Scientific electronic library.

ENDOGENOUS PROCESSES (a. endogenous processes; n. endogene Vorgange; f. processus endogenes, processus endogeniques; i. procesos endogenos) - geological processes associated with energy arising in the Earth. Endogenous processes include tectonic movements of the earth's crust, magmatism, metamorphism,. The main sources of energy for endogenous processes are heat and the redistribution of material in the interior of the Earth according to density (gravitational differentiation).

The deep heat of the Earth, according to most scientists, is predominantly of radioactive origin. A certain amount of heat is also released during gravitational differentiation. The continuous generation of heat in the bowels of the Earth leads to the formation of its flow to the surface (heat flow). At some depths in the bowels of the Earth, with a favorable combination of material composition, temperature and pressure, centers and layers of partial melting can arise. Such a layer in the upper mantle is the asthenosphere - the main source of magma formation; convection currents can arise in it, which are the presumed cause of vertical and horizontal movements in the lithosphere. Convection also occurs on the scale of the entire mantle, possibly separately in the lower and upper, in one way or another leading to large horizontal movements of lithospheric plates. Cooling of the latter leads to vertical subsidence (see). In the zones of volcanic belts of island arcs and continental margins, the main sources of magma in the mantle are associated with ultra-deep inclined faults (Wadati-Zavaritsky-Benioff seismofocal zones), extending beneath them from the ocean (to a depth of approximately 700 km). Under the influence of heat flow or directly the heat brought by rising deep magma, so-called crustal magma chambers arise in the earth's crust itself; reaching the near-surface parts of the crust, magma penetrates them in the form of intrusions (plutons) of various shapes or pours out onto the surface, forming volcanoes.

Gravitational differentiation led to the stratification of the Earth into geospheres of different densities. On the surface of the Earth, it also manifests itself in the form of tectonic movements, which, in turn, lead to tectonic deformations of the rocks of the earth’s crust and upper mantle; the accumulation and subsequent release of tectonic stress along active faults leads to earthquakes.

Both types of deep processes are closely related: radioactive heat, reducing the viscosity of the material, promotes its differentiation, and the latter accelerates the transfer of heat to the surface. It is assumed that the combination of these processes leads to uneven temporal transport of heat and light matter to the surface, which, in turn, can explain the presence of tectonomagmatic cycles in the history of the earth’s crust. Spatial irregularities of the same deep processes are used to explain the division of the earth's crust into more or less geologically active areas, for example, geosynclines and platforms. Endogenous processes are associated with the formation of the Earth's topography and the formation of many important

Questions

1.Endogenous and exogenous processes

.Earthquake

.Physical properties of minerals

.Epeirogenic movements

.Bibliography

1. EXOGENOUS AND ENDOGENOUS PROCESSES

Exogenous processes - geological processes occurring on the surface of the Earth and in the uppermost parts of the earth's crust (weathering, erosion, glacial activity, etc.); are caused mainly by the energy of solar radiation, gravity and the vital activity of organisms.

Erosion (from Latin erosio - erosion) is the destruction of rocks and soils by surface water flows and wind, including the separation and removal of fragments of material and accompanied by their deposition.

Often, especially in foreign literature, erosion is understood as any destructive activity of geological forces, such as sea surf, glaciers, gravity; in this case, erosion is synonymous with denudation. For them, however, there are also special terms: abrasion (wave erosion), exaration (glacial erosion), gravitational processes, solifluction, etc. The same term (deflation) is used in parallel with the concept of wind erosion, but the latter is much more common.

Based on the speed of development, erosion is divided into normal and accelerated. Normal always occurs in the presence of any pronounced runoff, occurs more slowly than soil formation and does not lead to noticeable changes in the level and shape of the earth's surface. Accelerated is faster than soil formation, leads to soil degradation and is accompanied by a noticeable change in topography. For reasons, natural and anthropogenic erosion are distinguished. It should be noted that anthropogenic erosion is not always accelerated, and vice versa.

The work of glaciers is the relief-forming activity of mountain and cover glaciers, consisting in the capture of rock particles by a moving glacier, their transfer and deposition when the ice melts.

Endogenous processes Endogenous processes are geological processes associated with energy arising in the depths of the solid Earth. Endogenous processes include tectonic processes, magmatism, metamorphism, and seismic activity.

Tectonic processes - the formation of faults and folds.

Magmatism is a term that combines effusive (volcanism) and intrusive (plutonism) processes in the development of folded and platform areas. Magmatism is understood as the totality of all geological processes, the driving force of which is magma and its derivatives.

Magmatism is a manifestation of the Earth's deep activity; it is closely related to its development, thermal history and tectonic evolution.

Magmatism is distinguished:

geosynclinal

platform

oceanic

magmatism of activation areas

By depth of manifestation:

abyssal

hypabyssal

surface

According to the composition of magma:

ultrabasic

basic

alkaline

In the modern geological era, magmatism is especially developed within the Pacific geosynclinal belt, mid-ocean ridges, reef zones of Africa and the Mediterranean, etc. The formation of a large number of diverse mineral deposits is associated with magmatism.

Seismic activity is a quantitative measure of the seismic regime, determined by the average number of earthquake sources in a certain range of energy magnitudes that occur in the territory under consideration during a certain observation time.

2. EARTHQUAKES

geological earth's crust epeirogenic

The effect of the internal forces of the Earth is most clearly revealed in the phenomenon of earthquakes, which are understood as shaking of the earth's crust caused by displacements of rocks in the bowels of the Earth.

Earthquake- a fairly common phenomenon. It is observed on many parts of continents, as well as on the bottom of oceans and seas (in the latter case they speak of a “seaquake”). The number of earthquakes on the globe reaches several hundred thousand per year, i.e., on average, one or two earthquakes occur per minute. The strength of an earthquake varies: most of them are detected only by highly sensitive instruments - seismographs, others are felt directly by a person. The number of the latter reaches two to three thousand per year, and they are distributed very unevenly - in some areas such strong earthquakes are very frequent, while in others they are unusually rare or even practically absent.

Earthquakes can be divided into endogenousassociated with processes occurring deep within the Earth, and exogenous, depending on processes occurring near the Earth's surface.

To natural earthquakesThese include volcanic earthquakes caused by volcanic eruptions and tectonic earthquakes caused by the movement of matter in the deep interior of the Earth.

To exogenous earthquakesinclude earthquakes occurring as a result of underground collapses associated with karst and some other phenomena, gas explosions, etc. Exogenous earthquakes can also be caused by processes occurring on the surface of the Earth itself: rock falls, meteorite impacts, falling water from great heights and other phenomena, as well as factors associated with human activity (artificial explosions, machine operation, etc.).

Genetically, earthquakes can be classified as follows: Natural

Endogenous: a) tectonic, b) volcanic. Exogenous: a) karst landslides, b) atmospheric c) from waves, waterfalls, etc. Artificial

a) from explosions, b) from artillery fire, c) from artificial rock collapse, d) from transport, etc.

In the geology course, only earthquakes associated with endogenous processes are considered.

When strong earthquakes occur in densely populated areas, they cause enormous harm to humans. In terms of disasters caused to humans, earthquakes cannot be compared with any other natural phenomenon. For example, in Japan, during the earthquake of September 1, 1923, which lasted only a few seconds, 128,266 houses were completely destroyed and 126,233 were partially destroyed, about 800 ships were lost, and 142,807 people were killed or missing. More than 100 thousand people were injured.

It is extremely difficult to describe the phenomenon of an earthquake, since the whole process lasts only a few seconds or minutes, and a person does not have time to perceive all the variety of changes taking place in nature during this time. Attention is usually focused only on the colossal destruction that occurs as a result of an earthquake.

This is how M. Gorky describes the earthquake that occurred in Italy in 1908, of which he was an eyewitness: “The earth hummed dully, groaned, hunched under our feet and worried, forming deep cracks - as if in the depths some huge worm, dormant for centuries, had woken up and was tossing and turning. ...Shuddering and staggering, the buildings tilted, cracks snaked along their white walls, like lightning, and the walls crumbled, falling asleep on the narrow streets and the people among them... The underground rumble, the rumble of stones, the squeal of wood drowned out the cries for help, the cries of madness. The earth is agitated like the sea, throwing palaces, shacks, temples, barracks, prisons, schools from its chest, destroying hundreds and thousands of women, children, rich and poor with each shudder. "

As a result of this earthquake, the city of Messina and a number of other settlements were destroyed.

The general sequence of all phenomena during an earthquake was studied by I.V. Mushketov during the largest Central Asian earthquake, the Alma-Ata earthquake of 1887.

On May 27, 1887, in the evening, as eyewitnesses wrote, there were no signs of an earthquake, but domestic animals behaved restlessly, did not take food, broke from their leash, etc. On the morning of May 28, at 4:35 a.m., an underground rumble was heard and quite strong push. The shaking lasted no more than a second. A few minutes later the hum resumed; it resembled the dull ringing of numerous powerful bells or the roar of passing heavy artillery. The roar was followed by strong crushing blows: plaster fell in houses, glass flew out, stoves collapsed, walls and ceilings fell: the streets were filled with gray dust. The most severely damaged were the massive stone buildings. The northern and southern walls of houses located along the meridian fell out, while the western and eastern walls were preserved. At first it seemed that the city no longer existed, that all the buildings were destroyed without exception. The shocks and tremors, although less severe, continued throughout the day. Many damaged but previously standing houses fell from these weaker tremors.

Landslides and cracks formed in the mountains, through which streams of underground water came to the surface in some places. The clayey soil on the mountain slopes, already heavily wetted by rain, began to creep, cluttering the river beds. Collected by the streams, this entire mass of earth, rubble, and boulders, in the form of thick mudflows, rushed to the foot of the mountains. One of these streams stretched for 10 km and was 0.5 km wide.

The destruction in the city of Almaty itself was enormous: out of 1,800 houses, only a few houses survived, but the number of human casualties was relatively small (332 people).

Numerous observations showed that the southern walls of houses collapsed first (a fraction of a second earlier), and then the northern ones, and that the bells in the Church of the Intercession (in the northern part of the city) struck a few seconds after the destruction that occurred in the southern part of the city. All this indicated that the center of the earthquake was south of the city.

Most of the cracks in the houses were also inclined to the south, or more precisely to the southeast (170°) at an angle of 40-60°. Analyzing the direction of the cracks, I.V. Mushketov came to the conclusion that the source of the earthquake waves was located at a depth of 10-12 km, 15 km south of Alma-Ata.

The deep center or focus of an earthquake is called the hypocenter. INIn plan it is outlined as a round or oval area.

Area located on the surface The earth above the hypocenter is calledepicenter . It is characterized by maximum destruction, with many objects moving vertically (bouncing), and cracks in houses are located very steeply, almost vertically.

The area of the epicenter of the Alma-Ata earthquake was determined to be 288 km ² (36 *8 km), and the area where the earthquake was most powerful covered an area of 6000 km ². Such an area was called pleistoseist (“pleisto” - largest and “seistos” - shaken).

The Alma-Ata earthquake continued for more than one day: after the tremors of May 28, 1887, tremors of lesser strength occurred for more than two years. at intervals of first several hours, and then days. In just two years there were over 600 strikes, increasingly weakening.

The history of the Earth describes earthquakes with even more tremors. For example, in 1870, tremors began in the province of Phocis in Greece, which continued for three years. In the first three days, the tremors followed every 3 minutes; during the first five months, about 500 thousand tremors occurred, of which 300 were destructive and followed each other with an average interval of 25 seconds. Over three years, over 750 thousand strikes occurred.

Thus, an earthquake does not occur as a result of a one-time event occurring at depth, but as a result of some long-term process of movement of matter in the inner parts of the globe.

Usually the initial large shock is followed by a chain of smaller shocks, and this entire period can be called the earthquake period. All shocks of one period come from a common hypocenter, which can sometimes shift during development, and therefore the epicenter also shifts.

This is clearly visible in a number of examples of Caucasian earthquakes, as well as the earthquake in the Ashgabat region, which occurred on October 6, 1948. The main shock followed at 1 hour 12 minutes without preliminary shocks and lasted 8-10 seconds. During this time, enormous destruction occurred in the city and surrounding villages. One-story houses made of raw bricks crumbled, and the roofs were covered with piles of bricks, household utensils, etc. Individual walls of more solidly built houses fell out, and pipes and stoves collapsed. It is interesting to note that round buildings (elevator, mosque, cathedral, etc.) withstood the shock better than ordinary quadrangular buildings.

