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The Earth's lithospheric plates are huge blocks. Their foundation is formed by strongly folded granite metamorphosed igneous rocks. The names of lithospheric plates will be given in the article below. From above they are covered with a three- to four-kilometer “cover.” It is formed from sedimentary rocks. The platform has a topography consisting of isolated mountain ranges and vast plains. Next, the theory of the movement of lithospheric plates will be considered.

The emergence of a hypothesis

The theory of the movement of lithospheric plates appeared at the beginning of the twentieth century. Subsequently, she was destined to play a major role in planetary exploration. The scientist Taylor, and after him Wegener, put forward the hypothesis that over time, lithospheric plates drift in a horizontal direction. However, in the thirties of the 20th century, a different opinion took hold. According to him, the movement of lithospheric plates was carried out vertically. This phenomenon was based on the process of differentiation of the planet's mantle matter. It came to be called fixism. This name was due to the fact that the permanently fixed position of sections of the crust relative to the mantle was recognized. But in 1960, after the discovery of a global system of mid-ocean ridges that encircle the entire planet and reach land in some areas, there was a return to the hypothesis of the early 20th century. However, the theory took on a new form. Block tectonics has become a leading hypothesis in sciences studying the structure of the planet.

Basic provisions

It was determined that large lithospheric plates exist. Their number is limited. There are also smaller lithospheric plates of the Earth. The boundaries between them are drawn according to the concentration in the earthquake foci.

The names of lithospheric plates correspond to the continental and oceanic regions located above them. There are only seven blocks with a huge area. The largest lithospheric plates are the South and North American, Euro-Asian, African, Antarctic, Pacific and Indo-Australian.

The blocks floating on the asthenosphere are distinguished by their solidity and rigidity. The above areas are the main lithospheric plates. In accordance with the initial ideas, it was believed that continents make their way through the ocean floor. In this case, the movement of lithospheric plates was carried out under the influence of an invisible force. As a result of the studies, it was revealed that the blocks float passively along the mantle material. It is worth noting that their direction is first vertical. Mantle material rises upward under the crest of the ridge. Then propagation occurs in both directions. Accordingly, the divergence of lithospheric plates is observed. This model represents the ocean floor as a giant one. It comes to the surface in the rift regions of mid-ocean ridges. Then it hides in deep-sea trenches.

The divergence of lithospheric plates provokes the expansion of ocean floors. However, the volume of the planet, despite this, remains constant. The fact is that the birth of new crust is compensated by its absorption in areas of subduction (underthrust) in deep-sea trenches.

Why do lithospheric plates move?

The reason is thermal convection of the planet's mantle material. The lithosphere is stretched and rises, which occurs above the ascending branches of convective currents. This provokes the movement of lithospheric plates to the sides. As the platform moves away from the mid-ocean rifts, the platform becomes denser. It becomes heavier, its surface sinks down. This explains the increase in ocean depth. As a result, the platform sinks into deep-sea trenches. As the heated mantle decays, it cools and sinks, forming basins that are filled with sediment.

Plate collision zones are areas where the crust and platform experience compression. In this regard, the power of the first increases. As a result, the upward movement of lithospheric plates begins. It leads to the formation of mountains.

Research

The study today is carried out using geodetic methods. They allow us to draw a conclusion about the continuity and ubiquity of processes. Collision zones of lithospheric plates are also identified. The lifting speed can be up to tens of millimeters.

Horizontally large lithospheric plates float somewhat faster. In this case, the speed can be up to ten centimeters over the course of a year. So, for example, St. Petersburg has already risen by a meter over the entire period of its existence. Scandinavian Peninsula - by 250 m in 25,000 years. Mantle material moves relatively slowly. However, as a result, earthquakes and other phenomena occur. This allows us to conclude about the high power of material movement.

Using the tectonic position of plates, researchers explain many geological phenomena. At the same time, during the study it became clear that the complexity of the processes occurring with the platform was much greater than it seemed at the very beginning of the hypothesis.

Plate tectonics could not explain changes in the intensity of deformation and movement, the presence of a global stable network of deep faults and some other phenomena. The question of the historical beginning of the action also remains open. Direct signs indicating plate tectonic processes have been known since the late Proterozoic period. However, a number of researchers recognize their manifestation from the Archean or Early Proterozoic.

Expanding Research Opportunities

The advent of seismic tomography led to the transition of this science to a qualitatively new level. In the mid-eighties of the last century, deep geodynamics became the most promising and youngest direction of all existing geosciences. However, new problems were solved using not only seismic tomography. Other sciences also came to the rescue. These include, in particular, experimental mineralogy.

Thanks to the availability of new equipment, it became possible to study the behavior of substances at temperatures and pressures corresponding to the maximum at the depths of the mantle. The research also used isotope geochemistry methods. This science studies, in particular, the isotopic balance of rare elements, as well as noble gases in various earthly shells. In this case, the indicators are compared with meteorite data. Geomagnetism methods are used, with the help of which scientists try to uncover the causes and mechanism of reversals in the magnetic field.

