell, ozokerite - a suffocating smell of carbon monoxide). The smell of hydrogen sulfide appears when hitting marcasite, pyrite, when rubbing quartz, fluorite, calcite. When the pieces of phosphorite rub against each other, the smell of burnt bone appears. Kaolinite, when wetted, acquires the smell of a stove.

Taste

Only minerals readily soluble in water evoke taste sensations (halite - salty taste, sylvin - bitter salty).

Roughness and greasiness

Talc, kaolinite are greasy, slightly smearing, rough - bauxite, chalk.

Hygroscopicity

This is the property of minerals to moisturize, attracting water molecules from the environment, including from the air (carnallite).

Some minerals react with acids. To identify minerals that are, by chemical composition, salts of carbonic acid, it is convenient to use the reaction of boiling them up with weak (5 - 10%) hydrochloric acid.

Metamorphism factors.

The change in magmatic and sedimentary rocks in the solid state under the influence of endogenous factors is called metamorphism.

The decisive influence on the metamorphism of rocks is exerted by pressure, temperature and fluids.

Temperature. The sources of heat in the earth's crust are the decay of radioactive elements; magmatic melts, which, when cooling, give off heat to the surrounding rocks; heated deep fluids; tectonic processes and a number of other factors. Geothermal gradient i.e. the number of degrees per 1 km of depth varies from place to place on the globe and the difference can be almost 100o C. Within stable, rigid blocks of the earth's crust, for example, on the shields of ancient platforms, the geothermal gradient does not exceed 6-10o C, while as in young growing mountain structures, it can reach almost 100o C. Temperature sharply accelerates the course of chemical reactions, promotes the recrystallization of matter, and strongly affects the processes of mineral formation. An increase in temperature leads to dehydration (dehydration) of minerals, the formation of higher-temperature mineral associations devoid of water, decarbonatization of limestones, etc. Usually, metamorphic transformations begin at T above 300o C, and stop when T reaches the melting point of rocks developed in a given place ...

Pressure is subdivided into all-round (lithostatic), due to the mass of overlying rocks, and stress, or one-sided, associated with tectonic directed movements. Comprehensive lithostatic pressure is associated not only with depth, but also with the density of rocks, and at a depth of 10 km can exceed 200 MPa, and at a depth of 30 km - 600-700 MPa. With a geothermal gradient of 25 deg / km, rock melting can begin at a depth of about 20 km. At high pressures, rocks turn into a plastic state - Unilateral stress pressure is best manifested in the upper part of the earth's crust of folded zones and is expressed in the formation of certain structural and textural features of the rock and specific stress minerals, such as glaucophane, disthene, etc. Stress pressure causes mechanical deformation of rocks, their crushing, sheathing, an increase in the solubility of minerals in the direction of pressure. Fluids penetrate into such mylonitized zones, under the influence of which the rocks undergo recrystallization.

Fluids, which include H2O, CO2, CO, CH4, H2, H2S, SO2 and others, transfer heat, dissolve rock minerals, transfer chemical elements, actively participate in chemical reactions and play the role of catalysts. The importance of fluids is illustrated by the fact that in<сухих системах>, t. s. devoid of fluids, even in the presence of high pressures and temperatures, metamorphic changes almost do not occur.

Sedimentary rocks.

Sedimentary rocks were formed on the surface of the lithosphere as a result of the accumulation of mineral masses obtained in the process of destruction of magmatic, metamorphic and sedimentary rocks. The processes of destruction of rocks of the lithosphere and the accumulation of new rocks on the surface of the earth are going on everywhere: in deserts, where the wind conducts vigorous work; along sea and ocean shores, where waves move debris; at the bottom of the deep parts of the seas and oceans, where dying organisms give rise to strata of sedimentary rocks. The formation conditions leave a significant imprint on the appearance of sedimentary rocks. In some cases, they consist of fragments of previously destroyed rocks, in others - from an accumulation of organic remains, in the third - from crystalline grains that have fallen out of solution.

