In the previous chapters, we talked about the reflection of geological structures in the relief and the influence on the relief of various types of tectonic movements, regardless of the time of manifestation of these movements.

It has now been found that the main role in the formation of the main features of the modern relief of endogenous origin belongs to the so-called the latest tectonic

Fig. 12. Scheme of the latest (Neogene-Quaternary) tectonic movements on the territory of the USSR (according to NI Nikolaev, greatly simplified): / - areas of very weakly expressed positive movements; 2-areas of weakly expressed linear positive movements; 3 - areas of intense arched uplifts; 4 - areas of weakly expressed linear uplifts and subsidence; 5 - areas of intense linear uplifts with large (o) and significant (b) gradients of vertical movements; 6 - areas of emerging (a) and prevailing (b) subsidence; 7-border areas strong earthquakes(7 points or more); c - boundary of manifestation of Neogene-Quaternary volcanism; 9 - the border of distribution of existing

movements, by which most researchers understand movements that took place in the Neogene-Quaternary time. This is quite convincingly evidenced, for example, by a comparison of the hypsometric map of the USSR and the map of the latest tectonic movements (Fig. 12). Thus, areas with weakly expressed vertical positive tectonic movements in the relief correspond to plains, low plateaus and plateaus with a thin cover of Quaternary deposits: the East European Plain, a significant part of the West Siberian Lowland, the Ustyurt Plateau, the Central Siberian Plateau.

The areas of intense tectonic subsidence, as a rule, correspond to lowlands with a thick layer of sediments of the Neogene-Quaternary age: the Caspian lowland, a significant part of the Turan lowland, the North Siberian lowland, the Kolyma lowland, etc. , Tien Shan, the mountains of the Baikal and Transbaikalia, etc.

Consequently, the relief-forming role of the latest tectonic movements manifested itself primarily in the deformation of the topographic surface, in the creation of positive and negative relief forms of various orders. Through the differentiation of the topographic surface, the latest tectonic movements control the location on the Earth's surface of areas of demolition and accumulation and, as a consequence, areas with a predominance of denudation (depleted) and accumulative relief. The speed, amplitude and contrast of the newest movements significantly affect the intensity of the manifestation of exogenous processes and are also reflected in the morphology and morphometry of the relief.

The expression in the modern relief of structures created by neotectonic movements depends on the type and nature of neotectonic movements, lithology of deformable strata, and specific physical and geographical conditions. Some structures are directly reflected in the relief, in place of others an inverted relief is formed, in the place of others - different types transitional forms from direct to inverted relief. The variety of relationships between topography and geological structures is especially characteristic of small structures. Large structures, as a rule, find direct expression in the relief.

Landforms owing their origin to neotectonic structures are called morphostructures. At present, there is no single interpretation of the term "morphostructure" either in relation to the scale of forms, or in relation to the nature of the correspondence between the structure and its expression in relief. Some researchers understand by morphostructures both straight and inverted, and any other relief that has arisen in the place of a geological structure, others - only a straight relief. The latter's point of view is perhaps more correct. Morphostructures we will call relief forms of different scales, the morphological appearance of which largely corresponds to the types of geological structures that created them.

The data at the disposal of geology and geomorphology indicate that the earth's crust undergoes deformations almost everywhere and of a different nature: vibrational, folding, and rupture-forming. For example, the territory of Fennoscandia and a significant part of the territory are currently uplifting. North America adjacent to Hudson Bay. The rates of uplift of these territories are very significant. In Fennoscandia, they are 10 mm per year (sea level marks made in the 18th century on the shores of the Gulf of Bothnia are raised above the current level by 1.5-2.0 m).

The shores of the North Sea within Holland and its neighboring regions are sinking, forcing residents to build dams to protect the territory from the attack of the sea.

Intense tectonic movements are experienced by areas of alpine folding and modern geosynclinal belts. According to available data, the Alps rose by 3-4 km during the Neogene-Quaternary time, the Caucasus and the Himalayas rose by 2-3 km only during the Quaternary time, and the Pamirs by 5 km. Against the background of uplifts, some areas within the areas of alpine folding experience intense subsidence. So, against the background of the uplift of the Greater and Lesser Caucasus, the Kuro-Araks lowland enclosed between them is experiencing intense subsidence. The evidence of the multidirectional movements existing here is the position of the coastlines of the ancient seas, the predecessors of the modern Caspian Sea. Coastal sediments of one of these seas - the Late Bakinsky one, the level of which was located at an absolute height of 10--12 m, is currently traced within the southeastern pericline of the Greater Caucasus and on the slopes of the Talysh mountains at absolute elevations of + 200-300 m, and within The Kuro-Araksin lowlands are penetrated by wells at absolute elevations of minus 250-300 m. Intensive tectonic movements are observed within the mid-ocean ridges.

The manifestation of neotectonic movements can be judged by the numerous and very diverse geomorphological features. Here are some of them: a) the presence of sea and river terraces, the formation of which is not associated with the impact of climate change; b) deformation of sea and river terraces and ancient surfaces of denudation alignment; c) deeply submerged or highly elevated coral reefs; d) submerged marine coastal forms and some underwater karst sources, the position of which cannot be

explain by eustatic fluctuations of 1 level of the World Ocean or other reasons;

e) antecedent valleys formed as a result of a river sawing through a tectonic rise on its way - an anticlinal fold or block (Fig. 13),

The manifestation of neotectonic movements can also be judged by a number of indirect signs. Fluvial landforms are sensitive to them. So, areas experiencing tectonic uplifts are usually characterized by an increase in density and depth

erosional dissection compared to tectonically stable territories or immersed. The morphological appearance of erosional forms also changes in such areas: the valleys usually become narrower, the slopes are steeper, there is a change in the longitudinal profile of rivers and abrupt changes in the direction of their flow in the plan, which cannot be explained by other reasons, etc. Thus, there is a close connection between the character and the intensity of the latest tectonic movements and the morphology of the relief. This connection makes it possible to widely use geomorphological methods in the study of neotectonic movements and the geological structure of the earth's crust.

1 Eustatic fluctuations are slow changes in the level of the World Ocean, occurring simultaneously and with the same sign over the entire ocean area due to an increase or decrease in the flow of water into the ocean.

In addition to the latest tectonic movements, there are so-called modern movements, under which, according to

V.E. Khain, understand the movements manifested in historical time and emerging now. The existence of such movements is evidenced by many historical and archaeological data, as well as data from repeated leveling. The high speeds of these movements noted in a number of cases dictate the urgent need to take them into account in the construction of long-term structures - canals, oil and gas pipelines, railways and etc.

CHAPTER 6. MAGMATISM AND RELIEF FORMATION

Magmatism plays an important and very diverse role in relief formation. This applies to both intrusive and effusive magmatism. Landforms associated with intrusive magmatism can be both the result of the direct influence of magmatic bodies (batholiths, laccoliths, etc.), and the result of the preparation of intrusive igneous rocks, which, as already mentioned, are often more resistant to external forces than the host their sedimentary rocks.

Batholiths are most often confined to the axial parts of the anticlinoria. They form large positive landforms, the surface of which is complicated by smaller forms, which owe their appearance to the influence of certain exogenous agents, depending on specific physical and geographical conditions.

Examples of rather large granite batholiths on the territory of the USSR are the massif in the western part of the Zeravshan ridge in Central Asia (Fig. 14), a large massif in the Kongur-Alagez ridge in the Transcaucasus.

Laccoliths occur alone or in groups and are often expressed in relief with positive forms in the form of domes "li" loafs ". Well-known laccoliths of the North Caucasus

Fig. 15. Laccoliths of Mineralnye Vody, North Caucasus (Fig. N. P. Kostenko)

(fig. 15) in the area of ​​the city of Mineral water: mountains Beshtau, Lysaya, Zheleznaya, Zmeinaya, etc. Typical laccoliths, well expressed in relief, are also known in Crimea (Ayu-Dag, Kastel mountains).

Vein-like branches often branch off from laccoliths and other intrusive bodies, called apophyses. They cut the host rocks in different directions. Prepared apophyses on the earth's surface form narrow, vertical or steeply dipping bodies, resembling crumbling walls (Fig. 16.5- B). Layered intrusions are expressed in relief in the form of steps, similar to the structural steps formed as a result of selective denudation in sedimentary rocks (Fig. 16, L-L). Prepared bed intrusions are widespread within the Central Siberian Plateau, where they are associated with intrusion of rocks. trap formation 1 .

Igneous bodies complicate folded structures and their reflection in the relief. Formations associated with the activity of effusive magmatism, or volcanism, are clearly reflected in the relief, which creates a completely original relief. Volcanism is an object of study by a special geological science - volcanology, but a number of aspects of the manifestation of volcanism are of direct importance for geomorphology.

Depending on the nature of the outlets, eruptions are distinguished areal, linear and central. Areal eruptions led to the formation of vast lava plateaus. The most famous of them are the lava plateaus of British Columbia and Deccan (India).

Fig. 16. Prepared intrusive bodies: BUT-BUT- bedded intrusion (sill); B-B cutting vein (dike)

Swede, troppar - rungs of the stairs.

The erupted masses can cover vast areas of the earth's surface with a continuous cover even during fracture volcanism.

In the modern geological era, the most common type of volcanic activity is the central type of eruption, in which magma flows from the depths to the surface to certain "points", usually located at the intersection of two or more faults. Magma is supplied through a narrow feeding channel. The products of the eruption are deposited periclinal (i.e., with a fall in all directions) relative to the outlet of the supply channel to the surface. Therefore, a more or less significant accumulative form — the volcano itself — usually rises above the center of the eruption (Fig. 17).

