Throughout the existence of the Earth, its surface has continuously changed. This process continues today. It proceeds extremely slowly and imperceptibly for a person and even many generations. However, it is these transformations that ultimately radically change the appearance of the Earth. Such processes are divided into exogenous (external) and endogenous (internal).
Classification
Exogenous processes are the result of the interaction of the planet’s shell with the hydrosphere, atmosphere and biosphere. They are studied in order to accurately determine the dynamics of the geological evolution of the Earth. Without exogenous processes, the patterns of development of the planet would not have developed. They are studied by the science of dynamic geology (or geomorphology).
Experts have adopted a universal classification of exogenous processes, divided into three groups. The first is weathering, which is a change in properties under the influence of not only wind, but also carbon dioxide, oxygen, the vital activity of organisms and water. The next type of exogenous processes is denudation. This is the destruction of rocks (and not a change in properties as in the case of weathering), their fragmentation by flowing waters and winds. The last type is accumulation. This is the formation of new ones due to sediments accumulated in depressions of the earth's relief as a result of weathering and denudation. Using the example of accumulation, we can note the clear interconnection of all exogenous processes.
Mechanical weathering
Physical weathering is also called mechanical weathering. As a result of such exogenous processes, rocks turn into blocks, sand and debris, and also disintegrate into fragments. The most important factor in physical weathering is insolation. Due to heating by the sun's rays and subsequent cooling, periodic changes in the volume of the rock occur. It causes cracking and disruption of bonds between minerals. The results of exogenous processes are obvious - the rock splits into pieces. The greater the temperature amplitude, the faster this happens.
The rate of crack formation depends on the properties of the rock, its foliation, layering, and cleavage of minerals. Mechanical failure can take several forms. From a material with a massive structure, pieces break off that look like scales, which is why this process is also called scaling. And granite breaks up into blocks with the shape of a parallelepiped.
Chemical destruction
Among other things, the dissolution of rocks is facilitated by the chemical action of water and air. Oxygen and carbon dioxide are the most active agents that are dangerous to the integrity of surfaces. Water carries salt solutions, and therefore its role in the process of chemical weathering is especially great. Such destruction can be expressed in a variety of forms: carbonation, oxidation and dissolution. In addition, chemical weathering leads to the formation of new minerals.
For thousands of years, water flows down surfaces every day and seeps through pores formed in decaying rocks. The liquid carries away a large number of elements, thereby leading to the decomposition of minerals. Therefore, we can say that there are no absolutely insoluble substances in nature. The only question is how long they retain their structure despite exogenous processes.
Oxidation
Oxidation mainly affects minerals, which include sulfur, iron, manganese, cobalt, nickel and some other elements. This chemical process is especially active in an environment saturated with air, oxygen and water. For example, in contact with moisture, metal oxides that are part of rocks become oxides, sulfides become sulfates, etc. All these processes directly affect the topography of the Earth.
As a result of oxidation, sediments of brown iron ore (orzands) accumulate in the lower layers of the soil. There are other examples of its influence on the terrain. Thus, weathered rocks containing iron are covered with brown crusts of limonite.
Organic weathering
Organisms also participate in the destruction of rocks. For example, lichens (the simplest plants) can settle on almost any surface. They support life by extracting nutrients using secreted organic acids. After the simplest plants, woody vegetation settles on rocks. In this case, the cracks become home to roots.
Characteristics of exogenous processes cannot do without mentioning worms, ants and termites. They make long and numerous underground passages and thereby contribute to the penetration of atmospheric air, which contains destructive carbon dioxide and moisture, into the soil.
Ice influence
Ice is an important geological factor. It plays a significant role in the formation of the earth's topography. In mountainous areas, ice moving along river valleys changes the shape of drains and smoothes surfaces. Geologists called this destruction exaration (gouging out). Moving ice performs another function. It transports clastic material that has broken off from rocks. Weathering products fall off the slopes of valleys and settle on the surface of the ice. Such eroded geological material is called a moraine.
No less important is ground ice, which forms in the soil and fills ground pores in permafrost and permafrost areas. Climate is also a contributing factor here. The lower the average temperature, the greater the depth of freezing. Where the ice melts in the summer, pressure waters rush to the surface of the earth. They destroy the relief and change its shape. Similar processes are repeated cyclically from year to year, for example, in the north of Russia.
Sea factor
The sea occupies about 70% of the surface of our planet and, without a doubt, has always been an important geological exogenous factor. Ocean water moves under the influence of wind, tidal currents and tidal currents. This process is associated with significant destruction of the earth's crust. The waves, which splash even with the weakest sea waves off the coast, constantly undermine the surrounding rocks. During a storm, the surf force can be several tons per square meter.