Sedimentary rocks, depending on their origin, differ sharply from each other. Therefore, they are usually divided into three groups:

Clastic origin

Chemical origin

Organogenic origin

Sedimentary rocks are of particular interest to builders as they serve as bases and environments for various structures and are commonly available as building materials. They are of secondary origin, since the initial material for their formation is the products of destruction of pre-existing rocks. The process of formation of sedimentary rocks proceeds according to the scheme: physical and chemical weathering of rocks, mechanical and chemical transfer, deposition and accumulation of products of their destruction and, finally, compaction and cementation of loose sediment with its transformation into rock. The general properties of sedimentary rocks are the same bedding forms in the form of layers, with which their characteristic textural features are associated - layering and porosity. The latter is especially important, since it has a great influence on the physical and mechanical properties of rocks: strength, density and average density, water absorption, frost resistance, mechanical processing, etc.

Sedimentary rocks are distinguished by a variety of structures with a wide variation in shape, particle size and their ratio in different representatives. They are characterized by a significant variety of mineral components, which are simpler in chemical composition and are mainly sedimentary new formations that coincide in composition with some magmatic minerals. Among the rock-forming minerals there are carbonates, sulfates, and hydrous silica precipitated from aqueous solutions; secondary (clay) weathering products of parent rocks - kaolinite, montmorillonite; micaceous minerals, A1 and Fe hydroxides; relict minerals that have remained unchanged are igneous quartz, feldspars, as well as fragments of rocks of various genesis and the remains of organisms. Some representatives of sedimentary rocks dissolve in water, for example, rock salt, gypsum, limestone.

Soil classification.

The classification of soils includes the following taxonomic units, distinguished by groups of characteristics:

Class - by the general nature of structural links;

Group - by the nature of structural bonds (taking into account their strength);

Subgroup - by origin and educational conditions;

Type - by material composition;

Type - by the name of the soil (taking into account the particle size and property indicators);

Varieties - in terms of quantitative indicators of material composition, properties and structure of soils.

The class of natural rocky soils - soils with rigid structural bonds (crystallization and cementation) are subdivided into groups, subgroups, types, types and varieties according to Table 1.

Class of natural dispersed soils - soils with water-colloidal and mechanical structural bonds are subdivided into groups, subgroups, types, types and varieties

Class of natural frozen soils * - soils with cryogenic structural bonds are subdivided into groups, subgroups, types, types and varieties

The class of technogenic (rocky, dispersed and frozen) soils - soils with various structural bonds formed as a result of human activity, are subdivided into groups, subgroups, types and types

Particular classifications by material composition, properties and structure of rocky, dispersed and frozen soils (varieties) are presented in Appendix B.

By their origin, rocks are divided into:

Magmatic, igneous, formed as a result of the solidification of magma; they have a crystalline structure and are classified as rocky;

Sedimentary; they were formed as a result of the destruction and weathering of rocks with the help of water and air and form rocky and non-rocky soils;

Metamorphic, which were formed as a result of the action on metamorphic and sedimentary rocks of high temperatures and high pressures; they are classified as rocky soils.

Verkhovoda, characteristic.

Verkhovodka is a temporary accumulation of groundwater in the aeration zone. This zone is located at a shallow depth from the surface, above the water table, where part of the pores of the rocks is occupied by bound water, the other part is occupied by air.

The upper waterway is formed over random aquicludes (or semi-aquicludes), in the role of which can be lenses of clays and loams in the sand, interlayers of denser rocks. During infiltration, water is temporarily retained and forms a kind of aquifer. Most often this is associated with a period of heavy snow melting, a period of rains. The rest of the time, the water of the upper water evaporates and seeps into the underlying groundwater.

Another feature of the top water is the possibility of its formation even in the absence of any waterproof interlayers in the aeration zone. For example, water abundantly enters the loam stratum, but due to low water permeability, permeation occurs slowly and in the upper part of the stratum, an overflow is formed. After a while, this water dissolves.

