Lithospheric plates and blocks. Names of the largest plates of the Earth. Versions of the formation of the planet. Useful video: lithospheric plates and modern relief
Lithospheric plates – large rigid blocks of the Earth’s lithosphere, bounded by seismically and tectonically active fault zones.
The plates, as a rule, are separated by deep faults and move through the viscous layer of the mantle relative to each other at a speed of 2-3 cm per year. Where continental plates converge, they collide and form mountain belts . When the continental and oceanic plates interact, the plate with the oceanic crust is pushed under the plate with the continental crust, resulting in the formation of deep-sea trenches and island arcs.
The movement of lithospheric plates is associated with the movement of matter in the mantle. In certain parts of the mantle there are powerful flows of heat and matter rising from its depths to the surface of the planet.
More than 90% of the Earth's surface is covered 13 -th largest lithospheric plates.
Rift– a huge fracture in the earth's crust, formed during its horizontal stretching (i.e., where the flows of heat and matter diverge). In rifts, magma outflows, new faults, horsts, and grabens arise. Mid-ocean ridges form.
First continental drift hypothesis (i.e. horizontal movement earth's crust) put forward at the beginning of the twentieth century A. Wegener. Created on its basis lithospheric theory t. According to this theory, the lithosphere is not a monolith, but consists of large and small plates “floating” on the asthenosphere. The boundary areas between lithospheric plates are called seismic belts - these are the most “restless” areas of the planet.
The earth's crust is divided into stable (platforms) and mobile areas (folded areas - geosynclines).
- powerful underwater mountain structures within the ocean floor, most often occupying a middle position. Near mid-ocean ridges, lithospheric plates move apart and young basaltic oceanic crust appears. The process is accompanied by intense volcanism and high seismicity.
Continental rift zones are, for example, the East African Rift System, the Baikal Rift System. Rifts, like mid-ocean ridges, are characterized by seismic activity and volcanism.
Plate tectonics- a hypothesis suggesting that the lithosphere is divided into large plates that move horizontally through the mantle. Near mid-ocean ridges, lithospheric plates move apart and grow due to material rising from the bowels of the Earth; in deep-sea trenches, one plate moves under another and is absorbed by the mantle. Fold structures are formed where plates collide.
How did continents and islands appear? What determines the name of the largest plates of the Earth? Where did our planet come from?
How it all began?
Everyone has thought at least once about the origin of our planet. For deeply religious people, everything is simple: God created the Earth in 7 days, period. They are unshakable in their confidence, even knowing the names of the largest lithospheric plates formed as a result of the evolution of the planet’s surface. For them, the birth of our stronghold is a miracle, and no arguments of geophysicists, naturalists and astronomers can convince them.
Scientists, however, have a different opinion, based on hypotheses and assumptions. They make guesses, put forward versions and come up with a name for everything. This also affected the largest plates of the Earth.
On this moment It is not known for certain how our firmament appeared, but there are many interesting opinions. It was the scientists who unanimously decided that there once existed a single gigantic continent, which, as a result of cataclysms and natural processes, split into parts. Scientists also came up with not only the names of the largest plates of the Earth, but also designated the small ones.
A theory bordering on science fiction
For example, Immanuel Kant and Pierre Laplace - scientists from Germany - believed that the Universe emerged from a gas nebula, and the Earth was a gradually cooling planet, the crust of which was nothing more than a cooled surface.
Another scientist, Otto Yulievich Schmidt, believed that the Sun, when passing through a gas and dust cloud, captured part of it with itself. His version is that our Earth was never a completely molten substance and was originally a cold planet.
According to the theory of the English scientist Fred Hoyle, the Sun had its own twin star, which exploded like a supernova. Almost all the fragments were thrown over vast distances, and the small number remaining around the Sun turned into planets. One of these fragments became the cradle of humanity.
Version as an axiom
The most common story of the origin of the Earth is as follows:
- About 7 billion years ago, the primary cold planet formed, after which its interior began to gradually warm up.
- Then, during the so-called “lunar era,” red-hot lava poured out onto the surface in gigantic quantities. This entailed the formation of the primary atmosphere and served as an impetus for the formation of the earth's crust - the lithosphere.
- Thanks to the primary atmosphere, oceans appeared on the planet, as a result of which the Earth was covered with a dense shell, representing the outlines of oceanic depressions and continental protrusions. In those distant times, the area of water significantly prevailed over the area of land. By the way, the earth’s crust and the upper part of the mantle are called the lithosphere, which forms lithospheric plates that make up the overall “shape” of the Earth. The names of the largest plates correspond to their geographical location.