The epicenter of the earthquake was located 25 km away. southeast of Ashgabat, in the area of the Karagaudan state farm. The epicentral region turned out to be elongated in a northwestern direction. The hypocenter was located at a depth of 15-20 km. The length of the pleistoseist region reached 80 km and its width 10 km. The period of the Ashgabat earthquake was long and consisted of many (more than 1000) tremors, the epicenters of which were located northwest of the main one within a narrow strip located in the foothills of Kopet-Dag

The hypocenters of all these aftershocks were at the same shallow depth (about 20-30 km) as the hypocenter of the main shock.

Earthquake hypocenters can be located not only under the surface of continents, but also under the bottom of seas and oceans. During seaquakes, the destruction of coastal cities is also very significant and is accompanied by human casualties.

The strongest earthquake occurred in 1775 in Portugal. The pleistoseist region of this earthquake covered a huge area; the epicenter was located under the bottom of the Bay of Biscay near the capital of Portugal, Lisbon, which was hit the hardest.

The first shock occurred on the afternoon of November 1 and was accompanied by a terrible roar. According to eyewitnesses, the ground rose up and then fell a full cubit. Houses fell with a terrible crash. The huge monastery on the mountain swayed so violently from side to side that it threatened to collapse every minute. The tremors continued for 8 minutes. A few hours later the earthquake resumed.

The Marble embankment collapsed and went under water. People and ships standing near the shore were drawn into the resulting water funnel. After the earthquake, the depth of the bay at the embankment site reached 200 m.

The sea retreated at the beginning of the earthquake, but then a huge wave 26 m high hit the shore and flooded the coast to a width of 15 km. There were three such waves, following one after another. What survived the earthquake was washed away and carried out to sea. More than 300 ships were destroyed or damaged in Lisbon harbor alone.

The waves of the Lisbon earthquake passed through the entire Atlantic Ocean: near Cadiz their height reached 20 m, on the African coast, off the coast of Tangier and Morocco - 6 m, on the islands of Funchal and Madera - up to 5 m. The waves crossed the Atlantic Ocean and were felt off the coast America on the islands of Martinique, Barbados, Antigua, etc. The Lisbon earthquake killed over 60 thousand people.

Such waves quite often arise during seaquakes; they are called tsutsnas. The speed of propagation of these waves ranges from 20 to 300 m/sec depending on: the depth of the ocean; wave height reaches 30 m.

The appearance of tsunamis and low tide waves is explained as follows. In the epicentral region, due to the deformation of the bottom, a pressure wave is formed that propagates upward. The sea in this place only swells strongly, short-term currents are formed on the surface, diverging in all directions, or “boils” with water being thrown up to a height of up to 0.3 m. All this is accompanied by a hum. The pressure wave is then transformed at the surface into tsunami waves, spreading out in different directions. Low tides before a tsunami are explained by the fact that water first rushes into an underwater hole, from which it is then pushed into the epicentral region.

When the epicenters occur in densely populated areas, earthquakes cause enormous disasters. The earthquakes in Japan were especially destructive, where over 1,500 years, 233 major earthquakes with a number of tremors exceeding 2 million were recorded.

Great disasters are caused by earthquakes in China. During the disaster on December 16, 1920, over 200 thousand people died in the Kansu region, and the main cause of death was the collapse of dwellings dug in the loess. Earthquakes of exceptional magnitude occurred in America. An earthquake in the Riobamba region in 1797 killed 40 thousand people and destroyed 80% of buildings. In 1812, the city of Caracas (Venezuela) was completely destroyed within 15 seconds. The city of Concepcion in Chile was repeatedly almost completely destroyed, the city of San Francisco was severely damaged in 1906. In Europe, the greatest destruction was observed after the earthquake in Sicily, where in 1693 50 villages were destroyed and over 60 thousand people died.

On the territory of the USSR, the most destructive earthquakes were in the south of Central Asia, in the Crimea (1927) and in the Caucasus. The city of Shemakha in Transcaucasia suffered especially often from earthquakes. It was destroyed in 1669, 1679, 1828, 1856, 1859, 1872, 1902. Until 1859, the city of Shemakha was the provincial center of Eastern Transcaucasia, but due to the earthquake the capital had to be moved to Baku. In Fig. 173 shows the location of the epicenters of the Shemakha earthquakes. Just as in Turkmenistan, they are located along a certain line extended in the northwest direction.

During earthquakes, significant changes occur on the surface of the Earth, expressed in the formation of cracks, dips, folds, the raising of individual areas on land, the formation of islands in the sea, etc. These disturbances, called seismic, often contribute to the formation of powerful landslides, landslides, mudflows and mudflows in the mountains, the emergence of new sources, the cessation of old ones, the formation of mud hills, gas emissions, etc. Disturbances formed after earthquakes are called post-seismic.

Phenomena. associated with earthquakes both on the surface of the Earth and in its interior are called seismic phenomena. The science that studies seismic phenomena is called seismology.

3. PHYSICAL PROPERTIES OF MINERALS

Although the main characteristics of minerals (chemical composition and internal crystal structure) are established on the basis of chemical analyzes and X-ray diffraction, they are indirectly reflected in properties that are easily observed or measured. To diagnose most minerals, it is enough to determine their luster, color, cleavage, hardness, and density.

Shine(metallic, semi-metallic and non-metallic - diamond, glass, greasy, waxy, silky, pearlescent, etc.) is determined by the amount of light reflected from the surface of the mineral and depends on its refractive index. Based on transparency, minerals are divided into transparent, translucent, translucent in thin fragments, and opaque. Quantitative determination of light refraction and light reflection is possible only under a microscope. Some opaque minerals reflect light strongly and have a metallic luster. This is common in ore minerals such as galena (lead mineral), chalcopyrite and bornite (copper minerals), argentite and acanthite (silver minerals). Most minerals absorb or transmit a significant portion of the light falling on them and have a non-metallic luster. Some minerals have a luster that transitions from metallic to non-metallic, which is called semi-metallic.

Minerals with a non-metallic luster are usually light-colored, some of them are transparent. Quartz, gypsum and light mica are often transparent. Other minerals (for example, milky white quartz) that transmit light, but through which objects cannot be clearly distinguished, are called translucent. Minerals containing metals differ from others in light transmission. If light passes through a mineral, at least in the thinnest edges of the grains, then it is, as a rule, non-metallic; if the light does not pass through, then it is ore. There are, however, exceptions: for example, light-colored sphalerite (zinc mineral) or cinnabar (mercury mineral) are often transparent or translucent.

Minerals differ in the qualitative characteristics of their non-metallic luster. The clay has a dull, earthy sheen. Quartz on the edges of crystals or on fracture surfaces is glassy, talc, which is divided into thin leaves along the cleavage planes, is mother-of-pearl. Bright, sparkling, like a diamond, shine is called diamond.

When light falls on a mineral with a non-metallic luster, it is partially reflected from the surface of the mineral and partially refracted at this boundary. Each substance is characterized by a certain refractive index. Because it can be measured with high precision, it is a very useful mineral diagnostic feature.

The nature of the luster depends on the refractive index, and both of them depend on the chemical composition and crystal structure of the mineral. In general, transparent minerals containing heavy metal atoms are characterized by high luster and a high refractive index. This group includes such common minerals as anglesite (lead sulfate), cassiterite (tin oxide) and titanite or sphene (calcium titanium silicate). Minerals composed of relatively light elements can also have high luster and a high refractive index if their atoms are tightly packed and held together by strong chemical bonds. A striking example is diamond, which consists of only one light element, carbon. To a lesser extent, this is also true for the mineral corundum (Al 2O 3), transparent colored varieties of which - ruby and sapphires - are precious stones. Although corundum is composed of light atoms of aluminum and oxygen, they are so tightly bound together that the mineral has a fairly strong luster and a relatively high refractive index.

Some glosses (oily, waxy, matte, silky, etc.) depend on the state of the surface of the mineral or on the structure of the mineral aggregate; a resinous luster is characteristic of many amorphous substances (including minerals containing the radioactive elements uranium or thorium).

Color- a simple and convenient diagnostic sign. Examples include brass yellow pyrite (FeS 2), lead-gray galena (PbS) and silver-white arsenopyrite (FeAsS 2). In other ore minerals with a metallic or semi-metallic luster, the characteristic color may be masked by the play of light in a thin surface film (tarnish). This is common to most copper minerals, especially bornite, which is called "peacock ore" because of its iridescent blue-green tarnish that quickly develops when freshly fractured. However, other copper minerals are painted in familiar colors: malachite - green, azurite - blue.

Some non-metallic minerals are unmistakably recognizable by the color determined by the main chemical element (yellow - sulfur and black - dark gray - graphite, etc.). Many non-metallic minerals consist of elements that do not provide them with a specific color, but they have colored varieties, the color of which is due to the presence of impurities of chemical elements in small quantities that are not comparable with the intensity of the color they cause. Such elements are called chromophores; their ions are characterized by selective absorption of light. For example, the deep purple amethyst owes its color to a trace amount of iron in quartz, while the deep green color of emerald is due to the small amount of chromium in beryl. Colors in normally colorless minerals can result from defects in the crystal structure (caused by unfilled atomic positions in the lattice or the incorporation of foreign ions), which can cause selective absorption of certain wavelengths in the white light spectrum. Then the minerals are painted in additional colors. Rubies, sapphires and alexandrites owe their color to precisely these light effects.

Colorless minerals can be colored by mechanical inclusions. Thus, thin scattered dissemination of hematite gives quartz a red color, chlorite - green. Milky quartz is clouded with gas-liquid inclusions. Although mineral color is one of the most easily determined properties in mineral diagnostics, it must be used with caution as it depends on many factors.

Despite the variability in the color of many minerals, the color of the mineral powder is very constant, and therefore is an important diagnostic feature. Typically, the color of a mineral powder is determined by the line (the so-called “line color”) that the mineral leaves when it is passed over an unglazed porcelain plate (biscuit). For example, the mineral fluorite comes in different colors, but its streak is always white.

Cleavage- very perfect, perfect, average (clear), imperfect (unclear) and very imperfect - is expressed in the ability of minerals to split in certain directions. A fracture (smooth, stepped, uneven, splintered, conchoidal, etc.) characterizes the surface of the split of a mineral that did not occur along cleavage. For example, quartz and tourmaline, whose fracture surface resembles a glass chip, have a conchoidal fracture. In other minerals, the fracture may be described as rough, jagged, or splintered. For many minerals, the characteristic is not fracture, but cleavage. This means that they cleave along smooth planes directly related to their crystal structure. The bonding forces between the planes of the crystal lattice can vary depending on the crystallographic direction. If they are much larger in some directions than in others, then the mineral will split across the weakest bond. Since cleavage is always parallel to the atomic planes, it can be designated by indicating crystallographic directions. For example, halite (NaCl) has cube cleavage, i.e. three mutually perpendicular directions of possible split. Cleavage is also characterized by the ease of manifestation and the quality of the resulting cleavage surface. Mica has very perfect cleavage in one direction, i.e. easily splits into very thin leaves with a smooth shiny surface. Topaz has perfect cleavage in one direction. Minerals can have two, three, four or six cleavage directions along which they are equally easy to split, or several cleavage directions of varying degrees. Some minerals have no cleavage at all. Since cleavage, as a manifestation of the internal structure of minerals, is their constant property, it serves as an important diagnostic feature.

Hardness- the resistance that the mineral provides when scratched. Hardness depends on the crystal structure: the more tightly the atoms in the structure of a mineral are connected to each other, the more difficult it is to scratch. Talc and graphite are soft plate-like minerals, built from layers of atoms bonded together by very weak forces. They are greasy to the touch: when rubbed against the skin of the hand, individual thin layers slip off. The hardest mineral is diamond, in which the carbon atoms are so tightly bonded that it can only be scratched by another diamond. At the beginning of the 19th century. Austrian mineralogist F. Moos arranged 10 minerals in increasing order of their hardness. Since then, they have been used as standards for the relative hardness of minerals, the so-called. Mohs scale (Table 1)

Table 1. MOH HARDNESS SCALE

MineralRelative hardnessTalc 1 Gypsum 2 Calcite 3 Fluorite 4 Apatite 5 Orthoclase 6 Quartz 7 Topaz 8 Corundum 9 Diamond 10

To determine the hardness of a mineral, it is necessary to identify the hardest mineral that it can scratch. The hardness of the mineral being examined will be greater than the hardness of the mineral it scratched, but less than the hardness of the next mineral on the Mohs scale. Bonding forces can vary depending on the crystallographic direction, and since hardness is a rough estimate of these forces, it can vary in different directions. This difference is usually small, with the exception of kyanite, which has a hardness of 5 in the direction parallel to the length of the crystal and 7 in the transverse direction.