In a volcanic process, it is almost always possible to distinguish two stages - explosive, or explosive, and eruptive, or the stage of ejection and accumulation of volcanic products. The channel-like path to the surface is broken through in the first stage. The release of lava to the surface is accompanied by an explosion. As a result top part the channel expands in a funnel, forming a negative relief form - a crater. Subsequent outpouring of lava and accumulation of pyroclastic material occurs along the periphery of this negative form. Depending on the stage of the volcano's activity, as well as the nature of the accumulation of eruption products, several morphogenetic types of volcanoes are distinguished: maars, extrusive domes, shield volcanoes, stratovolcanoes.

Maar- negative landform, usually funnel-shaped or cylindrical, formed as a result of a volcanic explosion. There are almost no volcanic accumulations along the edges of such a depression. All currently known maars are inactive, relict formations. Big number maars are described in the Eiffel region in Germany, in the Massif Central in France. Most maars in humid climates fill with water and turn into lakes. Sizes of maars - from 200 m to 3.5 km in diameter at a depth of 60 to 400 m

Fig. 17. Volcanic cones. Craters and barrancos on the slopes are clearly visible

1 Pyroclastic material is the general name for detrital material formed during volcanic eruptions.

Explosion craters, which, as a result of prolonged denudation, destroyed the surface part of the volcanic apparatus, are called explosion tubes. In a number of cases, ancient pipes of the explosion turn out to be filled with ultrabasic igneous rock - kimberlite. Kimberlite is a diamondiferous rock, and the vast majority of diamond deposits (in South Africa, Brazil, Yakutia) are associated with kimberlite pipes.

The morphology of accumulative volcanic formations largely depends on the composition of the effusive products.

Extrusion domes - volcanoes formed when acidic lava, for example, liparite, enters the surface. Such lava, due to rapid cooling and high viscosity, is unable to spread and give lava flows. It piles up directly above the mouth of the volcano and, quickly becoming covered with a cinder crust, takes the shape of a dome with a characteristic concentric
structure. The dimensions of such domes are up to several kilometers in diameter and not more than 500 m in height. Extrusion domes are known in the Massif Central, Armenia and elsewhere.

Shield volcanoes are formed during an eruption of the central type in those cases when liquid and mobile basaltic lava is erupting, capable of spreading over long distances from the center of the eruption. Overlapping each other, lava flows form a volcano with relatively gentle slopes - about 6- 8 degrees, rarely more. In some cases, only a narrow annular ridge with steeper slopes forms around the crater. The appearance of such shafts is associated with lava fountains, which throw slag onto the edge of the crater.

Shield volcanoes are very characteristic of Iceland's volcanic landscape. They are small and extinct here. Mount Dingya is an example of a shield volcano. Its base is about 6 km across, the relative height is about 500 m, and the crater is about 500 m in diameter. The geological section of the volcano is characterized by stratification due to the multiple eruptions of lava.

Another area in which shield volcanoes are particularly characteristic is Hawaii. Hawaiian volcanoes are much larger than Icelandic ones. The largest of the Hawaiian Islands is about. Hawaii - consists of three volcanoes (Mauna Kea, Mauna Loa and Kilauea) of the shield type. Of these, Mauna Loa rises above sea level to 4170 m. Despite such a huge size, the slopes of these mountains are very gentle. At the base of the volcanoes, the slope of the surface does not exceed 3 °, higher gradually increases to 10 °, and the ac of 3 km altitude decreases again. The tops of the volcanoes look like a lava plateau, in the middle of which there is a giant crater that looks like a lava lake.

Along with volcanoes that emit only liquid lava, there are those that erupt only solid debris - ash, sand, volcanic bombs, lapilli. These are the so-called slag volcanoes. They are formed when the lava is oversaturated with gases and its release is accompanied by explosions, during which the lava is sprayed, its splashes quickly solidify. In contrast to lava cones, the steepness of the slopes of cinder volcanoes is up to 45 °, i.e., it is close to the steepness of the natural slope. The slopes are steeper the rougher the material that composes them.

Slag cones are numerous in Armenia. Most of them here are confined to the slopes of larger stratovolcanoes; small forms are often formed directly on lava flows. These cones can grow very quickly. Thus, the cinder cone of Monte Nuova (Italy, the vicinity of Naples) arose within a few days literally out of the blue and is currently a hill up to 140 m high. The largest volcanic structures are stratovolcanoes. Both lava layers and layers of pyroclastic material are involved in the structure of stratovolcanoes. Many stratovolcanoes have an almost regular conical shape: Fujiyama in Japan, Klyuchevskaya and Kronotskaya solki in Kamchatka, Popokatepetl in Mexico, etc. (see Fig. 17). Among these formations, mountains with a height of 3-4 km are not uncommon. Some volcanoes are up to 6 km. Many stratovolcanoes carry eternal snows and glaciers on their peaks.

Many extinct or temporarily inactive volcanoes have craters occupied by lakes.

Many volcanoes have so-called caldera. These are very large, currently inactive craters, and modern craters are often located within the caldera. There are known calderas up to 30 km across. At the bottom of the calderas, the relief is relatively flat; the sides of the calderas facing the center of the eruption are always very steep. The formation of calderas is associated with the destruction of the volcano's vent by strong explosions. In some cases, the caldera is of failure origin. In extinct volcanoes, the expansion of the caldera may also be associated with the activity of exogenous agents.

A peculiar relief is formed by liquid products of volcanic eruptions. Lava, poured out from the central or side craters, flows down the slopes in the form of streams. As already mentioned, the fluidity of lava is determined by its composition. Very thick and viscous lava has time to solidify and lose its mobility even in the upper part of the slope. At very high viscosity, it can solidify in the vent, forming a giant "lava pillar" or "lava finger", as was the case, for example, during the eruption of the Pele volcano in Martinique in 1902. Usually, the lava flow looks like a flattened ridge stretching down the slope , with a very pronounced swelling at the end. Basalt lavas can give long streams that spread over many kilometers and even tens of kilometers and stop their movement on a plain or plateau adjacent to a volcano, or within the flat bottom of a caldera. Basalt flows 60-70 km long are not uncommon in Hawaii and Iceland.

Lava flows of liparite or andesite composition are much less developed. Their length rarely exceeds several kilometers. In general, for volcanoes emitting products of acidic or intermediate composition, a much larger part by volume is pyroclastic rather than lava material.

When solidified, the lava flow is first covered with a slag crust. If the crust breaks through in any place, the uncooled part of the lava flows out from under the crust. As a result, a cavity is formed - lava grotto, or lava cave. When the vault of the cave collapses, it turns into a negative surface relief form - lava trench. Troughs are very typical for the volcanic landscapes of Kamchatka.

The surface of the solidified stream acquires a kind of microrelief. The most common are two types of surface microrelief of lava flows: a) blocky microrelief and b) intestinal lava. Blocky lava flows are a chaotic heap of angular or melted blocks with numerous sinkholes and grottoes. Such lumpy forms arise at a high gas content in the composition of the lavas and at a relatively low flow temperature. Gut-like lavas are distinguished by a bizarre combination of frozen waves, winding folds, on the whole really resembling “piles of giant intestines or bundles of twisted ropes” (IS Shchukin). The formation of such a microrelief is typical for lavas with high temperature and with a relatively low content of volatile components.

The release of gases from a lava flow can be in the form of an explosion. In these cases, slag is piled up in the form of a cone on the surface of the flow. Such forms are called crucible. Sometimes they look like pillars up to several meters high. With a quieter and more prolonged release of gases and "cracks in the slag, so-called fumaroles. A number of fumarole release products condense under atmospheric conditions, and crater-like elevations formed by condensation products are formed around the gas outlet.

With fissured and areal outpourings of lava, vast spaces appear to be filled with lava, as it were. Iceland is a classic country of fissure eruptions. Here the overwhelming majority of volcanoes and lava flows are confined to a depression that cuts the island from the southwest to the northeast (the so-called Great Graben of Iceland). Here you can see lava sheets stretched along the faults, as well as gaping cracks, not yet completely filled with lavas. Fissure volcanism is also characteristic of the Armenian Highlands. More recently, fissure eruptions have taken place on the North Island of New Zealand.

The volume of lava flows erupting from cracks in Iceland's Big Graben reaches 10-12 cubic meters. km. Massive areal outpourings took place in the recent past in British Columbia, on the Deccan Plateau, in South Patagonia. Merged lava flows of different ages here form continuous plateaus with an area of ​​up to several tens and hundreds of thousands of square kilometers. So the lava plateau of Colombia has an area of ​​more than 500 thousand square kilometers, and the thickness of the lava composing it reaches 1100-

1800 m. The lavas filled all the negative forms of the previous relief, causing its almost perfect leveling. At present, the height of the plateau is from 400 to 1800 m. Valleys of numerous rivers are deeply cut into its surface. On the youngest lava sheets, a blocky microrelief, cinder cones, lava caves and trenches have been preserved here.

During underwater volcanic eruptions, the surface of the erupted magma flows quickly cools. Significant hydrostatic pressure of the water column prevents explosive processes. As a result, a kind of microrelief is formed. spherical, or pillow, lava.

Lava outpourings not only form specific landforms, but can significantly affect the existing relief. So, lava flows can affect the river network, cause its restructuring. By blocking river valleys, they contribute to catastrophic floods or dry land; loss of streams by it. Penetrating to the seashore and solidifying here, lava flows change the outlines of the coastline, form a special morphological type of sea coasts.

The outpouring of lavas and the ejection of pyroclastic material inevitably causes the formation of a mass deficit in the bowels of the Earth. The latter determines the rapid subsidence of parts of the earth's surface. In some cases, the beginning of the eruption is preceded by a noticeable uplift of the terrain. So, for example, before the eruption of Usu volcano on the island of Hokkaido, a large fault formed, along which a surface area of ​​about 3 km2 rose by 155 m in three months, and after the eruption it dropped by 95 m.