Giant rift
How did continents and lithospheric plates form? About 250 million years ago, the Earth looked completely different from what it does now. Then on our planet there was only one, simply gigantic continent called Pangea. Its total area was impressive and equal to the area of all existing continents, including islands. Pangea was washed on all sides by an ocean called Panthalassa. This huge ocean occupied the entire remaining surface of the planet.
However, the existence of the supercontinent turned out to be short-lived. Processes were seething inside the Earth, as a result of which the substance of the mantle began to spread in different directions, gradually stretching the continent. Because of this, Pangea first split into two parts, forming two continents - Laurasia and Gondwana. Then these continents gradually split into many parts, which gradually dispersed in different directions. In addition to new continents, lithospheric plates appeared. From the names of the largest plates, it becomes clear in which places giant faults formed.
The remains of Gondwana are the Australia and Antarctica we know, as well as the South African and African lithospheric plates. It has been proven that these plates are gradually moving apart in our time - the speed of movement is 2 cm per year.
The fragments of Laurasia turned into two lithospheric plates - North American and Eurasian. Moreover, Eurasia consists not only of a fragment of Laurasia, but also of parts of Gondwana. The names of the largest plates that form Eurasia are Hindustan, Arabian and Eurasian.
In education Eurasian continent Africa is directly involved. Its lithospheric plate is slowly moving closer to the Eurasian plate, forming mountains and hills. It was because of this “union” that the Carpathians, Pyrenees, Ore Mountains, Alps and Sudetes appeared.
List of lithospheric plates
The names of the largest plates are as follows:
- South American;
- Australian;
- Eurasian;
- North American;
- Antarctic;
- Pacific;
- South American;
- Hindustan.
Medium sized slabs are:
- Arabian;
- Nazca;
- Scotia;
- Philippine;
- Coconut;
- Juan de Fuca.
Fb.ru
What are lithospheric plates? Map of lithospheric plates
If you like interesting facts about nature, then you probably would like to know what lithospheric plates are.
So, lithospheric plates are huge blocks into which the solid surface layer of the earth is divided. Given the fact that the rock beneath them is molten, the plates move slowly, at a speed of 1 to 10 centimeters per year.
Today there are 13 largest lithospheric plates, which cover 90% earth's surface.
Largest lithospheric plates:
- Australian plate - 47,000,000 km²
- Antarctic plate - 60,900,000 km²
- Arabian subcontinent - 5,000,000 km²
- African plate - 61,300,000 km²
- Eurasian plate - 67,800,000 km²
- Hindustan plate - 11,900,000 km²
- Coconut Plate - 2,900,000 km²
- Nazca Plate - 15,600,000 km²
- Pacific plate - 103,300,000 km²
- North American Plate - 75,900,000 km²
- Somali Plate - 16,700,000 km²
- South American plate - 43,600,000 km²
- Philippine Plate - 5,500,000 km²
Here it must be said that there is a continental and oceanic crust. Some plates consist exclusively of one type of crust (for example, the Pacific plate), and some mixed types, when the plate begins in the ocean and smoothly passes to the continent. The thickness of these layers is 70-100 kilometers.
Lithospheric plates float on the surface of a partially molten layer of the earth - the mantle. When the plates move apart, liquid rock called magma fills the cracks between them. When magma solidifies, it forms new crystalline rocks. We’ll talk more about magma in the article on volcanoes.
Map of lithospheric plates
Largest lithospheric plates (13 pcs.) At the beginning of the 20th century, American F.B. Taylor and the German Alfred Wegener simultaneously came to the conclusion that the location of the continents was slowly changing. By the way, this is, to a large extent, the cause of earthquakes. But scientists were unable to explain how this happens until the 60s of the twentieth century, when the doctrine of geological processes on earth was developed. seabed.
Map of the location of lithospheric plates It was fossils that played the main role here. Fossilized remains of animals that clearly could not swim across the ocean were found on different continents. This led to the assumption that once all the continents were connected and animals calmly moved between them.
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Lithospheric plates
Lithospheric plates are the largest blocks of the lithosphere. The Earth's crust, together with part of the upper mantle, consists of several very large blocks called lithospheric plates. Their thickness varies - from 60 to 100 km. Most plates include both continental and oceanic crust. There are 13 main plates, of which 7 are the largest: American, African, Antarctic, Indo-Australian, Eurasian, Pacific, Amur.