Modern painting

The platform tectonics hypothesis continues to satisfactorily explain the process of crustal development over at least the last three billion years. At the same time, there are satellite measurements, according to which the fact is confirmed that the main lithospheric plates of the Earth do not stand still. As a result, a certain picture emerges.

In the cross section of the planet there are three most active layers. The thickness of each of them is several hundred kilometers. It is assumed that they are entrusted with playing the main role in global geodynamics. In 1972, Morgan substantiated the hypothesis of ascending mantle jets put forward in 1963 by Wilson. This theory explained the phenomenon of intraplate magnetism. The resulting plume tectonics has become increasingly popular over time.

Geodynamics

With its help, the interaction of rather complex processes that occur in the mantle and crust is examined. In accordance with the concept outlined by Artyushkov in his work “Geodynamics”, gravitational differentiation of matter acts as the main source of energy. This process is observed in the lower mantle.

After the heavy components (iron, etc.) are separated from the rock, a lighter mass of solids remains. It descends into the core. The placement of a lighter layer under a heavier one is unstable. In this regard, the accumulating material is periodically collected into fairly large blocks that float to the upper layers. The size of such formations is about one hundred kilometers. This material was the basis for the formation of the upper

The lower layer probably represents undifferentiated primary substance. During the evolution of the planet, due to the lower mantle, the upper mantle grows and the core increases. It is more likely that blocks of light material rise in the lower mantle along the channels. The mass temperature in them is quite high. The viscosity is significantly reduced. The increase in temperature is facilitated by the release of a large amount of potential energy during the rise of matter into the region of gravity at a distance of approximately 2000 km. In the course of movement along such a channel, strong heating of light masses occurs. In this regard, the substance enters the mantle at a fairly high temperature and significantly less weight in comparison with the surrounding elements.

Due to the reduced density, light material floats to the upper layers to a depth of 100-200 kilometers or less. As the pressure decreases, the melting point of the components of the substance decreases. After primary differentiation at the core-mantle level, secondary differentiation occurs. At shallow depths, the light substance partially undergoes melting. During differentiation, denser substances are released. They sink into the lower layers of the upper mantle. The released lighter components, accordingly, rise upward.

The complex of movements of substances in the mantle associated with the redistribution of masses having different densities as a result of differentiation is called chemical convection. The rise of light masses occurs with a periodicity of approximately 200 million years. However, penetration into the upper mantle is not observed everywhere. In the lower layer, the channels are located at a fairly large distance from each other (up to several thousand kilometers).

Lifting blocks

As mentioned above, in those zones where large masses of light heated material are introduced into the asthenosphere, partial melting and differentiation occurs. In the latter case, the release of components and their subsequent ascent are noted. They pass through the asthenosphere quite quickly. When reaching the lithosphere, their speed decreases. In some areas, the substance forms accumulations of anomalous mantle. They lie, as a rule, in the upper layers of the planet.

Anomalous mantle

Its composition approximately corresponds to normal mantle matter. The difference between the anomalous cluster is a higher temperature (up to 1300-1500 degrees) and a reduced speed of elastic longitudinal waves.

The entry of matter under the lithosphere provokes isostatic uplift. Due to the increased temperature, the anomalous cluster has a lower density than the normal mantle. In addition, there is a slight viscosity of the composition.

In the process of reaching the lithosphere, the anomalous mantle is quite quickly distributed along the base. At the same time, it displaces the denser and less heated substance of the asthenosphere. As the movement progresses, the anomalous accumulation fills those areas where the base of the platform is in an elevated state (traps), and it flows around deeply submerged areas. As a result, in the first case there is an isostatic rise. Above submerged areas, the crust remains stable.

Traps

The cooling process of the upper mantle layer and crust to a depth of about one hundred kilometers occurs slowly. Overall, it takes several hundred million years. In this regard, heterogeneities in the thickness of the lithosphere, explained by horizontal temperature differences, have a fairly large inertia. In the event that the trap is located near the upward flow of an anomalous accumulation from the depths, a large amount of substance is captured by a very heated substance. As a result, a fairly large mountain element is formed. In accordance with this scheme, high uplifts occur in the area of ​​epiplatform orogenesis in

Description of processes

In the trap, the anomalous layer is compressed by 1-2 kilometers during cooling. The crust located on top sinks. Sediment begins to accumulate in the formed trough. Their severity contributes to even greater subsidence of the lithosphere. As a result, the depth of the basin can be from 5 to 8 km. At the same time, when the mantle compacts in the lower part of the basalt layer in the crust, a phase transformation of the rock into eclogite and garnet granulite can be observed. Due to the heat flow escaping from the anomalous substance, the overlying mantle is heated and its viscosity decreases. In this regard, there is a gradual displacement of the normal accumulation.

Horizontal offsets

When uplifts form as anomalous mantle enters the crust on the continents and oceans, the potential energy stored in the upper layers of the planet increases. To discharge excess substances they tend to move apart. As a result, additional stresses are formed. They are associated with different types of movement of plates and crust.

