Exogenous processes are those processes that occur under the influence external forces. As a rule, they pose a danger to structures or people, which is why they are often called hazardous geological processes. It is clear that endogenous processes can also be dangerous, but they no longer belong to the field of engineering geology.
Most often (in the central zone of the Russian Federation) the following occur: frost heaving, uneven precipitation, suffusion, karst, landslides, flooding, waterlogging.
One of most important tasks research - discover them and study them.
Frost heaving typical for clay soils. Physically bound water, which is almost always present in them, freezes and increases the volume of the rock. The soil freezes to the structure (for example, a foundation block) and squeezes it out.
To prevent this from happening, foundations are buried below the depth of seasonal freezing and a sand cushion is used. Sand perfectly filters water and is not affected by this process.
Uneven precipitation arise in the case of different bearing capacity of soils. Under one part of the building, precipitation occurs more slowly and weakly than under another. This is a consequence of illiterate research and calculations. The possibility of developing such a process is determined during surveys, then in the project the foundation is calculated so that the precipitation everywhere (especially in the corners) is the same.
Eliminating the consequences of uneven precipitation is expensive. Typically, concrete is pumped under the settling parts.
Suffusion is the process of transporting soil particles by groundwater. Typical for sands of different grains in the presence of a vertical flow groundwater. Often suffusion is associated with karst. Dealing with it is quite difficult and expensive. If there are manifestations of suffusion or karst on your site (ponoras, sinkholes), it is better to refuse construction. It will be cheaper.
Karst- the process of rock dissolution (leaching). In the Central region, the most common carbonate type (limestones and dolomites dissolve), gypsum is also found. Carbonate karst develops very slowly. If there are karst forms, then the danger is not the karst itself, but the suffusion that is associated with it. Gypsum karst is dynamic (gypsum solubility is very high), if there are conditions for its development, then it is better not to get involved with construction.
Landslide processesThey are often found and are confined to slopes with a steepness of 3 degrees. There are about 10 types of landslides, and there are many classifications. Some can be easily defended against, while others are almost impossible to deal with. If you are building on a slope, spare no expense - consult with specialists . Mistakes in the case of landslides can be very costly.
The study of landslides, in short, comes down to determining the type, depth of capture, activity, size, geological section and physical and mechanical properties of soils. Next is performing stability calculations. Calculations are required to be carried out using several methods (usually three or more), but for them it is necessary to perform some non-standard soil studies. Correctly determined soil properties are the basis for stability calculations. Sometimes done mathematical modeling(in finite elements), but this is more expensive and not always justified. The result is the design of landslide prevention measures. This could be redevelopment of a slope, a retaining wall, piles, etc. If the slope is not creeping yet, but there is such a possibility, it is better to play it safe and make a calculation. Then there is a chance to get by with preventive measures (for example, leveling a slope).
Subsidence- the ability of loess and other silty soils to undergo additional deformations, reducing volume when moistened.
Erosion processes- washout and erosion of soils by surface water flows. There are several types of erosion: lateral, water, bottom, selective, linear, longitudinal and regressive. Separately, we can distinguish wind erosion (aeolian process) - the demolition and movement of sand particles under the influence of wind force, accompanied by the sorting of material.
Flooding- the process of raising the groundwater level to a certain critical level. Depending on the category of land, the depth to the groundwater level may vary in order to consider the area flooded (from 0.6 m for arable land to 4 m for the city). The usual method of control is drainage.
Waterlogging- the process of swamp formation. A wetland is an area where the peat thickness is 30 cm or more. If there is peat on the site, it is better to abandon it.
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Lecture 4
What is meant by geological process? These are physical and chemical processes occurring inside the Earth or on its surface and leading to changes in its composition, structure, topography and deep structure.
Traditionally, all geological processes are usually divided into two groups - endogenous And exogenous. This division is made according to the place of manifestation and energy source these processes.
Endogenous– these are internal processes; exogenous– external, superficial sources of energy for them are the energy of the sun and gravity (the Earth’s gravitational field).
TO endogenous processes include :
Magmatism(from the word magma) - the process associated with the birth, movement and transformation of magma into igneous rock
Tectonics(tectonic movements) – any mechanical movements the earth's crust - uplifts, subsidences, horizontal movements, etc.
Metamorphism– processes leading to changes in the composition and structure of rocks inside the Earth when physical and chemical parameters change, mainly T o and P, since with their increase the activity of solutions and the superheated vapor-gas phase sharply increases.
TO exogenous processes include processes that occur on or near the surface of the Earth, change its appearance and are associated with the activities of the atmosphere, hydrosphere and biosphere, namely:
a) the impact of wind (aeolian activity) - deflation (blowing), corrosion (grinding), soil erosion;
b) physical, chemical, underwater weathering (halmyrolysis);
c) the activity of flowing waters - river lateral and bottom erosion, transfer of material in the form of turbidity, bed and bottom sediments, as well as ice;
d) destructive and accumulating activity of glaciers, fluvioglacial deposits;
e) activity of sea, ocean and ground waters;
e) landslides, screes, landslides, mudflows.
For all exogenous processes, three features are manifested in their activity.
First- under certain conditions, they carry out destructive work and remove destruction products, while negative (decreased) forms of relief are formed and a general decrease in relief and smoothing of the land surface occurs (peniplanation). The process of destruction and removal of destruction products is called denudation. This process is very important, because it constantly exposes deeper parts of the earth's crust to the surface.
Second characteristic feature in the activity of exogenous processes is manifested in the fact that in other conditions they conduct creative activity - accumulation, which leads to the accumulation of destruction products and the formation of geological bodies. Between these two sides of activity there is third, namely, the transfer of destruction products occurs.
Each geological process (endogenous, exogenous) ultimately leads to some changes that do not pass without leaving a trace, but are fixed in some way. The most important geological documents that record the results of processes are: minerals, rocks, geological bodies, gas and water mixtures, physical fields. These are the real objects (or documents) that we see and examine.
Mineral- it's natural chemical compound or separate chemical elements, arising as a result of various physical and chemical processes occurring in the Earth and on its surface. Each mineral has a more or less constant composition, shape and physicochemical properties. Rocks are made up of minerals.
Rock is a natural association (set) of minerals of a certain origin that compose geological bodies.
Geological body- a certain volume inside or on the surface, composed of rock and having sharp boundaries with other geological bodies, for example, a layer, a quartz vein. The earth's crust is made up of geological bodies, and geological maps show the outcrops (boundaries) of geological bodies.
Questions for self-control
Define geology as a science and list the main objects of its study
Name the main ones scientific directions in the study of the lithosphere
List endogenous and exogenous processes and their main features
What is “denudation” and what processes are it caused by?