Speaking about the relief-forming role of effusive magmatism, it should be noted that during volcanic eruptions, sudden and very rapidly occurring changes in the relief and the general state of the surrounding area can occur. Such changes are especially great during explosive eruptions. For example, during the eruption of the Krakatau volcano in the Sunda Strait in 1883, which was in the nature of a series of explosions, most of the island was destroyed, and at this place the sea depths of up to 270 m were formed. and Sumatra. It caused enormous damage to the coastal regions of the islands, leading to the death of tens of thousands of residents. Another example of this kind is the eruption of the Katmai volcano in Alaska in 1912. Before the eruption, the Katmai volcano looked like a regular cone with a height of 2286 m.During the eruption, the entire upper part of the cone was destroyed by explosions and a caldera up to 4 km in diameter and up to 1100 m was formed depth.

The volcanic relief is further exposed to the influence of exogenous processes, leading to the formation of peculiar volcanic landscapes.

As you know, craters and summits of many large volcanoes are centers of mountain glaciation. Since the glacial landforms formed here do not have any fundamental features, they are not specifically considered. Fluvial forms of volcanic regions have their own specifics. Melt water, mud flows, which are often formed during volcanic eruptions, atmospheric waters significantly affect the slopes of volcanoes, especially those in the structure of which the main role belongs to pyroclastic material. In this case, a radial system of the ravine network is formed - the so-called barrancos. These are deep erosion grooves, diverging, as it were, along the radii from the top of the volcano (see Fig. 17).

Barrancos should be distinguished from furrows plowed in a loose cover of ash and lapilli in large blocks thrown out during the eruption. Such formations are often called sharrami. Sharrs, as original linear depressions, can then be transformed into erosional furrows. There is an opinion that a significant part of the barrancos was founded on the former sharrs.

The general pattern of the river network in volcanic regions is also often radial. Other distinctive features of river valleys in volcanic regions are waterfalls and rapids formed as a result of rivers crossing frozen lava flows or traps, as well as dam lakes or lake-like expansions of valleys in place of drained lakes that arise when a river is blocked by a lava flow. In places where ash accumulates, as well as on lava covers, due to the high permeability of rocks, over vast areas there may be no watercourses at all. Such areas have the appearance of rocky deserts.

Many volcanic regions are characterized by outcrops of pressurized hot waters called geysers. Hot deep waters contain many dissolved substances that precipitate when the waters are cooled. Therefore, the places where hot springs come out are surrounded by dripstone, often bizarre terraces. Geysers and their accompanying terraces are widely known in Yellowstone Park in the USA, in Kamchatka (Valley of Geysers), in New Zealand, and in Iceland.

In volcanic areas, there are also specific forms of weathering and denudation preparation. So, for example, thick basalt covers or flows of basaltic, less often andesitic, lava, when cooled and under the influence of atmospheric agents, are broken by cracks into columnar units. Quite often the detachments are polyhedral pillars that look very impressive in outcrops. The outcrops of cracks on the surface of the lava cover form a characteristic polygonal microrelief. Such spaces of lava outcrops, divided by a system of polygons - hexagons or pentagons, are called "Bridge giants".

With prolonged denudation of the volcanic relief, accumulations of pyroclastic material are destroyed first of all. More persistent lava and other igneous formations

are subjected to preparation by exogenous agents. Typical preparation forms are the above-mentioned dykes, as well as neck(prepared lava plugs frozen in the volcano's mouth).

Deep erosional dissection and slope denudation can lead to the division of the lava plateau into separate plateau-like uplands, sometimes far from each other. Such outlier forms are called Meuse(singular - mesa).

Fig. 18. Inversion of relief in the volcanic landscape. In the background, the primary position of the lava flow in the valley; foreground - the same lava flow prepared (according to Davis)

As a result of prolonged denudation in volcanic regions, inversion landforms can also arise. Thus, lava flows that originally occupied the relief depressions (valleys) can form an elongated table eminence that rises above the surrounding terrain due to the protective role of the armor layer of lava (Fig. 18).

Volcanic relief is widespread on the surface of the Earth. Until recently, speaking about the geography of volcanoes, they usually meant land volcanoes. Studies of recent decades have shown that there are no less volcanic forms in the oceans, and, apparently, even much more than on the continents. In the Pacific Ocean alone, there are at least 3 thousand underwater volcanoes.

The overwhelming majority of the newest and modern land volcanoes are confined to completely defined zones. One of these zones has a mainly meridional direction and stretches along the western coasts of both Americas. Another well-studied zone of volcanic regions has a latitudinal strike. It covers the areas adjacent to the Mediterranean Sea and stretches further to the east, where it intersects in the region of Indonesia with the third volcanic zone corresponding to the western edge of the Pacific Ocean. Within the third zone, most active volcanoes are confined to island arcs- garlands of islands framing the outskirts The Pacific adjacent to Asia and Australia. There are also many underwater volcanoes near the islands.

A relatively small number of volcanoes are confined to fault zones that cut through such ancient continental platforms as the African one.

In the ocean, many volcanoes form islands located far from the continents. Of the oceanic volcanic islands, one can name Hawaii, the Azores, Reunion, Tristan da Cunha and many others. Iceland is a special volcanic region. At first glance, the distribution of such volcanoes: seems irregular, sporadic. However, there is a fairly clear pattern in the distribution of these volcanoes as well. It will become clear after considering the main features of the morphology of planetary landforms.

Researchers of the topography and geological structure of the ocean floor unanimously note that flat-topped seamounts are often found here. guyots are submarine volcanoes, the tops of which were cut off by abrasion at a lower relative position of the sea level. Drilling and geophysical data show that the foundations of oceanic coral islands are also volcanic in origin. The widespread hilly ocean floor is mainly believed to be created by volcanic eruptions. All this testifies to a particularly widespread development of volcanic processes, namely in the limits of the oceans.

CHAPTER 7. EARTHQUAKES AS A FACTOR OF ENDOGENOUS RELIEF FORMATION

Like other endogenous factors, earthquakes have a significant relief-forming significance. The geomorphological role of earthquakes is expressed in the formation of cracks, in the displacement of blocks of the earth's crust along cracks in the vertical and horizontal directions, sometimes in folded deformations.

It is known, for example, that during the Ashgabat earthquake in 1948, many cracks of various sizes appeared on the surface of the earth as a result of strong tremors. Some of them stretched for many hundreds of meters, crossing hills and valleys, out of visible connection with the existing relief. Along them there was a movement of masses in a vertical direction with an amplitude sometimes up to 1 m.During the Belovodsk earthquake in 1885 (Kyrgyzstan), as a result of vertical displacement along the cracks of the earth's crust blocks, ledges up to 2.5 m high were formed. ) the embankment of Lisbon instantly sank under the water and in its place the depth of the bay reached 200 m.During the earthquake in Japan (1923), one part of Sagami Bay (south of Tokyo) with an area of ​​about 150 km 2 quickly rose by 200-250 m, and the other dropped by 150-200 m.

Often, as a result of earthquakes, structures of the graben type are formed, respectively, expressed in the relief in the form of negative forms. Thus, during the Gobi-Altai earthquake (1957), a graben 800 m wide, 2.7 km long, with an amplitude of displacement along cracks of up to 4 m was formed in the epicentral zone. cracks reached 20, and in some places even 60 m.As a result of the earthquake in the Baikal region in 1862, a significant section of the Kudarinskaya steppe (in the northeastern part of the Selenga delta) with an area of ​​about 260 km 2 sank, and at this place the Proval Bay, up to 8 m deep, was formed ...

Occasionally, during earthquakes, specific positive landforms can occur. Thus, during the earthquake in northern Mexico (1887), mounds up to 7 m high were formed between the two faults, and during the Assam earthquake in India, a number of islands moved into the sea, one of which was 150 m long and 25 m wide. cracks formed during earthquakes, water rose, carrying sand and clay to the surface. As a result, small bulk cones with a height of 1-1.5 m appeared, resembling miniature mud volcanoes. Sometimes, during earthquakes, deformations such as folded disturbances are formed. So, during the earthquake in Japan in 1891<на земной поверхности образовались волны высотой до 30 см и длиной от 3 до 10 м.

Due to the fact that many forms of relief that arise during earthquakes are relatively small in size, they are quickly destroyed under the influence of exogenous processes.

No less, and perhaps a more important relief-forming role is played by some processes caused by earthquakes and accompanying them. During earthquakes, as a result of strong tremors, “on the steep slopes of mountains, on the banks of rivers and seas, landslides, taluses, wasps appear and become more active, and landslides and mudslides in highly moistened rocks. Thus, during the Khait earthquake in Tajikistan (1949), large landslides and talus occurred, and the village of Khait was almost completely buried under a flood, the thickness of which reached several tens of meters. A tremendous collapse occurred in the Pamirs as a result of the 1911 earthquake. The collapsed mass blocked the river valley. Murghab, having formed a dam more than 5 km wide and up to 600 m high. It is believed that this is the same origin of the huge dam in the upper reaches of the river valley. Baksan in the Caucasus. Often, during earthquakes on steep mountain slopes, all the loose material accumulated on them begins to move, forming powerful talus plumes at the foot.

As a result of the Alma-Ata earthquake in 1911 on the northern slope of the Zailiyskiy Alatau, landslide and swelling bodies occupied an area of ​​more than 400 km 2.

Loose material accumulated at the foot of the mountain slopes, in the valleys of rivers and temporary streams as a result of the processes described above, can serve as a source for the occurrence of mudflows. Rushing down the valleys, mudflows do a tremendous destructive work, and when they leave the mountains, they form alluvial fans that are vast in area.

Landslides, landslides, movement of blocks of the earth's crust along ruptures cause changes in the hydraulic network: lakes are formed, new ones appear, old sources disappear. During the Andijan earthquake (1902) in the valley of the river. Mud volcanoes formed in Karadarya.

A certain relief-forming role is also played by those earthquakes, the centers of which are located in the sea, or, as they are sometimes called, - seaquakes. Under their influence, huge masses of loose, water-saturated bottom sediments move even on gentle slopes of the seabed.

Seaquakes in a number of cases cause the formation of giant sea waves - tsunamis, which, crashing onto the coast, not only cause tremendous destruction of human settlements and structures, but also have a significant impact on the morphology of sea coasts in some places.