The process of demolition and physical destruction of coastal rocks by sea water is called abrasion. It flows unevenly. An eroded bay, cape or isolated rocks may appear on the shore. In addition, the breaking waves create cliffs and ledges. The nature of destruction depends on the structure and composition of coastal rocks.
At the bottom of the oceans and seas, continuous processes of denudation take place. Intense currents contribute to this. During storms and other disasters, powerful deep waves are formed, which on their way encounter underwater slopes. When a collision occurs, the sludge liquefies and destroys the rock.
Wind work
The wind makes a difference like nothing else. It destroys rocks, transports small fragmentary material and deposits it in an even layer. At a speed of 3 meters per second, the wind moves leaves, at 10 meters it shakes thick branches, raises dust and sand, at 40 meters it uproots trees and demolishes houses. Dust devils and tornadoes do especially destructive work.
The process of wind blowing away rock particles is called deflation. In semi-deserts and deserts, it forms significant depressions on the surface composed of salt marshes. The wind acts more intensely if the ground is not protected by vegetation. Therefore, it deforms mountain basins especially strongly.
Interaction
The interaction of exogenous and endogenous geological processes plays a huge role in the formation. Nature is designed in such a way that some give rise to others. For example, external exogenous processes eventually lead to the appearance of cracks in the earth's crust. Through these holes, magma enters from the bowels of the planet. It spreads in the form of covers and forms new rocks.
Magmatism is not the only example of how the interaction of exogenous and endogenous processes works. Glaciers help level the terrain. This is an external exogenous process. As a result, a peneplain (a plain with small hills) is formed. Then, as a result of endogenous processes (tectonic movement of plates), this surface rises. Thus, internal and may contradict each other. The relationship between endogenous and exogenous processes is complex and multifaceted. Today it is studied in detail within the framework of geomorphology.
Endogenous and exogenous geological processes
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 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 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 underground waters (Erosion, Denudation), lakes and swamps, waters of seas and oceans (Abrasion), 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. So, for example, in conditions of manifestation specific processes weathering and sedimentation form ores of aluminum (bauxite), iron, nickel, etc.; 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.
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 solar system. 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.
Exogenous (from the Greek éxo - outside, outside) are geological processes that are caused by energy sources external to the Earth: solar radiation and gravitational field. They occur on the surface of the globe or in the near-surface zone of the lithosphere. These include hypergenesis (weathering), erosion, abrasion, sedimentogenesis, etc.
The opposite of exogenous processes, endogenous (from the Greek éndon - inside) geological processes are associated with energy arising in the depths of the solid part of the globe. The main sources of endogenous processes are considered to be heat and gravitational differentiation of matter by density with the immersion of heavier constituent elements. Endogenous processes include volcanism, seismicity, metamorphism, etc.
The use of ideas about exogenous and endogenous processes, colorfully illustrating the dynamics of processes in a stone shell in the struggle of opposites, confirms the validity of J. Baudrillard’s statement that “Any unitary system, if it wants to survive, must acquire binary regulation.” If there is an opposition, then the existence of a simulacrum, that is, a representation that hides the fact that it does not exist, is possible.
In the model real world nature, outlined by the laws of natural science, which have no exceptions, binary explanations are unacceptable. For example, two people are holding a stone in their hand. One of them declares that when he lowers the stone, it will fly to the Moon. This is his opinion. Another says that the stone will fall down. There is no need to argue with them which of them is right. There is a law of universal gravitation, according to which in 100% of cases the stone will fall down.
According to the second law of thermodynamics, a heated body in contact with a cold one will cool down in 100% of cases, heating the cold one.
If the actual observed structure of the lithosphere is made of amorphous basalt, below clay, then cemented clay - argillite, fine-crystalline shale, medium-crystalline gneiss and coarse-crystalline boundary, then the recrystallization of the substance with depth with increasing crystal size clearly indicates that thermal energy is not coming from under the granite. Otherwise, at depth there would be amorphous rocks, giving way to increasingly coarse-crystalline formations towards the surface.
Hence, there is no deep thermal energy, and, therefore, no endogenous geological processes. If there are no endogenous processes, then identifying the exogenous geological processes that are opposite to them loses its meaning.
What is there? In the rocky shell of the globe, as well as in the atmosphere, hydrosphere and biosphere, interconnected and constituting a single system of planet Earth, there is a circulation of energy and matter caused by the influx of solar radiation and the presence of gravitational field energy. This circulation of energy and matter in the lithosphere constitutes a system of geological processes.
The energy cycle consists of three links. 1. The initial link is the accumulation of energy by matter. 2. Intermediate link - release of accumulated energy. 3. The final link is the removal of released thermal energy.
The cycle of matter also consists of three links. 1. The initial link is mixing of different substances with averaging of the chemical composition. 2. Intermediate link - division of an averaged substance into two parts of different chemical composition. 3. The final link is the removal of one part that absorbed the released heat and became loose and light.