In general, the verkhovodka is characterized by: a temporary, more often seasonal nature, a small area of distribution, low thickness and free flow. In easily permeable rocks, for example, in sands, perforation occurs relatively rarely. Various loams and loess rocks are most typical for it.

Verkhovodka poses a significant danger to construction. Lying within the underground parts of buildings and structures (basements of boiler rooms), it can cause their flooding, if drainage or waterproofing measures were not provided in advance. Recently, as a result of significant water leaks (water pipes, pools), the emergence of upstream horizons has been noted on the territory of industrial facilities and new residential areas located in the zone of loess rocks. This poses a serious danger, since the soils of the foundations reduce their stability, and the operation of buildings and structures becomes more difficult.

During engineering and geological surveys, carried out in the dry season, the top water is not always detected. Therefore, its appearance for builders may be unexpected.

Water in the aeration zone.

As a rule, the aeration zone has soil layers of different water permeability. Therefore, during the rainfall, a temporary aquifer can form in the aeration zone, which is called the top water. The upper water is especially characteristic during the winter thaw and in spring, when a waterproof layer of seasonal permafrost still remains in the soil, and snow melting on the surface provides intensive saturation of the soil with water. Spring flooding is often the reason for flooding the basements of buildings.

The presence of moisture in the aeration zone is explained by the fact that all capillary-porous systems, in particular of which the aeration zone is composed of sands, has the ability to absorb moisture from the air, retain and accumulate it in its pores. After that, the accumulated moisture can "drain" from the aeration zone into the aquifer, replenishing its reserves. This ability increases with a decrease in soil moisture, a decrease in its temperature and an increase in its salt content. Due to the processes of intra-soil condensation of water vapor, even in deserts, where the air humidity is minimal, lenses of fresh water are formed under the dunes.

The aeration zone is located between the ground surface and the water table. The zone of saturation of rocks is located below the groundwater level. Groundwater in the saturation zone circulates in the form of permafrost, groundwater, artisan, fissure and permafrost waters. Verkhovodki are temporary accumulations of groundwater in the aeration zone. The upper waters are formed over the occasional aquifers - lenses of clays and loams; during infiltration, water is retained and forms aquifers. This is due to the period of heavy snow melting, the period of rains. It also appears due to the low water permeability of the soil.

To ensure the aeration zone, for the respiration of the roots, the correct decomposition of organic matter in the soil, gas exchange should occur, in which the entire volume of air in the root layer will be renewed in no more than 8 days. For normal growth and development of plants, the soil must simultaneously contain air and water in a certain ratio. With a lack of water, the roots of plants cannot supply the required amount of it to the leaves (soil drought). There is a lot of air in dry soil, as a result of which the activity of aerobic bacteria is activated, and this leads to the rapid decomposition of organic matter. With a low water content in the soil, the concentration of the soil solution increases and plants cannot use it. With an excess of water, the air content decreases and the respiration of the roots worsens, the processes of decomposition of organic matter slow down.

Thus, the amount of water in the soil determines the degree of supply of it to plants, the content of air in the soil, the thermal and nutritional regime in the soil, i.e. her fertility. The optimum soil moisture for different plants is different (table). the more nutrients in the soil, the higher the optimum moisture content.

Quicksands and pseudo-swimmers.

SWIMMING (a.drift sand, floating sand, running sand, quicksand; n. Schwimmsand; f. Terrain sulant, sable aquifere; and. Arena movediza, roca pastosa, fluidez de suelo) - loose, slightly lithified, water-saturated, mainly sandy rocks, able to spread and float.

Distinguish between true and false quicksand. True quicksand consists of fine-grained and silty sands, as well as soils containing hydrophilic colloids that act as a lubricant. A characteristic feature of these quicksands is their great mobility and the ability to quickly turn into a quicksand state with insignificant mechanical stress, especially with concussion or vibration. With low humidity and high density, quicksand has significant strength. At humidity above a certain critical level, quicksand can flow as a whole under the influence of minor stresses. When freezing, true quicksand undergoes strong heaving, weakly filters water, drying out, acquires cohesion. In contrast to highly dispersed plastic soils, the plastic properties of true quicksands are temporary and gradually disappear after the load is removed. False quicksands do not contain colloidal particles, and their quicksand properties are manifested at significant pressure gradients. As density increases, false quicksands often lose their quicksand properties.