For a less accurate determination of hardness, you can use the following, simpler, practical scale.

2 -2.5 Thumbnail 3 Silver coin 3.5 Bronze coin 5.5-6 Penknife blade 5.5-6 Window glass 6.5-7 File

In mineralogical practice, the measurement of absolute hardness values (the so-called microhardness) using a sclerometer device, which is expressed in kg/mm, is also used. 2.

Density.The mass of atoms of chemical elements varies from hydrogen (the lightest) to uranium (the heaviest). All other things being equal, the mass of a substance consisting of heavy atoms is greater than that of a substance consisting of light atoms. For example, two carbonates - aragonite and cerussite - have a similar internal structure, but aragonite contains light calcium atoms, and cerussite contains heavy lead atoms. As a result, the mass of cerussite exceeds the mass of aragonite of the same volume. The mass per unit volume of a mineral also depends on the atomic packing density. Calcite, like aragonite, is calcium carbonate, but in calcite the atoms are less densely packed, so it has less mass per unit volume than aragonite. The relative mass, or density, depends on the chemical composition and internal structure. Density is the ratio of the mass of a substance to the mass of the same volume of water at 4 ° C. So, if the mass of a mineral is 4 g, and the mass of the same volume of water is 1 g, then the density of the mineral is 4. In mineralogy, it is customary to express density in g/ cm 3.

Density is an important diagnostic feature of minerals and is not difficult to measure. First, the sample is weighed in air and then in water. Since a sample immersed in water is subject to an upward buoyant force, its weight there is less than in air. The weight loss is equal to the weight of water displaced. Thus, density is determined by the ratio of the mass of a sample in air to its weight loss in water.

Pyro-electricity.Some minerals, such as tourmaline, calamine, etc., become electrified when heated or cooled. This phenomenon can be observed by pollinating a cooling mineral with a mixture of sulfur and red lead powders. In this case, sulfur covers positively charged areas of the mineral surface, and minium covers areas with a negative charge.

Magneticity -This is the property of some minerals to act on a magnetic needle or be attracted by a magnet. To determine magnetism, use a magnetic needle placed on a sharp tripod, or a magnetic shoe or bar. It is also very convenient to use a magnetic needle or knife.

When testing for magnetism, three cases are possible:

a) when a mineral in its natural form (“by itself”) acts on a magnetic needle,

b) when the mineral becomes magnetic only after calcination in the reducing flame of a blowpipe

c) when the mineral does not exhibit magnetism either before or after calcination in a reducing flame. To calcinate with a reducing flame, you need to take small pieces of 2-3 mm in size.

Glow.Many minerals that do not glow on their own begin to glow under certain special conditions.

There are phosphorescence, luminescence, thermoluminescence and triboluminescence of minerals. Phosphorescence is the ability of a mineral to glow after exposure to one or another ray (willite). Luminescence is the ability to glow at the moment of irradiation (scheelite when irradiated with ultraviolet and cathode rays, calcite, etc.). Thermoluminescence - glow when heated (fluorite, apatite).

Triboluminescence - glow at the moment of scratching with a needle or splitting (mica, corundum).

Radioactivity.Many minerals containing elements such as niobium, tantalum, zirconium, rare earths, uranium, and thorium often have quite significant radioactivity, easily detectable even by household radiometers, which can serve as an important diagnostic sign.

To test for radioactivity, the background value is first measured and recorded, then the mineral is brought, possibly closer to the detector of the device. An increase in readings of more than 10-15% can serve as an indicator of the radioactivity of the mineral.

Electrical conductivity.A number of minerals have significant electrical conductivity, which allows them to be clearly distinguished from similar minerals. Can be checked with a regular household tester.

4. EPEIROGENIC MOVEMENTS OF THE EARTH'S CRUST

Epeirogenic movements- slow secular uplifts and subsidences of the earth's crust, which do not cause changes in the primary occurrence of layers. These vertical movements are oscillatory in nature and reversible, i.e. the rise may be replaced by a fall. These movements include:

Modern ones, which are recorded in human memory and can be measured instrumentally by repeated leveling. The speed of modern oscillatory movements on average does not exceed 1-2 cm/year, and in mountainous areas it can reach 20 cm/year.

Neotectonic movements are movements during the Neogene-Quaternary time (25 million years). Fundamentally, they are no different from modern ones. Neotectonic movements are recorded in modern relief and the main method of studying them is geomorphological. The speed of their movement is an order of magnitude lower, in mountainous areas - 1 cm/year; on the plains - 1 mm/year.

Ancient slow vertical movements are recorded in sections of sedimentary rocks. The speed of ancient oscillatory movements, according to scientists, is less than 0.001 mm/year.

Orogenic movementsoccur in two directions - horizontal and vertical. The first leads to the collapse of rocks and the formation of folds and thrusts, i.e. to the reduction of the earth's surface. Vertical movements lead to the raising of the area where folding occurs and often the appearance of mountain structures. Orogenic movements occur much faster than oscillatory movements.

They are accompanied by active effusive and intrusive magmatism, as well as metamorphism. In recent decades, these movements have been explained by the collision of large lithospheric plates, which move horizontally along the asthenospheric layer of the upper mantle.

TYPES OF TECTONIC FAULTS

Types of tectonic disturbances

a - folded (plicate) forms;

In most cases, their formation is associated with compaction or compression of the Earth's substance. Fold faults are morphologically divided into two main types: convex and concave. In the case of a horizontal cut, layers that are older in age are located in the core of the convex fold, and younger layers are located on the wings. Concave bends, on the other hand, have younger deposits in their cores. In folds, the convex wings are usually inclined to the sides from the axial surface.

b - discontinuous (disjunctive) forms

Discontinuous tectonic disturbances are those changes in which the continuity (integrity) of rocks is disrupted.

Faults are divided into two groups: faults without displacement of the rocks separated by them relative to each other and faults with displacement. The first ones are called tectonic cracks, or diaclases, the second ones are called paraclases.

BIBLIOGRAPHY

1. 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.

Povarennykh A.S., Onoprienko V.I. Mineralogy: past, present, future. - Kyiv: 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 21st century). - M.: Scientific world, 2003..

Khain V.E., Ryabukhin A.G. History and methodology of geological sciences. - M.: MSU, - 1996.

Hallem A. Great geological disputes. M.: Mir, 1985.

1. EXOGENOUS AND ENDOGENOUS PROCESSES

The work of glaciers is the relief-forming activity of mountain and cover glaciers, consisting in the capture of rock particles by a moving glacier, their transfer and deposition when the ice melts.

Tectonic processes - the formation of faults and folds.

Magmatism is a manifestation of the Earth's deep activity; it is closely related to its development, thermal history and tectonic evolution.

Magmatism is distinguished:

geosynclinal

platform

oceanic

magmatism of activation areas

By depth of manifestation:

abyssal

hypabyssal

surface

According to the composition of magma:

ultrabasic

basic

sour

alkaline

2. EARTHQUAKES

geological earth's crust epeirogenic

Earthquakes are a fairly common phenomenon. It is observed on many parts of continents, as well as on the bottom of oceans and seas (in the latter case they speak of a “seaquake”). The number of earthquakes on the globe reaches several hundred thousand per year, i.e., on average, one or two earthquakes occur per minute. The strength of an earthquake varies: most of them are detected only by highly sensitive instruments - seismographs, others are felt directly by a person. The number of the latter reaches two to three thousand per year, and they are distributed very unevenly - in some areas such strong earthquakes are very frequent, while in others they are unusually rare or even practically absent.

Earthquakes can be divided into endogenous, associated with processes occurring deep in the Earth, and exogenous, depending on processes occurring near the surface of the Earth.

Natural earthquakes include volcanic earthquakes, caused by volcanic eruptions, and tectonic earthquakes, caused by the movement of matter in the deep interior of the Earth.

Exogenous earthquakes include earthquakes that occur as a result of underground collapses associated with karst and some other phenomena, gas explosions, etc. Exogenous earthquakes can also be caused by processes occurring on the surface of the Earth itself: rock falls, meteorite impacts, falling water from great heights and other phenomena, as well as factors associated with human activity (artificial explosions, machine operation, etc.).

Genetically, earthquakes can be classified as follows: Natural

Endogenous: a) tectonic, b) volcanic. Exogenous: a) karst landslides, b) atmospheric c) from waves, waterfalls, etc. Artificial

a) from explosions, b) from artillery fire, c) from artificial rock collapse, d) from transport, etc.

In the geology course, only earthquakes associated with endogenous processes are considered.

As a result of this earthquake, the city of Messina and a number of other settlements were destroyed.

The general sequence of all phenomena during an earthquake was studied by I.V. Mushketov during the largest Central Asian earthquake, the Alma-Ata earthquake of 1887.

The destruction in the city of Almaty itself was enormous: out of 1,800 houses, only a few houses survived, but the number of human casualties was relatively small (332 people).

The deep center or focus of an earthquake is called the hypocenter. In plan it is outlined as a round or oval area.

The area located on the Earth's surface above the hypocenter is called the epicenter. It is characterized by maximum destruction, with many objects moving vertically (bouncing), and cracks in houses are located very steeply, almost vertically.

The area of the epicenter of the Alma-Ata earthquake was determined to be 288 km² (36 * 8 km), and the area where the earthquake was most powerful covered an area of 6000 km². Such an area was called pleistoseist (“pleisto” - largest and “seistos” - shaken).

Thus, an earthquake does not occur as a result of a one-time event occurring at depth, but as a result of some long-term process of movement of matter in the inner parts of the globe.

The hypocenters of all these aftershocks were at the same shallow depth (about 20-30 km) as the hypocenter of the main shock.

Drying the coast before a tsunami usually lasts several minutes and in exceptional cases reaches an hour. Tsunamis occur only during seaquakes when a certain section of the bottom collapses or rises.

During earthquakes, significant changes occur on the surface of the Earth, expressed in the formation of cracks, dips, folds, the raising of individual areas on land, the formation of islands in the sea, etc. These disturbances, called seismic, often contribute to the formation of powerful landslides, landslides, mudflows and mudflows in the mountains, the emergence of new sources, the cessation of old ones, the formation of mud hills, gas emissions, etc. Disturbances formed after earthquakes are called post-seismic.

Phenomena. associated with earthquakes both on the surface of the Earth and in its interior are called seismic phenomena. The science that studies seismic phenomena is called seismology.

3. PHYSICAL PROPERTIES OF MINERALS

Luster (metallic, semi-metallic and non-metallic - diamond, glass, greasy, waxy, silky, pearlescent, etc.) is determined by the amount of light reflected from the surface of the mineral and depends on its refractive index. Based on transparency, minerals are divided into transparent, translucent, translucent in thin fragments, and opaque. Quantitative determination of light refraction and light reflection is possible only under a microscope. Some opaque minerals reflect light strongly and have a metallic luster. This is common in ore minerals such as galena (lead mineral), chalcopyrite and bornite (copper minerals), argentite and acanthite (silver minerals). Most minerals absorb or transmit a significant portion of the light falling on them and have a non-metallic luster. Some minerals have a luster that transitions from metallic to non-metallic, which is called semi-metallic.

The nature of the luster depends on the refractive index, and both of them depend on the chemical composition and crystal structure of the mineral. In general, transparent minerals containing heavy metal atoms are characterized by high luster and a high refractive index. This group includes such common minerals as anglesite (lead sulfate), cassiterite (tin oxide) and titanite or sphene (calcium titanium silicate). Minerals composed of relatively light elements can also have high luster and a high refractive index if their atoms are tightly packed and held together by strong chemical bonds. A striking example is diamond, which consists of only one light element, carbon. To a lesser extent, this is true for the mineral corundum (Al2O3), the transparent colored varieties of which - ruby and sapphires - are precious stones. Although corundum is composed of light atoms of aluminum and oxygen, they are so tightly bound together that the mineral has a fairly strong luster and a relatively high refractive index.

Color is a simple and convenient diagnostic sign. Examples include brass-yellow pyrite (FeS2), lead-gray galena (PbS), and silvery-white arsenopyrite (FeAsS2). In other ore minerals with a metallic or semi-metallic luster, the characteristic color may be masked by the play of light in a thin surface film (tarnish). This is common to most copper minerals, especially bornite, which is called "peacock ore" because of its iridescent blue-green tarnish that quickly develops when freshly fractured. However, other copper minerals are painted in familiar colors: malachite is green, azurite is blue.