The essence of the initial link in the energy cycle of matter in the lithosphere is the absorption of incoming solar radiation by rocks on the land surface, which leads to their destruction into clay and debris (the process of hypergenesis). Destruction products accumulate enormous amounts of solar radiation in the form of potential free surface, internal, geochemical energy. Under the influence of gravity, the products of hypergenesis are carried to low areas, mixing, averaging their chemical composition. Ultimately, clay and sand are carried to the bottom of the seas, where they accumulate in layers (the process of sedimentogenesis). A layered shell of the lithosphere is formed, about 80% of which is clay. Chemical composition of clay = (granite + basalt)/2.
At the intermediate stage of the cycle, layers of clay sink into the depths, overlapping with new layers. Increasing lithostatic pressure (the mass of the overlying layers) leads to the squeezing of water with dissolved salts and gases from the clay, compression of clay minerals, and a decrease in the distances between their atoms. This causes recrystallization of the clay mass into crystalline schists, gneisses and granites. During recrystallization, potential energy (accumulated solar energy) transforms into kinetic heat, which is released from crystalline granite and absorbed by a water-silicate solution of basalt composition located in the pores between granite crystals.
The final stage of the cycle involves the removal of the heated basaltic solution to the surface of the lithosphere, where people call it lava. Volcanism is the final link in the cycle of energy and matter in the lithosphere, the essence of which is the removal of heated basalt solution formed during the recrystallization of clay into granite.
The thermal energy generated during the recrystallization of clay, rising to the surface of the lithosphere, creates for humans the illusion of the receipt of deep (endogenous) energy. In fact, it is released solar energy converted into heat. As soon as thermal energy occurs during recrystallization, it is immediately removed upward, so there is no endogenous energy (endogenous processes) at depth.
Thus, the idea of exogenous and endogenous processes is a simulacrum.
Nootic is the circulation of energy and matter in the lithosphere, caused by the influx of solar energy and the presence of a gravitational field.
The idea of exogenous and endogenous processes in geology is the result of the perception of the world of the stone shell of the globe as a person sees (wants to see) it. This determined the deductive and fragmentary way of thinking of geologists.
But the natural world was not created by man, and what it is like is unknown. To understand it, it is necessary to use an inductive and systematic way of thinking, which is implemented in the model of the cycle of energy and matter in the lithosphere, as a system of geological processes.
Questions
1.Endogenous and exogenous processes
Earthquake
.Physical properties of minerals
.Epeirogenic movements
.List of used literature
1. EXOGENOUS AND ENDOGENOUS PROCESSES
Exogenous processes are geological processes occurring on the surface of the Earth and in the most upper parts 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 large quantity various mineral deposits.
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 most distinct action internal forces The Earth is 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 talk about 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 rushed to the foot of the mountains in the form of thick mudflows. 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.
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.
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 into 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 233 earthquakes were recorded over 1,500 years. major earthquakes with the number of tremors exceeding 2 million.
Earthquakes in China cause great disasters. 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 almost completely destroyed several times. 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 like 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 a diamond consisting 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. Usually, 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 does 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 it. 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 (so-called microhardness) using a sclerometer device, which is expressed in kg/mm2, is also used. .
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/ cm3 .
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, 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.
LIST OF REFERENCES USED
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.
Hallam A. Great geological disputes. M.: Mir, 1985.
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.
Metamorphism 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.
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.
Exogenous 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 is the destruction of rocks and soils by surface water flows and wind, including the detachment and removal of fragments of material and accompanied by their deposition.
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.
Interactions:
The relief is formed as a result of the interaction of endogenous and exogenous processes.
21. Physical weathering of rocks:
Physical weathering of rocks is the process of mechanical fragmentation of rocks without changing the chemical composition of the minerals that form them.
Physical weathering actively occurs during large fluctuations in daily and seasonal temperatures, for example in hot deserts, where the soil surface sometimes heats up to 60 - 70°C and cools to almost 0°C at night.
The destruction process intensifies when water condenses and freezes in rock cracks, since when freezing, water expands and enormous power presses on the walls.
In dry climates, salts that crystallize in rock cracks play a similar role. Thus, calcium salt CaSO4, turning into gypsum (CaSO4 - 2H2O), increases in volume by 33%. As a result, individual fragments begin to fall away from the rock, broken by a network of cracks, and over time its surface may undergo complete mechanical destruction, which favors chemical weathering.