Quicksands complicate mining when driving mine workings, building pits, structures, tunnels, etc. As protective measures when driving in quicksands, special shields, caissons, sinkholes, freezing, advanced driving and fixing quicksands are used.

Types of water in rocks.

Depending on the physical state, mobility and the nature of the connection with the ground, several types of water in soils are distinguished: chemically and physically bound, capillary, free, solid and vaporous water.

Chemically bound water is part of some minerals, such as gypsum, copper sulfate. Water from such minerals can be removed in most cases only by heating to 300-400 C.

Physically bound water is retained on the surface of minerals and soil particles by molecular forces and can be removed from the soil only at a temperature of at least 90-120 C. This type of water is subdivided into hygroscopic and film water.

Hygroscopic water is formed due to the adsorption of water molecules by soil particles. On the surface of the particles, hygroscopic water is held together by molecular and electrical forces.

Film water forms a film over hygroscopic water when the moisture content of the soil exceeds its maximum hygroscopicity. This water can move from one soil particle to another.

Capillary water is formed in the pores of the soil after they are saturated with film water, fills the pores and thin cracks and moves in them under the action of capillary forces. downstream groundwater; capillary-raised, located in the form of a capillary zone above the groundwater level and closely associated with it; capillary-disconnected, located in the rest of the soil. Capillary water evaporates through the soil surface or plant leaves and plays an important role in soil saturation, groundwater regime and plant nutrition.

Free water is the most mobile and important component of groundwater. This liquid water is located in the pores and cracks in the soil and moves under the influence of gravity and hydrostatic pressure gradients.

Solid water is in the ground in the form of crystals, interlayers and ice lenses.

Water in a vaporous state fills, together with air, voids in soils not occupied by water.

Field testing of soils.

Field methods of studying soils are used when performing engineering and geological surveys, to assess the strength and deformation properties of soils, to obtain hydrogeological parameters, in conditions of natural bedding of rocks. Research is carried out on the site (route) of the designed or reconstructed engineering structures. Carrying out work requires special machinery and equipment. Field methods for studying soils have different purposes and solve various problems:

study of the physical, strength and deformation properties of soils in the conditions of their natural occurrence;

obtaining information about the conditions of occurrence of groundwater, layers of rocks, their genesis;

obtaining hydrogeological parameters and characteristics of the soil massif.

methods of field research of soils:

static sounding;

die test;

pressiometer test;

pillar shear test;

experimental filtration work.

Static sounding refers to special methods of obtaining engineering and geological information. Modern capabilities have significantly expanded the range of information that can be obtained using this field method of soil research. The depth of the test increased significantly up to 45 m (depending on the lithological composition of the massif).

Static sounding, as a method of field research of soils, has broad technological capabilities for sampling rocks and groundwater samples, as well as special research of soils in natural bedding conditions.

The materials obtained during static sounding can be used to solve the following main tasks:

dismemberment of the geological section into separate layers (engineering-geological elements), their identification by area and depth;

typification and classification of soils by composition, condition and properties;

study of the spatial variability of soil properties to select the most justified calculation models of foundations;

determination of indicators of physical and mechanical properties of soils based on both empirical interpretation formulas and analytical solutions;

solving problems of design and calculation of foundations (for example, determination of the design load on the pile, design soil resistance, settlement of the pile and pile foundation).

Annotation.

The purpose of the general course in the history and methodology of geological sciences is to give the graduating specialist a general idea of the development of geological sciences, to reveal the fundamental issues of the methodology of scientific research and the logic of building scientific research; reflect modern ideas about some of the philosophical problems of geology. An important objective of the course is to study the history of Russian geology against the general background of the development of geological knowledge. Creative development of the course involves independent study of geological and methodological literature and writing an abstract in the course plan.

Introduction.