The expansion of the ocean floor and the floating of continents are a consequence of the simultaneous expansion of the ridges and the subsidence of the platform into the mantle. Underneath the former are large masses of highly heated anomalous matter. In the axial part of these ridges the latter is located directly under the crust. The lithosphere here has significantly less thickness. At the same time, the anomalous mantle spreads in an area of ​​​​high pressure - in both directions from under the ridge. At the same time, it quite easily tears the ocean crust. The crevice is filled with basaltic magma. It, in turn, is melted from the anomalous mantle. In the process of solidification of magma, a new one is formed. This is how the bottom grows.

Process Features

Beneath the median ridges, the anomalous mantle has reduced viscosity due to increased temperature. The substance can spread quite quickly. In this regard, the growth of the bottom occurs at an increased rate. The oceanic asthenosphere also has relatively low viscosity.

The main lithospheric plates of the Earth float from ridges to subsidence sites. If these areas are located in the same ocean, then the process occurs at a relatively high speed. This situation is typical for the Pacific Ocean today. If expansion of the bottom and subsidence occur in different areas, then the continent located between them drifts in the direction where the deepening occurs. Under continents, the viscosity of the asthenosphere is higher than under the oceans. Due to the resulting friction, significant resistance to movement appears. The result is a reduction in the rate at which seafloor expansion occurs unless there is compensation for mantle subsidence in the same area. Thus, expansion in the Pacific Ocean is faster than in the Atlantic.

It is impossible to prove modern ideas about the evolution of life by direct methods. The experiment will last for millions of years (civilized society is no more than 10 thousand years old), and a time machine will most likely never be invented. How is truth obtained in this area of ​​knowledge? How to approach the burning question “Who came from whom”?

Modern biology has already accumulated a lot of indirect evidence and considerations in favor of evolution. Living organisms have common features - biochemical processes proceed in a similar way, there are similarities in external and internal structure and in individual development. If the embryos of a turtle and a rat are indistinguishable in the early stages of development, then is this suspicious similarity a hint of a single ancestor from which these animals descended over millions of years? It is about the ancestors of modern species that paleontology, the science of the fossil remains of living beings, will tell. Interesting facts that give food for thought are provided by biogeography - the science of the distribution of animals and plants.

EVIDENCE OF EVOLUTION
Morphological
Embryological
Paleontological
Biochemical
Biogeographic

1. Biochemical evidence of evolution.

1. All organisms, be they viruses, bacteria, plants, animals or fungi, have a surprisingly similar elementary chemical composition.

2. For all of them, proteins and nucleic acids play a particularly important role in life phenomena, which are always built according to a single principle and from similar components. A high degree of similarity is found not only in the structure of biological molecules, but also in the way they function. The principles of genetic coding, biosynthesis of proteins and nucleic acids are the same for all living things.

3. The vast majority of organisms use ATP as energy storage molecules; the mechanisms for breaking down sugars and the main energy cycle of the cell are also the same.

4.Most organisms have a cellular structure.

2.Embryological evidence of evolution.

Domestic and foreign scientists have discovered and deeply studied the similarities in the initial stages of embryonic development of animals. All multicellular animals go through the blastula and gastrula stages during individual development. The similarity of embryonic stages within individual types or classes is particularly clear. For example, in all terrestrial vertebrates, as well as in fish, the formation of gill arches is found, although these formations have no functional significance in adult organisms. This similarity of embryonic stages is explained by the unity of origin of all living organisms.

3. Morphological evidence of evolution.

Of particular value for proving the unity of the origin of the organic world are forms that combine the characteristics of several large systematic units. The existence of such intermediate forms indicates that in previous geological eras there lived organisms that were the ancestors of several systematic groups. A clear example of this is the single-celled organism Euglena verida. It simultaneously has characteristics typical of plants and protozoa.

The structure of the forelimbs of some vertebrates, despite the performance of completely different functions by these organs, is fundamentally similar in structure. Some bones in the skeleton of the limbs may be absent, others may be fused, the relative sizes of the bones may vary, but their homology is quite obvious. Homologous are those organs that develop from the same embryonic rudiments in a similar way.

Some organs or their parts do not function in adult animals and are superfluous for them - these are the so-called vestigial organs or rudiments. The presence of rudiments, as well as homologous organs, is also evidence of a common origin.

4. Paleontological evidence of evolution.

Paleontology points to the causes of evolutionary transformations. The evolution of horses is interesting in this regard. Climate change on Earth has caused changes in the horse's limbs. In parallel with the change in the limbs, a transformation of the entire organism took place: an increase in body size, changes in the shape of the skull and complication of the structure of the teeth, the emergence of a digestive tract characteristic of herbivorous mammals, and much more.

As a result of changes in external conditions under the influence of natural selection, a gradual transformation of small five-toed omnivores into large herbivores occurred. The richest paleontological material is one of the most convincing evidence of the evolutionary process that has been going on on our planet for more than 3 billion years.

5. Biogeographic evidence for evolution.

A clear indication of the evolutionary changes that have occurred and are ongoing is the spread of animals and plants across the surface of our planet. Comparison of the animal and plant world of different zones provides rich scientific material to prove the evolutionary process. The fauna and flora of the Paleoarctic and Neoarctic regions have much in common. This is explained by the fact that in the gap between the named areas there was a land bridge - the Bering Isthmus. Other areas have little in common.