Cleavage - very perfect, perfect, average (clear), imperfect (unclear) and very imperfect - is expressed in the ability of minerals to split in certain directions. A fracture (smooth, stepped, uneven, splintered, conchoidal, etc.) characterizes the surface of the split of a mineral that did not occur along cleavage. For example, quartz and tourmaline, whose fracture surface resembles a glass chip, have a conchoidal fracture. In other minerals, the fracture may be described as rough, jagged, or splintered. For many minerals, the characteristic is not fracture, but cleavage. This means that they cleave along smooth planes directly related to their crystal structure. The bonding forces between the planes of the crystal lattice can vary depending on the crystallographic direction. If they are much larger in some directions than in others, then the mineral will split across the weakest bond. Since cleavage is always parallel to the atomic planes, it can be designated by indicating crystallographic directions. For example, halite (NaCl) has cube cleavage, i.e. three mutually perpendicular directions of possible split. Cleavage is also characterized by the ease of manifestation and the quality of the resulting cleavage surface. Mica has very perfect cleavage in one direction, i.e. easily splits into very thin leaves with a smooth shiny surface. Topaz has perfect cleavage in one direction. Minerals can have two, three, four or six cleavage directions along which they are equally easy to split, or several cleavage directions of varying degrees. Some minerals have no cleavage at all. Since cleavage, as a manifestation of the internal structure of minerals, is their constant property, it serves as an important diagnostic feature.

Hardness is the resistance that a mineral offers when scratched. Hardness depends on the crystal structure: the more tightly the atoms in the structure of a mineral are connected to each other, the more difficult it is to scratch. Talc and graphite are soft plate-like minerals, built from layers of atoms bonded together by very weak forces. They are greasy to the touch: when rubbed against the skin of the hand, individual thin layers slip off. The hardest mineral is diamond, in which the carbon atoms are so tightly bonded that it can only be scratched by another diamond. At the beginning of the 19th century. Austrian mineralogist F. Moos arranged 10 minerals in increasing order of their hardness. Since then, they have been used as standards for the relative hardness of minerals, the so-called. Mohs scale (Table 1)

MOH HARDNESS SCALE

The density and mass of atoms of chemical elements varies from hydrogen (the lightest) to uranium (the heaviest). All other things being equal, the mass of a substance consisting of heavy atoms is greater than that of a substance consisting of light atoms. For example, two carbonates - aragonite and cerussite - have a similar internal structure, but aragonite contains light calcium atoms, and cerussite contains heavy lead atoms. As a result, the mass of cerussite exceeds the mass of aragonite of the same volume. The mass per unit volume of a mineral also depends on the atomic packing density. Calcite, like aragonite, is calcium carbonate, but in calcite the atoms are less densely packed, so it has less mass per unit volume than aragonite. The relative mass, or density, depends on the chemical composition and internal structure. Density is the ratio of the mass of a substance to the mass of the same volume of water at 4° C. So, if the mass of a mineral is 4 g, and the mass of the same volume of water is 1 g, then the density of the mineral is 4. In mineralogy, it is customary to express density in g/ cm3.

Pyro-electricity. Some minerals, such as tourmaline, calamine, etc., become electrified when heated or cooled. This phenomenon can be observed by pollinating a cooling mineral with a mixture of sulfur and red lead powders. In this case, sulfur covers positively charged areas of the mineral surface, and minium covers areas with a negative charge.

Magnetism is the property of some minerals to act on a magnetic needle or be attracted by a magnet. To determine magnetism, use a magnetic needle placed on a sharp tripod, or a magnetic shoe or bar. It is also very convenient to use a magnetic needle or knife.

When testing for magnetism, three cases are possible:

a) when a mineral in its natural form (“by itself”) acts on a magnetic needle,

b) when the mineral becomes magnetic only after calcination in the reducing flame of a blowpipe

c) when the mineral does not exhibit magnetism either before or after calcination in a reducing flame. To calcinate with a reducing flame, you need to take small pieces of 2-3 mm in size.

Glow. Many minerals that do not glow on their own begin to glow under certain special conditions.

Triboluminescence - glow at the moment of scratching with a needle or splitting (mica, corundum).

Radioactivity. Many minerals containing elements such as niobium, tantalum, zirconium, rare earths, uranium, and thorium often have quite significant radioactivity, easily detectable even by household radiometers, which can serve as an important diagnostic sign.

Electrical conductivity. A number of minerals have significant electrical conductivity, which allows them to be clearly distinguished from similar minerals. Can be checked with a regular household tester.

EPEIROGENIC MOVEMENTS OF THE EARTH'S CRUST

Epeirogenic movements are slow secular uplifts and subsidences of the earth's crust that do not cause changes in the primary occurrence of layers. These vertical movements are oscillatory in nature and reversible, i.e. the rise may be replaced by a fall. These movements include:

Ancient slow vertical movements are recorded in sections of sedimentary rocks. The speed of ancient oscillatory movements, according to scientists, is less than 0.001 mm/year.

Orogenic movements occur in two directions - horizontal and vertical. The first leads to the collapse of rocks and the formation of folds and thrusts, i.e. to the reduction of the earth's surface. Vertical movements lead to the raising of the area where folding occurs and often the appearance of mountain structures. Orogenic movements occur much faster than oscillatory movements.

TYPES OF TECTONIC FAULTS

Types of tectonic disturbances:

a – folded (plicate) forms;

In most cases, their formation is associated with compaction or compression of the Earth's substance. Fold faults are morphologically divided into two main types: convex and concave. In the case of a horizontal section, layers that are older in age are located in the core of the convex fold, and younger layers are located on the wings. Concave bends, on the other hand, have younger deposits in their cores. In folds, the convex wings are usually inclined to the sides from the axial surface.

b – discontinuous (disjunctive) forms

Discontinuous tectonic disturbances are those changes in which the continuity (integrity) of rocks is disrupted.

BIBLIOGRAPHY

1. 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.: Nauka, – 1981.

Povarennykh A.S., Onoprienko V.I. Mineralogy: past, present, future. – Kyiv: 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 21st century). – M.: Scientific world, 2003..

Khain V.E., Ryabukhin A.G. History and methodology of geological sciences. – M.: MSU, – 1996.

Hallem A. Great geological disputes. M.: Mir, 1985.

Ministry of Education and Science of the Russian Federation

Federal Agency for Education

State educational institution of higher education

Vocational education

"Ufa State Petroleum Technical University"
Department of Applied Ecology

1. CONCEPT OF PROCESSES……………………………………………………3

2. EXOGENOUS PROCESSES…………………………………………………..3

2.1 WEATHERING……………………………………………………...3

2.1.1PHYSICAL WEATHERING………………………….4

2.1.2 CHEMICAL WEATHERING………………………...5

2.2 GEOLOGICAL ACTIVITY OF WIND………………………6

2.2.1 DEFLATION AND CORROSION………………………………….7

2.2.2 TRANSFER……………………………………………………...8

2.2.3 ACCUMULATION AND EOLIAN DEPOSITION…………..8

^ 2.3 GEOLOGICAL ACTIVITY OF SURFACE

FLOWING WATER……………………………………………………………...9

2.4 GEOLOGICAL ACTIVITY OF GROUNDWATER…………… 10

2.5 GEOLOGICAL ACTIVITY OF GLACIERS………………. 12

2.6 GEOLOGICAL ACTIVITY OF OCEANS AND SEAS…… 12

3. ENDOGENOUS PROCESSES……………………………………………………………………. 13

3.1 MAGMATISM………………………………………………………. 13

3.2 METAMORPHISM……………………………………………………... 14

3.2.1 MAIN FACTORS OF METAMORPHISM………………. 14

3.2.2.METAMORPHISM FACIES……………………………. 15

3.3 EARTHQUAKE……………………………………………………15

LIST OF REFERENCES……………………… 16

^ CONCEPT OF PROCESSES

Throughout its existence, the Earth has gone through a long series of changes. In essence, she was never the same as in the previous moment. It changes continuously. Its composition, physical state, appearance, position in world space and relationship with other members of the solar system change.

Geology (Greek “geo” - earth, “logos” - study) is one of the most important sciences about the Earth. She studies the composition, structure, history of the development of the Earth and the processes occurring in its interior and on the surface. Modern geology uses the latest achievements and methods of a number of natural sciences - mathematics, physics, chemistry, biology, geography.

The subject of direct study of geology is the earth's crust and the underlying solid layer of the upper mantle - the lithosphere (Greek "lithos" - stone), which is of utmost importance for human life and activity.

One of several main directions in geology is dynamic geology, which studies various geological processes, landforms of the earth's surface, the relationships of rocks of different genesis, the nature of their occurrence and deformation. It is known that in the course of geological development, multiple changes occurred in the composition, state of matter, appearance of the Earth's surface and structure of the earth's crust. These transformations are associated with various geological processes and their interactions.

Among them there are two groups:

1) endogenous (Greek “endos” - inside), or internal, associated with the thermal effect of the Earth, stresses arising in its depths, with gravitational energy and its uneven distribution;

2) exogenous (Greek “exos” - outside, external), or external, causing significant changes in the surface and near-surface parts of the earth’s crust. These changes are associated with the radiant energy of the Sun, gravity, the continuous movement of water and air masses, the circulation of water on the surface and inside the earth's crust, with the vital activity of organisms and other factors. All exogenous processes are closely related to endogenous ones, which reflects the complexity and unity of the forces acting inside the Earth and on its surface. Geological processes modify the earth's crust and its surface, leading to the destruction and at the same time the creation of rocks. Exogenous processes are caused by the action of gravity and solar energy, and endogenous processes are caused by the influence of the internal heat of the Earth and gravity. All processes are interconnected, and their study allows us to use the method of actualism to understand the geological processes of the distant past.

^ 2. EXOGENOUS PROCESSES

The term “weathering,” which is widely used in the literature, does not reflect the essence and complexity of the natural processes defined by this concept. The unsuccessful term has led to the fact that researchers do not have a unified understanding of its essence. In any case, weathering should never be confused with the activity of the wind itself.

Weathering is a set of complex processes of qualitative and quantitative transformation of rocks and their constituent minerals, occurring under the influence of various agents acting on the surface of the earth, among which the main role is played by temperature fluctuations, freezing of water, acids, alkalis, carbon dioxide, the action of wind, organisms, etc. .d . Depending on the predominance of certain factors in a single and complex weathering process, two interrelated types are conventionally distinguished:

1) physical weathering and 2) chemical weathering.
^ 2.1.1PHYSICAL WEATHERING

In this type, temperature weathering is of greatest importance, which is associated with daily and seasonal temperature fluctuations, which causes either heating or cooling of the surface part of the rocks. Under the conditions of the earth's surface, especially in deserts, daily temperature fluctuations are quite significant. So in the summer, during the daytime, rocks heat up to + 80 0 C, and at night their temperature drops to + 20 0 C. Due to the sharp difference in thermal conductivity, coefficients of thermal expansion and compression, and anisotropy of the thermal properties of the minerals that make up the rocks, certain stresses arise. In addition to alternating heating and cooling, uneven heating of rocks also has a destructive effect, which is associated with different thermal properties, color and size of the minerals that make up the rocks.

Rocks can be multi-mineral or single-mineral. Multi-mineral rocks are subject to the greatest destruction as a result of the process of temperature weathering.

The process of temperature weathering, which causes mechanical disintegration of rocks, is especially characteristic of extra-arid and nival landscapes with a continental climate and a non-percolative type of moisture regime. This is especially evident in desert areas, where the amount of atmospheric precipitation is in the range of 100-250 mm/year (with colossal evaporation) and there is a sharp amplitude of daily temperatures on the surface of rocks unprotected by vegetation. Under these conditions, minerals, especially dark-colored ones, are heated to temperatures exceeding air temperature, which causes disintegration of rocks and clastic weathering products are formed on a consolidated undisturbed substrate. In deserts, peeling or desquamation is observed (Latin “desquamare” - to remove scales), when scales or thick plates parallel to the surface peel off from the smooth surface of rocks due to significant temperature fluctuations. This process can be observed especially well on individual blocks and boulders. Intense physical (mechanical) weathering occurs in areas with harsh climatic conditions (in polar and subpolar countries) with the presence of permafrost, caused by its excess surface moisture. Under these conditions, weathering is associated mainly with the wedging effect of freezing water in cracks and with other physical and mechanical processes associated with ice formation. Temperature fluctuations in the surface horizons of rocks, especially severe hypothermia in winter, lead to volumetric gradient stress and the formation of frost cracks, which are subsequently developed by water freezing in them. It is well known that when water freezes, its volume increases by more than 9% (P. A. Shumsky, 1954). As a result, pressure develops on the walls of large cracks, causing high disjoining stress, fragmentation of rocks and the formation of predominantly blocky material. This weathering is sometimes called frost weathering. The root system of growing trees also has a wedging effect on rocks. Mechanical work is also performed by a variety of burrowing animals. In conclusion, it should be said that purely physical weathering leads to fragmentation of rocks, to mechanical destruction without changing their mineralogical and chemical composition.