The plates lie on a plastic layer of the upper mantle (asthenosphere) and slowly move relative to each other at a speed of 1-6 cm per year. This fact was established by comparing photographs taken with artificial satellites Earth. They suggest that the configuration of continents and oceans in the future may be completely different from the present one, since it is known that the American lithospheric plate is moving towards the Pacific, and the Eurasian plate is moving closer to the African, Indo-Australian, and also the Pacific. The American and African lithospheric plates are slowly moving apart.
The forces that cause the divergence of lithospheric plates arise when the mantle material moves. Powerful upward flows of this substance push the plates apart, tearing apart the earth's crust, forming deep faults in it. Due to underwater outpourings of lavas along faults, strata of igneous rocks are formed. By freezing, they seem to heal wounds - cracks. However, the stretching increases again, and ruptures occur again. Thus, gradually building up, the lithospheric plates diverge in different directions.
There are fault zones on land, but most of them are in the ocean ridges at the bottom of the oceans, where the earth's crust is thinner. The largest fault on land is located in eastern Africa. It stretches for 4000 km. The width of this fault is 80-120 km. Its outskirts are dotted with extinct and active volcanoes.
Along other plate boundaries, plate collisions are observed. It happens in different ways. If plates, one of which has oceanic crust and the other continental, come closer together, then the lithospheric plate, covered by the sea, sinks under the continental one. This creates deep-sea trenches, island arcs (Japanese islands) or mountain ranges (Andes). If two plates collide, having continental crust, then the edges of these plates collapse into folds of rocks, volcanism and the formation of mountainous regions. This is how, for example, the Himalayas arose on the border of the Eurasian and Indo-Australian plates. The presence of mountainous areas in the internal parts of the lithospheric plate suggests that once there was a boundary between two plates that were firmly fused with each other and turned into a single, larger lithospheric plate. Thus, it is possible to make general conclusion: boundaries of lithospheric plates - moving areas to which volcanoes, earthquake zones, mountain areas, mid-ocean ridges, deep-sea depressions and trenches are confined. It is at the boundaries of lithospheric plates that ore minerals are formed, the origin of which is associated with magmatism.
geographyofrussia.com
The theory of lithospheric plates on the world map: which is the largest?
The theory of lithospheric plates is the most interesting direction in geography. As modern scientists suggest, the entire lithosphere is divided into blocks that drift in the upper layer. Their speed is 2-3 cm per year. They are called lithospheric plates.
Founder of the theory of lithospheric plates
Who founded the theory of lithospheric plates? A. Wegener was one of the first to make the assumption in 1920 that the plates move horizontally, but it was not supported. And only in the 60s, a survey of the ocean floor confirmed his assumption.
The resurrection of these ideas led to the creation modern theory tectonics. Its most important provisions were determined by a team of geophysicists from America D. Morgan, J. Oliver, L. Sykes and others in 1967-68.
Scientists cannot say for sure what causes such displacements and how the boundaries are formed. Back in 1910, Wegener believed that at the very beginning of the Paleozoic period the Earth consisted of two continents.
Laurasia covered the area of present-day Europe, Asia (India was not included), North America. It was the northern continent. Gondwana included South America, Africa, and Australia.
Somewhere two hundred million years ago, these two continents united into one - Pangea. And 180 million years ago it again divided into two. Subsequently, Laurasia and Gondwana were also divided. Due to this split, the oceans were formed. Moreover, Wegener found evidence that confirmed his hypothesis about a single continent.
Map of the world's lithospheric plates
Over the billions of years during which the plates moved, their fusion and separation occurred repeatedly. The strength and energy of continental movement is greatly influenced by the internal temperature of the Earth. As it increases, the speed of plate movement increases.
How many plates and how are lithospheric plates located on the world map today? Their boundaries are very arbitrary. Now there are 8 important plates. They cover 90% of the entire planet's territory:
- Australian;
- Antarctic;
- African;
- Eurasian;
- Hindustan;
- Pacific;
- North American;
- South American.
Scientists constantly inspect and analyze the ocean floor and explore faults. New slabs are opened and the lines of old ones are adjusted.
Largest lithospheric plate
What is the largest lithospheric plate? The most impressive is the Pacific plate, the crust of which has an oceanic type of composition. Its area is 10,300,000 km². The size of this slab, as well as the size Pacific Ocean are gradually decreasing.