22. Chemical weathering of rocks:
Chemical weathering is the process of chemically changing rocks and minerals and forming new, simpler compounds as a result of reactions of dissolution, hydrolysis, hydration and oxidation. The most important factors in chemical weathering are water, carbon dioxide and oxygen. Water acts as an active solvent for rocks and minerals, and carbon dioxide dissolved in water enhances the destructive effect of water. The main chemical reaction of water with minerals of igneous rocks - hydrolysis - leads to the replacement of cations of alkali and alkaline earth elements of the crystal lattice with hydrogen ions of dissociated water molecules. Hydration is also associated with the activity of water - the chemical process of adding water to minerals. As a result of the reaction, the surface of minerals is destroyed, which in turn enhances their interaction with the surrounding aqueous solution, gases and other weathering factors. The reaction of the addition of oxygen and the formation of oxides (acidic, basic, amphoteric, salt-forming) is called oxidation. Oxidative processes are widespread during the weathering of minerals containing metal salts, especially iron. As a result of chemical weathering, the physical state of minerals changes and their crystal lattice is destroyed. The rock is enriched with new (secondary) minerals and acquires properties such as cohesion, moisture capacity, ability to absorb, etc.
23. Organic weathering of rocks:
Weathering of rocks is a complex process in which there are several forms of its manifestation. 1st form - mechanical crushing of rocks and minerals without significantly changing them chemical properties- called mechanical or physical weathering. The 2nd form - a chemical change in a substance, leading to the transformation of original minerals into new ones - is called chemical weathering. 3rd form - organic (biological-chemical) weathering: minerals and rocks are physically and mainly chemically changed under the influence of the vital activity of organisms and organic matter formed during their decomposition.
Organic weathering:
The destruction of rocks by organisms is carried out by physical or chemical means. The simplest plants - lichens - are able to settle on any rock and extract nutrients from it using the organic acids they secrete; this is confirmed by experiments of planting lichens on smooth glass. After some time, cloudiness appeared on the glass, indicating its partial dissolution. The simplest plants prepare the ground for life on the surface of rocks of more highly organized plants.
Woody vegetation sometimes appears on the surface of rocks that do not have loose soil cover. Plant roots use cracks in the rock, gradually expanding them. They are capable of tearing apart even very dense rock, since the turgor, or pressure, developed in the cells of the root tissue reaches 60-100 atm. A significant role in the destruction of the earth's crust in its upper part is played by earthworms, ants and termites, which make numerous underground passages, facilitating the penetration of air containing moisture and CO2 into the soil - powerful factors of chemical weathering.
24. Minerals formed during the weathering of rocks:
WEATHERING DEPOSITS - deposits of minerals that arose in the weathering crust during the decomposition of rocks near the Earth's surface under the influence of water, carbon dioxide, oxygen, as well as organic and inorganic acids. Among weathering deposits, a distinction is made between infiltration deposits and residual deposits. Weathering deposits include some deposits of Fe, Mn, S, Ni ores, bauxite, kaolin, apatite, and barite.
Infiltration deposits include deposits of uranium, copper, and native sulfur ores. An example of this is the widespread deposits of uranium ores in sandstone layers (for example, the Colorado Plateau). Residual mineral deposits include deposits of silicate nickel, iron, manganese, bauxite, magnesite, and kaolin ores. Among them, the most typical are the nickel ore deposits of the CCCP (Southern Urals), Kuba, and North Caledonia.
25. Geological activity of wind:
Wind activity is one of the most important factors forming relief. Processes associated with the activity of wind are called aeolian (Aeolus is the god of the winds in Greek mythology).
The influence of wind on the terrain occurs in two directions:
Weathering is the destruction and transformation of rocks.
Movement of material - giant accumulations of sand or clay particles.
The destructive activity of wind consists of two processes - deflation and corrosion.
Deflation is the process of blowing and dispersing particles of loose rocks by the wind.
Corrosion (scrape, scrape) is the process of mechanical abrasion of rocks by debris carried by the wind. It involves turning, grinding, and drilling rocks.
26. Geological activity of the sea:
Seas and oceans occupy about 361 million km2. (70.8% of the entire earth's surface). The total volume of water is 10 times greater than the volume of land rising above the water level, which is 1370 million km2. This enormous mass of water is in constant motion and therefore performs great destructive and creative work. Over the long history of the development of the earth's crust, seas and oceans have changed their boundaries more than once. Almost the entire surface of modern land was repeatedly flooded with their waters. Thick layers of sediment accumulated at the bottom of the seas and oceans. From these sediments various sedimentary rocks were formed.
The geological activity of the sea mainly comes down to the destruction of rocks of the coast and bottom, the transfer of fragments of material and the deposition of sediments, from which sedimentary rocks of marine origin are subsequently formed.
The destructive activity of the sea consists of the destruction of the shores and bottom and is called abrasion, which is most evident near steep shores at great coastal depths. This is due to the high wave height and high pressure. The destructive activity is enhanced by the debris contained in sea water and air bubbles, which burst and a pressure difference occurs that is tens of times greater than the abrasion. Under the influence of sea waves, the shore gradually moves away and in its place (at a depth of 0 - 20 m) a flat platform is formed - a wave-cut or abrasion terrace, the width of which can be > 9 km, slope ~ 1°.