Thus, the distribution of animal and plant species over the surface of the planet and their grouping into biographical zones reflects the process of the historical development of the Earth and the evolution of living things.

Island fauna and flora.

To understand the evolutionary process, the flora and fauna of the islands are of interest. The composition of their flora and fauna depends entirely on the history of the origin of the islands. A huge number of diverse biographical facts indicate that the characteristics of the distribution of living beings on the planet are closely related to the transformation of the earth's crust and to the evolutionary changes of species.

December 10th, 2015

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According to modern plate theory The entire lithosphere is divided into separate blocks by narrow and active zones - deep faults - moving in the plastic layer of the upper mantle relative to each other at a speed of 2-3 cm per year. These blocks are called lithospheric plates.

The first suggestion about the horizontal movement of crustal blocks was made by Alfred Wegener in the 1920s within the framework of the “continental drift” hypothesis, but this hypothesis did not receive support at that time.

Only in the 1960s did studies of the ocean floor provide conclusive evidence of horizontal plate movements and ocean expansion processes due to the formation (spreading) of oceanic crust. The revival of ideas about the predominant role of horizontal movements occurred within the framework of the “mobilistic” trend, the development of which led to the development of the modern theory of plate tectonics. The main principles of plate tectonics were formulated in 1967-68 by a group of American geophysicists - W. J. Morgan, C. Le Pichon, J. Oliver, J. Isaacs, L. Sykes in the development of earlier (1961-62) ideas of American scientists G. Hess and R. Digtsa about the expansion (spreading) of the ocean floor.

It is argued that scientists are not entirely sure what causes these shifts and how the boundaries of tectonic plates are defined. There are countless different theories, but none completely explains all aspects of tectonic activity.

Let's at least find out how they imagine it now.

Wegener wrote: “In 1910, the idea of ​​​​moving continents first occurred to me ... when I was struck by the similarity of the outlines of the coasts on both sides of the Atlantic Ocean.” He suggested that in the early Paleozoic there were two large continents on Earth - Laurasia and Gondwana.

Laurasia was the northern continent, which included the territories of modern Europe, Asia without India and North America. The southern continent - Gondwana united the modern territories of South America, Africa, Antarctica, Australia and Hindustan.

Between Gondwana and Laurasia there was the first sea - Tethys, like a huge bay. The rest of the Earth's space was occupied by the Panthalassa Ocean.

About 200 million years ago, Gondwana and Laurasia were united into a single continent - Pangea (Pan - universal, Ge - earth)

About 180 million years ago, the continent of Pangea again began to separate into its component parts, which mixed on the surface of our planet. The division occurred as follows: first Laurasia and Gondwana reappeared, then Laurasia split, and then Gondwana split. Due to the split and divergence of parts of Pangea, oceans were formed. The Atlantic and Indian oceans can be considered young oceans; old - Quiet. The Arctic Ocean became isolated as landmass increased in the Northern Hemisphere.

A. Wegener found many confirmations of the existence of a single continent of the Earth. What seemed especially convincing to him was the existence in Africa and South America of the remains of ancient animals - listosaurs. These were reptiles, similar to small hippopotamuses, that lived only in freshwater bodies of water. This means that they could not swim huge distances in salty sea water. He found similar evidence in the plant world.

Interest in the hypothesis of continental movement in the 30s of the 20th century. decreased somewhat, but was revived again in the 60s, when, as a result of studies of the relief and geology of the ocean floor, data were obtained indicating the processes of expansion (spreading) of the oceanic crust and the “diving” of some parts of the crust under others (subduction).

Structure of the continental rift

The upper rocky part of the planet is divided into two shells, significantly different in rheological properties: a rigid and brittle lithosphere and an underlying plastic and mobile asthenosphere.
The base of the lithosphere is an isotherm approximately equal to 1300°C, which corresponds to the melting temperature (solidus) of the mantle material at lithostatic pressure existing at depths of the first hundreds of kilometers. Rocks in the Earth above this isotherm are quite cold and behave like rigid materials, while underlying rocks of the same composition are quite heated and deform relatively easily.

The lithosphere is divided into plates, constantly moving along the surface of the plastic asthenosphere. The lithosphere is divided into 8 large plates, dozens of medium plates and many small ones. Between the large and medium slabs there are belts composed of a mosaic of small crustal slabs.

Plate boundaries are areas of seismic, tectonic, and magmatic activity; the internal regions of the plates are weakly seismic and characterized by weak manifestation of endogenous processes.
More than 90% of the Earth's surface falls on 8 large lithospheric plates:

Some lithospheric plates are composed exclusively of oceanic crust (for example, the Pacific Plate), others include fragments of both oceanic and continental crust.

Rift formation scheme

There are three types of relative movements of plates: divergence (divergence), convergence (convergence) and shear movements.