Geological processes are divided into exogenous (external) and endogenous (internal).
Exogenous processes are caused by the energy received by the Earth from the Sun, the attraction of the Sun and Moon, the rotation of the Earth around its axis, and the action of gravity.
Endogenous processes are caused by the energy of the Earth's interior. Exogenous processes lead to the leveling of terrain forms. Under the influence of temperatures, under the influence of wind, water, sea surf, and glaciers, rocks are destroyed and transported to low areas of the earth's surface, mainly to the seas and oceans.
Exogenous processes occur on the earth's surface and in the upper parts of the earth's crust as a result of its interaction with the atmosphere, hydrosphere and biosphere. These processes produce destructive and creative work. The processes of weathering and denudation have a destructive effect.
6 Methods for studying geological processes, results
Geological research methods – Geological research studies mainly the upper horizons of the earth's crust directly in natural outcrops (outcrops of rocks on the Earth's surface from under sediment) and in artificial outcrops - mining workings (burrows, ditches, pits, quarries, mines, boreholes, etc.) . Geophysical methods are mainly used to study the deep parts of the globe. Objects of geological research are:
natural bodies that make up the upper horizons of the earth’s crust (rocks, ores, minerals, etc.), in particular their structure and composition;
arrangement of natural bodies in earth's crust, defining geological structure or the structure of the latter;
various geological processes, both external and internal, as a result of which natural bodies appeared and appear, change and disappear, and the relief of the earth’s surface is formed;
causes and patterns of occurrence and development of geological processes, as well as patterns of development of the Earth as a whole.
System of geological research methods
Geological research of a certain territory begins with the study and comparison of rocks observed on the surface of the Earth in various natural outcrops, as well as in artificial workings (pits, quarries, mines, etc.), thus conducting field research. Rocks are studied both in their natural occurrence and by taking samples, which are then subjected to laboratory research.
A mandatory element of a geologist’s field work is geological surveying, accompanied by compilation geological map and geological profiles. The map depicts the distribution of rocks, indicates their genesis and age, and, if necessary, also the composition of the rocks and the nature of their occurrence. Geological profiles reflect the relative vertical position of rock layers on mentally drawn sections. Geological maps and profiles serve as one of the main documents on the basis of which empirical generalizations and conclusions are made, the search for and exploration of mineral resources is justified, and conditions during the construction of engineering structures are assessed.
Physical-geological and engineering-geological processes and phenomena
Engineering geodynamics and its tasks
Geological processes and phenomena – call processes that occur in the earth’s crust under the influence of natural factors, and generate phenomena that change the natural situation and environment.
Processes associated with human production and construction activities are calledengineering-geological.
Engineering geodynamics studies geological and engineering-geological processes and phenomena with the aim of their quantitative forecast, establishing the intensity of their development, identifying the degree of threat to surrounding areas or structures being built.
Engineering geodynamics deals with issues of protection and use of the geological environment as an integral part of the external environment.
p.p.
Processes and determining factors
Types of phenomena
Action of climatic factors: weathering, permafrost processes
Weathering, cryogenic and post-cryogenic phenomena
Wind activity (aeolian pr-sy)
Waving, evoking
Surface water activity
Streak erosion, gully formation, geological activity of rivers, abrasion, mudflows
Groundwater activity
Suffusion, quicksand
Activity of surface and groundwater
Karst, subsidence
The effect of gravity on slopes (slope or gravitational processes)
Landslides, collapses, screes, kurums, avalanches.
Manifestation internal energy Earth
Seismic phenomena, volcanism.
The impact of human production and construction activities
Deformation of the base of structures, displacement of mining operations during underground work, subsidence of the earth's surface during the exploitation of mineral resources, increased seismic activity in connection with the construction of reservoirs.
Processes associated with the activity of weathering factors
Weathering is the process of continuous change and destruction of rocks under the influence of a number of external factors. The weathering process begins at the surface and spreads to depth, gradually changing the parent rock. As a result of weathering processes, a weathering crust or eluvium is formed, which is divided into (from bottom to top): monolithic, blocky, fine-clastic zones and a zone of fine crushing.
There are three types of weathering: physical, chemical and biological.
Physical weathering manifests itself in the mechanical destruction of rocks, which leads to a change in their granulometric composition and the formation of clastic soils.
Chemical weathering manifests itself in change chemical composition rocks as a result of dissolution, oxidation, hydration and dehydration of the minerals that make up the rock.
Biological weathering – destruction of rocks during the life of plants, animals and microorganisms.
Chemical and biological weathering is most intense in warm, humid climates, while physical weathering predominates in arid climates with sharp changes in day and night temperatures.
Measures to combat weathering: removal of eluvium that covers the slope and threatens collapses, landslides, shortage of soils to the design level if these soils are subject to rapid weathering.
Which processes and phenomena are called geological, and which are called engineering-geological? What is a process and phenomenon?
What is a determining factor and what types of geological processes are divided into depending on this factor?
Describe the types of weathering and the structure of the weathered zone.
Aeolian processes
The geological role of wind is determined by its energy and consists of two processes: destructive (rock) and transportable (deflation of loose sediments).
These processes lead to the knocking out of rock particles from the rock massif and the transfer of large amounts of fine-clastic material to lower parts of the relief, which forms a desert landscape.
Forms of aeolian deposits:
Dunes are sand hills that move slowly in the direction of the wind (speed 30 m/year).
Dunes are sandy ridge-shaped hills stretched along the coast, moving inland.
Ridge sands are deposits of aeolian sands elongated in the form of ridges or shafts in semi-desert areas.
Humpy sands are lower than ridge sands, hill-like formations with gentle slopes, covered with vegetation.
Measures to combat aeolian processes
The threat lies in the fact that when barchans or dunes move, huge masses of sand are displaced, which fill up roads, irrigation canals and structures, and populated areas.
Construction and operation require constant control of moving sands.
For this purpose, the following measures are applied:
Installation of shield fences along roads and canals to delay the movement of sand;
Consolidation of sands various types emulsions and solutions;
Phytomelioration - planting plants, creating forest belts, sowing herbs, etc.
Security questions:
List the types of wind activity and the areas where it occurs in the Republic of Kazakhstan.
Name the forms of aeolian deposits.
Name the measures to combat aeolian processes.
Processes associated with the activity of surface waters
The following processes are considered here: river erosion, sea (lake) abrasion, gully formation, mudflows.
River erosion
The erosive activity of the river is carried out in several different ways:
with the help of sediments carried by river flows, which act on the bedrock of the river bed as an abrasive material;
due to the dissolution of bed rocks (organic acids dissolved in water play an important role in this);
due to the hydraulic effect of water on the loose material of the bed (washing out loose particles);
Additional factors may include destruction of coastlines during ice drift, thermal erosion processes, etc.