If the sea level remains constant for a long time, then the steep coast gradually recedes and a boulder-pebble beach appears between it and the abrasion terrace. The coast changes from abrasive to accumulative.
The shores are intensively destroyed during the transgression (advance) of the sea and turn, emerging from below the water level, into a marine terrace during the regression of the sea. Examples: the shores of Norway and Novaya Zemlya. Abrasion does not occur with rapid continuous uplifts and on gentle banks.
The destruction of coastlines is also facilitated by sea ebbs and flows and sea currents (Gulf Stream).
Sea water transports substances in a colloidal, dissolved state and in the form of mechanical suspensions. It drags coarser material along the bottom.
27. Sediments of the sea shelf zone:
Seas and oceans occupy about 71% of the Earth's surface. The water is in constant movement, which leads to the destruction of banks (abrasion), movement huge amount clastic material and dissolved substances carried by rivers, and finally their deposition to form a variety of sediments.
Shelf (from English) - a continental shelf, is an underwater slightly inclined plain. The shelf is a leveled part of the underwater margin of the continent, adjacent to the land and characterized by a common geological structure. On the ocean side, the shelf is limited by a clearly defined edge located to depths of 100-200 m.
The main factors that determine the type of marine sediments are the nature of the relief and the depth of the seabed, the degree of distance from the coast, and climatic conditions.
The littoral zone is the coastal shallow part of the sea, which is periodically flooded during high tides and drained during low tides. This zone has a lot of air, light and nutrients. Sediments of the littoral zone are characterized primarily by strong variability, which is a consequence of the periodically changing hydrodynamic regime of water.
A beach is formed in the littoral zone. The beach is an accumulation of debris in the surf zone. The beaches are composed of a wide variety of materials - from large blocks to fine sand. Waves flowing onto the beach sort the material they carry out. As a result, areas enriched with heavy minerals may appear in the beach area, which leads to the formation of coastal-marine placers.
In areas of the littoral zone, where there are no strong waves, the nature of sediments is significantly different. The sediments here are predominantly fine-grained: silty and clayey. Sometimes the entire tidal zone is occupied by sandy-clayey silts.
The neritic zone is the area of shallow water that extends from the depth where waves cease to occur to the outer edge of the shelf. In this zone, terrigenous, organogenic and chemogenic sediments accumulate.
Terrigenous sediments are most widespread, due to the proximity of land. Among them, coarse sediments are distinguished: blocks, boulders, pebbles and gravel, as well as sandy, silty and clayey sediments. In general, the following distribution of sediments is observed in the shelf zone: coarse clastic material and sands accumulate near the shore, sands are followed by silty sediments, and even further away, clayey sediments (silts). Sediment sorting worsens as it hits the shore due to the weakening of the sorting work of waves.
28. Sediments of the continental slope, continental foot and ocean floor:
The main elements of the bottom topography of ocean basins are:
1) Continental shelf, 2) Continental slope with submarine canyons, 3) Continental foot, 4) System of mid-ocean ridges, 5) island arcs, 6) Ocean bed with abyssal plains, positive landforms (mainly volcanoes, guillotines and atolls ) and deep-sea trenches.
Continental slope - represents the margins of continents, submerged up to 200 - 300 m below sea level at their outer edge, from where a steeper descent of the seabed begins. The total shelf area is about 7 million km2, or about 2% of the bottom area of the World Ocean.
Continental slope with canyons. From the shelf edge the bottom drops steeper, forming a continental slope. Its width is from 15 to 30 km and it plunges to a depth of 2000 - 3000 m. It is cut by deep valleys - canyons up to 1200 m deep and having a V-shaped transverse profile. In the lower part, the canyons reach a depth of 2000 - 3000 and below sea level. The walls of the canyons are rocky, and the bottom sediments deposited at their mouths on the continental foot indicate that the canyons play the role of trays along which fine and coarse sedimentary material from the shelf is carried to great depths.
The continental foot is a sedimentary fringe with a gently inclined surface at the base of the continental slope. It is an analogue of piedmont alluvial plains formed by river sediments at the foot of mountain ranges.
In addition to deep-sea plains, the ocean floor also includes other large and small landforms.
29. Minerals and landforms of marine origin:
A significant percentage of minerals are found in the ocean.
Shell rock and shell sand are mined for the cement industry. The sea also supplies significant amounts of material for alluvial shores, islands, and dams.
However, the greatest interest is caused by iron-manganese nodules and phosphorites. Round or disc-shaped nodules and their aggregates are found over large areas of the ocean floor and gravitate toward zones of development of volcanoes and metal-bearing hydrotherms.
Pyrite nodules are typical for the geologically quiet Arctic Ocean, and disks of iron-manganese nodules have been found at the bottom of the rift valley of the Black Sea.