In the south it borders the Antarctic Plate. On the northern side it creates the Aleutian Trench, and on the western side - the Mariana Trench.
Not far from California, where the eastern border lies, the plate moves along the length of the North American. This is where the San Andreas Fault forms.
What happens when plates move
In their movement, lithospheric plates of the earth can diverge, merge, and slide with their neighbors. In the first option, tensile areas with cracks are formed between them along the boundary lines.
In the second option education is underway compression zones, which are accompanied by pushing (obduction) of plates onto each other. In the third case, faults are observed along the length of which they slide. In those places where the plates converge, they collide. This leads to the formation of mountains.
As a result of collision, lithospheric plates form:
- Tectonic faults called rift valleys. They are formed in stretch zones;
- In the case when a collision of plates with a continental type of crust occurs, then they speak of convergent boundaries. This causes the formation of large mountain systems. The Alpine-Himalayan system was the result of the collision of three plates: Eurasian, Indo-Australian, African;
- If plates having different types crust (one is continental, the other is oceanic), mountains are formed on the coast, and deep depressions (trenches) are formed in the ocean. An example of such a formation is the Andes and the Peruvian depression. It happens that island arcs (Japanese islands) are formed together with trenches. This is how the Mariana Islands and the Trench were formed.
The African lithospheric plate includes African continent and is of oceanic type. This is where the largest fault is located. Its length is 4000 km, and its width is 80-120. Its extremities are covered with numerous volcanoes, active and extinct.
The lithospheric plates of the world that have an oceanic type of crustal structure are often called oceanic. These include: Pacific, Coconut, Nazca. They occupy more than half the space of the World Ocean.
There are three of them in the Indian Ocean (Indo-Australian, African, Antarctic). The names of the plates correspond to the names of the continents that it washes. The lithospheric plates of the ocean are separated by underwater ridges.
Tectonics as a science
Plate tectonics studies their movement, as well as changes in the structure and composition of the Earth in a given area in a certain period of time. It assumes that it is not continents that drift, but lithospheric plates.
It is this movement that causes earthquakes and volcanic eruptions. It has been confirmed by satellites, but the nature of such movement and its mechanisms are still unknown.
vsesravnenie.ru
Movement of lithospheric plates. Large lithospheric plates. Names of lithospheric plates
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 has gained new uniform. 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 initially 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 conveyor belt. It comes to the surface in rift areas 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 point is that birth neocortex 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 ascending flows from the heated mantle fade, 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, volcanic eruptions 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 development of the crust of the oceans and continents 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 is considered sufficiently complex processes, which occur in the mantle and crust. 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 Earth's upper mantle.
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. An increase in temperature is facilitated by the release of a large volume potential energy in the process of lifting matter into the gravity region 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 quite long 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 usually lie in upper layers planets.
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 influx 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 fold belts.
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 anomalous substance emerging from heat flow the overlying mantle warms up 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 dump excess substances, they tend to disperse to the sides. 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. As magma solidifies, new oceanic crust forms. 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 with comparatively 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.
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Wonderful-planet - Lithospheric plates.
Details You are in the section: LithosphereLithospheric plates are large blocks of the earth's crust and parts of the upper mantle that make up the lithosphere.
What is the lithosphere composed of? - Main lithospheric plates. - Map of the Earth's lithosphere. - Movement of the lithosphere. - Lithospheric plates of Russia.
What is the lithosphere composed of?
The lithosphere is made up of large blocks called lithospheric plates. Lithospheric blocks are 1-10,000 km across, and their thickness varies from 60 to 100 km. Most of the lithospheric blocks include both continental and oceanic crust. Although there are cases when the lithospheric plate consists exclusively of oceanic crust (Pacific Plate).
Lithospheric plates consist of strongly folded igneous, metamorphosed and granitic rocks lying at the base, and a 3-4 kilometer layer of sedimentary rocks on top.
At the base of each continent lies one or more ancient platforms, along the border of which a chain of mountain ranges runs. Inside the platform, the relief is usually represented by flat plains with isolated mountain ranges.
The boundaries of lithospheric plates are characterized by high tectonic, seismic and volcanic activity. There are three types of plate boundaries: divergent, convergent and transform. The outlines of lithospheric plates are constantly changing. Large ones split, small ones are soldered together. Some plates may sink into the Earth's mantle.
As a rule, only three lithospheric plates converge at one point on the globe. A configuration where four or more plates converge at one point is unstable and quickly collapses over time.