The history of geology as part of the general history of natural science and world culture in general. The process of formation of geological knowledge and the development of economic, social, cultural and historical features of the state of society.

Methodology - the doctrine of the principles and logic of the construction of scientific research, forms and methods of scientific and cognitive activity. The place of geology in the system of natural sciences. Classification of the sciences of the geological cycle. The principles of the periodization of the history of geology.

1. History of geological sciences.

1.1. Pre-scientific stage in the development of geological knowledge (from antiquity to the middle of the 18th century).

The period of formation of human civilization (from ancient times to the 5th century BC). Accumulation of empirical knowledge about stones, ores, salts and groundwater.

Antique period (V century BC - V century AD). The origin of ideas about minerals, rocks and geological processes in the framework of natural philosophy. The origin of plutonism and neptunism. The main representatives of the school of Greco-Roman natural philosophy.

Scholastic period (V - XV centuries in Western Europe, VII - XVII centuries in other countries). Stagnation in the development of science, the predominance of church dogmas in Western Europe. Development of crafts and mining. Founding of the first universities. Arab civilization and its role in the development of natural science in the 7th - 13th centuries. Crafts of Ancient Rus, establishment in 1584 of the Order of Stone Affairs.

Revival period (XV - XVII to the middle of the XVIII century). Great geographical discoveries. Approval of the heliocentric picture of the world. Geological representations of Leonardo da Vinci, Bernard Palissy, Nikolaus Stenon, Georg Bauer (Agricola). Cosmogonic concepts of R. Descartes and G. Leibniz. Plutonism and Deluvianism. Development of geological knowledge in Russia in the era of Peter the Great's reforms. Creation of the Order of Mining Affairs (1700), Bergkollegii (1718), opening of the Academy of Sciences (1725).

1.2. The scientific stage in the development of geology (from the beginning of the nineteenth century). Transition period (second half of the 18th century).

Cosmogonic hypotheses by E. Kant and P. Laplace. Geological ideas of J. Buffon, M. V. Lomonosov. The origin of stratigraphy. A.G. Werner, his teaching and school. J. Hutton (Getton) and his "Theory of the Earth". Contradictions in the question of the role of external and internal processes in the development of the Earth. Development of crystallography. Opening of the Moscow University (1755) and the Higher Mining School (the future Mining Institute (1773)). Russian academic expeditions. VM Severgin and his role in the development of mineralogy.

The heroic period in the development of geology (first half of the 19th century). The birth of biostratigraphy and paleontology. The first tectonic hypothesis is the "uplift craters" hypothesis. Catastrophists and evolutionists - a historical dispute between two scientific camps. Development of the Phanerozoic stratigraphic scale. Start of geological mapping. Advances in the study of minerals. Beginning of the chemical stage in the study of minerals. The doctrine of syngonies, isomorphism and polymorphism and paragenesis of minerals.

C. Lyayel and his book "Fundamentals of Geology ..." (1830-1833). Discussions about the origin of exotic boulders. Formation of glacial theory. Creation of the first geological societies and national geological services. Geology in Russia in the first half of the nineteenth century.

The classical period of the development of geology (second half of the 19th century). Geological observations of Charles Darwin and the influence on the development of geology of his book "The Origin of Species by Natural Selection ...". A triumph of evolutionary ideas in geology. Elie de Beaumont's contraction hypothesis and its development in the works of E. Suess. The origin of the doctrine of geosynclines and platforms. Formation of paleogeography, geomorphology, hydrogeology.

Development of microscopic petrography. The emergence of the concept of magma, its types and differentiation. The origin of the doctrine of metamorphism, the formation of experimental petrography. Development of theoretical and genetic mineralogy. Advances in crystallography. Formation of the doctrine of ore deposits. The origin of oil geology. The first steps of geophysics in the study of the deep structure of the Earth. The beginning of international cooperation of geologists. The first international geological congresses. Foundation of the Geological Committee of Russia (1882).

