The movement of the plates of the earth's crust in America. Tectonic hypotheses

Lithospheric plates have high rigidity and are capable of maintaining their structure and shape unchanged for a long time in the absence of outside influences.

plate movement

Lithospheric plates are in constant motion. This movement, which occurs in the upper layers, is due to the presence of convective currents present in the mantle. Separately taken lithospheric plates approach, diverge and slide relative to each other. When the plates approach each other, compression zones arise and subsequent thrusting (obduction) of one of the plates onto the neighboring one, or subduction (subduction) of adjacent formations. When diverging, tension zones appear with characteristic cracks that appear along the boundaries. When sliding, faults are formed, in the plane of which nearby plates are observed.

Movement Results

In the areas of convergence of huge continental plates, when they collide, mountain ranges arise. In a similar way, the Himalayas mountain system arose at one time, formed on the border of the Indo-Australian and Eurasian plates. The result of the collision of oceanic lithospheric plates with continental formations are island arcs and deep-water depressions.

In the axial zones of the mid-ocean ridges, rifts (from the English. Rift - a fault, a crack, a crevice) of a characteristic structure arise. Similar formations of the linear tectonic structure of the earth's crust, having a length of hundreds and thousands of kilometers, with a width of tens or hundreds of kilometers, arise as a result of horizontal stretching of the earth's crust. Very large rifts are usually called rift systems, belts, or zones.

In view of the fact that each lithospheric plate is a single plate, increased seismic activity and volcanism are observed in its faults. These sources are located within fairly narrow zones, in the plane of which friction and mutual displacements of neighboring plates occur. These zones are called seismic belts. Deep-sea trenches, mid-ocean ridges and reefs are mobile areas of the earth's crust, they are located at the boundaries of individual lithospheric plates. This once again confirms that the course of the process of formation of the earth's crust in these places and is currently continuing quite intensively.

The importance of the theory of lithospheric plates cannot be denied. Since it is she who is able to explain the presence of mountains in some areas of the Earth, in others -. The theory of lithospheric plates makes it possible to explain and foresee the occurrence of catastrophic phenomena that can occur in the region of their boundaries.

Hello dear reader. Never before had I thought that I would have to write these lines. For quite a long time I did not dare to write down everything that I was destined to discover, if it can even be called that. I still sometimes wonder if I'm crazy.

One evening my daughter came up to me with a request to show on the map where and what kind of ocean is on our planet, and since I don’t have a printed physical map of the world at home, I opened an electronic map on the computergoogle,I switched her to the satellite view mode and began to slowly explain everything to her. When I got from the Pacific Ocean to the Atlantic Ocean and brought it closer to show my daughter better, it was like an electric shock and I suddenly saw what any person on our planet sees, but with completely different eyes. Like everyone else, until that moment I didn’t understand what I saw on the map, but then my eyes seemed to open. But all these are emotions, and you can’t cook cabbage soup out of emotions. So let's try together to see what the map revealed to megoogle,and nothing more or less was revealed - a trace of the collision of our Mother Earth with an unknown celestial body, which led to what is commonly called the Great Then.

Look carefully at the lower left corner of the photo and think: does this remind you of anything? I don’t know about you, but it reminds me of a clear trace from the impact of some rounded celestial body on the surface of our planet. Moreover, the impact was in front of the mainland of South America and Antarctica, which are now slightly concave from the impact in the direction of the impact and are separated in this place by the strait, which bears the name of the Drake Strait, the pirate who allegedly discovered this strait in the past.

In fact, this strait is a pothole left at the moment of impact and ending in a rounded “contact spot” of a celestial body with the surface of our planet. Let's look at this "contact patch" closer and more closely.

Zooming in, we see a rounded spot that has a concave surface and ends on the right, that is, from the side in the direction of impact, with a characteristic hill with an almost sheer edge, which again has characteristic elevations that come out on the surface of the oceans in the form of islands. In order to better understand the nature of the formation of this "contact patch", you can do the same experiment that I did. For the experiment, a wet sandy surface is required. The surface of the sand on the banks of a river or sea is perfect. During the experiment, it is necessary to make a smooth movement with your hand, during which you move your hand over the sand, then touch the sand with your finger and, without stopping the movement of your hand, put pressure on it, thereby raking up a certain amount of sand with your finger and then after a while tear off your finger from the surface of the sand. Have you done? And now look at the result of this simple experiment and you will see a picture completely similar to the one shown in the photo below.

There is another funny nuance. According to researchers, the north pole of our planet in the past has shifted by about two thousand kilometers. If we measure the length of the so-called rut at the bottom of the ocean in the Drake Passage and ending with a "contact spot", then it also approximately corresponds to two thousand kilometers. In the photo, I made a measurement using the programGoogle maps.Moreover, researchers cannot answer the question of what caused the pole shift. I do not undertake to assert with a probability of 100%, but still it is worth considering the question: was it not this catastrophe that caused the displacement of the poles of the planet Earth by these very two thousand kilometers?