^ 2.1.2 CHEMICAL WEATHERING

Simultaneously with physical weathering, in areas with a leaching type of moisture regime, processes of chemical change occur with the formation of new minerals. During mechanical disintegration of dense rocks, macrocracks are formed, which facilitates the penetration of water and gas into them and, in addition, increases the reaction surface of weathering rocks. This creates conditions for the activation of chemical and biogeochemical reactions. The penetration of water or the degree of moisture not only determines the transformation of rocks, but also determines the migration of the most mobile chemical components. This is especially clearly reflected in humid tropical zones, where high humidity, high thermal conditions and rich forest vegetation are combined. The latter has a huge biomass and a significant decline. This mass of dying organic matter is transformed and processed by microorganisms, resulting in large quantities of aggressive organic acids (solutions). The high concentration of hydrogen ions in acidic solutions contributes to the most intense chemical transformation of rocks, the extraction of cations from the crystal lattices of minerals and their involvement in migration.

Chemical weathering processes include oxidation, hydration, dissolution and hydrolysis.

Oxidation. It occurs especially intensely in minerals containing iron. An example is the oxidation of magnetite, which transforms into a more stable form - hematite (Fe 2 0 4 Fe 2 0 3). Such transformations have been identified in the ancient weathering crust of the KMA, where rich hematite ores are mined. Iron sulfides undergo intense oxidation (often together with hydration). So, for example, we can imagine the weathering of pyrite:

FeS 2 + mO 2 + nH 2 O FeS0 4 Fe 2 (SO 4) Fe 2 O 3. nH 2 O

Limonite (brown iron ore)

At some deposits of sulfide and other iron ores, “brown-iron ore hats” are observed, consisting of oxidized and hydrated weathering products. Air and water in ionized form destroy ferrous silicates and convert ferrous iron into ferric iron.

Hydration. Under the influence of water, hydration of minerals occurs, i.e. fixation of water molecules on the surface of individual sections of the crystalline structure of the mineral. An example of hydration is the transition of anhydrite to gypsum: anhydrite-CaSO 4 +2H 2 O CaSO 4. 2H 2 0 - gypsum. Hydrogoethite is also a hydrated variety: goethite - FeOOH + nH 2 O FeOH. nH 2 O - hydrogoethite.

The hydration process is also observed in more complex minerals - silicates.

Dissolution. Many compounds are characterized by a certain degree of solubility. Their dissolution occurs under the influence of water flowing down the surface of rocks and seeping through cracks and pores into the depths. The acceleration of dissolution processes is facilitated by the high concentration of hydrogen ions and the content of O 2, CO 2 and organic acids in water. Of the chemical compounds, chlorides have the best solubility - halite (table salt), sylvite, etc. In second place are sulfates - anhydrite and gypsum. In third place are carbonates - limestones and dolomites. During the dissolution of these rocks, various karst forms form on the surface and in the depths in a number of places.

Hydrolysis. When weathering silicates and aluminosilicates, hydrolysis is important, in which the structure of crystalline minerals is destroyed due to the action of water and ions dissolved in it and is replaced by a new one, significantly different from the original one and inherent in the newly formed supergene minerals. In this process, the following occurs: 1) the framework structure of feldspars turns into a layered one, characteristic of newly formed clay supergene minerals; 2) removal from the crystal lattice of feldspars of soluble compounds of strong bases (K, Na, Ca), which, interacting with CO 2, form true solutions of bicarbonates and carbonates (K 2 CO 3, Na 2 CO 3, CaCO 3). Under flushing conditions, carbonates and bicarbonates are carried outside the place of their formation. Under dry climate conditions, they remain in place, form films of varying thickness in places, or fall out at a small depth from the surface (carbonatization occurs); 3) partial removal of silica; 4) addition of hydroxyl ions.

The hydrolysis process occurs in stages with the sequential appearance of several minerals. Thus, during the supergene transformation of feldspars, hydromicas appear, which then transform into minerals of the kaolinite or galoysite group:

K (K,H 3 O)A1 2 (OH) 2 [A1Si 3 O 10]. H 2 O Al 4 (OH) 8

Orthoclase hydromica kaolinite

In temperate climatic zones, kaolinite is quite stable and as a result of its accumulation during weathering processes, kaolin deposits are formed. But in a humid tropical climate, further decomposition of kaolinite to free oxides and hydroxides can occur:

Al 4 (OH) 8 Al(OH) 3 + SiO 2. nH2O

Hydrargillite

Thus, aluminum oxides and hydroxides are formed, which are an integral part of aluminum ore - bauxite.

During the weathering of basic rocks and especially volcanic tuffs, among the resulting clay supergene minerals, along with hydromicas, montmorillonites (Al 2 Mg 3) (OH) 2* nH 2 O and the high-alumina mineral beidellite A1 2 (OH) 2 [A1Si 3 О 10 ]nН 2 O. When ultramafic rocks (ultrabasites) are weathered, nontronites, or ferruginous montmorillonites (FeAl 2)(OH) 2, are formed. nH 2 O. Under conditions of significant atmospheric humidification, nontronite is destroyed, and oxides and hydroxides of iron (the phenomenon of nontronite cooling) and aluminum are formed.
^ 2.2. GEOLOGICAL ACTIVITY OF WIND

Winds constantly blow on the earth's surface. The speed, strength and direction of winds vary. They are often hurricane-like in nature.

Wind is one of the most important exogenous factors that transform the Earth's topography and form specific deposits. This activity is most clearly manifested in deserts, which occupy about 20% of the surface of the continents, where strong winds are combined with a small amount of precipitation (the annual amount does not exceed 100-200 mm/year); sharp temperature fluctuations, sometimes reaching 50 o and above, which contributes to intense weathering processes; absence or sparse vegetation cover.

The wind does a lot of geological work: the destruction of the earth's surface (blowing, or deflation, grinding or corrosion), the transfer of destruction products and the deposition (accumulation) of these products in the form of clusters of various shapes. All processes caused by the activity of wind, the relief forms and sediments they create are called aeolian (Aeolus in ancient Greek mythology is the god of the winds).
^

2.2.1. DEFLATION AND CORRASION

Deflation is the blowing and scattering of loose rock particles (mainly sandy and silty) by the wind. The famous desert researcher B. A. Fedorovich distinguishes two types of deflation: areal and local.

Areal deflation is observed both within bedrock, subject to intense weathering processes, and especially on surfaces composed of river, sea, glacial sands and other loose sediments. In hard fractured rocks, the wind penetrates into all the cracks and blows loose weathering products out of them.

As a result of deflation, the surface of deserts in places where various clastic material develops is gradually cleared of sand and finer-earth particles (carried out by the wind) and only coarse fragments remain in place - rocky and gravelly material. Areal deflation sometimes manifests itself in the arid steppe regions of various countries, where strong drying winds periodically arise - “hot winds”, which blow away plowed soils, transporting large quantities of its particles over long distances.

Local deflation manifests itself in individual depressions in relief. Many researchers explain the origin of some large deep drainless basins in the deserts of Central Asia, Arabia and North Africa, the bottom of which in some places is many tens and even a few hundred meters below the level of the World Ocean, by deflation.

Corrosion is the mechanical processing of exposed rocks by the wind with the help of solid particles carried by it - grinding, grinding, drilling, etc.

Sand particles are lifted by the wind to different heights, but their greatest concentration is in the lower surface parts of the air flow (up to 1.0-2.0 m). Strong, long-lasting impacts of sand on the lower parts of rocky ledges undermine and, as it were, cut them, and they become thinner in comparison with the overlying ones. This is also facilitated by weathering processes that disrupt the solidity of the rock, which is accompanied by the rapid removal of destruction products. Thus, the interaction of deflation, sand transport, corrosion and weathering gives rocks in deserts their distinctive shapes.

Academician V. A. Obruchev in 1906 discovered in Dzungaria, bordering Eastern Kazakhstan, an entire “aeolian city”, consisting of bizarre structures and figures created in sandstones and variegated clays as a result of desert weathering, deflation and corrosion. If pebbles or small fragments of hard rock are encountered along the path of sand movement, they are abraded and ground along one or more flat edges. With sufficiently long-term exposure to wind-blown sand, pebbles and debris form aeolian polyhedra or trihedra with shiny polished edges and relatively sharp edges between them (Fig. 5.2). It should also be noted that corrosion and deflation also manifest themselves on the horizontal clayey surface of deserts, where, under stable winds of one direction, sand jets form separate long furrows or troughs with a depth of tens of centimeters to a few meters, separated by parallel, irregularly shaped ridges. Such formations in China are called yardangs.

2.2.2 TRANSFER

As the wind moves, it picks up sand and dust particles and carries them to various distances. Transfer is carried out either spasmodically, or by rolling them along the bottom, or in suspension. The difference in transport depends on the size of the particles, wind speed and the degree of turbulence. With winds of up to 7 m/s, about 90% of sand particles are transported in a layer of 5-10 cm from the Earth's surface; with strong winds (15-20 m/s), the sand rises several meters. Storm winds and hurricanes lift sand tens of meters in height and even roll over pebbles and flat crushed stone with a diameter of up to 3-5 cm or more. The process of moving sand grains is carried out in the form of jumps or leaps at a steep angle from several centimeters to several meters along curved trajectories. When they land, they strike and disturb other sand grains, which are involved in a spasmodic movement, or saltation (Latin “saltatio” - jump). This is how a continuous process of moving many sand grains occurs.

2.2.3 ACCUMULATION AND EOLIAN DEPOSITION

Simultaneously with diflation and transport, accumulation also occurs, resulting in the formation of aeolian continental deposits. Sands and loess stand out among them.

Aeolian sands are distinguished by significant sorting, good roundness, and a matte surface of the grains. These are predominantly fine-grained sands, the grain size of which is 0.25-0.1 mm.

The most common mineral in them is quartz, but other stable minerals (feldspars, etc.) are also found. Less persistent minerals, such as micas, are abraded and carried away during aeolian processing. The color of aeolian sands varies, most often light yellow, sometimes yellowish-brown, and sometimes reddish (during deflation of red earth weathering crusts). Deposited aeolian sands exhibit oblique or crisscross bedding, indicating directions of transport.

Aeolian loess (German “loess” - yellow earth) represents a unique genetic type of continental sediments. It is formed by the accumulation of suspended dust particles carried by the wind beyond the deserts and into their marginal parts and into mountainous areas. A characteristic set of features of loess is:

1) composition of silt particles of predominantly silty size - from 0.05 to 0.005 mm (more than 50%) with a subordinate value of clay and fine sandy fractions and an almost complete absence of larger particles;

2) absence of layering and uniformity throughout the entire thickness;

3) the presence of finely dispersed calcium carbonate and calcareous nodules;

4) diversity of mineral composition (quartz, feldspar, hornblende, mica, etc.);

5) the loess is penetrated by numerous short vertical tubular macropores;

6) increased total porosity, reaching 50-60% in places, which indicates underconsolidation;

7) subsidence under load and when moistened;

8) columnar vertical separation in natural outcrops, which may be due to the angularity of the shapes of mineral grains, providing strong adhesion. The thickness of loess ranges from a few to 100 m or more.

Particularly large thicknesses are noted in China, the formation of which by some researchers is assumed due to the removal of dust material from the deserts of Central Asia.

^
2.3 GEOLOGICAL ACTIVITY OF SURFACE FLUID WATER

Groundwater and temporary streams of atmospheric precipitation, flowing down ravines and gullies, are collected into permanent water streams - rivers. Full-flowing rivers perform a lot of geological work - destruction of rocks (erosion), transport and deposition (accumulation) of destruction products.

Erosion is carried out by the dynamic effect of water on rocks. In addition, the river flow wears away rocks with debris carried by the water, and the debris itself is destroyed and destroys the stream bed by friction when rolling. At the same time, water has a dissolving effect on rocks.

There are two types of erosion:

1) bottom, or deep, aimed at cutting the river flow into depth;

2) lateral, leading to the erosion of the banks and, in general, to the expansion of the valley.