The "critical" period in the development of geological sciences (10s - 50s of the twentieth century). Scientific revolution in natural science at the turn of the 19th - 20th centuries. Crisis in geotectonics. Collapse of the contraction hypothesis. Emergence of alternative tectonic hypotheses. The origin of the ideas of mobilism is the hypothesis of continental drift. Rejection of mobilism and the revival of the ideas of fixism. Further development of the theory of geosynclines and platforms. Formation of the doctrine of deep faults. The origin of neotectonics, tectonophysics. Further development of geophysics. Creation of a model of the shell structure of the Earth Formation of geophysical methods of exploration and geological interpretation of geophysical data.

The development of the sciences of matter. The use of X-ray structural analysis in the study of crystals, the emergence of crystal chemistry and structural mineralogy. The origin of geochemistry. The doctrine of the biosphere and noosphere. Development of petrology and its sections (petrochemistry, chemistry of magmas, space petrography). Development of the doctrine of metamorphism. Development of teaching about ore deposits; further development of hydrothermal theory. Mineragraphy. Thermobarometry. Advances in metallogeny.

Formation of lithology and advances in paleogeography. The origin of the doctrine of formations. Development of the geology of fossil fuels. Teaching about oil and gas basins. Coal geology. Further development of hydrogeology, development of the problem of vertical hydrochemical and hydrodynamic zoning of groundwater. Hydrogeological mapping. The origin of permafrost science.

The latest period in the development of geology (60s - 90s of the twentieth century). Technical re-equipment of geology: electron microscope, microprobe, mass spectrometer, computer, deep-water and ultra-deep drilling, exploration of the Earth from space, etc. Beginning of intensive geological and geophysical study of the oceans and planets of the solar system. Revival of mobilism in geotectonics. Establishment of the asthenosphere. Paleomagnetism. The hypothesis of expansion (spreading) of the ocean floor. New global tectonics or plate tectonics is a new paradigm of geology. Other alternative mobilist concepts.

"Digital revolution" in geophysics, development of methods of exploration geophysics and marine geophysics. Advances in the study of the earth's crust and upper mantle.

Advances in paleontology; new groups of fossil remains, stages in the development of the organic world and evolution of the biosphere, extinction of large systematic groups and global biocenotic crises. Development of stratigraphy, introduction of new methods: magneto- and seismostratigraphy, radio chronometry; study of the Precambrian stratigraphy.

Further development of the sciences of terrestrial matter. Cosmochemistry and isotope geochemistry, experimental mineralogy and petrology; development of the doctrine of metamorphic facies; geochemical methods of prospecting for ore deposits.

Development of the theoretical foundations of oil and gas geology.

Comparative planetology and its significance for deciphering the early stages of the development of the Earth. Further development of hydrogeology, engineering geology and geocryology. The emergence of a new direction in geology - ecological geology. International cooperation of geologists. Current state and near-term prospects of geology. From tectonics of lithospheric plates to the general global geodynamic model of the Earth. Global geodynamic models and geoecology. Social, ideological, economic functions of geology. A brief overview of modern problems in geology.

History of teaching geology and scientific schools of geologists at Moscow University.

2. Methodology of geological sciences.

2.1. Object and subject of geology, their change in the course of the development of science. Geological form of development of matter. Methods of geological sciences (general scientific, special). Laws in geology. The problem of time in geology.

2..2. General laws of development of geological sciences. Processes of differentiation and integration of geological sciences. Scientific revolutions in geology.

2.3. The principles of building scientific research. Fixation of the subject of the search, formulation of the problem, definition of the problem of research methods. A hypothetical model, the basics of its construction. Theoretical model, the foundations of its construction and development. Facts, their place and significance in scientific research.

2.4. The role of the paradigm in empirical and theoretical research. The concept of a model approach in geological research. System analysis and its principles. Features of the system model of geological objects. Fractality of geological objects. Self-organization processes of matter and principles of building geological models. The laws of nonequilibrium thermodynamics and geodynamic processes.