Like volcanoes, earthquakes on the surface of the globe are unevenly distributed: in some regions they occur frequently and reach great strength, in others they are rare and weak. High seismicity is characteristic of the Mediterranean belt of folded structures from Gibraltar to the Malay Archipelago and the peripheral parts of the Pacific Ocean. The mid-ocean ridges, the region of the great lakes of East Africa and some other territories are distinguished by significant seismicity.

If we compare the maps of the geography of volcanoes and earthquakes, it is easy to see that earthquakes are confined to the same areas in which most of the active and extinct volcanoes are concentrated. Of course, this is not a simple geographical coincidence, but the result of the unity of the manifestations of the inner forces of the Earth. This unity is revealed even more clearly when comparing the map of the distribution of volcanoes and earthquakes with the map of the latest tectonic movements. The comparison gives grounds to conclude that both volcanoes and earthquakes are confined to the areas of the most intense recent tectonic movements.

CHAPTER 8. STRUCTURE OF THE EARTH'S CREST AND PLANETARY FORMS OF THE RELIEF

Some forms of mega-, macro- and mesorelief were considered above, the formation of which is caused by the activity of endogenous processes (see Chap. 5, 6, 7). The largest landforms - planetary - also owe their origin to internal

the forces of the Earth, underlying the formation of various types of the earth's crust.

Geophysical data, and in particular deep seismic sounding, indicate that the earth's crust under continents and oceanic troughs has a different structure, therefore, continental and oceanic types of the earth's crust are distinguished (Fig. 19).

Continental crust is characterized by high thickness - on average 35 km, in some places - up to 75 km. It has three "layers".

Above, there is a sedimentary layer formed from sedimentary rocks of various composition, age, genesis and degree of dislocation. Its thickness varies from zero to 15 km. Below there is a granite layer, consisting mainly of felsic rocks, similar in composition to granite. The greatest thickness of the granite layer is noted under the young high mountains, where it reaches 50 km. Within the flat areas of the continents, the thickness of the granite layer drops to 10 km.

Under the granite layer lies a basalt layer, which also received its name conditionally: seismic waves pass through it at the same speeds with which, under experimental conditions, they pass through basalts and rocks close to them. The true composition of the basalt layer within the continents is still unknown. Its thickness within the mountainous countries reaches 15 km, and within the leveled parts of the continents - 25-30 km.

Organic bark dramatically different from the mainland. On most of the ocean floor, its thickness ranges from 5 to 10 km. Its structure is also peculiar: under the sedimentary layer with a thickness of several kilometers to several hundred meters lies an intermediate layer of variable thickness, which is often simply called the "second layer". Seismic waves propagate in it at higher speeds than in the sedimentary, but less than in the granite layer. It is believed that the intermediate layer consists of compacted sedimentary rocks penetrated by volcanic formations. Recently, this layer has received the name "oceanic basement". Basalt layer 4-7 km thick lies under it. Thus, the most important specific feature of the oceanic crust is its low thickness and the absence of a granite layer.

The earth's crust has a special structure in the areas of transition from continents to oceans - in modern geosynclinal belts, where it is distinguished by its variegated and complex structure. On the example of the western margin of the Pacific Ocean, it can be seen that the marginal geosynclinal regions usually consist of three main elements - the basins of the deep-sea seas, island arcs, and deep-sea trenches. The spaces corresponding to the deep-sea depressions of the seas (Caribbean, Japanese, etc.) have a crust that resembles an oceanic crust in its structure. There is no granite layer, but the thickness of the crust is much greater due to the increase in the thickness of the sedimentary layer. Large land masses bordering such seas (for example, the Japanese Islands) are composed of a crust similar in structure to the mainland. A characteristic feature of the transitional areas is also a complex combination and abrupt transitions from one type of crust to another, intense volcanism and high seismicity. This type of structure of the earth's crust can be called geosynclinal.

The crust under the mid-oceanic ridges is characterized by peculiar features. She stands out in a special, so-called riftogenic type of the earth's crust. Details of the structure of the bark
this type is not yet entirely clear. Its most important feature is its occurrence under sedimentary or intermediate layers of rocks, in which elastic waves propagate at speeds equal to 7.3-7.8 km / s, i.e. much higher than in the basalt layer, but lower than in the mantle. ... It is possible that a mixture of crustal and mantle matter occurs here. This assumption was further confirmed in 1974 by the results of deep-water drilling carried out south of the Azores on the Mid-Atlantic Ridge.

The largest planetary landforms correspond to each of the above types of the earth's crust (Fig. 19, 20). Continents correspond to the continental type of the earth's crust. They form the main land masses. Over a large area, continents can be flooded by the waters of the oceans. The submerged parts of the continents were named underwater outskirts of the continents. In the geophysical and geomorphological sense, the boundaries of the continents should be considered the lowest boundary of the underwater margin of the continents, where the granite layer pinches out and the continental type crust is replaced by the oceanic one.

Fig. 20. Scheme of the ratio of various types of the earth's crust and planetary landforms:

/ - continents (a) and their underwater margins (b) - continental type crust; 2 - transition zones - geosynclinal type crust; 3 - ocean bed - oceanic type crust; 4 - mid-oceanic ridges - phytogenic type of the earth's crust

The oceanic type of the earth's crust corresponds to the ocean floor.

The intricately constructed crust of the geosynclinal type is reflected in the relief of geosynclinal belts or zones of transition from continents to oceans. Below, for brevity, we will refer to them as transition zones.

The rift type of the earth's crust corresponds in the relief to the planetary system of mid-oceanic ridges.

Each planetary form of relief is characterized by the originality of its inherent forms of mega- and macro-relief, in the overwhelming majority of cases also due to differences in the structure or structure of the earth's crust.

Turning to the description of the mega-relief of the named largest planetary landforms of the Earth, it should be emphasized that with the above identification of planetary morphostructures, the coastline loses its significance as the most important physical and geographical boundary separating the land from the seabed. However, its role is undoubtedly great, since the conditions of relief formation on the seabed and on land are significantly different.

It should also be noted that on the continents, which are very complex formations, along with ancient and young platforms, very young morphostructures are widespread, which owe their origin to the Alpine mountain-building movements and have not yet completely lost the features inherent in geosynclinal regions. However, these morphostructures are characterized by the already formed continental crust.

In connection with these circumstances, the further description of the forms of the land mega-relief is given, if possible, separately from the mega-relief of the seabed. Accordingly, the review of the mega-relief of the continents includes a general description of the plains and mountains of the land, including "and young epigeosynclinal mountain structures. In the review of the transition zones, the main attention is paid to the marine (oceanic) elements of this megamorphostructure.

CHAPTER 9. MEGA RELIEF OF MATERIKS

The area of ​​the continents, together with the underwater margin, as well as alpine epigeosynclinal continental formations and areas with continental type crust within the transition zones, is approximately 230 million square kilometers.

In terms of structure, the continents are complex heterogeneous bodies formed during the long evolution of the lithosphere and the earth's crust. The complexity of evolution and the sequence of different stages of formation of continents are reflected in their tectonic and geological structure. By the nature of tectonic activity and the direction of geological development within the continents, more stable (more stable) areas are distinguished, which have received the names platforms, and areas with greater tectonic mobility (mobility) - geosynclinal areas. The heterogeneity of the structure and development of platforms and geosynclinal regions determines the difference in the relief within them and makes it possible to distinguish two main types of morphostructures within the continents - platform and geosynclinal. A closer look shows that both platform and geosynclinal regions are far from homogeneous in terms of geological structure, development, and age. This heterogeneity
is reflected in the relief of continents, in various types of morphostructures of different orders.

5. Ignatenko I.V., Khavkina N.V. Podburs of the Far North-East of the USSR // Geography and genesis of soils

Magadan region. - Vladivostok: Publishing house of the Far East Scientific Center of the Academy of Sciences of the USSR. - S. 93-117.

6. Classification and diagnostics of soils in Russia / L.L. Shishov [and others]. - Smolensk: Oikumena, 2004 .-- 342 p.

7. Soil-geographical zoning of the USSR. - M .: Publishing house of the Academy of Sciences of the USSR, 1962 .-- 422 p.

8. Soil Science / ed. V.A. Kovdy, B.G. Rozanov. - Part 2. - M .: Higher. shk., 1988. - 367 p.

UDC 631.48 (571.61) E.P. Sinelnikov, T.A. Chekannikova

COMPARATIVE ESTIMATION OF THE INTENSITY AND DIRECTION OF THE PROCESSES OF TRANSFORMATION OF THE MATERIAL COMPOSITION OF THE BLEACHED SOILS OF THE PLAIN TERRITORIES OF THE PRIMORSKY REGION AND SODY-PODZOLY CARBONATE SOILS OF THE SOUTHERN TAILS

WESTERN SIBERIA

The article provides a detailed analysis of the processes of transformation of the material composition of soils in Southern Siberia and Primorye. No significant differences in the intensity and direction of the leading elementary soil processes were revealed.

Key words: Primorsky Krai, Western Siberia, sod-podzolic soils, calcareous soils, comparative assessment.

E.P. Sinelnikov, T.A. Chekannikova

COMPARATIVE ASSESSMENT OF PROFILE MATERIAL STRUCTURE TRANSFORMATION PROCESSES INTENSITY AND ORIENTATION ON THE FLAT TERRITORIES BLEACHED SOILS OF PRIMORSKY KRAI AND CESPITOSE-PODZOLIC CARBONATE SOILS IN THE WESTERN SIBERIA

The detailed analysis of soils material structure transformation processes in the southern Siberia and Primorsky Krai is conducted. Essential distinctions in the intensity and orientation of leading elementary soil processes are not revealed.

Key words: Primorsky Krai, Western Siberia, cespitose-podzolic soils, carbonate soils, comparative assessment.