In the initial stages of river development, bottom erosion predominates, which tends to develop an equilibrium profile in relation to the basis of erosion - the level of the basin into which it flows. The basis of erosion determines the development of the entire river system - the main river with its tributaries of different orders. The original profile on which the river is laid is usually characterized by various irregularities created before the formation of the valley. Such unevenness can be caused by various factors: the presence of outcrops in the river bed of rocks of heterogeneous stability (lithological factor); lakes on the path of the river (climatic factor); structural forms - various folds, breaks, their combination (tectonic factor) and other forms. As the equilibrium profile develops and the channel slopes decrease, bottom erosion gradually weakens and lateral erosion begins to affect itself more and more, aimed at eroding the banks and expanding the valley. This is especially evident during periods of floods, when the speed and degree of turbulence of the flow increases sharply, especially in the core part, which causes transverse circulation. The resulting vortex movements of water in the bottom layer contribute to the active erosion of the bottom in the core part of the channel, and part of the bottom sediments is carried to the shore. The accumulation of sediment leads to a distortion of the cross-sectional shape of the channel, the straightness of the flow is disrupted, as a result of which the flow core shifts to one of the banks. Intensified erosion of one bank and accumulation of sediment on the other begins, which causes the formation of a bend in the river. Such primary bends, gradually developing, turn into bends, which play a large role in the formation of river valleys.

Rivers transport large amounts of debris of varying sizes, from fine silt particles and sand to large debris. Its transfer is carried out by dragging (rolling) along the bottom of the largest fragments and in a suspended state of sand, silt and finer particles. Transported debris further enhances deep erosion. They are, as it were, erosion tools that crush, destroy, and polish the rocks that make up the bottom of the riverbed, but they themselves are crushed and abraded to form sand, gravel, and pebbles. The transported materials carried along the bottom and suspended are called solid river runoff. In addition to debris, rivers also transport dissolved mineral compounds. The river waters of humid areas are dominated by Ca and Mg carbonates, which account for about 60% of the ion runoff (O. A. Alekin). Compounds of Fe and Mn are found in small quantities, often forming colloidal solutions. In river waters of arid regions, in addition to carbonates, chlorides and sulfates play a significant role.

Along with erosion and the transfer of various material, its accumulation (deposition) also occurs. In the first stages of river development, when erosion processes predominate, the deposits that appear in places turn out to be unstable and, as the flow speed increases during floods, they are again captured by the flow and move downstream. But as the equilibrium profile develops and the valleys expand, permanent deposits are formed, called alluvial, or alluvium (Latin “alluvio” - sediment, alluvium).
^

2.4. GEOLOGICAL ACTIVITY OF GROUNDWATER

Groundwater includes all water located in the pores and cracks of rocks. They are widespread in the earth’s crust, and their study is of great importance in solving issues: water supply to settlements and industrial enterprises, hydraulic engineering, industrial and civil construction, land reclamation activities, resort and sanatorium business, etc.

The geological activity of groundwater is great. They are associated with karst processes in soluble rocks, the sliding of earth masses along the slopes of ravines, rivers and seas, the destruction of mineral deposits and their formation in new places, the removal of various compounds and heat from deep zones of the earth's crust.

Karst is the process of dissolution, or leaching of fissured soluble rocks by underground and surface waters, as a result of which negative depressions of relief are formed on the surface of the Earth and various cavities, channels and caves in the depths. For the first time, such widely developed processes were studied in detail on the coast of the Adriatic Sea, on the Karst plateau near Trieste, from where they got their name. Soluble rocks include salts, gypsum, limestone, dolomite, and chalk. In accordance with this, salt, gypsum and carbonate karst are distinguished. Carbonate karst is the most studied, which is associated with a significant areal distribution of limestone, dolomite, and chalk.

Necessary conditions for the development of karst are:

1) the presence of soluble rocks;

2) rock fracturing, allowing water penetration;

3) the dissolving ability of water.
Surface karst forms include:

1) karras, or scars, small depressions in the form of potholes and furrows with a depth of several centimeters to 1-2 m;

2) pores - vertical or inclined holes that go deep and absorb surface water;

3) karst sinkholes, which are most widespread both in mountainous regions and on the plains. Among them, according to development conditions, the following stand out:

A) surface leaching funnels associated with the dissolving activity of meteoric waters;

B) failure craters, formed by the collapse of the arches of underground karst cavities;

4) large karst basins, at the bottom of which karst sinkholes can develop;

5) the largest karst forms are fields, well known in Yugoslavia and other areas;

6) karst wells and mines, reaching depths of over 1000 m in places and being, as it were, transitional to underground karst forms.

Underground karst forms include various channels and caves. The largest underground forms are karst caves, which are a system of horizontal or several inclined channels, often complexly branching and forming huge halls or grottoes. This unevenness in outline is apparently due to the nature of the complex fracturing of the rocks, and possibly to the heterogeneity of the latter. There are many lakes at the bottom of a number of caves; underground watercourses (rivers) flow through other caves, which, when moving, produce not only a chemical effect (leaching), but also erosion (erosion). The presence of constant water flows in caves is often associated with the absorption of surface river runoff. In karst massifs, disappearing rivers (partially or completely) and periodically disappearing lakes are known.

Various displacements of rocks that make up the steep coastal slopes of river valleys, lakes and seas are associated with the activity of underground and surface waters and other factors. Such gravitational displacements, in addition to screes and landslides, also include landslides. It is in landslide processes that groundwater plays an important role. Landslides are understood as large displacements of various rocks along a slope, spreading in some areas over large spaces and depths. Landslides often have a very complex structure; they can consist of a series of blocks sliding down along sliding planes with the tilting of layers of displaced rock towards the bedrock.

Landslide processes occur under the influence of many factors, including:

1) significant steepness of coastal slopes and the formation of cracks in the side wall;

2) erosion of the banks by the river (Volga region and other rivers) or abrasion by the sea (Crimea, Caucasus), which increases the stress state of the slope and disrupts the existing balance;

3) a large amount of precipitation and an increase in the degree of water content of slope rocks with both surface and groundwater. In some cases, landslides occur precisely during or at the end of intense precipitation. Particularly large landslides are caused by floods;

4) the influence of groundwater is determined by two factors - suffusion and hydrodynamic pressure. Suffusion, or undermining, caused by groundwater sources emerging on a slope, carrying small particles of water-bearing rock and chemically soluble substances from the aquifer. As a result, this leads to loosening of the aquifer, which naturally causes instability in the higher part of the slope, and it slides; hydrodynamic pressure created by groundwater when it reaches the surface of a slope. This is especially evident when the water level in the river changes during floods, when river waters infiltrate into the sides of the valley and the groundwater level rises. The decline in low water in the river occurs relatively quickly, and the decline in groundwater levels is relatively slow (lags behind). As a result of such a gap between the levels of river and groundwater, the squeezing out of the slope part of the aquifer can occur, followed by the sliding of rocks located above;

5) the fall of rocks towards a river or sea, especially if they contain clays, which, under the influence of water and weathering processes, acquire plastic properties;

6) anthropogenic impact on the slopes (artificial cutting of the slope and increasing its steepness, additional load on the slopes with the installation of various structures, destruction of beaches, deforestation, etc.).

Thus, in the complex of factors contributing to landslide processes, groundwater plays a significant and sometimes decisive role. In all cases, when deciding on the construction of certain structures near slopes, their stability is studied in detail, and measures to combat landslides are developed in each specific case. In a number of places there are special anti-landslide stations.
^ 2.5. GEOLOGICAL ACTIVITY OF GLACIERS

Glaciers are a large natural body consisting of crystalline ice formed on the surface of the earth as a result of the accumulation and subsequent transformation of solid atmospheric precipitation and is in motion.

When glaciers move, a number of interconnected geological processes occur:

1) destruction of rocks of the subglacial bed with the formation of clastic material of various shapes and sizes (from thin sand particles to large boulders);

2) transport of rock fragments on the surface and inside glaciers, as well as those frozen into the bottom parts of the ice or transported by dragging along the bottom;

3) accumulation of clastic material, which occurs both during glacier movement and during deglaciation. The entire complex of these processes and their results can be observed in mountain glaciers, especially where glaciers previously extended many kilometers beyond modern boundaries. The destructive work of glaciers is called exaration (from the Latin “exaratio” - plowing out). It manifests itself especially intensely at large ice thicknesses, creating enormous pressure on the subglacial bed. Various blocks of rocks are captured and broken out, crushed, and worn away.

Glaciers, saturated with fragmental material frozen into the bottom parts of the ice, when moving along rocks, leave various strokes, scratches, furrows on their surface - glacial scars, which are oriented in the direction of movement of the glacier.

During their movement, glaciers transport a huge amount of various clastic material, consisting mainly of products of supraglacial and subglacial weathering, as well as fragments resulting from the mechanical destruction of rocks by moving glaciers. All this debris that enters, is transported and deposited by the glacier is called a moraine. Among the moving moraine material, a distinction is made between surface (lateral and median), internal and bottom moraines. The deposited material is called coastal and terminal moraines.

Coastal moraines are ridges of debris located along the slopes of glacial valleys. Terminal moraines form at the end of glaciers, where they completely melt.
^ 2.6. GEOLOGICAL ACTIVITY OF OCEANS AND SEAS

It is known that the surface of the globe is 510 million km 2, of which about 361 million km 2, or 70.8%, is occupied by oceans and seas, and 149 million km 2, or 29.2%, is land. Thus, the area occupied by oceans and seas is almost 2.5 times greater than the land area. In marine basins, as seas and oceans are usually called, complex processes of energetic destruction, movement of destruction products, deposition of sediments and the formation of various sedimentary rocks take place.

Geological activity of the sea in the form of destruction of rocks, shores and bottom is called abrasion. Abrasion processes are directly dependent on the characteristics of water movement, the intensity and direction of blowing winds and currents.

The main destructive work is carried out by: the sea surf, and to a lesser extent various currents (coastal, bottom, ebb and flow).

^ ENDOGENOUS PROCESSES

3.1.MAGMATISM

Igneous rocks, formed from liquid melt - magma, play a huge role in the structure of the earth's crust. These rocks were formed in different ways. Large volumes of them froze at various depths, before reaching the surface, and had a strong impact on the host rocks with high temperatures, hot solutions and gases. This is how intrusive (Latin “intrusio” - penetrate, introduce) bodies were formed. If magmatic melts erupted to the surface, volcanic eruptions occurred, which, depending on the composition of the magma, were calm or catastrophic. This type of magmatism is called effusive (Latin “effusio” - outpouring), which is not entirely accurate. Often, volcanic eruptions are explosive in nature, in which the magma does not pour out, but explodes and finely crushed crystals and frozen droplets of glass - melt - fall onto the earth's surface. Such eruptions are called explosive (Latin “explosio” - to explode). Therefore, speaking about magmatism (from the Greek “magma” - plastic, pasty, viscous mass), one should distinguish between intrusive processes associated with the formation and movement of magma below the Earth’s surface, and volcanic processes caused by the release of magma onto the earth’s surface. Both of these processes are inextricably linked, and the manifestation of one or the other of them depends on the depth and method of formation of magma, its temperature, the amount of dissolved gases, the geological structure of the area, the nature and speed of movements of the earth’s crust, etc.

Magmatism is distinguished:

Geosynclinal

Platform

Oceanic

Magmatism of activation areas
By depth of manifestation:

Abyssal

Hypabyssal

Surface
According to the composition of magma:

Ultrabasic

Basic

Alkaline
In the modern geological era, magmatism is especially developed within the Pacific geosynclinal belt, mid-ocean ridges, reef zones of Africa and the Mediterranean, etc. The formation of a large number of diverse mineral deposits is associated with magmatism.

If a liquid magmatic melt reaches the earth's surface, it erupts, the nature of which is determined by the composition of the melt, its temperature, pressure, concentration of volatile components and other parameters. One of the most important reasons for magma eruptions is its degassing. It is the gases contained in the melt that serve as the “driver” that causes the eruption. Depending on the amount of gases, their composition and temperature, they can be released from the magma relatively calmly, then an outpouring occurs - the effusion of lava flows. When the gases are separated quickly, the melt boils instantly and the magma bursts with expanding gas bubbles, causing a powerful explosive eruption - an explosion. If the magma is viscous and its temperature is low, then the melt is slowly squeezed out, squeezed out to the surface, and magma extrusion occurs.