A significant amount of phosphorus is dissolved in ocean water. The concentration of phosphates at a depth of 100 meters varies from 0.5 to 2 or more micrograms per liter. Phosphate concentrations are especially significant on the shelf. These concentrations are probably secondary. The original source of phosphorus is volcanic eruptions that occurred in the distant past. Phosphorus was then transferred in a relay race from minerals to living matter and vice versa. Large burials of phosphorus-rich sediments form deposits of phosphorites, usually enriched in uranium and other heavy metals.
Seabed topography:
The relief of the ocean floor is not much different in its complexity from the relief of land, and often the intensity of the vertical dissection of the bottom is greater than the surface of the continents.
Most of the ocean floor is occupied by oceanic platforms, which are areas of the crust that have lost significant mobility and ability to deform.
There are four main forms of relief of the ocean floor: the underwater margin of continents, the transition zone, the ocean floor and mid-ocean ridges.
The submarine margin consists of a shelf, a continental slope and a continental foot.
*The shelf is shallow water zones around the continents, extending from the coastline to a sharp bend in the bottom surface at an average depth of 140 m (in specific cases, the depth of the shelf can vary from several tens to several hundred meters). The average shelf width is 70-80 km, and the greatest is in the area of the Canadian Arctic Archipelago (up to 1400 km)
*The next form of underwater continental margin, the continental slope, is a relatively steep (slope of 3-6°) part of the bottom located at the outer edge of the shelf. Off the coast of volcanic and coral islands, slopes can reach 40-50°. The width of the slope is 20-100 km.
*The continental foot is an inclined, often slightly undulating plain, bordering the base of the continental slope at depths of 2-4 km. The continental foot can be both narrow and wide (up to 600-1000 km wide) and have a stepped surface. It is characterized by a significant thickness of sedimentary rocks (up to 3 km or more)..
*The area of the ocean floor exceeds 200 million km2, i.e. makes up approximately 60% of the area of the World Ocean. The characteristic features of the bed are the widespread development of flat relief, the presence of large mountain systems and hills not associated with the median ridges, as well as the oceanic type of the earth's crust.
The most extensive forms of the ocean floor are ocean basins, submerged to a depth of 4-6 km and representing flat and hilly abyssal plains.
*The mid-ocean ridges are characterized by high seismic activity, expressed by modern volcanism and earthquake sources.
30. Geological activity of lakes:
It is characterized by both destructive and creative work, i.e. accumulation of sedimentary material.
Coastal erosion is carried out only by waves and rarely by currents. Naturally, in large lakes with a large water surface, the destructive effect of waves is stronger. But if the lake is ancient, then the coastlines have already been determined, the equilibrium profile has been reached, and the waves, rolling onto narrow beaches, only carry sand and pebbles over short distances. If the lake is young, then abrasion tends to cut off the shores and achieve an equilibrium profile. Therefore, the lake seems to expand its borders. A similar phenomenon is observed in recently created large reservoirs, in which waves cut off the banks at a speed of 5-7 m per year. As a rule, lake shores are covered with vegetation, which reduces wave impact. Sedimentation in lakes occurs both due to the supply of clastic material by rivers and through biogenic and chemogenic routes. Rivers flowing into lakes, like temporary water streams, carry with them material of various sizes, which is deposited near the shore or spread throughout the lake, where the suspended matter precipitates.
Organogenic sedimentation is caused by abundant vegetation in shallow waters, well heated by the Sun. The banks are covered with various herbs. And algae grows under water. In winter, after the vegetation dies, it accumulates at the bottom, forming a layer rich in organic matter. Phytoplankton develops in the surface layer of water and blooms in summer. In autumn, when there are algae, grass and phytoplankton. They sink to the bottom, where a silty layer saturated with organic matter forms. Because At the bottom of stagnant lakes there is almost no oxygen, then anaerobic bacteria transform the sludge into a fatty, jelly-like mass - sapropel, containing up to 60-65% carbon, which is used as fertilizer or therapeutic mud. Sapropel layers have a thickness of 5-6 meters, although sometimes they reach 30 and even 40 m, as, for example, in Lake Pereyaslav on the Russian Plain. The reserves of valuable sapropel are huge and in Belarus alone amount to 3.75 billion m3, where their intensive extraction takes place.
In some lakes, uncured layers of limestone are formed - shell rocks or diatomites, formed from diatoms with a flint skeleton. Many lakes these days are subject to heavy anthropogenic load, which changes their hydrological regime, reduces water transparency, and sharply increases the content of nitrogen and phosphorus. The technogenic impact on lakes consists of reducing catchment areas, redistributing groundwater flows, and using lake waters as coolants for power plants, including nuclear power plants.