Evaluation of the degree of differentiation of the material composition of the soil profile as a result of the action of various elementary soil processes has long been an integral part of studies of the genetic properties of the soil cover in any region. The basis of such analyzes was laid by the work of A.A. Rode,

The features of the differentiation of the material composition of soils in the southern part of the Russian Far East, in comparison with soils of other regions close in genetic parameters, were studied

C.V. Zonnom, L.P. Rubtsova and E.N. Rudneva, G.I. Ivanov and others. The result of these studies, based mainly on the analysis of genetic indicators, was the statement about the predominance of the processes of lessivation, bleaching, pseudopodzolization and the complete exclusion of the processes of podzolization.

In this communication, we have made an attempt to compare the direction and intensity of the transformation processes of the material composition of the profile of bleached soils in the plains of Primorye with soddy podzolic residual calcareous soils of Western Siberia on the basis of quantitative indicators of the balance of the main elements of the material composition.

The choice of Siberian soils as a comparative option is not accidental and is conditioned by the following conditions. First, the residual calcareous soddy-podzolic soils of Siberia were formed on mantle loams with an increased content of clay particles and exchangeable bases, which excludes fundamental differences already at the first stage of analysis. Secondly, it is the availability of detailed monographic data and balance calculations of the transformation of the material composition, published by I.M. Hajiyev, which greatly simplifies the implementation of our task.

For a comparative analysis, we used the data of I.M. Gadzhiev in sections 6-73 (soddy-podzolic soils) and 9-73 (soddy-slightly podzolic soils). As bleached soil options

In Primorye, we took brown-bleached and meadow gley-slightly bleached soils. The initial data of these soils, as well as the assessment of the transformation of their material composition, depending on the geomorphological location and degree of bleaching, are presented in our previous communication. The main indicators of sod-podzolic soils are presented in Table 1.

Analysis of the data in Table 1 of this communication and Table 1 of the previous one shows two significant points: firstly, it is a rather close composition of the parent rocks, and secondly, the clearly pronounced division of the profiles of all analyzed sections into accumulative-eluvial and illuvial parts. So, according to E.P. Sinelnikov, the content of clay particles in the parent rock of the Primorye plains is 73-75%, for the southern taiga of Western Siberia 57-62%. The amount of silt fraction was 40-45 and 35-36 percent, respectively. The total value of exchangeable Ca and Md cations in lacustrine-alluvial deposits of Primorye is 22-26 meq per 100 grams of soil, in mantle loams of Siberia 33-34, the value of actual acidity is 5.9-6.3 and 7.1-7.5 units, respectively. ... pH. The residual carbonate content of the rocks is manifested in the properties of the parent rocks of the analyzed sections of Siberia, but its effect on the physicochemical state of the upper horizons is minimal, especially in medium and highly podzolic soils.

Investigating the problem of differentiation of the profile of sod-podzolic soils, I.M. Gadzhiev notes a clear separation of the eluvial part, depleted in sesquioxides and enriched in silica, and the illuvial part, to some extent enriched in the main components of the material composition, in comparison with the overlying horizons. At the same time, no noticeable accumulation of oxides was found here in relation to the original rock, and even decreased. A similar pattern is manifested in the bleached soils of Primorye.

Referring to the works of A.A. Rode, I.M. Gadzhiev believes that this fact confirms the regularity of the behavior of the substance during the podzol-forming process, the essence of which "... consists in the total destruction of the mineral base of soils and the transit discharge of the resulting products far beyond the soil profile." In particular, according to the balance calculations of I.M. Gadzhiev, the total amount of depilation of the total thickness of the soil horizons relative to the parent rock ranges from 42-44% in highly podzolic soil to 1.5-2 in slightly podzolic soil.

Table 1

The main indicators of the material composition of the residual-carbonate sod-podzolic soils of Western Siberia (calculated according to I.M. Gadzhiev)

Horizon Calculated power, cm Particle content<0,001 мм Плотность, г/см3 Валовый состав почвы в целом, % Состав крупнозема, % Состав ила, %

2 o c o o c o c o o o o) 1_1_ co o 2 2 o co co o 2 a) o_ co o count< 2 о со о од < со о од О) 1_1_ со о /2 о со со о 2 а) о_ со о од < 2 о СО со о од < со о од О) 1_1_ со о £ /2 о со со о 2 а) о_ со о од <

Section 6-73 Sod-strongly podzolic

A1 4 23 1.10 74.7 14.2 4.3 7.5 5.1 79.3 11.1 3.1 10.3 5.7 58.2 25.1 8.5 3.2 4, 6

A2 20 23 1.32 73.8 14.3 4.2 7.4 5.4 78.6 11.1 2.7 10.4 6.4 56.8 25.3 9.4 3.1 4, 2

Bh 18 40 1.43 70.0 16.7 5.5 5.9 4.8 74.4 14.3 4.0 7.5 5.6 55.8 27.9 12.7 2.6 3, four

B1 31 45 1.55 67.4 17.3 5.6 5.6 4.8 76.6 10.9 1.3 11.3 11.5 55.2 26.5 10.8 2.8 3, eight

B2 27 40 1.53 68.4 18.3 6.2 5.2 4.6 77.0 11.8 2.7 9.7 6.7 55.5 26.7 10.8 2.9 3, eight

BC 24 38 1.52 68.4 16.7 5.6 5.7 4.6 76.3 11.1 2.6 10.2 6.8 55.7 25.9 10.9 2.9 3, eight

C 10 36 1.52 68.4 16.2 6.3 5.7 4.5 75.7 10.8 1.7 10.0 10.4 55.9 25.7 11.3 2.9 3, five

A1 6 23 0.89 72.0 14.6 4.3 7.0 5.0 76.1 12.0 2.6 9.7 7.3 56.6 24.2 10.8 3.1 3, five

A2 8 29 1.20 72.1 14.4 4.6 7.0 4.9 78.2 10.4 2.2 11.2 7.3 56.4 24.5 10.6 3.1 3, 6

Bh 30 40 1.35 69.0 15.3 5.7 6.2 4.3 77.4 8.7 2.1 8.1 11.3 55.3 26.1 11.6 2.8 3, five

B1 22 42 1.46 67.5 17.6 6.2 5.3 4.4 75.4 11.1 2.6 10.0 6.8 55.2 27.6 11.9 2.7 3, 6

B2 18 42 1.45 67.7 16.8 5.6 5.7 4.7 76.3 9.8 1.5 12.3 10.6 54.8 27.3 11.8 2.7 3, 7

BC 38 41 1.46 67.4 16.9 5.6 5.6 4.7 75.2 11.0 2.1 10.5 8.3 54.7 26.5 11.4 2.7 3, 6

C 10 35 1.48 67.4 16.0 5.5 5.9 4.1 74.2 11.5 2.7 8.9 8.6 55.2 25.4 10.7 2.9 3, 7

Similar calculations performed by the author for chernozemic and gray forest soils showed complete identity of the direction and rate of restructuring of the material composition in comparison with the automorphic soils of the southern taiga subzone of Siberia. Wherein ". The chernozem leached in the composition of silt, iron and aluminum from the soil horizons, in comparison with the original rock, practically repeats the soddy-slightly podzolic soil, the dark-gray forest podzol soil is close to the sod-medium podzolic soil, and the light gray forest podzol is close to the sod-podzolic soil according to these parameters. This state of affairs allowed the author to conclude that the formation of modern soddy-podzolic soils occurs on an already well-differentiated mineral base, in general, deeply eluvially transformed in comparison with the original rock, therefore it is hardly appropriate to attribute eluvial-illuvial differentiation of the profile only due to the podzol-forming process in its modern sense ”.

The compositional closest to the original rock is horizon C of weakly podzolic soil, and in terms of the analyzed thickness of the modern soil profile, it contained 4537 tons of silt, 2176 tons of aluminum and 790 tons of iron per hectare. In a similarly thick profile of highly podzolic soil, similar indicators were: 5240, 2585 and 1162 tons per hectare. That is, only due to the increased migration of substances in the highly podzolic soil profile, equal in thickness to the original parent rock, 884 tons of silt, 409 tons of aluminum and 372 tons of iron should have been removed. If we translate these indicators per cubic meter, then we get, respectively: 88.4; 40.9 and 37.2 kg. In reality, the profile of a highly podzolic soil, according to I.M. Gadzhiev, relative to the parent rock lost 15.7 kg of silica, 19.8 kg of aluminum and 11 kg of iron per m3.

If we consider the loss of the analyzed substances in the profile of the soddy-strongly podzolic soil relative to the initial content of substances in the rock of the weakly podzolic soil, then we find that the loss of silt will be 135 kg / m3, and the accumulation of aluminum, on the contrary, will be 7.5 kg and iron 3.4 kg.

To understand the essence of the ongoing processes of transformation of the material composition of soddy-podzolic soils in Western Siberia and to compare the results with the bleached soils of the Primorye plains, we decomposed, using the method of V.A. Targulian, the gross content of basic oxides for the share falling on coarse earth (> 0.001 mm) and silt fraction. The results obtained for the soddy podzolic soils of Siberia are presented in Table 2 (the corresponding indicators for the bleached soils of Primorye are given in.