The main lithospheric plates of the Earth.
Most of the earth's surface, about 90%, is covered by 14 major lithospheric plates. This:
- Australian plate
- Antarctic plate
- Arabian subcontinent
- African plate
- Eurasian plate
- Hindustan plate
- Plate Coconut
- Nazca Plate
- Pacific Plate
- Scotia Plate
- North American Plate
- Somali plate
- South American Plate
- Philippine plate
Fig 1. Map of the Earth's lithospheric plates.
Movement of the Earth's lithosphere.
Lithospheric plates constantly move relative to each other at speeds of up to several tens of centimeters per year. This fact was recorded by photographs taken from artificial Earth satellites. It is currently known that the American lithospheric plate is moving towards the Pacific, and the Eurasian plate is moving closer to the African, Indo-Australian, and also the Pacific. The American and African lithospheric plates are slowly moving apart.
Lithospheric plates - the main components of the lithosphere - lie on a plastic layer of the upper mantle - the asthenosphere. It is she who plays the main role in the movement of the earth's crust. The substance of the asthenosphere, as a result of thermal convection (heat transfer in the form of jets and streams), slowly “flows,” dragging along blocks of the lithosphere and causing their horizontal movements. If the substance of the asthenosphere rises or falls, this leads to vertical movement of the earth's crust. The speed of vertical movement of the lithosphere is much less than horizontal - only up to 1-2 tens of millimeters per year.
With the vertical movement of the lithosphere above the ascending branches of convective currents of the asthenosphere, ruptures of lithospheric plates occur and faults are formed. Lava rushes into the fractures and, as it cools, fills the empty cavities with thicknesses of igneous rocks. But then the increasing stretching of the moving lithospheric plates again leads to a fault. Thus, gradually growing in places of faults, lithospheric plates diverge in different directions. This strip of horizontal plate divergence is called the rift zone. As you move away from the rift zone, the lithosphere cools, becomes heavier, thickens and, as a result, sinks deeper into the mantle, forming areas of decreased relief.
Fracture zones are observed both on land and in the ocean. The largest continental fault, more than 4000 km long and 80-120 km wide, is located in Africa. On the slopes of the fault there are a large number of active and dormant volcanoes.
At this time, a collision of lithospheric plates occurs on the boundary opposite to the fault. This collision can proceed in different ways depending on the types of colliding plates.
- If oceanic and continental plates collide, the first one sinks under the second one. This creates deep-sea trenches, island arcs (Japanese islands) or mountain ranges (Andes).
- If two continental lithospheric plates collide, then at this point the edges of the plates are crushed into folds, which leads to the formation of volcanoes and mountain ranges. Thus, the Himalayas arose on the border of the Eurasian and Indo-Australian plates. In general, if there are mountains in the center of the continent, this means that it was once the site of a collision between two lithospheric plates fused into one.
Thus, the earth's crust is in constant motion. In its irreversible development, mobile areas - geosynclines - are transformed through long-term transformations into relatively quiet areas - platforms.
Lithospheric plates of Russia.
Russia is located on four lithospheric plates.
- The Eurasian plate - most of the western and northern parts of the country,
- North American plate - northeastern part of Russia,
- Amur lithospheric plate - southern Siberia,
- Sea of Okhotsk plate – Sea of Okhotsk and its coast.
Figure 2. Map of lithospheric plates in Russia.
In the structure of lithospheric plates, relatively flat ancient platforms and mobile folded belts are distinguished. In stable areas of the platforms there are plains, and in the area of fold belts there are mountain ranges.
Figure 3. Tectonic structure of Russia.
Russia is located on two ancient platforms (East European and Siberian). Within the platforms there are slabs and shields. A plate is a section of the earth's crust, the folded base of which is covered with a layer of sedimentary rocks. Shields, unlike slabs, have very little sediment and only a thin layer of soil.
In Russia, the Baltic Shield on the East European Platform and the Aldan and Anabar Shields on the Siberian Platform are distinguished.
Figure 4. Platforms, slabs and shields on the territory of Russia.
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A lithospheric plate is... What is a lithospheric plate?
A lithospheric plate is a large, stable section of the earth's crust, part of the lithosphere. According to the theory of plate tectonics, lithospheric plates are bounded by zones of seismic, volcanic and tectonic activity - plate boundaries. There are three types of plate boundaries: divergent, convergent and transform.
From geometric considerations it is clear that only three plates can converge at one point. A configuration in which four or more plates converge at one point is unstable and will quickly collapse over time.