Erosion can be aimed at deepening the bottom of the valley - bottom (or deep) erosion, or at eroding the banks and widening the valley - lateral erosion. These two types of erosion act together.
Development of deep (a) and lateral (b) erosion
The intensity of deep erosion is determined primarily by the slope of the channel (and, accordingly, the energy of the flow). When deep erosion predominates, deep incisions with steep banks and V-shaped section river valley, the floodplain is developed fragmentarily (on islands and small areas near the convex banks of bends). In the relief, such areas are often represented by deep canyons.
The intensity of lateral erosion depends on the angle of approach of the flow to the shore. Rod - a line connecting the points of highest speeds on the surface of the water. In straight sections, the core is usually located near the middle of the watercourse; under such conditions, lateral erosion does not occur. In winding sections, the stream is deflected towards one of the banks, which leads to compression of the flow and its “running” onto this bank, accompanied by erosion of the latter. “Pressing” the flow to the shore causes the formation of a circulation current, the bottom branch of which is directed to the opposite shore. Since the bottom layers are most saturated with clastic material (including that formed due to bank erosion), the material moves from the eroded bank to the opposite one, where it accumulates in the form of a riverbed shoal. The formation of a riverbank shallow leads to an even greater curvature of the channel and deviation of the stream towards the eroded bank, determining the direction of lateral and deep erosion. The highest rate of bank erosion is observed where the flow core is pressed against it. Upstream and downstream there is a sequential change in the zone of very strong erosion - strong, medium, weak and, finally, the bank stops eroding and turns into a riverbank shoal. Thus, the bending of the channel leads to the formation of zones of acceleration and deceleration of the flow and transverse circulation, alternating along the coast, directed from the concave to the convex coast.
Various conditions of interaction of river flow with river banks (according to R.S. Chalov):
A – the core passes in the middle of the channel, the banks are not washed away;
b – the flow approaches the shore at an angle, causing compression of the jets and erosion of the shore;
at an accumulative shoal is formed on the opposite shore
(h – excess of the water level at the concave shore at the average level in this section).
According to the mechanism described above, in the process of bank erosion, sharp bends of the river valley - meanders - are formed. Narrow “partitions” between meanders can be eroded during floods, which leads to straightening of the river bed and the formation of oxbow lakes. An oxbow lake is a closed body of water, usually of an oblong winding or horseshoe shape, formed as a result of the complete or partial separation of a section of a river from its former bed. Oxbow lakes can maintain a connection with the river for some time, but gradually their entrances are filled with river sediments - they turn into oxbow lakes, and then into swamps or damp meadows.
In the bed of meandering rivers, with a decrease in the bed slope and tortuosity, alluvial islands can appear. In wide areas of the valley, with relatively straight contours of the channel and floodplain, a series of such islands can form, which leads to the branching of the channel - its division into several streams. These islands move downstream, constantly changing their shape.
The rate of erosion is determined by a combination of a number of factors: flow energy, bedrock composition, vegetation development, intensity of technogenic impact, etc. The dependence of the rate of bank erosion on the rock composition is given in the table.
River erosion often leads to the activation of other exogenous geological processes. Thus, intense deep erosion leads to the formation of canyons and V-shaped valleys with steep slopes, on which landslide and scree processes actively manifest themselves. The undermining of high banks composed of difficult-to-erode rocks due to lateral erosion leads to the development of landslides, screes and landslides.
Marine (lake) abrasion
In terms of the threat to structures, the more important is the destructive activity of the sea or abrasion, which leads to the retreat of the shore edge towards the land, the collapse of large blocks of rock, the destruction of protective structures and the occurrence of secondary phenomena such as landslides.
Factors contributing to the occurrence of abrasion are divided into two groups:
Wind and tidal waves, solid debris carried by waves and sea currents;
Lithological composition and conditions of occurrence of rocks in the coastal strip, water resistance of rocks, shape of the coastal slope.
The determining factor in abrasion is the energy of wind and tidal waves, which is formed under the influence of wind and has high erosion energy.
Sea currents with relatively low speed practical significance they do not have a role in the erosion process, but they play a large role in the erosion process.
Thus, the main destructive factor of abrasion is the impact force of the wave.
The second group of factors depends on the rocks of the coastal slope. This is primarily the lithological and petrographic composition of the rocks. Slopes composed of loose sandy-clayey deposits are destroyed much faster than those composed of rocks.
Rock conditions also play a role significant role when the shore is destroyed. In the case of formations falling towards the shore, its collapse occurs most quickly, because water cuts off a whole pack of layers or the full thickness of the layer. With a horizontal occurrence, the destruction of the coast slows down somewhat, and it proceeds most slowly when the layers gently dip towards the sea.
Also, the water resistance of rocks plays a big role in determining the intensity of abrasion. The shape and steepness of the coastal slope plays a very important role.
Measures to combat shore recycling:
Gully formation.
The formation of ravines begins with the formation of erosion grooves - transitional forms from planar to linear erosion of the surface of the slopes. Furrows arise due to the flat runoff of rain and melt water when small streams merge in the lowest parts of the slope. Further erosion in the furrows leads to the formation of larger forms - potholes. Potholes are characterized by steep, unturfed sides and a longitudinal profile close to that of the slope. Due to the largest and fastest growing potholes, in the process of their deepening and expansion, ravines are formed that have a longitudinal profile different from the profile of the slope. The bottom of young ravines is uneven. As the ravine deepens further, the profile of the ravine gradually levels out due to the development of deep erosion, aimed at approaching the base level of erosion. The upper part of the ravine is a steep ledge, due to the erosion of which the ravine moves up the slope. This process of growth upstream of a stream is called regressive or backward erosion. The growth rate of ravines can be very high and reach several meters per year; When developing gullies that complicate the slopes of ravines, a branching gully system may arise. As the ravine develops, its source approaches the watershed, and its mouth approaches the erosion base; its longitudinal profile acquires a concave shape, and its transverse profile becomes V-shaped, with steep, unturfed slopes. Under conditions of insignificant deepening speed, the ravine expands, it acquires a U-shaped profile and then turns into a ravine - an erosional form characterized by the presence of a flat bottom and gentle slopes fixed by vegetation.
The water flow moving along the bottom of ravines and gullies during rains and melting of solid sediments transports small debris material. In the lower reaches of a ravine, where the energy of the flow decreases, gully alluvial cones can form.