The entire profile of the studied soils is quite distinctly divided into four zones: accumulative (horizons A1), eluvial (horizons A2 and Bh), illuvial (horizons B1, B2 and BC), and parent rock (horizons C), relative to which all calculations of Table 2. This division allows for a more contrasting assessment of the essence and direction of the processes of transformation of the material composition within a specific soil profile and a total assessment of the balance of the material composition.

table 2

The main indicators of the balance of the material composition of residual carbonate sod-podzolic

soils relative to parent rock, kg / m3

Gori - Mechanical elements Content in coarse soil Content in silt fraction

Coarse earth Silt SiO2 AІ2Oz Fe2Oz SiO2 AІ2Oz Fe2Oz

1 2 ± 1 2 ± 1 2 ± 1 2 ± 1 2 ± 1 2 ± 1 2 ± 1 2 ±

Section 6-73 Sod-sil podzolic

A1 37 34 -3 23 10 -13 28 27 -1 4 4 0 0.6 1.0 +0.4 13 6 -7 6 2 -4 2.5 0.8 -1.7

A2 187 201 +14 117 63 -54 142 158 +16 20 22 +2 3.2 5.4 +2.2 65 36 -29 30 16 -14 12.6 5.9 -6.7

Bh 168 200 +32 105 58 -47 127 149 +22 18 28 +10 2.9 8.0 +5.1 58 32 -26 27 16 -11 11.3 6.6 -4.7

B1 290 287 -3 181 197 +12 219 220 +1 31 31 0 5.0 9.7 -1.3 101 107 +6 47 54 +7 19.5 24.5 +5.0

B2 253 225 -27 157 187 +30 191 173 -18 27 27 0 4.3 6.1 +1.8 88 104 +16 41 50 +9 17.0 20.0 +3.0

BC 225 217 -8 140 148 +8 170 165 -5 24 24 0 3.8 5.6 +1.8 78 82 +4 36 38 +2 15.1 15.9 +0.8

Section 9-73 Sod-slightly podzolic

A1 57 41 -16 32 12 -20 42 31 -11 6 5 -1 1.6 1.1 -0.5 18 7 -11 8 3 -5 3.4 1.3 -2.1

A2 80 68 -12 42 28 -14 56 53 -3 9 7 -2 2.1 1.5 -0.6 24 16 -8 11 7 -4 4.6 2.9 -1.7

Bh 285 242 -43 159 163 +4 211 187 -24 33 21 -12 7.8 5.1 -2.7 88 90 +2 41 43 +2 17.1 18.9 +1.8

B1 209 185 -24 117 136 +19 155 139 -15 24 20 -4 5.7 4.8 -0.9 65 75 +10 30 38 +8 12.5 16.2 +3.7

B2 171 152 -19 96 109 +13 127 116 -11 20 15 -5 4.7 2.3 -2.4 53 59 +6 25 30 +5 ​​10.3 12.8 +2.5

BC 361 329 -32 202 225 +23 267 248 -19 41 36 -5 9.9 6.9 -3.0 112 123 +11 52 60 +8 21.7 25.4 +3.7

Note. 1 - initial values; 2 - current content.

From the data in Table 2 it can be seen that the direction and intensity of the transformation processes of the material composition of "related" pairs of soils are far from unambiguous. In the eluvial zone of the highly podzolic soil profile, there is an accumulation of coarse soil fractions relative to the parent rock (+46 kg / m3) and silt removal (-101 kg). In the illuvial zone of these soils, on the contrary, large earth is removed (-38 kg) and silt accumulates (+50 kg). The total balance of coarse earth as a whole along the profile is clearly neutral (+5 kg), taking into account some conventionality of the calculated indicators. The total sludge balance is negative -64 kg.

In the soddy-weakly podzolic soil in all zones of the profile, a decrease in the proportion of coarse soil relative to the parent rock is observed, in total -146 kg. The accumulation of the silt fraction (55 kg) is typical only for the illuvial part, and according to this indicator, the horizons B of both strongly podzolic and weakly podzolic soils are practically close, 50-55 kg / m3, but the total accumulation of silt in horizons B prevails over its removal from the eluvial accumulative zone (+25 kg).

Thus, in soils of different degrees of podzol content, the nature of the redistribution of mechanical elements is different both in direction and in quantitative indicators. In strongly podzolic soil, there is a more powerful removal of silt from the surface horizons outside the soil profile, while in weakly podzolic soil, on the contrary, a weak removal of silt is observed with an intensive removal of coarse soil from almost the entire thickness of the soil profile.

In the brown-bleached soil of Primorye (BO), the direction of the processes of redistribution of mechanical elements is of the same type as the highly podzolic soil, but the intensity (contrast) is significantly higher. So, the accumulation of coarse earth in the mountains. А2 was 100 kg, and the removal from the illuvial strata was 183, which is -81 kg in total, at +5 in highly podzolic soil. Sludge is actively transported along the entire eluvial-accumulative part of the profile (-167 kg), while its accumulation in the B horizons is only 104 kg. The total balance of silt in the CP soil is -63 kg, which is almost identical to highly podzolic soil. In poorly bleached meadow gley soil (LH otb), the direction of the processes of redistribution of mechanical elements is practically the same type as BO soil, but the intensity is much lower, although the total balance of elements is quite close and even exceeds the indicator of more bleached soil.

Consequently, the intensity of the bleaching process does not really correlate with the nature of the redistribution of mechanical elements, although the brown-bleached soils are much older and have passed the stage of meadow gley soils in the past.

Analyzing the total and individual participation of the main oxides (AI2O3, Fe2O3) in the material composition of the coarse earth and silt of individual zones of the soil profile of the sections relative to the parent rock, the following features and patterns can be identified.

In the A1 horizon of highly podzolic soil, with the removal of 3 kg of coarse soil, the amount of oxides is 1.6 kg; in the eluvial part of the profile, the sum of basic oxides is 11 kg higher than the mass of coarse soil, and in the illuvial part, on the contrary, the mass of coarse earth is 14 kg more than the sum of oxides.

In the humus horizon of weakly podzolic soil, the proportion of coarse earth is 4 kg more than the total content of oxides, in the eluvial zone this excess was 10, and in the illuvial part - 20 kg.

In the A1 and A2 horizons of the bleak of Primorye, the mass of coarse earth practically coincides with the mass of the main oxides, and in the B horizons it exceeds by almost 50 kg. In the eluvial-accumulative part of the profile of the meadow gley, poorly bleached soil, the regularity remains, that is, the mass of coarse soil coincides with the mass of oxides, and in the illuvial horizons B it is 20 kg more.

In assessing the analyzed values, the redistribution of mechanical elements and basic oxides of the material composition of the soil is of great importance for the thickness of the calculated layer, therefore, for a real comparison of the direction and intensity of the processes, the obtained balance values ​​should be reduced to a layer equal in thickness. Taking into account the low thickness of the humus horizon of virgin podzolic soils, the calculated layer cannot be more than 5 cm.The results of such recalculations are given in Table 3.

The results of recalculation to equal thickness of the analyzed soil layer clearly show a fundamental difference in the redistribution of the material composition of the soddy-podzolic soils of Siberia and the bleached soils of Primorye, depending on the severity of the main processes of soil formation.

Table 3

Balance of mechanical elements and basic oxides (kg) in the design layer 5x100x100 cm

in relation to parent rock

Layer, horizons Mechanical elements Coarse earth (> 0.001) Silt fraction (<0,001)

>0,001 <0,001 SiO2 AІ2Oз Fe2Oз Ба- ланс SiO2 AІ2Oз Fe2Oз Баланс

Sod-strongly podzolic soil

A1 -3.7 -16.2 -1.2 0 +0.5 -0.7 -8.7 -5.0 -2.1 -5.8

A2 + B +6.0 -13.3 +5.0 +1.6 +0.9 +7.5 -7.1 -3.2 -1.5 -11.9

B -2.3, +3.0 -1.3 0 +0.1 -1.2 +1.6 +1.1 +0.5 +3.2

Sod-slightly podzolic soil

A1 -13.3 -16.6 -9.1 -0.8 -0.4 -10.3 -9.1 -4.1 -1.7 -14.9

A2 + B -7.1 -1.3 -3.5 -1.8 -0.4 -5.7 +0.8 -0.3 0 +0.5

B -3.0 +2.2 -1.8 -0.6 -0.3 -2.7 +1.1 +0.8 +0.4 +2.3

Brown-bleached soil

A1 +0.6 -22.2 0 +0.9 0 +0.9 -11.4 -8.1 -2.2 -21.7

A2 -9.9 -17.7 +5.4 +2.7 +0.9 +1.9 -8.9 -7.2 -1.8 -17.9

B -9.1 +5.2 -6.4 +0.1 -0.1 -6.4 -2.5 -0.5 +0.5 +2.7

Meadow gley poorly bleached soil

A1 -1.1 -19.0 -0.8 0 +0.3 -0.5 -0.1 -5.9 -2.2 -18.1

A2 +0.5 -13.0 +0.9 +1.0 +0.2 +2.1 -7.0 -3.7 -1.8 -12.4

B -6.6 +2.5 -5.6 +0.4 +0.2 -5.0 +1.9 +0.3 +0.5 +2.3

In particular, only in weakly podzolic soils is the maximum removal of coarse soil over the entire profile relative to the original rock observed. In this case, the maximum falls on the humus horizon. The accumulation of coarse soil in the eluvial part of the bleached soil profile is 2-3 times higher than in highly podzolic soil.

In all analyzed sections, there is an intensive removal of silt from the humus horizon: from 16 kg in podzolic soils to 19-22 in bleached soils. In the eluvial part of the profile, the removal of silt is somewhat less and is practically the same for all sections (13-17 kg). The only exception is the section of weakly podzolic soil, where the removal of silt is minimal - 1.3 kg. In the illuvial part of the profile of all sections, there is an accumulation of silt from 2 to 5 kg per soil layer 5 cm, which is absolutely not equivalent to its removal from the overlying strata.

Most researchers of podzolic and related soils are inclined to believe that the main criterion for the decay of sludge (podzol formation) or its homogeneity along the profile (lessivation) is the indicator of the molecular ratio SiO2 / R2O3, although there are some contradictions. In particular, S.V. Zonn et al. Emphasize that under conditions of frequent changes in reducing and oxidizing conditions, which is typical for Primorye, there is a significant change in not light, namely large fractions of the granulometric composition of soils, and especially in the content of iron, which, when released, passes into a segregated state. And this, according to the authors, is the fundamental difference between the chemistry of brown-bleached soils from sod-podzolic soils.

Based on these provisions, we compared the molecular ratios SiO2 / R2Oz and AІ2Oz / Fe2Oz in the “krupno-zem” and silt sections, taking their value in the parent rock as 100%. Naturally, a value of less than 100% indicates a relative accumulation of sesquioxides in a certain part of the soil profile, and, conversely, a value of more than 100% indicates a decrease in them. The data obtained are presented in table 4.

