How do exogenous processes differ from endogenous ones? Endogenous and exogenous geological processes

ENDOGENOUS PROCESSES (a. endogenous processes; n. endogene Vorgange; f. processus endogenes, processus endogeniques; i. procesos endogenos) - geological processes associated with the 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 material composition, temperature and pressure, pockets and layers of partial melting may occur. 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 rocks 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

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

1. Concept of processes

2. Exogenous processes

2.1 Weathering

2.1.1 Physical weathering

2.1.2 Chemical weathering

2.2 Geological activity wind

2.2.1 Deflation and corrosion

2.2.2 Transfer

2.2.3 Accumulation and aeolian deposits

2.3 Geological activity of surface flowing waters

2.4 Geological activity of groundwater

2.5 Geological activity of glaciers

3. Endogenous processes

3.1 Magmatism

3.2 Metamorphism

3.3 Earthquake

List of used literature

1. Concept of processes

Throughout its existence, the Earth has gone through a long series of changes. It changes continuously. Its composition changes, physical state, appearance, position in world space and relationship with other members of the solar system.

Geology 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.

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 during geological development there were multiple changes 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.

2. Exogenous processes

2.1 Vweathering

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.

2.1.1 Fisical weathering

In this type, temperature weathering is of greatest importance, which is associated with daily and seasonal fluctuations temperatures, which causes either heating or cooling of the surface part of rocks. Under the conditions of the earth's surface, especially in deserts, daily temperature fluctuations are quite significant. So in the summer daytime rocks heat up to + 800C, and at night their temperature drops to + 200C. Due to the sharp difference in thermal conductivity, coefficients of thermal expansion and compression, and anisotropy of the thermal properties of the minerals composing 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 and single-mineral. Many mineral rocks are subject to the greatest destruction as a result of the process of temperature weathering.

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%. 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.

2.1.2 Xchemical weathering

Simultaneously with physical weathering in areas with a leaching type of moisture regime, processes also occur chemical change 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 reflected in humid tropical zones, where high humidity, high thermal conditions and rich forest vegetation are combined. Chemical weathering processes include oxidation, hydration, dissolution and hydrolysis.

2.2 Ggeological wind activity

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 50o and above, which contributes to intense weathering processes; absence or sparse vegetation cover.

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

2.2.1 DEflation and Corrasion

Deflation is the blowing and scattering of loose rock particles (mainly sandy and silty) by the wind. There are 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, fluvio-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.

Local deflation manifests itself in individual depressions in relief.

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

2.2.2 Prenos

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.

2.2.3 Aaccumulation and aeolian deposits

Simultaneously with deflation 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 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.

Aeolian loess (German “loess” - yellow earth) is a peculiar genetic type 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 importance 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) variety 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 capacities are noted in China.

2.3 Ggeological activity of surface flowsatsneeze waters

Groundwater and temporary streams of atmospheric precipitation, flowing down ravines and gullies, are collected into permanent water streams - rivers. Full-flowing rivers perform a great deal 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. Sediment accumulation leads to shape distortion cross section 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 that play a large role in the formation of river valleys.

Rivers transport large amounts of debris of various 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.

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 when 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 Ggeological activity of groundwater

Groundwater includes all water located in the pores and cracks of rocks. They are widespread in the earth's crust, and studying them has great importance when resolving issues: water supply to settlements and industrial enterprises, hydraulic engineering, industrial and civil engineering, carrying out 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.

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.

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) sinkholes formed by the collapse of the arches of underground karst cavities;

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

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.

2.5 Ggeological activity of glaciers

Glaciers are natural body large size, consisting of crystal ice, formed on the surface of the earth as a result of the accumulation and subsequent transformation of solid atmospheric precipitation and 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 diverse clastic material, consisting mainly of products of supra-glacial and sub-glacial weathering, as well as fragments resulting from the mechanical destruction of rocks by moving glaciers.

3. 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

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. exogenous endogenous geology weathering

Gaseous or volatile products, as shown above, play decisive role during volcanic eruptions and their composition is very complex and has not been fully studied due to difficulties in determining the composition of the gas phase in magma located deep under the Earth's surface.

Liquid volcanic products are represented by lava - magma that has reached the surface and is already highly degassed. The term "lava" comes from Latin word“laver” (to wash, wash) mud flows used to be 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 Mmetamorphism

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

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.

There are 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

Dynamo metamorphism 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.

3.3 Zearthquakes

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, at first glance, be the most insignificant, for example, the filling of a reservoir, rapid change atmospheric pressure, ocean tides etc.

List of used literature

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.: graduate School, 2005. - 575 p.: ill.

4. Internet

Posted on Allbest.ru

...

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 physical weathering - 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 chemical exposure 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 the most different 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 into the soil, which contains destructive carbon dioxide and moisture.

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 areas of perennial and permafrost. 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 terrain 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 occur. 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 and transports debris. small size 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.

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.); mainly due to energy 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, 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, driving force 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 modern geological epoch 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 energy value, which arise 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 high altitude 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 narrow streets and people among them... The underground rumble, the rumble of stones, the squeal of wood drown 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 came to the surface in some places underground water. 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 internal parts 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 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 233 earthquakes were recorded over 1,500 years. major earthquakes with the number of tremors exceeding 2 million.

Great disasters are caused by earthquakes in China. During the disaster on December 16, 1920, more than 200 thousand people died in the Kansu region, and main reason The deaths were 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 like in Turkmenistan, they are located along a certain line, elongated in a 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 and 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 chemical analyzes and X-ray diffraction method, 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. Since this indicator can be measured with high accuracy, it is a very useful diagnostic feature of minerals.

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 case Transparent minerals containing heavy metal atoms are distinguished by their high luster and 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 sheen 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 is colored different colors, but his line 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 internal structure 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 connected to each other 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 less precise definition 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). Other than that equal conditions 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 environment and then in the 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 the mineral is in natural form(“by itself”) acts on the 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. 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 recorded in sections 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 in 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.