Literature

Belousov V.V. Essays on the history of geology. At the origins of Earth science (geology until the end of the 18th century). - M., - 1993.
Vernadsky V.I. Selected works on the history of science. - M .: Science, - 1981.
T. Kuhn, The Structure of Scientific Revolutions, Moscow: Progress, 1975.
A.S. Povarenykh, V.I. Onoprienko Mineralogy: past, present, future. - Kiev: Naukova Dumka, - 1985.
Modern ideas of theoretical geology. - L .: Nedra, - 1984.
Khain V.E. The main problems of modern geology (geology on the threshold of the XXI century) .- M .: Scientific world, 2003 ..
Khain V.E., Ryabukhin A.G. History and methodology of geological sciences. - M .: Moscow State University, - 1996.
Hallem A. Great Geological Disputes. M.: Mir, 1985.

In 2014, a strange hole in the ground was found in the central region of the Yamal Peninsula: a round crater had a diameter of about 20 meters and a depth of about 50 meters. Its origin has remained a mystery ever since. A group of scientists from Moscow State University, having examined samples of permafrost, found that this funnel was formed due to a phenomenon that had not previously been observed on Earth. Published last week in the magazine Scientific Reports The article describes its formation in terms of cryovolcanism, thereby not only proposing a new mechanism for the formation of these unusual craters, but also describing the terrestrial cryovolcano for the first time.

In the summer of 2014, an unusual geological formation was found in the central part of the Yamal Peninsula near the Bovanenkovskoye gas field: an almost round crater with a diameter of 20 meters and a depth of about 50 meters (Fig. 1). Many hypotheses have been put forward about its origin, including the fall of a meteorite and the migration of biogenic gases due to thawing of permafrost (see, for example, M. Leibman et al., 2014. New permafrost feature-deep crater in central Yamal (West Siberia, Russia ) as a response to local climate fluctuations, V. Olenchenko et al., 2015. Results of geophysical surveys of the area of "Yamal crater", the new geological structure), but they all had their drawbacks. In principle, the formation of crater-like structures as a result of geocryological processes is a rare but not extraordinary phenomenon (J. Mackay, 1979. Pingos of the Tuktoyaktuk Peninsula Area, Northwest Territories). For example, in 2017 on Yamal, the formation of two similar craters, but much smaller in size, was recorded.

The Yamal crater is located in the permafrost zone with average annual temperatures from −1 ° C to −5 ° C and a volume fraction of ice of 30–65%, often concentrated in ice lenses. Thanks to modern technologies, it was even possible to find out the approximate time of formation of the structure: until 2013, according to space images, there was a large heaving mound in place of the crater (see the picture of the day "Pingo or heaving mounds"), about 8 meters in height and 50-55 meters in diameter.

Along the line crossing the crater, the scientists drilled several boreholes and obtained cores (cylindrical pillars of rock taken out of the borehole) of permafrost (Fig. 2). One of the wells, located five meters north of the crater, exposed a large lens of ice at a depth of 5.8 m. Despite the fact that the depth of this well was 17 m, it was not possible to reach the lower boundary of the lens. Samples were taken from this lens and adjacent wells for further study. They consisted of ice, humic acids and mineral inclusions. Analyzes have shown that scientists are dealing with two different types of permafrost containing ancient marine sediments: the first type is almost untouched by thermokarst (the process of thawing and destruction of permafrost), and the second, on the contrary, is intensively processed by it. Ice in samples of the first type contained small amounts of metals and organic carbon, while ice from samples of the second type contained carbon compounds of organic origin up to 3.5 g / liter and inclusions of dark brown solutions of alkaline composition (pH 8–9.5). Another difference was observed between the ice and sedimentary components of the samples: the concentration of metals was insignificant in ancient sediments (with the exception of SiO 2, CaO, Na 2 O) and relatively high in ice samples. This can be interpreted as the result of a long-term interaction of groundwater and melt water, which leads to the idea that a lake with a large thawed zone under it (talik) once existed in the place of the crater.