Divergent boundaries are boundaries along which plates move apart. The geodynamic situation in which the process of horizontal stretching of the earth's crust occurs, accompanied by the appearance of extended linearly elongated slot or ditch-like depressions, is called rifting. These boundaries are confined to continental rifts and mid-ocean ridges in ocean basins. The term "rift" (from the English rift - gap, crack, gap) is applied to large linear structures of deep origin, formed during the stretching of the earth's crust. In terms of structure, they are graben-like structures. Rifts can form on both continental and oceanic crust, forming a single global system oriented relative to the geoid axis. In this case, the evolution of continental rifts can lead to a break in the continuity of the continental crust and the transformation of this rift into an oceanic rift (if the expansion of the rift stops before the stage of rupture of the continental crust, it is filled with sediments, turning into an aulacogen).

The process of plate separation in zones of oceanic rifts (mid-ocean ridges) is accompanied by the formation of new oceanic crust due to magmatic basaltic melt coming from the asthenosphere. This process of formation of new oceanic crust due to the influx of mantle material is called spreading (from the English spread - to spread, unfold).

The structure of the mid-ocean ridge. 1 – asthenosphere, 2 – ultrabasic rocks, 3 – basic rocks (gabbroids), 4 – complex of parallel dikes, 5 – basalts of the ocean floor, 6 – segments of the oceanic crust formed at different times (I-V as they become more ancient), 7 – near-surface igneous chamber (with ultrabasic magma in the lower part and basic magma in the upper), 8 – sediments of the ocean floor (1-3 as they accumulate)

During spreading, each extension pulse is accompanied by the arrival of a new portion of mantle melts, which, when solidified, build up the edges of plates diverging from the MOR axis. It is in these zones that the formation of young oceanic crust occurs.

Collision of continental and oceanic lithospheric plates

Subduction is the process of pushing an oceanic plate under a continental or other oceanic one. Subduction zones are confined to the axial parts of deep-sea trenches associated with island arcs (which are elements of active margins). Subduction boundaries account for about 80% of the length of all convergent boundaries.

When the continental and oceanic plates collide, a natural phenomenon is the displacement of the oceanic (heavier) plate under the edge of the continental one; When two oceans collide, the more ancient (that is, cooler and denser) of them sinks.

Subduction zones have a characteristic structure: their typical elements are a deep-sea trench - a volcanic island arc - a back-arc basin. A deep-sea trench is formed in the zone of bending and underthrusting of the subducting plate. As this plate sinks, it begins to lose water (found in abundance in sediments and minerals), the latter, as is known, significantly reduces the melting temperature of rocks, which leads to the formation of melting centers that feed volcanoes of island arcs. In the rear of a volcanic arc, some stretching usually occurs, which determines the formation of a back-arc basin. In the back-arc basin zone, stretching can be so significant that it leads to rupture of the plate crust and the opening of a basin with oceanic crust (the so-called back-arc spreading process).

The volume of oceanic crust absorbed in subduction zones is equal to the volume of crust emerging in spreading zones. This position emphasizes the idea that the volume of the Earth is constant. But this opinion is not the only and definitively proven one. It is possible that the volume of the plane changes pulsatingly, or that it decreases due to cooling.

The immersion of the subducting plate into the mantle is traced by the foci of earthquakes that occur at the contact of the plates and inside the subducting plate (colder and, therefore, more fragile than the surrounding mantle rocks). This seismofocal zone is called the Benioff-Zavaritsky zone. In subduction zones, the process of formation of new continental crust begins. A much rarer process of interaction between the continental and oceanic plates is the process of obduction - the pushing of part of the oceanic lithosphere onto the edge of the continental plate. It should be emphasized that during this process, the ocean plate is separated, and only its upper part - the crust and several kilometers of the upper mantle - moves forward.

Collision of continental plates

When continental plates collide, the crust of which is lighter than the mantle material and, as a result, is not able to sink into it, a collision process occurs. During the collision, the edges of colliding continental plates are crushed, crushed, and systems of large thrusts are formed, which leads to the growth of mountain structures with a complex fold-thrust structure. A classic example of such a process is the collision of the Hindustan plate with the Eurasian plate, accompanied by the growth of the grandiose mountain systems of the Himalayas and Tibet. The collision process replaces the subduction process, completing the closure of the ocean basin. Moreover, at the beginning of the collision process, when the edges of the continents have already moved closer together, the collision is combined with the process of subduction (the remnants of the oceanic crust continue to sink under the edge of the continent). Large-scale regional metamorphism and intrusive granitoid magmatism are typical for collision processes. These processes lead to the creation of a new continental crust (with its typical granite-gneiss layer).

The main reason for plate movement is mantle convection, caused by mantle thermogravitational currents.

The source of energy for these currents is the difference in temperature between the central regions of the Earth and the temperature of its near-surface parts. In this case, the main part of the endogenous heat is released at the boundary of the core and the mantle during the process of deep differentiation, which determines the disintegration of the primary chondritic substance, during which the metal part rushes to the center, building up the core of the planet, and the silicate part is concentrated in the mantle, where it further undergoes differentiation.

