Contour map of the lithosphere. Tectonics of lithospheric plates. Movement of tectonic plates

Plate tectonics– modern geological theory about the movement and interaction of lithospheric plates.
The word tectonics comes from the Greek "tecton" - "builder" or "a carpenter", In tectonics, plates are giant blocks of the lithosphere.
According to this theory, the entire lithosphere is divided into parts - lithospheric plates, which are separated by deep tectonic faults and move through the viscous layer of the asthenosphere relative to each other at a speed of 2-16 cm per year.
There are 7 large lithospheric plates and about 10 smaller plates (the number of plates in different sources miscellaneous).


When lithospheric plates collide, the earth's crust is destroyed, and when they diverge, a new one is formed. At the edges of the plates, where the stress within the Earth is strongest, various processes occur: strong earthquakes, volcanic eruptions and the formation of mountains. It is along the edges of lithospheric plates that the largest landforms are formed - mountain ranges and deep-sea trenches.

Why do lithospheric plates move?
The direction and movement of lithospheric plates is influenced by internal processes occurring in the upper mantle - the movement of matter in the mantle.
When lithospheric plates diverge in one place, then in another place their opposite edges collide with other lithospheric plates.

Convergence of oceanic and continental lithospheric plates



A thinner oceanic lithospheric plate “dives” under a powerful continental lithospheric plate, creating a deep depression or trench on the surface.
The area where this happens is called subductive. As the plate sinks into the mantle it begins to melt. The crust of the upper plate is compressed and mountains grow on it. Some of them are volcanoes formed by magma.

Lithospheric plates

Discovery of continental drift.

World map showing the location of the main lithospheric plates. Each plate is surrounded by oceanic ridges,
from the axes of which there is tension (thick lines), zones of collision and subduction (jagged lines) and/or
transform faults (thin lines). Names are given only for some of the largest plates.
Arrows indicate directions relative movements slabs

At the beginning of the 20th century, a German meteorologist Alfred Wegener began to collect and study information about the flora and fauna of the continents separated by the Atlantic Ocean. He also carefully examined everything that was then known about their geology and paleontology, about the fossil remains of organisms found on them. After analyzing the data obtained, Weneger came to the conclusion that various continents, including South America and Africa, formed a single whole in the distant past. He discovered, for example, that some geological structures South America, which abruptly end with the coastline of the Atlantic Ocean, have, as it were, a continuation in Africa. He cut out these continents from the map, moved these cuttings towards each other and saw that the geological features of these continents coincided, as if continuing each other.

He also discovered that there were geological signs of an ancient glaciation that swept across Australia, India and South Africa, and noticed that it was possible to combine these continents in such a way that their glaciated areas would form a single area. Based on his research, Wegener published the book “The Origin of Continents and Oceans” in Germany (1915), in which he put forward his theory of “continental drift.” But the author of this book could not defend his theory convincingly enough; he selected some facts to support it quite arbitrarily. Largely for these reasons, his hypothesis was not accepted by most scientists at the time. For example, eminent physicists of that time stated that continents cannot drift like ships at sea, since the outer parts of the lithosphere are very rigid. They also pointed out that the centrifugal forces resulting from the Earth's rotation on its axis were too weak to move the continents, as Wegener assumed.

But Wegener was still on the right track. The revival of Wegener's ideas in the form of the theory of plate tectonics occurred in the 1950s and 1960s. During these years, studies of the ocean floor, which began during the Second World War, were carried out. American Navy, while developing submarines, was very interested in learning as much as possible about the ocean floor. Perhaps this is the one rare case, when military interests benefited science. At that time, and even until the 1960s, the ocean floor was almost unexplored territory. Geologists said then that we know more about the surface of the Moon facing us than about seabed. The US Navy was generous and paid well. Oceanographic research quickly became widespread. Although a significant part of the research results was classified, the discoveries made pushed Earth science to a new, higher level of understanding of the processes occurring on Earth.

One of the main results of intensive research of the ocean floor has been new knowledge about its topography. Previous knowledge about the seabed, collected over a long history sea ​​travel, were extremely insufficient. The most first depth measurements were made using the simplest methods - measuring cables. The lot was thrown overboard and the length of the etched cable was measured. But these measurements were limited to shallow, coastal areas.

At the beginning of the 20th century, echo sounders appeared on ships, which were continuously improved. Measurements carried out in the 1950s and 1960s using echo sounders provided a lot of information about the topography of the ocean floor. The principle of operation of an echo sounder is to measure the time required for a sound pulse to travel from the ship to the seabed and back. Knowing the speed of sound in sea water, it is easy to calculate the depth of the sea at any location. The echo sounder can operate continuously, around the clock, no matter what the ship is doing.