There are two fundamentally different types Earth's crust - continental crust and oceanic crust. Some lithospheric plates are composed exclusively of oceanic crust (an example is the largest Pacific plate), others consist of a block of continental crust welded into the oceanic crust.
Lithospheric plates constantly change their shape; they can split as a result of rifting and weld together, forming a single plate as a result of collision. Lithospheric plates can also sink into the planet's mantle, reaching deep into the core. On the other hand, the division of the earth's crust into plates is ambiguous, and as geological knowledge accumulates, new plates are identified, and some plate boundaries are recognized as non-existent. Therefore, the outlines of the plates change over time in this sense. This is especially true for small plates, for which geologists have proposed many kinematic reconstructions, often mutually exclusive.
Map of lithospheric plates Tectonics plates (preserved surfaces)
More than 90% of the Earth's surface is covered by the 14 largest lithospheric plates:
Medium slabs:
Microplates
Disappeared slabs:
Vanished Oceans:
Supercontinents:
Notes
Calculation of the thickness of a slab foundation
lithospheric plate- A large rigid block of the Earth’s lithosphere, bounded by seismically and tectonically active fault zones, according to plate tectonics, such blocks move along the asthenosphere. → Fig. 251, p. 551 Syn.: tectonic plate… Dictionary of Geography
A large (several thousand km across) block of the earth’s crust, including not only the continental crust, but also the associated oceanic crust; bounded on all sides by seismically and tectonically active fault zones... Big Encyclopedic Dictionary
A large (several thousand kilometers in diameter) block of the earth’s crust, including not only the continental crust, but also the oceanic crust associated with it; bounded on all sides by seismically and tectonically active fault zones. * * * LITHOSPHERIC… … encyclopedic Dictionary
A large (several thousand km in diameter) block of the earth's crust, including not only the continental crust, but also the oxanic layer associated with it. bark; bounded on all sides by seismically and tectonically active fault zones... Natural science. encyclopedic Dictionary
The Juan de Fuca lithospheric plate (named after the navigator Juan de Fuca, a Greek by nationality who served Spain) is tectonic ... Wikipedia
A 3D model showing the position of the remnants of the Farallon plate deep in the Earth's mantle... Wikipedia
- ... Wikipedia
- (Spanish: Nazca) lithospheric plate located in the eastern part of the Pacific Ocean. The plate got its name from the name of the area of the same name in Peru. The earth's crust is of oceanic type. On the eastern border of the Nazca plate... Wikipedia was formed
According to modern plate theories 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.
A feature of lithospheric plates is their rigidity and ability in the absence external influences long time maintain unchanged shape and structure.
Lithospheric plates are mobile. Their movement along the surface of the asthenosphere occurs under the influence of convective currents in the mantle. Individual lithospheric plates can move apart, move closer together, or slide relative to each other. In the first case, tension zones with cracks along the boundaries of the plates appear between the plates, in the second - compression zones, accompanied by the pushing of one plate onto another (thrusting - obduction; thrusting - subduction), in the third - shear zones - faults along which sliding of neighboring plates occurs .
Where continental plates converge, they collide and mountain belts are formed. This is how, for example, the Himalaya mountain system arose on the border of the Eurasian and Indo-Australian plates (Fig. 1).
Rice. 1. Collision of continental lithospheric plates
When the continental and oceanic plates interact, the plate with the oceanic crust moves under the plate with the continental crust (Fig. 2).
Rice. 2. Collision of continental and oceanic lithospheric plates
As a result of the collision of continental and oceanic lithospheric plates, deep-sea trenches and island arcs are formed.
The divergence of lithospheric plates and the resulting formation of the oceanic crust is shown in Fig. 3.
The axial zones of mid-ocean ridges are characterized by rifts(from English rift - crevice, crack, fault) - large linear tectonic structure the earth's crust with a length of hundreds, thousands, a width of tens and sometimes hundreds of kilometers, formed mainly during horizontal stretching of the crust (Fig. 4). Very large rifts are called rift belts, zones or systems.
Since the lithospheric plate is a single plate, each of its faults is a source seismic activity and volcanism. These sources are concentrated within relatively narrow zones along which mutual movements and friction of adjacent plates occur. These zones are called seismic belts. Reefs, mid-ocean ridges and deep-sea trenches are mobile regions of the Earth and are located at the boundaries of lithospheric plates. This indicates that the process of formation of the earth's crust in these zones is currently occurring very intensively.