Analysis of the data in Table 4 makes it possible to note that, judging by the ratio of SiO2 / R2O3 of the clay fraction, there are clearly no significant differences between the horizons of podzolic soils (± 7%). In the sections of bleached soils, this tendency persists, but the level of expansion of molecular ratios in the A1 and A2 horizons reaches 15-25%, depending on the degree of bleaching.

The value of the AІ2Oz / Fe2Oz ratio in the clay fraction of the section of weakly podzolic and highly bleached soil is really stable over all horizons and, on the contrary, significantly differs from highly podzolic and

poorly bleached soils. That is, it is impossible to draw an unambiguous conclusion about the degree of differentiation of sludge depending on the severity of the main process of podzol formation or bleaching in the sections under consideration.

Table 4

Analysis of the magnitude of molecular ratios relative to the parent rock

Sod-podzolic soils Bleached soils

strong - weak - strong - weak

podzolic podzolic bleached bleached

Horizon 3 O3 2 SI / 2 o s / e 3 O3 2 1_1_ / 3 O3 s 3 O3 2 si 2 o s / e 3 O3 2 1_1_ / 3 O3 s 3 O3 2 SI 2 o s / e 3 O3 2 1_1_ / 3 O3 s 3 O3 2 si 2 o s / e 3 O3 2 1_1_ / 3 O3<

Fraction of "coarse earth" (> 0.001 mm)

A1 103 55 109 110 108 97 100 100

A2 104 64 126 110 115 87 112 105

B 97 64 138 160 101 87 80 103

C 100 100 100 120 100 100 100 100

Fraction "silt" (< 0,00" мм)

A1 110 131 107 94 126 104 124 120

A2 107 120 107 97 115 98 103 122

B 100 108 93 100 100 102 100 107

C 100 100 100 100 100 100 100 100

The ratio А12О3 / Рв20з in coarse earth is somewhat more expressive in the profile of highly podzolic soil (-40; -45%) and chill -13%. In the sections of soils with a weak expression of the prevailing EPP type, this ratio has an opposite positive trend (+5; + 10%), and the maximum deviation from the parent rock (+ 60%) is in horizon B of weakly podzolic soil.

Thus, neither the initial data on the material composition, nor attempts to analyze them using various calculated indicators revealed clearly expressed differences both between podzolic and bleached soil types, and depending on the severity of the leading type of the elementary soil formation process, in this case, podzol formation and loessivage. ...

Obviously, the fundamental differences in their manifestation are due to more dynamic processes and phenomena associated with humus formation, physicochemical state and redox processes.

Literature

1. Gadzhiev I.M. Evolution of soils in the southern taiga of Western Siberia. - Novosibirsk: Nauka, 1982 .-- 278 p.

2. Zonn S.V. On brown forest and brown pseudopodzolic soils of the Soviet Union // Genesis and geography

phia of soils. - M .: Nauka, 1966 .-- P.17-43.

3. Zonn S.V., Nechaeva E.G., Sapozhnikov A.P. Processes of pseudopodzolization and loessivation in forest soils of southern Primorye // Pochvovedenie. - 1969. - No. 7. - P.3-16.

4. Ivanov G.I. Soil formation in the south of the Far East. - M .: Nauka, 1976 .-- 200 p.

5. Organization, composition and genesis of soddy-pale-podzolic soil on cover loams / V.А. Tar-gulyan [and others]. - M., 1974 .-- 55 p.

6. Podzolic soils of the central and eastern parts of the European territory of the USSR (on loamy soil-forming rocks). - L .: Nauka, 1980 .-- 301 p.

7. Rode A.A. Soil-forming processes and their study by the stationary method // Principles of organization and methods of stationary study of soils. - M .: Nauka, 1976 .-- S. 5-34.

8. Rubtsova P.P., Rudneva E.N. On some properties of brown forest soils in the foothills of the Carpathians and the plains of the Amur region // Pochvovedenie. - 1967. - No. 9. - S. 71-79.

9. Sinelnikov E.P. Optimization of the properties and regimes of periodically waterlogged soils / FEB DOP RAS, Primorskaya State Agricultural Academy. - Ussuriisk, 2000 .-- 296 p.

10. Sinelnikov E.P., Chekannikova T.A. Comparative analysis of the balance of the material composition of soils with different degrees of bleaching of the plain part of Primorsky Krai // Vestn. KrasGAU. - 2011. - No. 12 (63). - S.87-92.

UDC 631.4: 551.4 E.O. Makushkin

DIAGNOSTICS OF SOILS IN THE UPPER REGIONS OF THE DELTA r. SELENGI *

The article presents diagnostics of soils in the upper reaches of the river delta. Selenga based on morphogenetic and physicochemical properties of soils.

Key words: delta, soil, diagnostics, morphology, reaction, humus content, type, subtype.

E.O.Makushkin SOILS DIAGNOSTICS IN THE SELENGA RIVER DELTA UPPER REACHES

The soils diagnostics in the Selenga river delta upper reaches on the basis of soils morphogenetic, physical and chemical properties is presented in the article.

Key words: delta, soil, diagnostics, morphology, reaction, humus content, type, subtype.

Introduction. The uniqueness of the river delta Selenga is that it is the only freshwater delta ecosystem in the world with an area of ​​more than 1,000 km2, included in the list of specially protected natural objects of the Ramsar Convention. Therefore, it is of interest to study its ecosystems, including soil ones.

Earlier, in the light of the new classification of soils in Russia, we diagnosed the soils of elevated areas of the near-terrace floodplain and a large island (island) Sennaya in the middle part of the delta, small and large islands in the peripheral part of the delta.

Purpose. To carry out classification diagnostics of the soils in the upper reaches of the delta, taking into account the presence of a certain contrast in the landscape and the specificity of the influence of natural and climatic factors on soil formation.

Objects and Methods. The objects of research were the alluvial soils of the upper reaches of the river delta. Selenga. Key sites were represented in the riverbed and central floodplain of the main river channel near the village (s.) Of Murzino, Kabansky District of the Republic of Buryatia, as well as on islands with local names: Dwelling (opposite the village of Murzino), Svinyachiy (800 m from the village of Murzino) upstream).

Comparative geographical, physicochemical and morphogenetic methods were used in the work. The classification position of soils is given according to. In the methodological aspect, taking into account the requirements, the work focuses primarily on the morphogenetic and physicochemical properties of the upper humus horizons. The buried horizons were numbered, starting from the bottom of the soil profile, in Roman capital numerals, as is customary in the study of soil formation in river floodplains.

Results and discussion. About s. Murzino, a number of soil sections were laid. The first three soil sections were laid along a transect in sections from the low-lying facies in front of the artificial dam, directly near the village towards the main left channel of the Selenga River, formed in

In the previous chapters, it was about the reflection of geological structures in the relief and about the influence on the relief of various types of tectonic movements, regardless of the time of manifestation of these movements. It has now been established that the main role in the formation of the main features of the modern relief of endogenous origin belongs to the so-called recent tectonic movements, by which researchers most often understand movements that took place in the Neogene-Quaternary. This is convincingly evidenced, for example, by a comparison of large relief features on a hypsometric map of the former USSR and a map of the latest tectonic movements on the same territory (Fig. 12). Thus, areas with weakly expressed vertical positive tectonic movements in the relief correspond to plains, low plateaus and plateaus with a thin cover of Quaternary deposits: the East European Plain, a significant part of the West Siberian Plain, the Ustyurt Plateau, the Central Siberian Plateau.
Areas of intense tectonic subsidence, as a rule, correspond to low-lying plains with thick sediments

Fig. 12. Scheme of the latest (Neogene-Quaternary) tectonic movements in the territory of the former USSR (according to N.I. Nikolaev, greatly simplified):
1 - areas of very weakly expressed positive movements; 2 - areas of weakly expressed linear positive movements; 3 - areas of intense arched uplifts; 4 - areas of weakly expressed linear uplifts and subsidence; 5 - areas of intense linear uplifts with large (a) and significant (b) gradients of vertical movements; 6 - areas of emerging (a) and prevailing (b) subsidence; 7 - border of areas of strong earthquakes (7 points or more); 8 - boundary of manifestation of Neogene-Quaternary volcanism; 9 - the boundary of the distribution of existing
volcanoes

Neogene-Quaternary age: the Caspian lowland, a significant part of the Turan lowland, the northern part of the West Siberian plain, the Kolyma lowland, etc. The mountains of the Caucasus, Pamir, Tien Shan, the Baikal and Transbaikal mountains, etc. correspond to areas of intense, predominantly positive tectonic movements.
Consequently, the relief-forming role of the latest tectonic movements manifested itself, first of all, in the deformation of the topographic surface, in the creation of positive and negative relief forms of various orders. Through the differentiation of the topographic surface, the latest tectonic movements “control” the location on the Earth's surface of areas of demolition and accumulation and, as a consequence, areas with a predominance of denudation (worked-out) and accumulative relief. The speed, amplitude and contrast of the newest movements significantly affect the intensity of the manifestation of exogenous processes and are also reflected in the morphology and morphometry of the relief.
The expression in the modern relief of geological structures depends on the type and nature of neotectonic movements, the lithology of the rocks composing them, and specific physical and geographical conditions. Some structures are directly reflected in the relief, in place of others an inverted relief is formed (as mentioned above), in the place of others, various types of transitional forms from direct to inverted relief are formed. A variety of relationships between topography and geological structures is especially characteristic of small structures; large structures, as a rule, find direct expression in the topography.
Landforms of the earth's surface, in the formation of which the main role belongs to endogenous processes and in the morphology of which geological structures are clearly reflected, are called morphostructures. This concept was introduced in 1946 by I.P. Gerasimov. However, to date, there is no consensus among researchers in the interpretation of the concept of "morphostructure" neither in relation to the scale of forms, nor in relation to the nature of the correspondence between the structure and its expression in relief. Some researchers understand by morphostructures both straight and inverted, and any other relief that has arisen in the place of a geological structure, others - only a straight relief. Some researchers refer to morphostructures only active geological structures, and prepared, passive structures are called lithomorphic structures.
The data at the disposal of geology and geomorphology indicate that the earth's crust undergoes deformations almost everywhere and of a different nature. So, at present, the territory of Fennoscandia and a significant part of the territory of North America adjacent to the Hudson Bay are experiencing uplift. The rates of uplift of these territories are very significant. In Fennoscandia, immediately after the glacier melted, they were 10-13 cm / year, at present - about 10 mm / year (sea level marks made in the 18th century on the shores of the Gulf of Bothnia are raised above the current level by 1.5-2, 0 m) (fig. 13). The shores of the North Sea within Holland and its neighboring regions are sinking, forcing residents to build dams to protect the territory from the attack of the sea.
Intense tectonic movements are experienced by areas of alpine folding and modern geosynclinal belts. According to reports, the Alps, Himalayas and Pamirs are beyond the Neogene