Measures to combat gully formation:
Sat down
The origin of temporary mountain streams is associated with heavy rains and intense melting of snow and glaciers. In the upper part of the mountain slopes, a system of converging potholes and gullies forms a drainage basin. Below is the drainage channel - the channel along which water moves. The significant slope of the channel determines the high energy of the flow; along the path of movement it picks up a large amount of debris of different sizes. Saturation with debris can turn a water flow into a mudflow - a temporary destructive flow overloaded with mud and stone material. In a mud-stone flow, which has a significantly higher density than water and high kinetic energy, even blocks up to several meters in size can move. Mudflows can also form when large masses of debris collapse into mountain rivers, or when glacial or dammed lakes break through.
When entering the foothill plain, the speed of water or mud-stone flows decreases, the streams branch, and the transported material is deposited, forming a temporary mountain stream alluvial cone in the form of a semicircle, the surface of which is inclined towards the foothill plain.
Methods for combating mudflows
There are active and passive methods struggle.
Passive ones represent the fight against flows in the area of transit and unloading, i.e. at the moment when the mudflow had already begun. This method provides for the construction of retaining walls, slope tracing and the installation of special mudflow storage facilities along the path of the mudflow.
Active methods of fighting mudflows involve activities within the nutrition area, i.e. in the places where the mudflow originates:
Diversion of the liquid phase of the surface flow from the site of future mudflow occurrence;
Preservation of soil vegetation within the outbreak;
Planting the slope with herbaceous or shrub plants, securing the hard surface of the slope;
Systematic observation of glaciers and artificial regulation of their volume.
Security questions:
Name all the processes associated with the activity of surface waters and their determining factor.
What determines the intensity of gully formation?
Describe the stages of development of a ravine.
Draw a diagram of measures to combat ravines.
What is the geological activity of rivers and what are its consequences?
List measures to combat the adverse effects of water erosion.
Name the factors that determine the wave activity of seas and lakes; what does this activity lead to?
Processes associated with groundwater activity
Suffusion
Suffusion is the process of removing soil particles (mechanical suffusion) or easily soluble salts(chemical suffusion) by a flow of underground water with the formation of voids, craters, failures, sometimes accompanied by subsidence of the earth's surface.
Suffusion occurs most actively under the following conditions:
The hydraulic gradient must be greater than 5, which ensures turbulent movement;
The ratio of large and small fractions should be more than 1:20.
The most active suffusion occurs at the contact of two layers if the ratio of filtration coefficients is more than two.
For each soil rock, there are critical speeds, starting from which the suffusion process is activated.
Chemical suffusion occurs in saline soils. When studying suffusion, they carry out following works:
The geomorphology of the area is being studied;
Hydrogeological conditions;
The regime and physical and mechanical properties of aquiferous soil, especially close to the surface, are being studied.
Forms of manifestation of suffosion: suffosion sediment, loess karst, suffosion landslides.
Measures to combat suffusion
Correct selection of a water intake well filter, installation of bulk filters, gravel filters.
Preventing water from reaching areas prone to suffusion through drainage.
Protection of clay-inhabited rocks by installing special coatings (waterproofing).
Reducing the velocity of groundwater near structures by creating artificial barriers to flow.
Reclamation methods to reduce the water conductivity of rocks (bituminization, clayization).
Quicksands
Quicksand are sandy-clayey, water-saturated soils that behave like viscous liquids. When they are opened by a recess, they liquefy and begin to move towards the recess. When free, they have no load-bearing capacity.
According to their composition and properties, quicksand can be true or false.
False soils are ordinary uncohesive separate-grained soils, which turn into a quicksand state as a result of complete water saturation and the occurrence of hydrodynamic pressure of a moving soil flow in them.
True quicksand can be varied in their granulometric composition - from sand to loam. In these soils there are structural bonds of a colloidal nature. They have high hydrophilicity and low strength. During impacts, shocks, and vibrations, part of the bound water is released, the soil structure is destroyed and it liquefies (thixotropy).
Control methods: freezing, silicization, electrofusion, drainage, electric drainage.
Security questions:
List and briefly describe the processes associated with groundwater activity. What is the main determining factor of these processes?
What is suffusion and in what types and forms does it manifest itself?
What are quicksand and what is the property of their thixotropy?
Processes associated with the activity of surface and groundwater
Subsidence in loess soils
Discussed in detail in the chapter “Soils of special composition and properties.”
Methods to combat drawdowns
Construction of water protection devices and drainage structures.
Application of methods for reclamation of loess rocks: mechanical compaction, roasting, etc.
Karst
Karstom called the process of dissolution of rocks and the formation of specific forms of karst relief.
For the active development of karst, the following conditions are necessary: the presence of easily soluble karst rocks, provided they are located above the base of erosion, the dissolving activity of surface and groundwater is determined by the mineralization, pressure and chemical composition of surface and groundwater and the speed of their movement.
Great value During the process of karst formation, it acquires an erosion base - the lowest absolute level to which groundwater flows. In this regard, it is possible to distinguish zones of karst development: aeration zone, zone of seasonal level fluctuations, zone of deep circulation.
Engineering-geological assessment of karst and control methods.
As methods for studying karst, one should first highlight the work of identifying signs of karst and determining the intensity of development. For this purpose, there is a classification of the territory according to its resistance to karst. Rocks are considered unstable if 5-10 karst sinkholes are formed per 1 km 2 per year, sustainable 1 funnel per 1 km 2 .
Karst caves.
Karst failure.
Fighting methods
Territory planning;
Surface water drainage;
Captage or drainage of groundwater;
Installation of anti-filtration curtains;
Consolidation of karst rocks using technical reclamation methods.
Landslides
A landslide should be understood as the movement of masses of rocks down a slope under the influence of gravity, associated in some cases with the activity of surface and groundwater and having the nature of sliding or displacement of rocks along a slope.
Landslide elements:
Vao vypora is an elevation formed at the base of a slope and consisting of disturbed and crushed soils.
The body of a landslide is the entire mass of sliding material along a soil slope, limited in depth by the sliding surface (mirror).
Landslide terraces are a series of ledges located one below the other and oriented parallel to the edge of the slope.
The failure wall is the upper part of the sliding surface, formed as a result of the downward displacement of the landslide body.
Above the landslide ledge is an area adjacent to the landslide, located above the edge of the slope, not subject to landslide.
The sliding surface (sliding surface) is the surface along which the landslide moves.
Signs of a landslide
For timely prediction of a landslide, the following set of features to be analyzed is recommended:
Landslide cracks are a system of various cracks that form a sliding surface over time.
The formation of a landslide circus is determined by repeated leveling.
Formation of cracks on the future sliding surface (detected by drilling).
The presence of shafts at the foot of the landslide slope.
Presence of landslide ledges (by leveling).
The presence of stagnation of water, swampy areas within the landslide circus, which appears when the slope moves as a result of disruption of the hydrogeology of aqueous soils.
The presence of hilly areas on the slope, formed as a result of the flow of loose soil around rocks over harder areas of the sliding surface.