Rice. 3. Divergence of lithospheric plates in the zone among the oceanic ridge
Rice. 4. Rift formation scheme
Most of the faults of lithospheric plates occur at the bottom of the oceans, where the earth’s crust is thinner, but they also occur on land. The largest fault on land is located in eastern Africa. It stretches for 4000 km. The width of this fault is 80-120 km.
Currently, seven of the largest plates can be distinguished (Fig. 5). Of these, the largest in area is the Pacific, which consists entirely of oceanic lithosphere. As a rule, the Nazca plate, which is several times smaller in size than each of the seven largest ones, is also classified as large. At the same time, scientists suggest that in fact the Nazca plate is much larger than we see on the map (see Fig. 5), since a significant part of it went under neighboring plates. This plate also consists only of oceanic lithosphere.
Rice. 5. Earth's lithospheric plates
An example of a plate that includes both continental and oceanic lithosphere is, for example, the Indo-Australian lithospheric plate. The Arabian plate consists almost entirely of continental lithosphere.
The theory of lithospheric plates is important. First of all, it can explain why there are mountains in some places on Earth and plains in others. Using the theory of lithospheric plates, it is possible to explain and predict catastrophic phenomena that occur at plate boundaries.
Rice. 6. The shapes of the continents really seem compatible.
Continental drift theory
The theory of lithospheric plates originates from the theory of continental drift. Back in the 19th century. many geographers have noted that when looking at a map, one can notice that the coasts of Africa and South America seem compatible when approaching (Fig. 6).
The emergence of the hypothesis of continental movement is associated with the name of the German scientist Alfred Wegener(1880-1930) (Fig. 7), who most fully developed this idea.
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 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. Southern mainland— 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) (Fig. 8).
Rice. 8. The existence of a single continent of Pangea (white - land, dots - shallow sea)
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.
Rice. 9. Location and directions of continental drift during the Cretaceous period 180 million years ago
A. Wegener found many confirmations of the existence of a single continent of the Earth. He found the existence in Africa and in South America 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 vast 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).
As noted above, the boundaries of lithospheric plates are divided into divergent(spreading zones), convergent(subduction and obduction zones) and transform.
Spreading zones (Fig. 7.4, 7.5) are confined to mid-ocean ridges (MOR). Spreading(eng. spreading) – the process of generation of ocean crust in the rift zones of mid-ocean ridges (MOR). It consists in the fact that, under the influence of tension, the crust splits and diverges to the sides, and the resulting crack is filled with basalt melt. Thus, the bottom expands, and its age naturally increases in age symmetrically on both sides of the MOR axis. Term seafloor spreading suggested by R. Dietz (1961). And the process itself is considered as oceanic rifting, the basis of which is expansion through magmatic wedging. It may develop as a continuation of continental rifting (see section 7.4.6). The expansion in ocean rifts is caused by mantle convection - its ascending flows or mantle plumes.
Subduction zones – boundaries between lithospheric plates along which one plate subsides under another (Fig. 7.4, 7.5).
Subduction(Latin sub – under, ductio – leading; the term was borrowed from Alpine geology) – the process of pushing the oceanic crust under the continental (marginal-continental type of subduction zones and its varieties - Andean, Sunda and Japanese types) or oceanic crust under the oceanic (Mariana type of subduction zones) when they come together, caused by the moving apart of the plates in the spreading zone (Fig. 7.4 - 7.7). Subduction zone confined to the deep-sea trench. During subduction, rapid gravitational subsidence of the oceanic crust into the asthenosphere occurs, with sediments of the deep-sea trench being pulled into the same place, with accompanying manifestations of folding, ruptures, metamorphism and magmatism. Subduction occurs due to the descending branch of convective cells.