Fig. 13. Glacioisostatic uplift of the Baltic Shield after the disappearance of the last ice sheet (according to NI Nikolaev):
1 - isohypsum (m); 2 - border of the Caledonids; 3 - border of the Baltic shield

vertical time have risen by several kilometers. Against the background of uplifts, some areas within the areas of alpine folding experience intense subsidence. Thus, against the background of the rise of the Greater and Lesser Caucasus, the Kura-Araks lowland enclosed between them is experiencing intense subsidence. The evidence of the multidirectional movements existing here is the position of the coastlines of the ancient seas, the predecessors of the modern Caspian Sea. The coastal sediments of one of these seas - the Late Bakinsky one, the level of which is located at an absolute height of 10-12 m, is currently traced within the southeastern pericline of the Greater Caucasus and on the slopes of the Talysh mountains at absolute elevations of +300 and +200 m, respectively, and in within the Kura-Araksin lowland, they were penetrated by wells at absolute elevations of -250-300 m.

The manifestation of neotectonic movements can be judged by the numerous and very diverse geomorphological features: 1) the presence of sea and river terraces, the formation of which is not associated with the impact of climate change or any other reasons; 2) deformation of sea and river terraces and ancient surfaces of denudation alignment; 3) deeply submerged or highly elevated coral reefs; 4) submerged marine coastal forms and some underwater karst sources, the position of which cannot be explained by eustatic fluctuations in the level of the World Ocean or other reasons; 5) antecedent valleys, formed as a result of sawing by the river arising on its
paths of tectonic rise - an anticlinal fold or an uplifting block formed by faults (Fig. 14).
Fig. 14. Antecedent through gorges of the river arms. Gerdymanchay at the eastern end of the Kara-Maryanskaya ridge (Azerbaijan, after V.A.Grossheim)
The manifestation of neotectonic movements can also be judged by a number of indirect signs. Fluvial landforms are sensitive to them. Thus, areas experiencing tectonic uplifts are usually characterized by an increase in the density and depth of erosional dissection in comparison with territories that are tectonically stable or undergoing subsidence. In such areas, the morphological appearance of erosional forms also changes: the valleys usually become narrower, the slopes are steeper, there is a change in the longitudinal profile of rivers and sharp changes in the direction of their flow in the plan, which cannot be explained by other reasons, etc. All these (and a number of others) features allow using the geomorphological method to identify positive tectonic structures, in particular, when searching for oil and gas fields.
Depending on the ratio of the rates of tectonic movements (T) and denudation processes (D), the relief can develop in an ascending or descending manner. If T gt; D, the relief is developing in an ascending type. In this case, the absolute heights of the area experiencing uplifts increase, which
stimulates the intensification of deep erosion of permanent and temporary watercourses and leads to an increase in relative heights. Formed river valleys such as gorges, gorges and canyons, characterized by steep or even steep slopes, which, in turn, leads to the intensive development of landslide (under favorable hydrogeological conditions) and landslide-talus processes. Due to the sharp prevalence of deep erosion over lateral erosion in river valleys, floodplains and river terraces are poorly developed or completely absent. The longitudinal profiles of the rivers are characterized by large slopes and undeveloped: more or less gentle slopes in the areas where easily eroded rocks emerge alternate with rapids and ledges at the places where rocks resistant to erosion emerge. An increase in the intensity of denudation processes contributes to the rapid removal of loose products of rock destruction, which results in good exposure of “fresh” rocks that have not yet undergone destruction, preparation of more resistant rocks and, as a result, a clear reflection of geological structures in the relief (relief structure), especially in conditions arid climate. An increase in the absolute heights, length and steepness of slopes leads not only to the intensification of previously existing relief-forming processes, but also to the emergence of new ones: snow avalanches and mudflows, and when the territory rises above the climatic snow boundary, to processes associated with the activity of ice and snow. As a result, a new type of relief is formed in the upper part of the mountains - alpine, the characteristics of which were given above. Thus, a change in quantitative characteristics - an increase in absolute and relative heights, length and steepness of slopes - leads to qualitative changes in the entire complex of relief-forming processes. These changes are reflected in the territories adjacent to the rising mountains: the nature of the correlative deposits changes here. As the mountains grow, the amount and size of clastic material, carried away by permanent and temporary streams, increase.
If Tlt; D, the process of relief formation develops in the opposite direction: the absolute and relative heights decrease, the slopes flatten, the river valleys expand, alluvium begins to accumulate at their bottom, the longitudinal profiles of the rivers flatten out and become flatter, the intensity of erosion and slope processes decreases. When the mountains fall below the snow boundary, the relief-forming activity of snow and ice ceases. The accumulation of clastic material at the bottom of erosional forms and slopes leads to shading of the structure.

topography, a decrease in the area of ​​emergence of fresh rocks. The peaks and crests of the ridges take on rounded outlines. All this leads to a decrease in the amount of removed debris and its size.
The noted connection between changes in relief-forming processes in areas experiencing uplift and the nature of correlative sediments accumulating in the subsidence area makes it possible to use correlative relief. That is why geomorphologists study not only the relief itself, but also its constituent rocks, in particular correlative deposits.
Thus, there is a close relationship between the nature and intensity of recent tectonic movements, the morphology of the relief at different stages of its development, and correlative deposits. This connection makes it possible to widely use geomorphological methods in the study of neotectonic movements and the geological structure of the earth's crust.
In addition to the latest tectonic movements, there are so-called modern movements, which are understood as movements that manifested themselves in historical time and are manifested now. The existence of such movements is evidenced by many historical and archaeological data, as well as data from repeated leveling. The high speeds of these movements noted in a number of cases (up to 10 cm per year or more) dictate the need to take them into account in the construction of long-term structures - canals, oil and gas pipelines, railways, etc.

Relatively stable areas of the earth's crust are called platforms. They develop on the site of consolidated folded structures that arose during the closure of geosynclines. These are vast, mostly flat areas of the earth's crust, often of an irregular polygonal shape. This shape is due to large marginal faults separating the platforms from the adjacent mobile geosynclinal regions. Examples in Russia are the Russian (East European) and Siberian platforms. Platforms have the following features.
In the structure of the platform, there are two main structural layers - lower and upper. The lower tier was formed during the geosynclinal (pre-platform) stage of development and consists of highly dislocated metamorphosed rocks pierced by intrusions and deep faults. It is called the foundation, folded base or platform plinth. The upper tier is a sedimentary platform cover, composed of calm sedimentary rocks. In some places, the foundation protrudes to the surface. Such sections of platforms are called shields. Areas of platforms on which the foundation is submerged and covered everywhere by a sedimentary cover are called slabs.
Relatively weak and slow small amplitudes, vertical oscillatory movements of the earth's crust. At the same time, movements of the same sign - slow sagging or slow uplift - capture large areas of the platforms and can change in time. Periodic transgressions and regressions of sea basins are associated with the oscillatory nature of tectonic movements in the development of platforms. Some parts of the platforms are still flooded by epicontinental seas - the Baltic, North, etc.
The relatively small thickness of sedimentary rocks of the platform cover is usually up to 2-4 km, i.e., several times less than in geosynclinal areas, which changes gradually.
The composition of sedimentary rocks is more or less uniform. In epicontinental platform seas, either carbonate rocks - limestones, dolomites, or shallow-water sandy-clayey deposits - accumulate. Of the minerals here, in some places, there was the formation of sedimentary iron and manganese ores, phosphorites, bauxites, etc. During periods of regression, continental deposits - lacustrine, alluvial, boggy, accumulated on the site of the former seas, and aeolian and lagoon in an arid climate. The formation of iron ores (in swamps and lakes), coals and salts is associated with these stages of continental development.
Horizontal or almost horizontal bedding of layers of sedimentary rocks, complicated in places by isolated gently sloping masonry (discontinuous folding). The largest structural elements of the platforms - syneclises - are huge gentle isometric depressions - troughs, occupying vast areas, reaching hundreds and even thousands of kilometers across. They are distinguished by a very gentle fall of layers - the first meters per kilometer, which corresponds to an angle of inclination of several minutes. An example is the Moscow syneclise with a central part near Moscow. Its cross-section (from north to south) reaches 1300 km, and the fall of layers is 2-2.5 m / km. Large, gentle platform uplifts are called anteclises. An example of them is the Belarusian and Voronezh anteclises. In addition to syneclises and anteclises, within the platforms there are gutter-like tectonic depressions, linearly oriented and bounded by deep faults, stretching for many hundreds of kilometers with a width from tens to 100-200 km. These depressions were named by NS Shatsky aulacogenes (Greek? Aulacon? - furrow). They are characterized by increased tectonic activity, large thickness of sedimentary rocks (for example, the Dnieper-Donetsk depression). Of the smaller folded forms, there are shafts, brachiskladders, domes, flexures.