Increase in rock moisture and disruption of the structure in the sliding surface zone (determined by geophysical methods).
Violation of the integrity of layers and changes in the elements of their occurrence.
Violation of the integrity of buildings and structures.
Landslide classifications
Savarensky classification
Principle: relationship between the position of the sliding surface and the bedding surface.
Asequential - this landslide manifests itself in homogeneous rocks, when the sliding surface is outlined along the line of greatest weakening of the structural bonds between particles. Most often, such a landslide occurs in sandy soils.
Consequential - common in layered massifs, with the slip plane parallel to the bedding plane. Typically, failure occurs along the base of the most weakened layer.
Incidental – the most catastrophic in nature of manifestation. Here, the stability of the slope is determined by the mechanical strength of the bearing layer. Such landslides are typical for the banks of rivers and lakes.
Rodionov classification
Principle: The reason that causes a landslide to move depends on its structure.
There are 3 main types of landslides:
Structural landslides are those where displacement occurs as a result of a change in the structure of rocks (weathering).
Consistent - most often occur in clayey rocks as a result of changes in humidity, and therefore the consistency of the soil.
Suffusion landslides - occur most often in sandy rocks due to the weakening of structural bonds during intense suffusion.
Popov classification
Principle: according to age and genesis.
There are 2 groups: modern landslides, ancient landslides.
In turn, modern landslides according to their development phase are divided into moving, suspended, stopped, and completed.
According to the phase of development, ancient landslides are divided into ancient and buried.
Drannikov classification
By the nature of the displacement and the depth of capture.
Surface landslides covering the depth of seasonal changes: slumping, solifluction flows.
Deep landslides: step, sliding, extrusion, suffosion landslides.
Quantitative methods slope stability assessment
Of great importance for forecasting is the calculation of slope stability, which depends on two groups of factors.
Stimulating the occurrence of a landslide or movement (mass, configuration, geological structure, presence of vegetation, mechanical influences, various geological processes such as weathering, changes in relief, geotectonics, erosion, abrasion);
Another group of factors includes reasons that prevent the occurrence of landslides (increasing the base of erosion, climate, development of vegetation on the slope).
The first group of factors determines the increase in strength properties that hold the slope.
The second group can be represented as a set of factors that shift the slope. A slope stability coefficient was proposed, which is equal to:
Where the sum signs show the totality of these characteristics taken for individual landslide blocks:
WITH i – adhesion coefficient
tg i – angle of internal friction.
P i – the mass of a given block, which contributes to sliding.
M i is a collection
From this formula it can be seen that if Ku>1, then the slope is stable, if Ku<1, то происходит оползень. и если Ку=1, то склон находится в неустойчивом состоянии.
Using this formula, during normal operation, observations of all parameters are carried out, based on the results of which graphs of the dependence Ku = are constructed.f( t)
The following situations are possible:
The graph is decreasing, approaching the Ku line<1, что говорит о снижении устойчивости склона (ситуация требует срочного вмешательства).
The position of the slope is quite reliable and stable; in this case, various kinds of restrictions on elephants are possible (construction, water consumption, dynamic loads) depending on the proximity of the Ku=1 graph.
It speaks of an increase in slope stability, which is determined by natural factors and the phase of development of the slope.
Landslide Study Methods
The calculation method is based on determining Ku and calculating the sliding surface.
The modeling method is based on making models of the slope and artificially increasing the forces that reduce the stability of the slope.
Method of analogy - here the identity of the geological, geomorphological structure of a given slope is established with the slope, the location of which has been studied for a long time.
Historical-geological method - this method involves comparing the geological conditions of the landslide at the present time and in the past and, in connection with this, assessing the phase of development of the landslide.
Accounting methods - involves taking into account the balances of all earth masses and the influence of factors that change the stability of the slope.
Dynamics of the landslide process
A landslide, as experience shows, goes through three stages of development:
Preparatory – lies in the fact that various factors. At this stage, the main task of geologists is to assess the K slope, indirectly study the emerging sliding surface, and analyze landslides developing in this phase in the past.
The displacement of earthen ramparts is not yet a landslide, but under the influence of factors that reduce the stability of the slope, individual movements of parts and the massif as a whole begin to appear.
The landslide process itself is characterized by the moment when Ku<1. Задача геологов – изучение механизма смещения, создание легенды процессов для архива.
Methods for studying landslide processes
Study of archival materials for the region.
Collection of meteorological and climatic data, study of hydrogeological conditions.
Conducting engineering-geological surveys on a scale: for the region - 1:50,000, for the site - 1:2,000 and larger. Including:
Mining and drilling works.
Hydrometric works.
Laboratory determination of indicators.
Field experimental work.
Stationary observations.
Geophysical work.
Landslide control methods
All methods of struggle can be divided into the following areas:
Development of measures that lead to the neutralization or reduction of activities that reduce the stability of the slope.
Development of measures to increase slope stability.
Measures aimed at reducing the amplitude of slope stability fluctuations.
The first group of activities includes the following:
combating the processing of river and lake banks;
artificial or natural drainage preventing access to p.v. to the sliding surface;
prohibition of the construction of structures within the landslide slope, construction of structures that create dynamic loads near the slope.
The second group of activities includes:
artificially securing the slope with driven piles;
installation of retaining walls, construction of drainage systems and other measures that reduce water inflows to landslide areas.
The third group of methods includes preventive measures:
prohibition of drilling and blasting operations and geological excavation within the landslide area.
Prohibition of construction of structures with dynamic loads.
Landslides, rockfalls, screes
Collapses is a sudden collapse of large masses of rock from mountain slopes, accompanied by overturning and crushing. They arise as a result of weakening of internal bonds due to weathering and moistening of rocks.
According to the composition of the collapsed rocks, landslides are divided into stone, earthen and mixed.
Rockfalls - or fallouts are the fall of individual stones or blocks from the slopes. The cause of rockfalls is most often precipitation, which leads to an increase in the force of gravity on the slope and a decrease in the force of friction and adhesion.
Screes - an accumulation of blocky or detrital material on a slope and at its base is called.
The angle formed by a scree with a horizontal plane is called the angle of repose and depends on the size and degree of rounding of the particles: the larger the fragments and the greater their angularity, the steeper the angle of the scree and vice versa. Depending on these conditions, screes are divided into active, fading and stationary.
Kurums are called screes consisting of coarse material, located in most cases at the foot of the slope in the form of a trail and having very flat surfaces.
Methods of dealing with landslides and screes
Landslides, rockfalls, and screes pose a great threat to the existence of various structures in the mountains and foothills. In all cases, control methods are divided into:
Preventative, aimed at preventing the phenomenon or stopping its development in the initial stage.