Now let's ask ourselves a question: what happened after the celestial body hit the planet tangentially and again went into the vastness of space? You ask: why on a tangent and why did it necessarily leave, and not break through the surface and plunge into the bowels of the planet? This is also very easy to explain. Do not forget about the direction of rotation of our planet. It was precisely the combination of circumstances that the celestial body gave during the rotation of our planet that saved it from destruction and allowed the celestial body to slip and go away, so to speak, and not burrow into the bowels of the planet. No less fortunate was that the blow fell into the ocean in front of the mainland, and not into the mainland itself, since the waters of the ocean somewhat dampened the blow and played the role of a kind of lubricant when the celestial bodies came into contact, but this fact also had the reverse side of the coin - the ocean waters played and its destructive role already after the separation of the body and its departure into space.

Now let's see what happened next. I think no one needs to prove that the impact that led to the formation of the Drake Strait resulted in the formation of a huge multi-kilometer wave, which rushed forward at great speed, sweeping away everything in its path. Let's trace the path of this wave.

The wave crossed the Atlantic Ocean and the southern tip of Africa became the first obstacle in its path, although it suffered relatively little, as the wave touched it with its edge and slightly turned to the south, where it flew into Australia. But Australia was much less fortunate. She took the hit of the wave and was practically washed away, which is very clearly visible on the map.

Then the wave crossed the Pacific Ocean and passed between the Americas, again hooking North America with its edge. We see the consequences of this both on the map and in the films of Sklyarov, who very picturesquely painted the consequences of the Great Flood in North America. If someone has not watched or has already forgotten, then they can review these films, since they have long been posted for free access on the Internet. These are very informative films, though not everything in them should be taken seriously.

Then the wave crossed the Atlantic Ocean for the second time and with all its mass at full speed hit the northern tip of Africa, sweeping away and washing away everything in its path. This is also perfectly visible on the map. From my point of view, we owe such a strange arrangement of deserts on the surface of our planet not at all to the vagaries of climate and not to reckless human activity, but to the destructive and merciless impact of the wave during the Great Flood, which not only swept away everything in its path, but literally this word washed away everything, including not only buildings and vegetation, but also the fertile layer of soil on the surface of the continents of our planet.

After Africa, the wave swept through Asia and again crossed the Pacific Ocean and, passing through the cut between our mainland and North America, went to the North Pole through Greenland. Having reached the north pole of our planet, the wave extinguished itself, because it also exhausted its power, sequentially slowing down on the continents that it flew into and finally caught up with itself at the north pole.

After that, the water of the already extinct wave began to roll back from the North Pole to the south. Part of the water passed through our mainland. It is this that can explain the hitherto flooded northern tip of our mainland and the Gulf of Finland, abandoned by land, and the cities of Western Europe, including our Petrograd and Moscow, buried under a multi-meter layer of earth that was brought back from the North Pole.

Map of tectonic plates and faults in the Earth's crust

If there was an impact of a celestial body, then it is quite reasonable to look for its consequences in the thickness of the Earth's crust. After all, a blow of such force simply could not leave any traces. Let's turn to the map of tectonic plates and faults in the Earth's crust.

What do we see on this map? The map clearly shows a tectonic fault at the site not only of the trace left by the celestial body, but also around the so-called "contact spot" at the place of separation of the celestial body from the Earth's surface. And these faults once again confirm the correctness of my conclusions about the impact of a certain celestial body. And the blow was of such force that not only demolished the isthmus between South America and Antarctica, but also led to the formation of a tectonic fault in the Earth's crust in this place.

Oddities in the trajectory of the wave on the surface of the planet

I think it’s worth talking about another aspect of the wave’s movement, namely, its non-straightness and unexpected deviations in one direction or the other. We were all taught from childhood to believe that we live on a planet that has the shape of a ball, which is slightly flattened from the poles.

I have been of the same opinion myself for quite some time. And what was my surprise when, in 2012, I came across the results of a study by the European Space Agency ESA using data obtained by the GOCE (Gravity field and steady-state Ocean Circulation Explorer - a satellite for studying the gravitational field and constant ocean currents).

Below I give some photographs of the present form of our planet. Moreover, it is worth considering the fact that this is the shape of the planet itself, without taking into account the waters on its surface that form the world ocean. You can ask a completely legitimate question: what do these photos have to do with the topic discussed here? From my point of view, the most that neither is direct. After all, not only does the wave move along the surface of a celestial body that has an irregular shape, but its movement is affected by the impact of the wave front.