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Rice. 7.5. Global system of modern continental and oceanic rifts, main subduction and collision zones, passive (intraplate) continental margins. A – ocean rifts (spreading zones) and transform faults; b – continental rifts; V – subduction zones: island-arc and marginal-continental (double line); G – collision zones; d – passive continental margins; e – transform continental margins (including passive ones); and – vectors relative movements lithospheric plates, according to J. Minster, T. Jordan (1978) and K. Chase (1978), with additions; in spreading zones – up to 15-18 cm/year in each direction, in subduction zones – up to 12 cm/year. Rift zones: SA - Mid-Atlantic; Am-A – American-Antarctic; Af-A - African-Antarctic; USI – Southwestern Indian Ocean; A-I – Arabian-Indian; VA – East African; Kr – Krasnomorskaya; JVI – South-Eastern Indian Ocean; Av-A – Australian-Antarctic; UT – South Pacific; VT – East Pacific; AF – Western Chilean; G – Galapagos; Cl – Californian; BH – Rio Grande – Basins and Ranges; HF – Gorda – Juan de Fuca; NG – Nansen-Hakkel; M – Momskaya; B – Baikalskaya; R - Rhine. Subduction zones: 1 – Tonga-Kermadec, 2 – New Hebridean, 3 – Solomon, 4 – New British, 5 – Sunda, 6 – Manila, 7 – Philippine, 8 – Ryukyu, 9 – Mariana, 10 – Izu-Bonin, 11 – Japanese, 12 – Kuril-Kamchatka, 13 – Aleutian, 14 – Cascade Mountains, 15 – Central American, 16 – Lesser Antilles, 17 – Andean, 18 – Southern Antilles (Scotia), 19 – Aeolian (Calabrian), 20 – Aegean (Cretan), 21 - Mekran. |
Depending on the tectonic effect of the interaction of lithospheric plates in different subduction zones, and often in neighboring segments of the same zone, several modes can be distinguished - subduction accretion, subduction erosion and neutral mode.
Subduction accretion mode characterized by the fact that above the subduction zone an accretionary prism is formed that is increasingly increasing in size, having a complex isoclinal-scale internal structure and building up a continental margin or island arc.
Subduction erosion regime suggests the possibility of destruction of the hanging wall of the subduction zone (subcrustal, basal or frontal erosion) as a result of the capture of sialic crust material during subduction and its movement to depth into the region of magma formation.
Neutral subduction mode characterized by the pushing of almost undeformed layers under the hanging wing.
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Obduction – a tectonic process, as a result of which the oceanic crust is pushed onto the continental crust (Fig. 7.8).
The possibility of such a process is confirmed by the findings ophiolites(relics of oceanic crust) in folded belts of different ages. In the thrust fragments of the oceanic crust, only the upper part of the oceanic lithosphere is represented: sediments of the 1st layer, basalts and dolerite dikes of the 2nd layer, gabbroids and a layered hypermafic-mafic complex of the 3rd layer, and up to 10 kilometers of peridotites of the upper mantle. This means that during obduction, the upper part of the oceanic lithosphere was peeled off and pushed onto the continental margin. The rest of the lithosphere moved in the subduction zone to depth, where it underwent structural and metamorphic transformations.
The geodynamic mechanisms of obduction are varied, but the main ones are obduction at the boundary of the ocean basin and obduction during its closure.
Education (English education - extraction) - the process of bringing back to the surface tectonites and metamorphites that were previously formed in the subduction zone as a result of ongoing divergence. This is possible if the subducting ridge extends along the continental margin and if its inherent spreading rate exceeds the rate of subduction of the ridge under the continent. Where the spreading rate is less than the rate of ridge subduction, eduction does not occur (for example, the interaction of the Chilean ridge with the Andean margin).
Accretion – growth in the process of underthrusting the oceanic crust of the edge of the continent by heterogeneous terranes adjacent to it. Regional compression processes caused by the collision of microcontinents, island arcs, or other “terranes” with continental margins are usually accompanied by the development of ridges consisting of rocks from intermediate basins or from the rocks of these terranes themselves. This is how, in particular, flysch, ophiolitic, metamorphic tectonic nappes are formed with the formation of nappes in front of the front due to their destruction by olistostromes, and at the base of the nappes - mixtites (tectonic melange).
Collision (lat. collisio– collision) – a collision of structures of different ages and different genesis, for example, lithospheric plates (Fig. 7.5). It develops where the continental lithosphere converges with the continental one: their further oncoming movement is difficult, it is compensated by the deformation of the lithosphere, its thickening and “clumping” in folded structures and mountain building. In this case, internal tectonic stratification of the lithosphere is manifested, its division into plates that experience horizontal movements and disharmonious deformations. The collision process is dominated by deep inclined lateral-shear counter exchanges of rock masses within the earth's crust. Under conditions of crowding and thickening of the crust, palinogenic pockets of granitic magma are formed.
Along with the “continent-continent” collision, there can sometimes be a “continent-island arc” or two island arcs collision. But it is more correct to use it for intercontinental interactions. An example of maximum collision is some sections of the Alpine-Himalayan belt.