Engineering, aimed at eliminating the action of the process or reducing its intensity.
In places where powerful, permanent rock slides develop, protective reinforced concrete galleries or even tunnels are installed. Stopping the movement of kurums is much more difficult, and here the main method of control comes down to draining the clayey litter on which they are located. In rock formations, cementation of fractured rocks is used.
Security questions:
Give a general engineering-geological assessment of slope processes.
What is a landslide? List the elements of a landslide.
Name the determining and accompanying factors that cause landslides.
What are the natural conditions that accompany the active development of landslides of various types?
What are the characteristics of different types of landslides?
How is the degree of slope stability assessed? What methods do you know for calculating stability?
Tell us about measures to combat landslides.
What is a rock fall? Give a classification of landslides.
What are screes and what types are they divided into?
What are kurums and what explains their mobility?
List preventive measures to combat slope processes.
Processes associated with freezing and thawing of rocks
(permafrost processes)
Structure of the permafrost layer
Rocks that have a negative temperature and contain ice are called frozen.
TOseasonally frozen - These include rocks that thaw in the summer and freeze in the winter.
Permafrost Rocks are those rocks that remain frozen for hundreds and thousands of years. The zone of permafrost development is calledcryolithozone .
Vertically, the cryolithozone is divided into two parts:
The top layer is the active layer or the layer of seasonal freezing and thawing.
The lower one is actually frozen soils, rocks, the temperature of which is never positive.
In the geological section, two types of permafrost are distinguished: merging and non-merging.
Confluent permafrost is a geological structure in which the active layer, when frozen, directly transforms into permafrost.
Non-merging permafrost is a structure of the geological section when a layer of thawed soil remains between the frozen active layer and frozen soils, i.e. The thawing layer turned out to be greater than the freezing layer.
Geological phenomena of the permafrost zone
Frost heaving - this is an increase in the volume of water-saturated soils as a result of the expansion of water in the pores during freezing.
Frost heaving manifests itself in the form of abysses - elevations of the earth's surface 0.2-0.5 m high, elongated in the form of heaving mounds, which are formed as a result of the raising of rocks of the active layer by the underlying mass of ice, continuously increasing in volume as a result of recharge under frozen waters.
Thermokarst is a phenomenon of subsidence and subsequent formation of dips, saucers, and craters on the surface of permafrost during thawing and ice accumulation in the spring.
Naledi - Naledi differ from heave mounds in that they are a cloak-like, stream-like accumulation of ice on the surface of the earth, formed as a result of the outflow and freezing of river or groundwater.
Solifluction is the name given to the movement of loose water-saturated sediments from slopes under the influence of gravity as a result of thawing of permafrost.
Measures to combat permafrost phenomena and processes
Construction of structures without taking into account the frozen state of the soil. This applies to rocky and semi-rocky frozen soils and other rocks that do not give significant subsidence after thawing.
Construction of structures in compliance with the conditions for maintaining the thermal regime throughout the entire period of their operation. This option is applicable in the case of high icy soil content, which threatens unacceptable deformations of the base when heat comes from the structure.
Construction of structures that allow significant deformation of the base in conditions of soil thawing (coarse clastic ice deposits in which uplift of the base soil is excluded).
Construction with preliminary thawing of soils and the use of various methods for their compaction and improvement.
Security questions:
Describe the distribution of permafrost.
Give a description of the permafrost zone and types of permafrost.
What types of permafrost are divided into?
Describe cryogenic and post-creogenic processes and explain the difference between them.
List the measures used to combat cryogenic and post-cryogenic phenomena.
Processes associated with seismicity
An earthquake is usually understood as intense vibrations of the earth's surface caused by strong underground tremors resulting from the release of a huge amount of internal energy of the Earth.
The point at which a seismic shock occurs, lying at some depth from the surface, is called the hypocenter. The projection of the hypocenter onto the daylight surface is called the epicenter.
Based on their origin, there are five types of earthquakes:
Tetanic , caused by tectonic movements of the earth's crust and making up the vast majority of earthquakes. They are characterized by a wide areal distribution and high intensity.
Volcanic, associated with volcanic eruptions. They have a local distribution, but can be very powerful.
Denudation (landslide, failure), generated by the fall of large masses of rocks from the slopes or failures in the process of karst formation. They also have a local character and a relatively high magnitude.
Technogenic, resulting from explosions carried out for engineering and construction purposes.
Marine (seaquakes or tsunamis), associated with the rise of the seabed and the resulting destructive sea wave.
The intensity of an earthquake depends on the composition and condition of the rocks in the environment in which seismic waves propagate, the depth of the groundwater level, tectonic disturbances, the nature of the relief and the depth of the earthquake source.
Principles of anti-seismic construction
When designing buildings and structures in seismic areas, the intensity and frequency of seismic impacts should be taken into account. For this purpose, seismic zoning maps have been compiled, which give an idea of the zones where earthquakes occur and their intensity.
The destruction of a structure begins depending on its distance from the epicenter of the earthquake, either as a result of a vertical shock or under the influence of a horizontal shear component of a surface wave.
The immediate cause of structural failure is the inertial force resulting from a seismic shock in the mass of the structure.
If the period of vibration of the base coincides with the natural vibration of the structure, the magnitude of the inertial forces can increase several times compared to the calculated value. Therefore, when choosing a site for a future structure, it is necessary that the period of natural vibrations of the structures differ sharply from the period of vibrations of the base.
The basic principles of survey and construction in seismically active areas are as follows:
Carrying out seismic microzoning to clarify the increment in magnitude and performing calculations of the structure taking into account seismic forces.
When choosing optimal conditions for the placement of future structures, it is necessary to avoid areas composed of loose, waterlogged or water-saturated soils.
Structures should not be placed on areas of sharply rugged terrain or in areas where slope or karst processes develop.
Security questions:
What is meant by an earthquake and what are the causes of this phenomenon?
What types of waves transmit oscillatory movements during an earthquake?
What types of earthquakes do you know?
How can you estimate the strength of an earthquake?
What natural factors influence the intensity of an earthquake? What are earthquake harbingers and what does earthquake forecasting come down to?
What are the principles of anti-seismic zoning?
Processes associated with human engineering
Processes caused by static loads from engineering-geological structures and built-up areas.
The determining factor in this process is the pressure from the weight of the building and structure transmitted to the foundation soils. The process of settlement from structures is also observed on bulk and alluvial soils that are not sufficiently “packed” after laying the foundation.
Deformation of the foundation soil as a result of compaction by loads from structures.
This deformation is called settlement and is expressed in a change in the elevation of the earth's surface under the structure or in a change in the power of the core.
Acceptable This is called a settlement of a structure that does not lead to disruption of its operation.
Processes caused by dynamic loads and explosions.