Nowadays, the topography of the ocean floor has become easier to map: equipment installed on Earth satellites accurately measures the “height” of the sea surface. There is no need to send ships to sea. Interestingly, the differences in sea level from place to place accurately reflect the topography of the seafloor. This is explained by the fact that slight variations in gravity and the bottom affect the sea surface level in a particular place. For example, over a place where there is a large volcano of enormous mass, the sea level rises compared to neighboring areas. On the contrary, above a deep ditch or basin, the sea level is lower than above raised areas of the seabed. It was impossible to “consider” such details of the seabed relief when studying it from board ships.

The results of research of the seabed in the 60s of the 20th century raised many questions for science. Until this time, scientists believed that the bottom of the deep seas were calm, flat areas of the earth's surface, covered with a thick layer of silt and other sediments washed away from the continents over an infinitely long time.

However, the received research materials showed that the seabed has a completely different topography: instead of a flat surface on the ocean floor, mountain ranges of enormous length, deep ditches (rifts), steep cliffs and largest volcanoes. In particular, Atlantic Ocean It is cut exactly down the middle by the Mid-Atlantic Ridge, which follows all the protrusions and depressions of the coastline on each side of the ocean. The ridge rises an average of 2.5 km above the deepest parts of the ocean; Almost along its entire length, along the axial line of the ridge, there is a rift, i.e. a gorge or valley with steep sides. In the North Atlantic Ocean, the Mid-Atlantic Ridge rises above the ocean's surface to form the island of Iceland.

This ridge is only part of a system of ridges that stretches across all the oceans. The ridges surround Antarctica, extend in two branches into the Indian Ocean and to the Arabian Sea, bend along the shores of the eastern part Pacific Ocean, approach lower California, appear off the coast of the northwestern United States.

Why was this system of underwater ridges not buried under a layer of sediment carried from the continents? What is the connection between these ridges and the drift of continents and tectonic plates?

The answers to these questions are obtained from the results of a study ... of the magnetic properties of the rocks that make up the ocean floor. Geophysicists, wanting to know as much as possible about the seabed, along with other work, took measurements magnetic field along numerous research vessel routes. It was discovered that, unlike the structure of the magnetic field of continents, which is usually very complex, the pattern of magnetic anomalies on the ocean floor differs in a certain pattern. The reason for this phenomenon was not clear at first. And in the 60s of the 20th century, American scientists conducted an aerial magnetic survey of the Atlantic Ocean south of Iceland. The results were striking: magnetic field patterns above the seafloor varied symmetrically around the centerline of the ridge. At the same time, the graph of changes in the magnetic field along the route crossing the ridge was basically the same on different routes. When the measurement points and measured magnetic field strengths were plotted on a map and isolines (lines of equal values ​​of magnetic field characteristics) were drawn, they formed a striped zebra-like pattern. A similar pattern, but with less pronounced symmetry, was previously obtained when studying the magnetic field in the northeastern part of the Pacific Ocean. And here the nature of the field differed sharply from the structure of the field above the continents. As scientific data accumulated, it became clear that symmetry in the magnetic field pattern was observed throughout the ocean ridge system. The reason for this phenomenon lies in the following physical processes.

Rocks erupted from the Earth's interior cool from their original molten state, and the iron-containing materials formed in them are magnetized by the Earth's magnetic field. All elementary magnets of these minerals are oriented in the same way under the influence of the surrounding magnetic field of the Earth. This magnetization is a continuous process in time. This means that a graph of the magnetic field along a route crossing a ridge is a kind of fossil record of changes in the magnetic field during the formation of rocks. This record is stored for a long time. As would be expected, geophysical surveys along routes directed perpendicular to the location of the Mid-Atlantic Ridge have shown that rocks located exactly above the ridge axis are highly magnetized in the direction of the Earth's modern magnetic field. The symmetrical zebra-shaped magnetic field pattern indicates that the seafloor is magnetized differently in different areas parallel to the direction of the ridge. We are talking not only about the different strength (intensity) of the magnetic field of different sections of the seabed, but also about the different direction of their magnetization. This has already become a major scientific discovery: it turned out that the Earth’s magnetic field has repeatedly changed its polarity over the course of geological time. Evidence of the periodic change of the Earth's magnetic poles was also obtained by studying the magnetization of rocks on the continents. It was found that in areas where large basalt masses accumulate, one part of the basalt flows has a direction of magnetization corresponding to the direction of the modern magnetic field of the Earth, while other flows are magnetized in the opposite direction.