Chemogenic deposits are especially characteristic of lakes in arid zones, where water evaporates intensively and therefore table and potassium salts (NaCl), (KCl, MgCl2), boron compounds, sulfur and others precipitate. Depending on the most characteristic chemogenic sediments, lakes are divided into sulfate, chloride, and borate. The latter are characteristic of the Caspian lowland (Baskunchak, Elton, Aral).
31. Geological activity of running water:
Rivers move soil, stones and other rocks. Running water has no small force; in the fast, disorderly flow, large stones crumble into small pieces. The geological activity of rivers, like other flowing waters, is expressed mainly by: 1) erosion, destruction of rocks, 2) transfer of eroded material either in dissolved form or in mechanical suspension, 3) deposition of transported material to places more or less distant from that area . Erosion is most pronounced in the upper reaches where the slopes are steeper. Groundwater includes all natural waters located under the surface of the Earth in a mobile state, which wash away the soil layer. River sediments fertilize the soil and level the earth's surface.
32. Concepts of equilibrium profile, bottom and lateral erosion:
Equilibrium profile (watercourse) - the longitudinal profile of the watercourse bed in the form of a smooth curve, steeper in the upper reaches and almost horizontal in the lower reaches; Throughout its entire length, such a flow should not produce bottom erosion. The shape of the equilibrium profile depends on the change of a number of factors along the river (water flow, the nature of sediment, rock characteristics, channel shape, etc.) that influence erosion-accumulation processes. However, the determining factor is the nature of the relief along the river valley. Thus, the exit of a river from a mountainous region to a plain causes a rapid decrease in the slopes of the riverbed.
The equilibrium profile of a river is the limiting shape of the profile to which a watercourse tends with a stable base of erosion.
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.
Linear erosion occurs in small areas of the surface and leads to the dismemberment of the earth's surface and the formation of various erosion forms (gulleys, ravines, beams, valleys).
Types of linear erosion
Deep (bottom) - destruction of the bottom of the watercourse bed. Bottom erosion is directed from the mouth upstream and occurs until the bottom reaches the erosion base level.
Lateral - destruction of the banks.
In every permanent and temporary watercourse (river, ravine), both forms of erosion can always be found, but in the first stages of development, deep erosion predominates, and in subsequent stages, lateral erosion.
33. Landforms and minerals of river origin:
River landforms are erosive and accumulative landforms that arise as a result of the work of flowing waters, both temporary and permanent. These include different types of valleys, erosional ledges and slopes (also formed by gravitational processes), terraces, floodplains, complicated by oxbow lakes, riverbed levees, riverbed dunes, waterfalls, rapids, alluvial fans, dry deltas, deltas (together with the sea). Carbonate rocks cf. Carboniferous, limestone, clay, carbonaceous shales.
34. Geological activity of swamps:
A swamp is an area of land (or landscape) characterized by excess moisture, sewage or running water, but without a permanent layer of water on the surface. A swamp is characterized by the deposition on the soil surface of incompletely decomposed organic matter, which later turns into peat. The peat layer in swamps is at least 30 cm; if less, then it is simply wetlands.
The main result of the geological work of bogs is the accumulation of peat. In addition to peat, other sediments, including mineral ones, are often formed. The color of peat is usually dark. In fresh (not compacted) peat, moisture is 85-95%, mineral impurities are from 2 to 20% of the dry mass of peat. Bog peat varies in the amount of ash residue. The most ash is produced by lowland peat (8-20%), the least by transitional peat (4-6%) and the least by high-moor peat (2-4%). Depending on the predominance of vegetation, woody, herbal and moss peat are distinguished.
35. Geological work of glaciers:
Moving masses of ice perform enormous geological work. The ice carries frozen stone blocks (Fig. 3), scratching the bed of the ice stream, tearing off pieces of rock and grinding them, shifting rock layers. The ice plows up soft rocks, forming grooves and basins in them. Stones frozen into the ice smooth out and cover the rocks with streaks, forming sheep's foreheads, curly rocks and streaked boulders.
Going down to the sea, the glacier breaks off, and mountains of floating ice are formed - icebergs, which melt over the years. Icebergs can carry boulders, blocks and other broken rock material.
As you move from the mountains below the snow line and across the continent, the ice melts, just as the continental ice of the Ice Ages melted in the relatively recent geological past. Melted ice leaves behind coarse, heterogeneous, unsorted, non-layered clastic material. Most often these are boulder sandy red-brown loams and clays or gray heterogeneous clayey sands with boulders. Boulders of varying sizes (from centimeters to several meters in diameter) consist of granite, gabbro, quartzite, limestone and generally rocks of different petrographic composition. This is explained by the fact that the glacier brings material from afar and at the same time captures fragments and blocks of local rock.
37. Genetic classification of sedimentary rocks:
Based on their origin and geological features, all rocks are divided into 3 classes:
Sedimentary
Igneous
Metamorphic.