The main feature of the studied samples is the unusually high concentration of gases, reaching 20% by volume in some samples. These are mainly CO 2 and N 2. But methane - the alleged culprit for the formation of the crater - turned out to be small (first percent). This, as well as the results of isotope analysis, indicated that the source of the gases was not the Bovanenkovo field, as previously thought. The predominance among hydrocarbons of higher normal alkanes (C 19 H 40 and compounds with b O higher number of carbon atoms) showed that they were formed as a result of decomposition of plant remains.

Based on the results of mathematical modeling, the sequence of events preceding the formation of the crater was established. First, under a long-lived thermokarst lake (liquid water at a positive temperature), the permafrost thaws (Fig. 3, A), forming a talik about the size of a modern dry lake, in the center of which there is a crater. According to geocryologists, the formation of a 60–70 meter thaw zone takes about 3000 years. When the lake dries up, the thawed zone begins to freeze back from the edges to the center (Fig. 3, C). At the final stages of the lake's life, its bottom freezes, forming an ice cover over the not yet completely frozen talik (Fig. 3, C). The remaining water under the pressure of growing ice begins to squeeze outward, forming a heaving mound that has existed for the last hundred years (Fig. 3, D).

Based on the gas content in the studied samples, it is assumed that the dissolved gases accounted for about 14 volume percent of the talik. During freezing, some of these gases migrated into the surrounding rocks, avoiding freezing, and some (mainly CO 2, which is highly soluble in water) remained in the talik, increasing the pressure and promoting the formation of heaving mounds. Because of the water under the frozen ice cover 6–8 meters thick, the pressure in the talik can reach 5 bar, but it takes about 10 bar to break through. This value is quite achievable if we take into account the contribution of the gas component. In the lower part of the talik, the pressure reaches 15 bar, which makes possible the formation of CO 2 clathrates (a scenario that is realized if the liquid is saturated with gas). If there were not enough gas, then when the pingo was destroyed, only a small release of water would occur, but in no way an eruption and crater formation.

Before the eruption, a layered structure was observed in the talik: thawed soils with a large amount of carbon dioxide clathrates at the bottom, water with dissolved gas in the middle, and mainly gas in the upper part (Fig. 4, A). The eruption was provoked by the formation of ice wedges along cracks in the frozen cap and consisted of three stages:
1) Pneumatic stage (first minutes): degassing from the upper chamber of the talik, emission of jets of carbon dioxide (Fig. 4, C). Scattering of soil over long distances and damage to vegetation by a cold gas jet.
2) Hydraulic stage (several hours): the outpouring of water from the crater (Fig. 4, C) - the release of pressure caused foaming of gas-saturated water (effect similar to a stream of champagne after removing the cork). Full break through of the ice cap and the beginning of the formation of the wall around the crater.
3) Phreatic stage (5–25 hours): decomposition of gas hydrates in the lower soil layer and its removal to the surface with emerging foam (Fig. 4, D). Since the decomposition of gas hydrates is a rather slow process, this phase is the longest part of the eruption.

Such a reconstruction of events suggests that the formation of the Yamal crater is a full-fledged phenomenon, "Elements", 02/07/2014 and Analysis of the gravitational field of Enceladus also indicates the presence of liquid water on it, "Elements", 04/07/2014, as well as the article by JS Kargel , 1995. Cryovolcanism on the icy satellites). Traces of past cryovolcanic activity are abundant in the outer solar system. A serious study of these objects began in 1979-1989, after the flights of Voyager probes past the icy moons of the gas giants, but their direct study was not available until now, since not a single cryovolcano was discovered on Earth. Now it looks like scientists are getting this opportunity.

Earlier it was assumed that cryovolcanism requires a heat source located under the cryovolcano. This is partly true, but the work under discussion shows that such processes can occur not only due to water heating, but also due to its crystallization: ice crystallization in gas-saturated systems leads to pressure surges and can, for example, serve as an explanation for water jets on Enceladus ( JH Waite Jr et al., 2009. Liquid water on Enceladus from observations of ammonia and 40 Ar in the plume). The data obtained in the study of the Yamal crater may provide a fresh look at eruptions on ice bodies.