It became clear to researchers that seafloor magnetic stripes, magnetic polarity fluctuations and continental drift are all interconnected phenomena. The zebra-shaped pattern of magnetization distribution of seafloor rocks reflects the sequence of changes in the polarity of the earth's magnetic field. Most geologists are now convinced that seafloor movement away from ocean faults is a reality.

New oceanic crust is formed by lava that continuously flows from deep within the axial parts of oceanic ridges. The magnetic pattern of the seafloor rocks is symmetrical on both sides of the ridge axis because the newly arrived portion of lava is magnetized when it solidifies into solid rock and expands evenly on both sides of the median fault. Since the dates of changes in the polarity of the Earth's magnetic field have become known as a result of the analysis of rocks on land, the magnetic stripes of the ocean floor can be considered as a kind of time scale.

During its eruption along the ridge and subsequent solidification, the basalt becomes magnetized
under the influence of the Earth's magnetic field and then diverges away from the fault.

The rate of emergence of a new section of the seabed can be quite simply calculated by measuring the distance from the ridge axis, where the age of the seabed is zero, to the stripes corresponding to known periods of reversal of the magnetic field polarity.

The rate of formation of the seabed varies from place to place; its value, calculated from the location of the magnetic stripes, averages several centimeters per year. Continents located on opposite sides of the Atlantic Ocean are moving away from each other at this speed. For this reason, the oceans are not covered with a thick layer of sediment; they (the oceans) are very young on a geological scale. At a speed of a few centimeters per year (this is very slow, of course), the Atlantic Ocean could have formed in two hundred million years, which by geological standards is not that long. The bottom of any of the oceans existing on Earth is not much older. Compared to the rocks of the continents, the age of the ocean floor is much younger.

Thus, it has been proven that the continents on both sides of the Atlantic Ocean are moving apart at a rate that depends on the rate of formation of new sections of the seabed on the axis of the Mid-Atlantic Ridge. Both the continents and the oceanic crust move together as one because... they are parts of the same lithospheric plate.

Vladimir Kalanov,
"Knowledge is power"

Lithospheric plates - This large blocks earth's crust and parts of the upper mantle that make up the lithosphere.

What is the lithosphere composed of?

At this time, on the boundary opposite to the fault, collision of lithospheric plates. 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.

  • Eurasian plate– most of the western and northern parts of the country,
  • North American Plate– northeastern part of Russia,
  • Amur lithospheric plate– south of 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, as opposed to 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.


Then surely you would like to know what are lithospheric plates.

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% of the 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.

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, what it is. But scientists were unable to explain how this happens until the 60s of the twentieth century, when the doctrine of geological processes on the seabed was developed.


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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What do we know about the lithosphere?

Tectonic plates are large, stable sections of the Earth's crust that are components of the lithosphere. If we turn to tectonics, the science that studies lithospheric platforms, we learn that large areas of the earth's crust are limited on all sides by specific zones: volcanic, tectonic and seismic activity. It is at the junctions of neighboring plates that phenomena occur that, as a rule, have catastrophic consequences. These include both volcanic eruptions and earthquakes that are strong on the scale of seismic activity. In the process of studying the planet, plate tectonics played a very important role. Its significance can be compared to the discovery of DNA or the heliocentric concept in astronomy.

If we recall geometry, we can imagine that one point can be the point of contact between the boundaries of three or more plates. Studies of the tectonic structure of the earth's crust show that the most dangerous and rapidly collapsing are the junctions of four or more platforms. This formation is the most unstable.

The lithosphere is divided into two types of plates, different in their characteristics: continental and oceanic. It is worth highlighting the Pacific platform, composed of oceanic crust. Most others consist of what is called a block, where a continental plate is welded into an oceanic one.

The arrangement of the platforms shows that about 90% of the surface of our planet consists of 13 large, stable sections of the earth's crust. The remaining 10% falls on small formations.

Scientists have compiled a map of the largest tectonic plates:

  • Australian;
  • Arabian subcontinent;
  • Antarctic;
  • African;
  • Hindustan;
  • Eurasian;
  • Nazca Plate;
  • Plate Coconut;
  • Pacific;
  • North and South American platforms;
  • Scotia Plate;
  • Philippine plate.

From theory we know that the solid shell of the earth (lithosphere) consists not only of plates that form the relief of the planet’s surface, but also of the deep part - the mantle. Continental platforms have a thickness from 35 km (in flat areas) to 70 km (in mountain ranges). Scientists have proven that the slab is thickest in the Himalaya zone. Here the thickness of the platform reaches 90 km. The thinnest lithosphere is found in the ocean zone. Its thickness does not exceed 10 km, and in some areas this figure is 5 km. Based on information about the depth at which the earthquake epicenter is located and the speed of propagation of seismic waves, the thickness of sections of the earth's crust is calculated.