According to the method of their formation, sedimentary rocks are divided into three main genetic groups:
Clastic rocks (breccias, conglomerates, sands, silts) are coarse products of predominantly mechanical destruction of parent rocks, usually inheriting the most stable mineral associations of the latter;
Clay rocks are dispersed products of deep chemical transformation of silicate and aluminosilicate minerals of parent rocks, transformed into new mineral species;
Chemogenic, biochemogenic and organogenic rocks are products of direct precipitation from solutions (for example, salts), with the participation of organisms (for example, siliceous rocks), accumulation of organic substances (for example, coals) or waste products of organisms (for example, organogenic limestones).
A characteristic feature of sedimentary rocks, associated with the conditions of formation, is their layering and occurrence in the form of more or less regular geological bodies (layers).
38. Structures and textures of sedimentary rocks:
Sedimentary rocks are formed only on the surface of the earth's crust during the destruction of any pre-existing rocks, as a result of the vital activity and death of organisms and precipitation from supersaturated solutions.
Structure is understood as the internal structure of a rock, a set of characteristics determined by the degree of crystallinity, absolute and relative sizes, shape, relative position and methods of combining mineral components.
Structure is the most important characteristic of a rock, expressing its grain size.
Texture refers to the features of the external structure of a rock, characterizing the degree of its homogeneity and continuity.
Internal textures are divided into non-layered and layered.
39. Shapes of geological bodies composed of sedimentary rocks:
Sedimentary rocks form layers, layers, lenses and other geological bodies different shapes and size, lying in the earth's crust normally horizontally, obliquely or in the form of complex folds. The internal structure of these bodies, determined by the orientation and mutual arrangement of grains (or particles) and the way the space is filled, is called the texture of sedimentary rocks. Most of these rocks are characterized by a layered texture: the types of texture depend on the conditions of their formation (mainly on the dynamics of the environment).
The formation of sedimentary rocks occurs according to the following scheme: the emergence of initial products through the destruction of parent rocks, the transfer of matter by water, wind, and glacier and its deposition on the land surface and in water basins. As a result, a loose and porous sediment, saturated with water, completely or partially, is formed, composed of heterogeneous components.
40. Origin and forms of occurrence of groundwater:
Based on their origin, groundwater can be divided into infiltration and sedimentation.
Infiltration water is formed by seepage, penetration of atmospheric precipitation and surface water into porous and fractured rocks. Groundwater and some artesian waters are of infiltration origin.
Sedimentation waters are waters formed during the process of sedimentation. Sediments deposited in an aquatic environment are saturated with the water of the basin in which sedimentation occurs.
Forms of occurrence of groundwater:
Water, filling the pores, cracks and voids of rocks, can be present in them in three phases: liquid, vapor and solid. The last phase is most typical for permafrost zones, as well as for areas of the globe with negative winter temperatures.
Gravitational water, i.e. water subject to the forces of gravity, can fill the pores and voids of rock layers (in sands, sandstones, etc.) - this is formation water or be found in rock cracks (in granites, basalts, etc. .) are fissure waters. Stratified-fissure waters are also known, contained in cracks of porous rocks (some sandstones and other sedimentary deposits). Finally, water can fill voids, channels, tubes of karst rocks - these are karst waters (in limestones, dolomites, salts, etc.).
41. Water properties of rocks:
The main water properties of soils include humidity, moisture capacity, water loss, water permeability, and capillarity.
Moisture holding capacity is the property of a rock to contain a certain amount of water in its pores.
Total moisture capacity is the amount of water that fills all the voids in the rock.
The actual water holding capacity is determined by the amount of water actually contained in the rock.
Capillary water capacity is the amount of water retained by a rock in capillaries when draining freely. The greater the water permeability of the rock, the smaller the capillary moisture capacity.
Fluid yield refers to the amount of gravitational water that can be contained in a rock and which it can give up when pumped. Water loss can be expressed as a percentage ratio of the volume of water freely flowing from the rock to the volume of the rock.
The water saturation of rocks represents the amount of water that is given off by the rock. According to the degree of water abundance, rocks are divided into highly water-rich with a well flow rate of more than 10 l/s, water-abundant with a well flow rate of 1 - 10 l/s, low-water-abundant - 0.1 - 1 l/s.
Water-pumping rocks, as well as layers, lenses, etc., are those in which pores, cracks and other voids are filled with gravitational waters - gravity-aquifer, capillary and film-aquifer waters.
Water permeability is the property of rocks to allow water to pass through due to the presence of pores, cracks and other voids in them. The amount of water permeability is determined by the water permeability coefficient. According to the degree of water permeability, rocks can be divided into permeable, semi-permeable and waterproof.
Water resistance is the property of rocks not to allow water to pass through. These include, for example, unfractured limestones, crystalline shales, etc.