Rocks heated in the central zones of the Earth expand, their density decreases, and they float up, giving way to sinking colder and therefore heavier masses that have already given up some of the heat in the near-surface zones. This process of heat transfer occurs continuously, resulting in the formation of ordered closed convective cells. In this case, in the upper part of the cell, the flow of matter occurs almost in a horizontal plane, and it is this part of the flow that determines the horizontal movement of the matter of the asthenosphere and the plates located on it. In general, the ascending branches of convective cells are located under the zones of divergent boundaries (MOR and continental rifts), while the descending branches are located under the zones of convergent boundaries. Thus, the main reason for the movement of lithospheric plates is “dragging” by convective currents. In addition, a number of other factors act on the slabs. In particular, the surface of the asthenosphere turns out to be somewhat elevated above the zones of ascending branches and more depressed in the zones of subsidence, which determines the gravitational “sliding” of the lithospheric plate located on an inclined plastic surface. Additionally, there are processes of drawing heavy cold oceanic lithosphere in subduction zones into the hot, and as a consequence less dense, asthenosphere, as well as hydraulic wedging by basalts in the MOR zones.

The main driving forces of plate tectonics are applied to the base of the intraplate parts of the lithosphere - the mantle drag forces FDO under the oceans and FDC under the continents, the magnitude of which depends primarily on the speed of the asthenospheric flow, and the latter is determined by the viscosity and thickness of the asthenospheric layer. Since the thickness of the asthenosphere under the continents is much less, and the viscosity is much greater than under the oceans, the magnitude of the FDC force is almost an order of magnitude lower than the FDO value. Under the continents, especially their ancient parts (continental shields), the asthenosphere almost pinches out, so the continents seem to be “stranded.” Since most lithospheric plates of the modern Earth include both oceanic and continental parts, it should be expected that the presence of a continent in the plate should, in general, “slow down” the movement of the entire plate. This is how it actually happens (the fastest moving almost purely oceanic plates are the Pacific, Cocos and Nazca; the slowest are the Eurasian, North American, South American, Antarctic and African plates, a significant part of whose area is occupied by continents). Finally, at convergent plate boundaries, where the heavy and cold edges of lithospheric plates (slabs) sink into the mantle, their negative buoyancy creates the FNB force (an index in the designation of force - from the English negative buoyance). The action of the latter leads to the fact that the subducting part of the plate sinks in the asthenosphere and pulls the entire plate along with it, thereby increasing the speed of its movement. Obviously, the FNB force acts sporadically and only in certain geodynamic settings, for example in the cases of slab failure across the 670 km divide described above.

Thus, the mechanisms that set lithospheric plates in motion can be conditionally classified into the following two groups: 1) associated with the forces of mantle drag mechanism applied to any points of the base of the plates, in the figure - forces FDO and FDC; 2) associated with forces applied to the edges of the slabs (edge-force mechanism), in the figure - FRP and FNB forces. The role of one or another driving mechanism, as well as certain forces, is assessed individually for each lithospheric plate.

The combination of these processes reflects the general geodynamic process, covering areas from the surface to the deep zones of the Earth. Currently, two-cell mantle convection with closed cells is developing in the Earth's mantle (according to the model of through-mantle convection) or separate convection in the upper and lower mantle with the accumulation of slabs under subduction zones (according to the two-tier model). The probable poles of the rise of mantle material are located in northeastern Africa (approximately under the junction zone of the African, Somali and Arabian plates) and in the Easter Island region (under the middle ridge of the Pacific Ocean - the East Pacific Rise). The equator of subsidence of mantle matter passes approximately along a continuous chain of convergent plate boundaries along the periphery of the Pacific and eastern Indian Oceans. The modern regime of mantle convection, which began approximately 200 million years ago with the collapse of Pangea and gave rise to modern oceans, will in the future be replaced by a single-cell regime (according to the model of through-mantle convection convection) or (according to an alternative model) convection will become through the mantle due to the collapse of slabs through the 670 km section. This may lead to a collision of continents and the formation of a new supercontinent, the fifth in the history of the Earth.

Plate movements obey the laws of spherical geometry and can be described based on Euler's theorem. Euler's rotation theorem states that any rotation of three-dimensional space has an axis. Thus, rotation can be described by three parameters: the coordinates of the rotation axis (for example, its latitude and longitude) and the rotation angle. Based on this position, the position of the continents in past geological eras can be reconstructed. An analysis of the movements of the continents led to the conclusion that every 400-600 million years they unite into a single supercontinent, which subsequently undergoes disintegration. As a result of the split of such a supercontinent Pangea, which occurred 200-150 million years ago, modern continents were formed.

Plate tectonics was the first general geological concept that could be tested. Such a check was carried out. In the 70s a deep-sea drilling program was organized. As part of this program, several hundred wells were drilled by the Glomar Challenger drilling vessel, which showed good agreement between ages estimated from magnetic anomalies and ages determined from basalts or sedimentary horizons. The distribution diagram of sections of the oceanic crust of different ages is shown in Fig.:

Age of the ocean crust based on magnetic anomalies (Kennet, 1987): 1 - areas of missing data and land; 2–8 - age: 2 - Holocene, Pleistocene, Pliocene (0–5 million years); 3 - Miocene (5–23 million years); 4 - Oligocene (23–38 million years); 5 - Eocene (38–53 million years); 6 - Paleocene (53–65 million years) 7 - Cretaceous (65–135 million years) 8 - Jurassic (135–190 million years)