Dynamic loads arise during the operation of various mechanisms, in places of constant traffic, as well as during mining. In rocks, dynamic loads lead to the opening of cracks and landslide phenomena.
Processes that occur during underground mining.
Development of solid p.i. underground method, with the formation of large-volume cavities, leads to the emergence of rock pressure in these cavities, which leads to the movement of rocks towards the mine. The displacement begins to develop from the workings and has the following zones:
Collapses - closest to the mined-out space, where the rock is characterized by a complete loss of internal bond strength;
Fractures – characterized by a break in the continuity of rocks with the formation of cracks from several millimeters to meters;
Smooth movements are a zone of movements and deformations that are not accompanied by a violation of continuity.
Processes arising during the implementation of water management activities.
Long-term moistening of the surface layer of soil through systematic irrigation and transportation of water through the canals of the irrigation network leads to a violation of the existing hydrogeological conditions of the territory: an increase in the level of groundwater, changes in their chemical composition, and salinization of surface horizons.
Processes caused by the creation of large reservoirs in river valleys.
The construction of large waterworks in river valleys causes the activation of exogenous and endogenous processes in the surrounding geological environment. Activation of the former leads to reworking of the banks of the reservoir, erosion, landslides, landslides, as well as suffusion, karst and subsidence caused by the backing up of groundwater, activation of the latter leads to seismic activity, expressed in the appearance of initially weak, and over time, intensifying local earthquakes.
The appearance of seismic tremors in seismically inactive areas or a sharp revival of seismic activity in connection with the construction and filling of reservoirs.
The additional load from water when filling the reservoir contributes to the lowering of its bed, affects the change in pore pressure in the formations and leads to the release of seismic energy, which causes an earthquake.
Security questions:
What processes and phenomena are called engineering-geological and how does it differ from natural geological processes?
What is foundation soil settlement and what causes it? What is the difference between settlement and subsidence?
What can result in soil uplift from under the structure?
Topic: General information. Endogenous geological processes
1. Classification of geological processes. Endogenous processes.
2. Tectonic movements of the earth's crust.
3. Tectonic processes and phenomena. Forms of tectonic dislocations.
4. Weathering. Eluvium
1. Classification of geological processes. Endogenous processes.
Geological are processes occurring in the interior of the Earth or on its surface and associated with the formation, movement or destruction of rocks. These processes are constantly changing the appearance of our planet.
Distinguish endogenous(internal dynamics) and exogenous(external dynamics) processes.
The main driving force endogenous processes is the energy that is released due to the redistribution of matter in the bowels of the Earth, the radioactive transformation of elements, and chemical reactions.
These include: magmatism, metamorphism, volcanism, earthquakes and rock formation.
Exogenous processes act under the influence of solar energy. They are manifested in the interaction of the lithosphere with the atmosphere, hydrosphere and biosphere.
Endogenous (internal) processes are those geological processes whose origin is associated with the deep interior of the Earth. The substance of the globe develops in all its parts, including the deep ones. In the bowels of the Earth, under its outer shells, complex physical-mechanical and physical-chemical transformations of matter occur, as a result of which powerful forces arise that act on the earth’s crust and radically transform the latter. These transformative processes are called endogenous processes.
Endogenous processes are most clearly expressed in the phenomena of volcanism, which are understood as processes associated with the movement of magma both into the upper layers of the earth's crust and onto its surface.
The phenomena of volcanism acquaint people with matter located in the depths of the globe, with its physical state and chemical composition. Manifestations of surface volcanism do not occur everywhere, but are confined to certain areas of the earth's crust, the position and area of which have changed during geological history.
Magma, penetrating into the earth's crust, very often does not reach the surface, but solidifies somewhere at depth, forming deep, intrusive rocks (granite, gabbro, etc.). The phenomenon of magma intrusion into the earth's crust is called deep volcanism, or plutonism.
The second type of endogenous processes are earthquakes, which manifest themselves in certain areas of the earth's surface in the form of short-term tremors or tremors. The phenomena of earthquakes, as well as volcanism, have always captured the human imagination. In cases where shocks occurred in populated areas, earthquakes brought significant disasters to humanity: the death of many people, destruction of buildings, etc.
In addition to short-term and strong vibrations such as earthquakes, the earth's crust experiences vibrations during which some parts of it sink and others rise. The movements occur very slowly at a speed of several centimeters or even millimeters per century; they are inaccessible to direct observations without instruments. But since these movements occur everywhere and continuously for many millions of years, their final results are very significant.
As a result of these oscillatory movements, many areas that were previously dry land have become the bottom of the ocean and, conversely, some areas of the earth's surface, now rising hundreds and even thousands of meters above sea level, retain evidence that they were once under water. The intensity of oscillatory movements is not the same: in some areas of the earth's crust, the subsidence or uplift is more significant, in others it is less significant.
One of the most striking manifestations of internal forces is folding and discontinuous deformations of the earth's crust. These phenomena, in most cases inaccessible to direct observation, are clearly reflected in the nature of the occurrence of sedimentary rocks that make up the earth's crust. Sediments of the seas and oceans, falling out of the water, usually fall in even horizontal layers. As a result of folding, these horizontally lying layers turn out to be assembled into various types of folds, and sometimes torn or pushed over each other.
The phenomenon of collapse and rupture of layers contributes to the formation of hills and mountains, depressions and basins. Many scientists attributed the main role in the formation of mountains to the phenomenon of folded deformations, believing that rocks, crumpling into folds, swell the earth's surface and form hills. This process is called orogenesis (“oros” - in Greek, elevation, “genesis” - formation). It has now been established that oscillatory movements play no less a role in the formation of mountains than folded ones, therefore the term “orogenesis”, having lost its original meaning, began to be used less frequently.
Folded deformations appear only in certain, most mobile and most permeable to magma areas of the earth's crust, called geosynclines. In contrast, stable areas with weak tectonic activity are called platforms.
Folding deformations, earthquakes, and especially volcanism contribute to significant changes in the rocks that make up the earth's crust. Due to compression, they become denser and harder, and under the influence of high temperatures they are burned and even melted. The action of vapors and gases released from magma contributes to the formation of new minerals in rocks. All these phenomena of transformation of rocks under the influence of endogenous processes are called metamorphism (“metamorphism” means transformation in Greek) and are also associated with deep forces.
Endogenous processes therefore include volcanism, earthquakes, oscillatory movements (or epeirogenesis), folding and faulting, and metamorphism.
Of all types of endogenous phenomena, only oscillatory movements, as mentioned earlier, appear more or less uniformly throughout the entire earth's crust; all other phenomena are concentrated mainly in the moving geosynclinal belts of the Earth.