Thus, the method and rate of separation of volatiles determines the three main forms of eruptions: effusive, explosive and extrusive. Volcanic products from eruptions are liquid, solid and gaseous

Gaseous or volatile products, as shown above, play a decisive role in volcanic eruptions and their composition is very complex and is far from fully understood due to the difficulties in determining the composition of the gas phase in magma located deep under the Earth's surface. According to direct measurements, various active volcanoes contain among the volatiles water vapor, carbon dioxide (CO 2), carbon monoxide (CO), nitrogen (N 2), sulfur dioxide (SO 2), sulfur oxide (III) (SO 3) , sulfur gas (S), hydrogen (H 2), ammonia (NH 3), hydrogen chloride (HCL), hydrogen fluoride (HF), hydrogen sulfide (H 2 S), methane (CH 4), boric acid (H 3 BO 2), chlorine (Cl), argon and others, although H 2 O and CO 2 predominate. Chlorides of alkali metals and iron are present. The composition of gases and their concentration vary greatly within one volcano from place to place and over time; they depend on temperature and, in the most general form, on the degree of degassing of the mantle, i.e. on the type of earth's crust.

Liquid volcanic products are represented by lava - magma that has reached the surface and is already highly degassed. The term "lava" comes from the Latin word "laver" (to wash, wash) and previously mud flows were called lava. The main properties of lava - chemical composition, viscosity, temperature, volatile content - determine the nature of effusive eruptions, the shape and extent of lava flows.

3.2.METAMORPHISM

Metamorphism (Greek metamorphoómai - undergoing transformation, being transformed) is the process of solid-phase mineral and structural changes in rocks under the influence of temperature and pressure in the presence of a fluid.

There is isochemical metamorphism, in which the chemical composition of the rock changes insignificantly, and non-isochemical metamorphism (metasomatosis), which is characterized by a noticeable change in the chemical composition of the rock as a result of the transfer of components by fluid.

Based on the size of the distribution areas of metamorphic rocks, their structural position and the causes of metamorphism, the following are distinguished:

Regional metamorphism, which affects significant volumes of the earth's crust and is distributed over large areas

Ultra-high pressure metamorphism

Contact metamorphism is confined to igneous intrusions, and occurs from the heat of cooling magma

Dynamometamorphism occurs in fault zones and is associated with significant deformation of rocks

Impact metamorphism, which occurs when a meteorite suddenly hits the surface of a planet.
^ 3.2.1 MAIN FACTORS OF METAMORPHISM

The main factors of metamorphism are temperature, pressure and fluid.

With increasing temperature, metamorphic reactions occur with the decomposition of water-containing phases (chlorites, mica, amphiboles). As the pressure increases, reactions occur with a decrease in the volume of the phases. At temperatures above 600 °C, partial melting of some rocks begins, melts are formed, which go to the upper horizons, leaving a refractory residue - restite.
Fluids are the volatile components of metamorphic systems. These are primarily water and carbon dioxide. Less commonly, oxygen, hydrogen, hydrocarbons, halogen compounds and some others can play a role. In the presence of a fluid, the stability region of many phases (especially those containing these volatile components) changes. In their presence, rock melting begins at much lower temperatures.
^ 3.2.2.METAMORPHISM FACIES

Metamorphic rocks are very diverse. More than 20 minerals have been identified as rock-forming minerals. Rocks of similar composition, but formed under different thermodynamic conditions, can have completely different mineral compositions. The first researchers of metamorphic complexes found that several characteristic, widespread associations could be identified that formed under different thermodynamic conditions. The first division of metamorphic rocks according to the thermodynamic conditions of formation was made by Eskola. In rocks of basaltic composition, he identified greenschists, epidote rocks, amphibolites, granulites and eclogites. Subsequent studies showed the logic and content of this division.

Subsequently, an intensive experimental study of mineral reactions began, and through the efforts of many researchers, a diagram of metamorphism facies was compiled - a P-T diagram, which shows the semi-stability of individual minerals and mineral associations. The facies diagram has become one of the main tools for analyzing metamorphic assemblages. Geologists, having determined the mineral composition of the rock, correlated it with any facies, and based on the appearance and disappearance of minerals, they compiled maps of isograds - lines of equal temperatures. In an almost modern version, the scheme of metamorphic facies was published by a group of scientists led by V.S. Sobolev at the Siberian Branch of the USSR Academy of Sciences.

3.3.EARTHQUAKES

An earthquake is any vibration of the earth's surface caused by natural causes, among which tectonic processes are of primary importance. In some places, earthquakes occur frequently and reach great strength.

On the coasts, the sea retreats, exposing the bottom, and then a giant wave hits the shore, sweeping away everything in its path, carrying the remains of buildings into the sea. Major earthquakes are accompanied by numerous casualties among the population, who die under the ruins of buildings, from fires, and finally, simply from the resulting panic. An earthquake is a disaster, a catastrophe, therefore, enormous efforts are spent on predicting possible seismic shocks, on identifying earthquake-prone areas, on measures designed to make industrial and civil buildings earthquake-resistant, which leads to large additional costs in construction.

Any earthquake is a tectonic deformation of the earth's crust or upper mantle, occurring due to the fact that the accumulated stress at some point exceeded the strength of the rocks in a given place. The discharge of these stresses causes seismic vibrations in the form of waves, which, upon reaching the earth's surface, cause destruction. The “trigger” that causes the release of tension may be, at first glance, the most insignificant, for example, the filling of a reservoir, a rapid change in atmospheric pressure, ocean tides, etc.

^ LIST OF REFERENCES USED

1. G. P. Gorshkov, A. F. Yakusheva General geology. Third edition. - Moscow University Publishing House, 1973-589 pp.: ill.

2. N.V. Koronovsky, A.F. Yakusheva Fundamentals of Geology - 213 pp.: ill.

3. V.P. Ananyev, A.D. Potapov Engineering Geology. Third edition, revised and corrected. - M.: Higher School, 2005. - 575 pp.: ill.

Endogenous processes - geological processes associated with energy arising in the bowels of the Earth. Endogenous processes include tectonic movements of the earth's crust, magmatism, metamorphism, seismic and tectonic processes. The main sources of energy for endogenous processes are heat and the redistribution of material in the interior of the Earth according to density (gravitational differentiation). These are processes of internal dynamics: they occur as a result of the influence of energy sources internal to the Earth. The deep heat of the Earth, according to most scientists, is predominantly of radioactive origin. A certain amount of heat is also released during gravitational differentiation. The continuous generation of heat in the bowels of the Earth leads to the formation of its flow to the surface (heat flow). At some depths in the bowels of the Earth, with a favorable combination of material composition, temperature and pressure, centers and layers of partial melting can arise. Such a layer in the upper mantle is the asthenosphere - the main source of magma formation; convection currents can arise in it, which are the presumed cause of vertical and horizontal movements in the lithosphere. Convection also occurs on the scale of the entire mantle, possibly separately in the lower and upper layers, in one way or another leading to large horizontal movements of lithospheric plates. The cooling of the latter leads to vertical subsidence (plate tectonics). In the zones of volcanic belts of island arcs and continental margins, the main sources of magma in the mantle are associated with ultra-deep inclined faults (Wadati-Zavaritsky-Benioff seismofocal zones) extending beneath them from the ocean (to a depth of approximately 700 km). Under the influence of heat flow or directly the heat brought by rising deep magma, so-called crustal magma centers appear in the earth's crust itself; reaching the near-surface parts of the crust, magma penetrates them in the form of intrusions (plutons) of various shapes or pours out onto the surface, forming volcanoes. Gravitational differentiation led to the stratification of the Earth into geospheres of different densities. On the surface of the Earth, it also manifests itself in the form of tectonic movements, which, in turn, lead to tectonic deformations of the rocks of the earth’s crust and upper mantle; the accumulation and subsequent release of tectonic stresses along active faults lead to earthquakes. Both types of deep processes are closely related: radioactive heat, reducing the viscosity of the material, promotes its differentiation, and the latter accelerates the transfer of heat to the surface. It is assumed that the combination of these processes leads to uneven temporal transport of heat and light matter to the surface, which, in turn, can explain the presence of tectonomagmatic cycles in the history of the earth’s crust. Spatial irregularities of the same deep processes are used to explain the division of the earth's crust into more or less geologically active areas, for example, geosynclines and platforms. The formation of the Earth's topography and the formation of many important minerals are associated with endogenous processes.

Exogenous- geological processes caused by energy sources external to the Earth (mainly solar radiation) in combination with gravity. Electrochemical processes occur on the surface and in the near-surface zone of the earth’s crust in the form of its mechanical and physicochemical interaction with the hydrosphere and atmosphere. These include: Weathering, geological activity of wind (aeolian processes, Deflation), flowing surface and groundwater (Erosion, Denudation), lakes and swamps, waters of seas and oceans (Abrasia), glaciers (Exaration). The main forms of manifestation of environmental damage on the Earth's surface are: destruction of rocks and chemical transformation of the minerals composing them (physical, chemical, and organic weathering); removal and transfer of loosened and soluble products of rock destruction by water, wind and glaciers; deposition (accumulation) of these products in the form of sediments on land or at the bottom of water basins and their gradual transformation into sedimentary rocks (Sedimentogenesis, Diagenesis, Catagenesis). Energy, in combination with endogenous processes, participates in the formation of the Earth's topography and in the formation of sedimentary rock strata and associated mineral deposits. For example, under conditions of specific weathering and sedimentation processes, ores of aluminum (bauxite), iron, nickel, etc. are formed; as a result of selective deposition of minerals by water flows, placers of gold and diamonds are formed; under conditions favorable to the accumulation of organic matter and sedimentary rock strata enriched with it, combustible minerals arise.

7-Chemical and mineral composition of the earth’s crust

The composition of the earth's crust includes all known chemical elements. But they are distributed unevenly in it. The most common 8 elements (oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium), which make up 99.03% of the total weight of the earth's crust; the remaining elements (their majority) account for only 0.97%, i.e. less than 1%. In nature, due to geochemical processes, significant accumulations of a chemical element are often formed and its deposits arise, while other elements are in a dispersed state. That is why some elements that make up a small percentage of the earth's crust, such as gold, find practical use, and other elements that are more widely distributed in the earth's crust, such as gallium (it is contained in the earth's crust almost twice more than gold) are not widely used, although they have very valuable qualities (gallium is used for the manufacture of solar photocells used in space shipbuilding). There is more “rare” vanadium in our understanding in the earth’s crust than “common” copper, but it does not form large accumulations. There are tens of millions of tons of radium in the earth's crust, but it is in dispersed form and is therefore a “rare” element. Total uranium reserves amount to trillions of tons, but it is dispersed and rarely forms deposits. The chemical elements that make up the earth's crust are not always in a free state. For the most part, they form natural chemical compounds - minerals; A mineral is a component of a rock formed as a result of physical and chemical processes that have occurred and are occurring inside the Earth and on its surface. A mineral is a substance of a certain atomic, ionic, or molecular structure, stable at certain temperatures and pressures. Currently, some minerals are also obtained artificially. The absolute majority are solid, crystalline substances (quartz, etc.). There are liquid minerals (native mercury) and gaseous (methane). In the form of free chemical elements, or, as they are called, native elements, there are gold, copper, silver, platinum, carbon (diamond and graphite), sulfur and some others. Chemical elements such as molybdenum, tungsten, aluminum, silicon and many others are found in nature only in the form of compounds with other elements. Man extracts the chemical elements he needs from natural compounds, which serve as ore for obtaining these elements. Thus, ore refers to minerals or rocks from which pure chemical elements (metals and non-metals) can be extracted industrially. Minerals are mostly found in the earth's crust together, in groups, forming large natural natural accumulations, the so-called rocks. Rocks are mineral aggregates consisting of several minerals, or large accumulations of them. For example, the rock granite consists of three main minerals: quartz, feldspar and mica. The exception is rocks consisting of a single mineral, such as marble, consisting of calcite. Minerals and rocks that are used and can be used in the national economy are called minerals. Among the minerals, there are metallic ones, from which metals are extracted, non-metallic ones, used as building stone, ceramic raw materials, raw materials for the chemical industry, mineral fertilizers, etc., fossil fuels - coal, oil, flammable gases, oil shale, peat. Mineral accumulations containing useful components in quantities sufficient for their economically profitable extraction represent mineral deposits. 8- Prevalence of chemical elements in the earth's crust

Element	% mass
Oxygen	49.5
Silicon	25.3
Aluminum	7.5
Iron	5.08
Calcium	3.39
Sodium	2.63
Potassium	2.4
Magnesium	1.93
Hydrogen	0.97
Titanium	0.62
Carbon	0.1
Manganese	0.09
Phosphorus	0.08
Fluorine	0.065
Sulfur	0.05
Barium	0.05
Chlorine	0.045
Strontium	0.04
Rubidium	0.031
Zirconium	0.02
Chromium	0.02
Vanadium	0.015
Nitrogen	0.01
Copper	0.01
Nickel	0.008
Zinc	0.005
Tin	0.004
Cobalt	0.003
Lead	0.0016
Arsenic	0.0005
Bor	0.0003
Uranus	0.0003
Bromine	0.00016
Iodine	0.00003
Silver	0.00001
Mercury	0.000007
Gold	0.0000005
Platinum	0.0000005
Radium	0.0000000001

9- General information about minerals

Mineral(from Late Latin "minera" - ore) - a natural solid with a certain chemical composition, physical properties and crystalline structure, formed as a result of natural physical and chemical processes and is an integral part of the Earth's Crust, rocks, ores, meteorites and other planets of the Solar systems. The science of mineralogy is the study of minerals.