At the end of the 80s. Another experiment to test the movement of lithospheric plates was completed. It was based on measuring baselines relative to distant quasars. Points were selected on two plates at which, using modern radio telescopes, the distance to the quasars and their declination angle were determined, and, accordingly, the distances between the points on the two plates were calculated, i.e., the base line was determined. The accuracy of the determination was a few centimeters. After several years, the measurements were repeated. A very good agreement was obtained between the results calculated from magnetic anomalies and the data determined from the baselines

Diagram illustrating the results of measurements of the mutual movement of lithospheric plates obtained by the very long baseline interferometry method - ISDB (Carter, Robertson, 1987). The movement of the plates changes the length of the baseline between radio telescopes located on different plates. The map of the Northern Hemisphere shows baselines from which sufficient data have been obtained using the ISDB method to make a reliable estimate of the rate of change in their length (in centimeters per year). The numbers in parentheses indicate the amount of plate displacement calculated from the theoretical model. In almost all cases the calculated and measured values ​​are very close

Thus, plate tectonics has been tested over the years by a number of independent methods. It is recognized by the world scientific community as the paradigm of geology at the present time.

Knowing the position of the poles and the speed of modern movement of lithospheric plates, the speed of spreading and absorption of the ocean floor, it is possible to outline the path of movement of the continents in the future and imagine their position for a certain period of time.

This forecast was made by American geologists R. Dietz and J. Holden. In 50 million years, according to their assumptions, the Atlantic and Indian oceans will expand at the expense of the Pacific, Africa will shift to the north and thanks to this the Mediterranean Sea will gradually be eliminated. The Strait of Gibraltar will disappear, and a “turned” Spain will close the Bay of Biscay. Africa will be split by the great African faults and its eastern part will shift to the northeast. The Red Sea will expand so much that it will separate the Sinai Peninsula from Africa, Arabia will move to the northeast and close the Persian Gulf. India will increasingly move towards Asia, which means the Himalayan mountains will grow. California will separate from North America along the San Andreas Fault, and a new ocean basin will begin to form in this place. Significant changes will occur in the southern hemisphere. Australia will cross the equator and come into contact with Eurasia. This forecast requires significant clarification. Much here still remains debatable and unclear.

An interesting article caught my eye on RIA Novosti...

I don't know why this made the news. It’s also not very clear what superpowers have to do with it...
In my opinion, this is a rather interesting article, which sets out interesting, sometimes even impressive, facts about the human body =)

If this interests you and is not difficult, write in the comments what exactly surprised/amazed/shocked you most of all of the above?
I tried to make my own list of what was particularly impressive from this, but it included too much, almost half =)

51 facts that prove that a person has superpowers

They all prove that you have enormous potential. Essentially, you are a superhero.

1. The human heart, removed from the chest as in the Indiana Jones movie, is actually capable of beating for a short period of time because it has its own electrical system and will continue to draw electricity from the surrounding air.

2. Stomach acid is so strong that your body creates a whole new stomach lining every 3-4 days.

3. The human nose can recognize and remember 50,000 unique odors, but this is completely incomparable to the capabilities of a dog in this area.

4. You sneeze at 160 kilometers per hour or more.

5. The length of your blood vessels is 96,000 kilometers, and this is enough to circle the equator approximately two and a half times.

6. Every day, your heart creates enough energy to drive a truck 20 miles. Throughout a person's life, the heart produces such an amount of energy that it would be enough for this truck to cover the distance from the Earth to the Moon and back.

7. On average, a person sheds about 50 kilograms of skin between birth and age 70, which is comparable to the weight of a short person.

8. If you look at the sky on a clear night and can see Andromeda, this means that your eyes are so sensitive that they are able to distinguish a faint spot of light located in the nearest neighboring galaxy and distant from us at a distance of 2.5 million light years.

9. A person can snore, making a sound of about 80 decibels, which is comparable to sleeping next to a working jackhammer destroying cement. Noise levels above 85 decibels are considered harmful to the human ear.

10. A person produces enough saliva during his life to fill about two swimming pools, that is, about 24,000 liters.

13. Neurons fire at a speed of 240 kilometers per hour.

14. In addition to the five senses, you actually have a meta-sense called proprioception, which combines your brain's knowledge of what your muscles are doing with the sense of the size and shape of your body, and thus gives you an idea about where your body parts are in relation to each other. Therefore, you can easily touch your nose with your finger with your eyes closed.

15. Your heart rate, as well as your facial expressions, change depending on the music you listen to.

16. Your brain, when it's awake, can produce enough electricity to power one light bulb.

17. When compared, your bones will be stronger than steel, since a comparable steel beam will weigh four or five times more. A cubic meter of bone can, in principle, support a weight of 10,000 kilograms, which is roughly the weight of five standard pickup trucks.

18. And despite the fact that they are stronger than steel, your bones are 31% water.

19. If the human eye were a digital camera, it would have a resolution of 576 megapixels. By comparison, the Mamiya DSLR was the most powerful camera I could find, with a resolution of 80 megapixels and an impressive retail price of $34,000.