No matter how cyclopean the dimensions of the wave, but these factors cannot be discounted, because what we consider to be a straight line on the surface of a globe that has the shape of a regular ball, in fact, turns out to be far from a rectilinear trajectory and vice versa - what in reality is a rectilinear trajectory on irregularly shaped surfaces on the globe will turn into an intricate curve.

And we have not yet considered the fact that when moving along the surface of the planet, the wave repeatedly encountered various obstacles in the form of continents on its way. And if we return to the supposed trajectory of the wave on the surface of our planet, we can see that for the first time it touched Africa and Australia with its peripheral part, and not with the entire front. This could not but affect not only the trajectory of movement itself, but also the growth of the wave front, which, each time it met an obstacle, was partially cut off and the wave had to start growing again. And if we consider the moment of its passage between the two Americas, then one cannot help but notice the fact that at the same time the wave front was not only truncated once again, but part of the wave turned south due to reflection and washed away the coast of South America.

Approximate time of the disaster

Now let's try to find out when this catastrophe happened. To do this, it would be possible to equip an expedition to the crash site, examine it in detail, take all kinds of soil and rock samples and try to study them in laboratories, then follow the route of the Great Flood and do the same work again. But all this would have cost a lot of money, would have dragged on for many, many years, and it is not at all necessary that my whole life would be enough to carry out these works.

But is all this really necessary and is it possible to do without such expensive and resource-intensive measures at least for the time being, at first? I believe that at this stage, in order to establish the approximate time of the catastrophe, we will be able to make do with information obtained earlier and now in open sources, as we have already done when considering the planetary catastrophe that led to the Great Flood.

To do this, we should turn to the physical maps of the world of various centuries and establish when the Drake Strait appeared on them. After all, earlier we established that it was the Drake Passage that was formed as a result and at the site of this planetary catastrophe.

Below are the physical maps that I was able to find in the public domain and the authenticity of which does not cause much distrust.

Here is a map of the World dated 1570 AD

As we can see, there is no Drake Passage on this map and S America is still connected to Antarctica. And this means that in the sixteenth century there was no catastrophe yet.

Let's take a map from the early seventeenth century and see if the Drake Passage and the peculiar outlines of South America and Antarctica appeared on the map in the seventeenth century. After all, navigators could not fail to notice such a change in the landscape of the planet.

Here is a map dating from the early seventeenth century. Unfortunately, I do not have a more accurate dating, as in the case of the first map. On the resource where I found this map, there was just such a dating "beginning of the seventeenth century." But in this case it is not of a fundamental nature.

The fact is that on this map both South America and Antarctica and the jumper between them are in their place, and therefore either the catastrophe has not happened yet, or the cartographer did not know about what happened, although it is hard to believe, knowing the scale of the catastrophe and that’s it. the consequences to which it has led.

Here is another card. This time, the dating of the map is more accurate. It also dates from the seventeenth century - this is 1630 from the birth of Christ.

And what do we see on this map? Although the outlines of the continents are drawn on it and not as well as in the previous one, it is clearly visible that the strait in its modern form is not on the map.

Well, apparently, in this case, the picture described when considering the previous card is repeated. We continue to move along the timeline towards our days and once again take a map that is more recent than the previous one.

This time I did not find a physical map of the world. I found a map of North and South America, in addition, Antarctica is not displayed on it at all. But it's not that important. After all, we remember the outlines of the southern tip of South America from previous maps, and we can notice any changes in them even without Antarctica. But with the dating of the map this time, there is complete order - it is dated to the very end of the seventeenth century, namely 1686 from the birth of Christ.

Let's look at South America and compare its outlines with what we saw on the previous map.

On this map, we finally see the antediluvian outlines of South America and the isthmus connecting South America with Antarctica at the site of the modern and familiar Drake Strait, and the most familiar modern South America with a curved towards the "contact spot" southern end.

What conclusions can be drawn from all of the above? There are two fairly simple and obvious conclusions:

Which of these conclusions is correct and which is false, to my great regret, I cannot judge, because the available information is clearly not enough for this.

Disaster confirmation

Where can one find confirmation of the fact of the catastrophe, except for the physical maps that we talked about above. I'm afraid to seem unoriginal, but the answer will be quite prorst: firstly, under our feet, and secondly, in works of art, namely in the paintings of artists. I doubt that any of the eyewitnesses could capture the wave itself, but the consequences of this tragedy were quite captured. There were a fairly large number of artists who painted pictures that reflected a picture of terrible devastation that reigned in the seventeenth and eighteenth centuries in the place of Egypt, modern Western Europe and Mother Russia. But it was prudently announced to us that these artists did not paint from life, but displayed on their canvases the so-called imaginary world they had. I will cite the work of only a few fairly prominent representatives of this genre:

This is what the familiar antiquities of Egypt, which have already become familiar to us, looked like before they were dug out from under a thick layer of sand in the literal sense of the word.