The term "mineral" means a solid natural inorganic crystalline substance. But sometimes it is considered in an unjustifiably expanded context, classifying some organic, amorphous and other natural products as minerals, in particular some rocks, which in a strict sense cannot be classified as minerals.

· Some natural substances that are liquids under normal conditions are also considered minerals (for example, native mercury, which comes to a crystalline state at a lower temperature). Water, on the contrary, is not classified as a mineral, considering it as a liquid state (melt) of the mineral ice.

· Some organic substances - oil, asphalt, bitumen - are often mistakenly classified as minerals.

· Some minerals are in an amorphous state and do not have a crystalline structure. This applies mainly to the so-called. metamict minerals, which have the external form of crystals, but are in an amorphous, glass-like state due to the destruction of their original crystal lattice under the influence of hard radioactive radiation from the radioactive elements included in their composition (U, Th, etc.). There are clearly crystalline minerals, amorphous - metacolloids (for example, opal, lechatelierite, etc.) and metamict minerals, which have the external form of crystals, but are in an amorphous, glass-like state.

End of work -

This topic belongs to the section:

Origin and early history of the earth

Any magmatic melt consists of liquid gas and solid crystals that tend to an equilibrium state depending on changes... physical and chemical properties... petrographic composition of the earth's crust...

If you need additional material on this topic, or you did not find what you were looking for, we recommend using the search in our database of works:

What will we do with the received material:

If this material was useful to you, you can save it to your page on social networks:

All topics in this section:

Origin and early history of the Earth
Education of planet Earth. The formation process of each of the planets in the solar system had its own characteristics. About 5 billion years ago, at a distance of 150 million km from the Sun, our planet was born. When falling

Internal structure
The Earth, like other terrestrial planets, has a layered internal structure. It consists of hard silicate shells (crust, extremely viscous mantle), and metallic

Atmosphere, hydrosphere, biosphere of the Earth
Atmosphere is a shell of gas surrounding a celestial body. Its characteristics depend on the size, mass, temperature, rotation speed and chemical composition of a given celestial body, and that

Atmospheric composition
In the high layers of the atmosphere, the composition of the air changes under the influence of hard radiation from the Sun, which leads to the disintegration of oxygen molecules into atoms. Atomic oxygen is the main component

Thermal regime of the Earth
Internal heat of the Earth. The thermal regime of the Earth consists of two types: external heat, received in the form of solar radiation, and internal heat, originating in the bowels of the planet. The sun gives the earth enormous

Chemical composition of magma
Magma contains almost all the chemical elements of the periodic table, including: Si, Al, Fe, Ca, Mg, K, Ti, Na, as well as various volatile components (carbon oxides, hydrogen sulfide, hydrogen

Types of magma
Basaltic - (mafic) magma appears to be more widespread. It contains about 50% silica, aluminum, calcium, and jelly are present in significant quantities

Genesis of minerals
Minerals can be formed under different conditions, in different parts of the earth's crust. Some of them are formed from molten magma, which can solidify both at depth and on the surface when volcanic.

Endogenous processes
Endogenous processes of mineral formation, as a rule, are associated with the penetration into the earth's crust and solidification of hot underground melts, called magmas. At the same time, endogenous mineral formation

Exogenous processes
exogenous processes occur under completely different conditions than the processes of endogenous mineral formation. Exogenous mineral formation leads to physical and chemical decomposition of what would

Metamorphic processes
No matter how rocks are formed and no matter how stable and strong they are, when exposed to different conditions they begin to change. Rocks formed as a result of changes in the composition of silt

Internal structure of minerals
Based on their internal structure, minerals are divided into crystalline (kitchen salt) and amorphous (opal). In minerals with a crystalline structure, elementary particles (atoms, molecules) are dissolved

Physical
Minerals are determined by physical properties, which are determined by the material composition and structure of the crystal lattice of the mineral. This is the color of the mineral and its powder, shine, transparent

Sulfides in nature
Under natural conditions, sulfur occurs predominantly in two valence states of the S2 anion, which forms S2- sulfides, and the S6+ cation, which enters the sulfate system.

Description
This group includes fluoride, chloride and very rare bromide and iodide compounds. Fluoride compounds (fluorides), genetically related to magmatic activity, they are sublimates

Properties
Trivalent anions 3−, 3− and 3− have relatively large sizes, so they are most stable

Genesis
As for the conditions for the formation of numerous minerals belonging to this class, it should be said that the vast majority of them, especially aqueous compounds, are associated with exogenous processes

Structural types of silicates
The structural structure of all silicates is based on the close connection between silicon and oxygen; this connection comes from the crystal chemical principle, namely from the ratio of the radii of the Si (0.39Å) and O ions (

Structure, texture, forms of occurrence of rocks
Structure – 1. for igneous and metasomatic rocks, a set of characteristics of a rock, determined by the degree of crystallinity, the size and shape of crystals, and the way they are formed

Forms of occurrence of rocks
The occurrence patterns of igneous rocks differ significantly between rocks formed at some depth (intrusive) and rocks erupted to the surface (effusive). Basic functions

Carbonatites
Carbonatites are endogenous accumulations of calcite, dolomite and other carbonates, spatially and genetically associated with intrusions of ultrabasic alkaline composition of the central type,

Forms of occurrence of intrusive rocks
The intrusion of magma into various rocks that make up the earth's crust leads to the formation of intrusive bodies (intrusives, intrusive massifs, plutons). Depending on how the intrus interact

Composition of metamorphic rocks
The chemical composition of metamorphic rocks is diverse and depends primarily on the composition of the original ones. However, the composition may differ from the composition of the original rocks, since during metamorphism

Structure of metamorphic rocks
The structures and textures of metamorphic rocks arise during recrystallization in the solid state of primary sedimentary and igneous rocks under the influence of lithostatic pressure, temp.

Forms of occurrence of metamorphic rocks
Since the source material of metamorphic rocks is sedimentary and igneous rocks, their occurrence patterns must coincide with the occurrence patterns of these rocks. So based on sedimentary rocks

Hypergenesis and weathering crust
HYPERGENESIS - (from hyper... and “genesis”), a set of processes of chemical and physical transformation of mineral substances in the upper parts of the earth’s crust and on its surface (at low temperatures

Fossils
Fossils (lat. fossilis - fossil) - fossil remains of organisms or traces of their vital activity belonging to previous geological eras. Detected by people when

Geological survey
Geological survey - One of the main methods of studying the geological structure of the upper parts of the earth's crust of any region and identifying its prospects for mineral resources

Grabens, ramps, rifts
A graben (German "graben" - to dig) is a structure bounded on both sides by faults. (Fig. 3, 4). A completely unique tectonic type is represented by the

Geological history of the Earth's development
Material from Wikipedia - the free encyclopedia Geological time presented on the diagram is called a geological clock, showing the relative length of eras in the history of the Earth from

Neoarchaean era
Neoarchean - geological era, part of the Archean. Covers the time period from 2.8 to 2.5 billion years ago. The period is determined only chronometrically; the geological layer of the earth's rocks is not distinguished. So

Paleoproterozoic era
Paleoproterozoic is a geological era, part of the Proterozoic, which began 2.5 billion years ago and ended 1.6 billion years ago. At this time, the first stabilization of the continents begins. At that time

Neoproterozoic era
Neoproterozoic is a geochronological era (the last era of the Proterozoic), which began 1000 million years ago and ended 542 million years ago. From a geological point of view, it is characterized by the collapse of the ancient su

Ediacaran period
The Ediacaran is the last geological period of the Neoproterozoic, Proterozoic and entire Precambrian, immediately before the Cambrian. Lasted from approximately 635 to 542 million years BC. e. Name of period of formation

Phanerozoic eon
The Phanerozoic Eon is a geological eon that began ~542 million years ago and continues into modern times, the time of “manifest” life. The beginning of the Phanerozoic eon is considered to be the Cambrian period, when the

Palaeozoic
Paleozoic era, Paleozoic, PZ - geological era of ancient life of planet Earth. The most ancient era in the Phanerozoic eon, follows the Neoproterozoic era, after it comes the Mesozoic era. Paleozoic

Carboniferous period
The Carboniferous period, abbreviated Carboniferous (C) is a geological period in the Upper Paleozoic 359.2 ± 2.5-299 ± 0.8 million years ago. Named because of the strong

Mesozoic era
The Mesozoic is a period of time in the geological history of the Earth from 251 million to 65 million years ago, one of the three eras of the Phanerozoic. It was first isolated in 1841 by British geologist John Phillips. Mesozoic - era

Cenozoic era
Cenozoic (Cenozoic era) is an era in the geological history of the Earth spanning 65.5 million years, from the great extinction of species at the end of the Cretaceous period to the present

Paleocene era
Paleocene is the geological epoch of the Paleogene period. This is the first Paleogene epoch followed by the Eocene. The Paleocene covers the period from 66.5 to 55.8 million years ago. The Paleocene begins the third

Pliocene Epoch
The Pliocene is an epoch of the Neogene period that began 5.332 million years ago and ended 2.588 million years ago. The Pliocene epoch is preceded by the Miocene epoch, and the successor is

Quaternary period
The Quaternary period, or Anthropocene - the geological period, the modern stage of the history of the Earth, ends with the Cenozoic. It began 2.6 million years ago and continues to this day. This is the shortest geological

Pleistocene era
Pleistocene - the most numerous and καινός - new, modern) - the era of the Quaternary period, which began 2.588 million years ago and ended 11.7 thousand years ago

Mineral reserves
(mineral resources) - the amount of mineral raw materials and organic minerals in the bowels of the Earth, on its surface, at the bottom of reservoirs and in the volume of surface and groundwater. Stocks of useful

Reserve valuation
The amount of reserves is estimated based on geological exploration data in relation to existing production technologies. These data make it possible to calculate the volume of mineral bodies, and when multiplying the volume

Inventory categories
Based on the degree of reliability of reserve determination, they are divided into categories. In the Russian Federation, there is a classification of mineral reserves dividing them into four categories: A, B, C1

On-balance sheet and off-balance sheet reserves
Mineral reserves, according to their suitability for use in the national economy, are divided into on-balance and off-balance. Balance sheet reserves include such mineral reserves as

Operational intelligence
PRODUCTION EXPLORATION is the stage of geological exploration carried out during the development of a field. Planned and carried out in conjunction with mining development plans, ahead of mining operations

Mineral exploration
Exploration of mineral deposits (geological exploration) - a set of studies and work carried out with the aim of identifying and assessing mineral reserves

Age of rocks
The relative age of rocks is the establishment of which rocks formed earlier and which later. The stratigraphic method is based on the fact that the age of the layer during normal occurrence

Balance reserves
BALANCE MINERAL RESERVES - a group of mineral reserves, the use of which is economically feasible with existing or industrially mastered progressive technology and

Folded dislocations
Plicative disturbances (from the Latin plico - fold) - disturbances in the primary occurrence of rocks (that is, the dislocation itself)), which lead to the occurrence of bends in rocks of various types

Forecast resources
FORECAST RESOURCES - possible amount of minerals in geologically poorly studied areas of the earth and hydrosphere. Estimation of predicted resources is made on the basis of general geological predictions

Geological sections and methods for their construction
GEOLOGICAL SECTION, geological profile - a vertical section of the earth's crust from the surface to depth. Geological sections are compiled based on geological maps, geological observation data and

Ecological crises in the history of the earth
An ecological crisis is a tense state of relations between humanity and nature, characterized by a discrepancy in the development of production forces and production relations in humans

Geological development of continents and ocean basins
According to the hypothesis of the primacy of the oceans, the earth's oceanic crust arose even before the formation of the oxygen-nitrogen atmosphere and covered the entire globe. The primary crust consisted of basic magmas