20. In addition, experts believe that the human eye can distinguish 10 million different colors.

21. If DNA could be unwoven, then its length, taking into account all the cells in your body, would be 16 billion kilometers, which is equal to the distance from Earth to Pluto and back.

22. Over the course of a lifetime, your brain's long-term memory can store up to 1 quadrillion (1 million billion) individual bits of information.

23. The human brain, especially the prefrontal cortex, which helps us develop social skills and communication with others, continues to develop into our 40s and beyond.

24. Over the course of an average lifespan, a person's heart pumps about 1.5 million barrels of blood—enough to fill 200 railroad tank cars.

25. Your body produces 180 million red blood cells per hour.

26. A normal pregnancy lasts nine months, but the longest recorded pregnancy was 375 days, that is, 12.5 months.

27. During pregnancy, if the mother's organs are damaged, the fetus in the womb sends stem cells to repair the damaged organ.

28. Taking one step requires the work of 200 muscles.

29. Researchers have discovered 1,458 new species of bacteria in belly buttons.

30. Most astronauts grow five centimeters taller in space.

31. 6 billion steps of the DNA helix are contained in one cell.

32. For every fertilized egg, there are 200-500 million sperm trying to pass on their DNA.

33. By the time you die, you will have spent a third of your life sleeping.

34. One study found that you can reset your brain's internal sleep-wake clock (circadian rhythm) by shining a beam of light onto the back of your knee.

35. A person is able to go without food for two months.

36. Your tongue is not the only place where taste buds are located - they are also found in the stomach, intestinal tract, pancreas, lungs, anus, testicles and brain.

37. New physical connections are created between neurons in the brain every time you remember something.

38. It has been scientifically proven that even a small dose of electricity changes the way the brain works, and this usually results in a reduction in empathy.

39. You can survive without oxygen for 5-10 minutes, but after that your brain cells will begin to die.

40. Your brain is 60% fat.

41. The human brain will feed on itself, and this will be a last attempt to avoid starvation (the same thing happens during extreme dieting or malnutrition).

42. The vagina has the ability to cleanse itself.

43. Phobias may represent memories passed down in genes by ancestors.

44. Your automatically programmed response to certain stimuli is called an emotion.

45. Long-term memory creates permanent physical changes in the brain.

46. ​​If you try to convey a certain emotion with your facial expression, you will actually begin to feel that emotion.

47. The human eye is capable of seeing only a small part of the visual field at a time, and therefore the eye makes 2-3 saccades (jump-like automatic eye movements) per second in order to get the full picture.

48. When you remember something, you do not turn to the original memory, but to a creative recreation of certain ideas, in which gaps are often discovered, as well as completely new components.

49. Your brain forgets information in order to protect itself from information overload and unpleasant emotional experiences, which allows you to think more quickly and absorb new information more easily.

50. The brain is able to perform new tasks, including learning new pieces of music during REM sleep. REM sleep appears to enhance performance on tasks using procedural memory, or subconscious knowledge of the order of actions.

51. Society has a “canonical perspective,” which means that we all see certain things the same way. Example: When researchers asked people in different parts of the world to draw a coffee cup, almost everyone drew the coffee cup looking at it slightly from above and shifting the perspective slightly to the right or left, but no one drew it looking down from above.

There are two types of lithosphere. The oceanic lithosphere has oceanic crust about 6 km thick. It is mostly covered by the sea. The continental lithosphere is covered by continental crust with a thickness of 35 to 70 km. Most of this crust protrudes above, forming land.

Plates

Rocks and minerals

Moving plates

The plates of the earth's crust are constantly moving in different directions, although very slowly. The average speed of their movement is 5 cm per year. Your nails grow at about the same rate. Since all the plates fit tightly together, the movement of any one of them affects the surrounding plates, causing them to gradually move. Plates can move in different ways, which can be seen at their boundaries, but the reasons that cause plate movement are not yet known to scientists. Apparently, this process may have neither beginning nor end. Nevertheless, some theories claim that one type of plate movement can be, so to speak, “primary”, and from it all other plates begin to move.

One type of plate movement is the “diving” of one plate under another. Some scholars believe that it is this type of movement that causes all other plate movements. At some boundaries, molten rock pushing up to the surface between two plates solidifies at their edges, pushing the plates apart. This process can also cause all the other plates to move. It is also believed that, in addition to the primary shock, the movement of plates is stimulated by giant heat flows circulating in the mantle (see article ““).

Drifting continents

Scientists believe that since the formation of the primary earth's crust, the movement of plates has changed the position, shape and size of continents and oceans. This process was called tectonics slabs. Various proofs of this theory are given. For example, the outlines of continents such as South America and Africa look as if they once formed a single whole. Undoubted similarities were also discovered in the structure and age of the rocks that make up the ancient mountain ranges on both continents.

1. According to scientists, the land masses that now form South America and Africa were connected to each other more than 200 million years ago.

2. Apparently, the floor of the Atlantic Ocean gradually expanded as new rock formed at plate boundaries.

3. Currently, South America and Africa are moving away from each other at a rate of about 3.5 cm per year due to plate movement.