The process of formation of lithospheric plates

The lithosphere consists mainly of crystalline substances, formed as a result of cooling of magma when reaching the surface. The description of the platform structure indicates their heterogeneity. The process of formation of the earth's crust took place over a long period, and continues to this day. Through microcracks in the rock, molten liquid magma came to the surface, creating new bizarre shapes. Its properties changed depending on the change in temperature, and new substances were formed. For this reason, minerals that are located at different depths differ in their characteristics.

The surface of the earth's crust depends on the influence of the hydrosphere and atmosphere. Weathering occurs constantly. Under the influence of this process, forms change, and minerals are crushed, changing their characteristics while maintaining the same chemical composition. As a result of weathering, the surface became looser, cracks and microdepressions appeared. In these places deposits appeared, which we know as soil.

Tectonic plate map

At first glance, the lithosphere appears to be stable. Its upper part is such, but the lower part, which is distinguished by viscosity and fluidity, is movable. The lithosphere is divided into a certain number of parts, the so-called tectonic plates. Scientists cannot say how many parts the earth's crust consists of, since in addition to large platforms, there are also smaller formations. The names of the largest slabs were given above. The process of formation of the earth's crust occurs constantly. We do not notice this, since these actions occur very slowly, but by comparing the results of observations for different periods, we can see how many centimeters per year the boundaries of the formations shift. For this reason, the tectonic map of the world is constantly updated.

Coconut tectonic plate

The Cocos platform is a typical representative of the oceanic parts of the earth's crust. It is located in the Pacific region. In the west, its border runs along the ridge of the East Pacific Rise, and in the east its border can be defined by a conventional line along the coast North America from California to the Isthmus of Panama. This plate is being pushed under the neighboring Caribbean Plate. This zone is characterized by high seismic activity.

Mexico suffers the most from earthquakes in this region. Among all the countries of America, it is on its territory that the most extinct and active volcanoes are located. The country has experienced a large number of earthquakes with a magnitude greater than 8. The region is quite densely populated, so in addition to destruction, seismic activity leads to a large number victims. Unlike Cocos, located in another part of the planet, the Australian and West Siberian platforms are stable.

Movement of tectonic plates

For a long time, scientists have been trying to figure out why one region of the planet has mountainous terrain and another is flat, and why earthquakes and volcanic eruptions occur. Various hypotheses were based primarily on the knowledge that was available. Only after the 50s of the twentieth century was it possible to study the earth's crust in more detail. We studied mountains formed at places where plates broke, chemical composition these plates, and also created maps of regions with tectonic activity.

In the study of tectonics, the hypothesis of the movements of lithospheric plates has occupied a special place. Back at the beginning of the twentieth century, German geophysicist A. Wegener put forward a bold theory about why they move. He carefully examined the outline of the western coast of Africa and the eastern coast of South America. The starting point in his research was precisely the similarity of the outlines of these continents. He suggested that perhaps these continents were previously a single whole, and then a break occurred and parts of the Earth’s crust began to shift.

His research affected the processes of volcanism, stretching of the surface of the ocean floor, and the viscous-liquid structure of the globe. It was the works of A. Wegener that served as the basis for research conducted in the 60s of the last century. They became the foundation for the emergence of the theory of “lithospheric plate tectonics.”

This hypothesis described the model of the Earth as follows: tectonic platforms, having a rigid structure and having different masses, were located on the plastic substance of the asthenosphere. They were in a very unstable state and were constantly moving. For a simpler understanding, we can draw an analogy with icebergs that constantly drift in ocean waters. Likewise, tectonic structures, being on plastic matter, are constantly moving. During displacements, the plates constantly collided, overlapped one another, and joints and zones of moving apart plates appeared. This process occurred due to the difference in mass. In places of collisions, areas with increased tectonic activity were formed, mountains arose, earthquakes and volcanic eruptions occurred.

The rate of displacement was no more than 18 cm per year. Faults formed, into which magma entered from the deep layers of the lithosphere. For this reason, the rocks that make up the oceanic platforms are of different ages. But scientists have put forward an even more incredible theory. According to some representatives scientific world, the magma came to the surface and gradually cooled, creating new structure the bottom, while the “excesses” of the earth’s crust, under the influence of plate drift, sank into the earth’s interior and again turned into liquid magma. Be that as it may, continental movements continue to occur in our time, and for this reason new maps are being created to further study the process of drift of tectonic structures.