Endogenous processes radically change the nature of the earth's crust and, in particular, its surface; they lead to the creation of the main forms of relief of the Earth's surface - mountainous countries and individual hills, huge depressions - reservoirs of oceanic and sea water, etc.
Forms created by endogenous forces are in turn subject to the action of exogenous forces. The hills are eroded by rivers and blown by the winds; At the foot of the hills, powerful proluvial-deluvial plumes accumulate, depressions are filled with sediments, and the banks of the depressions are eroded by waves. Endogenous forces tend to dismember and complicate the relief of the earth's surface, and exogenous forces denudate, i.e., level the earth's surface. The development of the earth's crust and its surface occurs through the interaction of exogenous and endogenous processes.
2. Tectonic processes and phenomena. Forms of tectonic dislocations.
Tectonic disturbances are movements of matter in the earth's crust under the influence of processes occurring in the deeper interior of the Earth. These movements cause tectonic disturbances, i.e. changes in the primary occurrence of rocks. These changes are especially clearly observed in the example of sedimentary rocks, which are initially deposited in the form of horizontally lying layers, and due to tectonic disturbances they are crushed into folds or torn into separate scales and blocks. Tectonic movements ultimately create the observable structure of the earth's crust, i.e. they are creative movements (“tectonos” in Greek - creative). As a result of these movements, the main irregularities in the relief of the Earth's surface arise.
Tectonic movements can be divided into two types: radial – oscillatory, or epeirogenic movements, and tangential , orogenic. In the first type of movement, stresses are transmitted in a direction close to the radius of the Earth, in the second - tangentially to the surface of the earth's crust. Very often these movements are interconnected, or one type of movement gives rise to another. As a result of these types of movements, three types of tectonic deformations are created: 1) deformations of large deflections and uplifts; 2) folded; 3) explosive.
The first type of tectonic deformation, caused by radial movements in its pure form, is expressed in gentle uplifts and depressions of the earth's crust, most often of a large radius. The vibrations that cause the formation of such forms, unlike seismic vibrations, occur relatively slowly, do not cause tangible destruction and are not amenable to direct human observation.
Folding deformations are caused by tangential movements and are expressed in the form of folds that form long or wide bunches, sometimes short, quickly fading wrinkles.
The third type of tectonic deformation is characterized by the formation of ruptures in the earth's crust and the movement of individual sections of it along the cracks of these ruptures. Fault faults are very often derived from the first two types, but to a greater extent from fold faults. It is not always possible to establish the cause of a particular deformation, since, in addition to the above types of movements, deformations can occur due to the intrusion of magma, etc.
Tectonic processes lead to disturbances in the occurrence of GP. These violations are called dislocations.
3. Forms of occurrence of layers and dislocations.
1 anticline 2 syncline
Main types of discontinuous dislocations:
EARTHQUAKES
Earthquakes- tremors and vibrations of the Earth's surface caused by natural causes (mainly tectonic processes), or (sometimes) artificial processes (explosions, filling of reservoirs, collapse of underground cavities in mine workings). Small tremors can also be caused by the rise of lava during volcanic eruptions.
About a million earthquakes occur throughout the Earth each year, but most are so small that they go unnoticed. Really strong earthquakes, capable of causing widespread destruction, occur on the planet about once every two weeks. Most of them fall on the bottom of the oceans, and therefore are not accompanied by catastrophic consequences (if an earthquake under the ocean does not occur without a tsunami).
Earthquakes are best known for the devastation they can cause. Destructions of buildings and structures are caused by soil vibrations or giant tidal waves (tsunamis) that occur during seismic displacements on the seabed.
ERUPTIONS
Vesuvian type. Named after the famous volcano Vesuvius, located in Italy near Naples. Known for his catastrophic eruption, which broke out in 79 AD. e., which is colorfully described by the ancient Roman scientist Plipius the Younger. Then, under a layer of volcanic ash and mud flows, three cities were buried - Herculaneum, Pompeii, Stabia. This type is characterized by strong explosive eruptions due to periodic blockage of the volcano's vent, as well as the subsequent outpouring of lava flows.
Hawaiian type its peculiarity is that basaltic melts flow here relatively calmly, without explosions; the melt is weakly saturated with gases and has low viscosity, although unusually spectacular lava fountains sometimes appear. As a result of such an eruption, the volcano has very gentle slopes on which several craters are located.
Pele type Which is characterized by hot ash clouds and the growth of a dome in the crater of a volcano. For the first time, a directed explosion was observed on this volcano, covering a large area.
Vulcano type. The Vulcano volcano, located on the Aeolian Islands, is also very famous - after all, the term “volcano” itself comes from here. It is characterized by the eruption of relatively acidic volcanic products (andesite-dacite composition). Due to the high viscosity of the melt, the volcano's crater becomes clogged; the accumulated vapors and gases explode this plug, throwing ash and other lava particles of various shapes and sizes to great heights.
4. Weathering. Eluvium.
Exogenous processes include weathering processes,
Weathering(a. weathering, degradation, disengagement; n. Verwitterung; f. alteration; i. meteorizacion) - the process of destruction and change of rock in the conditions of the earth's surface under the influence of mechanical and chemical influences of the atmosphere, ground and surface waters and organisms. Based on the nature of the environment in which weathering occurs, a distinction is made between atmospheric (or terrestrial) weathering and underwater (or halmyrolysis). The main types of weathering by the type of impact on rocks; physical, chemical and organic (biological).
Physical weathering causes the destruction of rock into fragments and occurs due to a rapid change in the volume of the surface parts of the rocks and their subsequent cracking under the influence of sharp daily temperature fluctuations, freezing and thawing of water in cracks. (high mountain regions, polar and desert zones, tundra, dry climate).
Chemical weathering leads to a change in the chemical composition of the rock through processes of oxidation, hydration, etc., with the formation of minerals that are more resistant to the conditions of the earth's surface. (humid areas, tropics, subtropics).
Biological weathering boils down to mechanical and chemical changes in rocks caused by the vital activity of organisms. Biological factors play an important role in a unique type of weathering - soil formation. (in many climate zones).
Eluvium- products of weathering of rocks remaining at the site of their formation.
Eluvium accumulates there on horizontal or slightly inclined surfaces, where denudation is weakened. It forms a weathering crust and is characterized by the absence of material sorting and layering. The size of elivia pieces (mechanical composition) ranges from blocks to clays. In many areas, placers of those minerals that were contained in bedrock are concentrated in the eluvium.
Security questions:
1. Give toclassification of geological processes.
2. What is meant by endogenous processes.
3. Name the types of ttectonic movements of the earth's crust.
4. List tectonic processes and phenomena.
5. Name the forms of tectonic dislocations.
6. What is meant by weathering.
7. What is meant by eluvium.