But what was in Europe at that time? Giovanni Battista Piranesi, Hubert Robert and Charles-Louis Clerisseau will help us understand.

But these are far from all the facts that can be cited in support of the catastrophe and which I have yet to systematize and describe. There are also cities covered with earth for several meters in Mother Russia, there is the Gulf of Finland, which is also covered with earth and became truly navigable only at the end of the nineteenth century, when the world's first sea channel was dug along its bottom. There are salty sands of the Moskva River, sea shells and damn fingers, which I dug out in the forest sands in the Bryansk region as a kid. Yes, and Bryansk itself, which, according to the official historical legend, got its name from the wilds, supposedly in the place of which it stands, though it does not smell like wilds in the Bryansk region, but this is the subject of a separate discussion and God willing, in the future I will publish my thoughts on this topic. There are deposits of bones and carcasses of mammoths, the meat of which was fed to dogs in Siberia at the end of the twentieth century. All this I will consider in more detail in the next part of this article.

In the meantime, I appeal to all readers who have spent their time and effort and read the article to the end. Do not be reluctant - express any critical remarks, point out inaccuracies and errors in my reasoning. Feel free to ask any questions - I will definitely answer them!

December 10th, 2015

Clickable

According to modern theories of lithospheric plates 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.

Alfred Wegener first suggested horizontal movement of crustal blocks in the 1920s as part of the “continental drift” hypothesis, but this hypothesis did not receive support at that time.

Only in the 1960s, studies of the ocean floor provided indisputable evidence of the horizontal movement of plates and the processes of expansion of the oceans due to the formation (spreading) of the oceanic crust. The revival of ideas about the predominant role of horizontal movements occurred within the framework of the "mobilistic" direction, the development of which led to the development of the modern theory of plate tectonics. The main provisions 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. Digts on the expansion (spreading) of the ocean floor.

It is argued that scientists are not entirely sure what causes these very shifts and how the boundaries of tectonic plates were designated. There are countless different theories, but none of them fully 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 the 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 mainland, which included the territories of modern Europe, Asia without India and North America. The southern mainland - Gondwana united the modern territories of South America, Africa, Antarctica, Australia and Hindustan.

Between Gondwana and Laurasia 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)

Approximately 180 million years ago, the mainland of Pangea again began to be divided into constituent parts, which mixed up on the surface of our planet. The division took place as follows: first, Laurasia and Gondwana reappeared, then Laurasia divided, and then Gondwana also split. Due to the split and divergence of parts of Pangea, oceans were formed. The young oceans can be considered the Atlantic and Indian; old - Quiet. The Arctic Ocean became isolated with the increase in land mass in the Northern Hemisphere.

A. Wegener found a lot of evidence for the existence of a single continent of the Earth. The existence in Africa and South America of the remains of ancient animals - leafosaurs seemed especially convincing to him. These were reptiles, similar to small hippos, that lived only in freshwater reservoirs. 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 the movement of the continents in the 30s of the XX century. decreased slightly, but in the 60s it revived again, 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).

The structure of the continental rift

The upper stone part of the planet is divided into two shells, which differ significantly 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 mantle material at lithostatic pressure existing at depths of a few hundreds of kilometers. The rocks lying in the Earth above this isotherm are quite cold and behave like a rigid material, while the 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 inner areas of the plates are weakly seismic and are characterized by a 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.

Diagram of rift formation

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

Divergent boundaries are boundaries along which plates move apart. The geodynamic setting in which the process of horizontal stretching of the earth's crust occurs, accompanied by the appearance of extended linearly elongated fissured or ravine-shaped 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 be laid both on the 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 break of the continental crust, it is filled with sediments, turning into an aulacogen).

The process of plate expansion in the zones of oceanic rifts (mid-ocean ridges) is accompanied by the formation of a new oceanic crust due to magmatic basalt melts coming from the asthenosphere. Such a process of formation of a new oceanic crust due to the influx of mantle matter 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 - ocean floor basalts, 6 - oceanic crust segments that formed at different times (I-V as they age), 7 - near-surface igneous chamber (with ultrabasic magma in the lower part and basic in the upper part), 8 – sediments of the ocean floor (1-3 as they accumulate)

In the course of spreading, each stretching pulse is accompanied by the inflow of a new portion of mantle melts, which, while solidifying, build up the edges of the 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 subduction of an oceanic plate under a continental or other oceanic one. The subduction zones are confined to the axial parts of deep-sea trenches conjugated with island arcs (which are elements of active margins). Subduction boundaries account for about 80% of the length of all convergent boundaries.

When continental and oceanic plates collide, a natural phenomenon is the subduction of the oceanic (heavier) plate under the edge of the continental one; when two oceanic ones collide, the older one (that is, the cooler and denser) of them sinks.

The subduction zones have a characteristic structure: their typical elements are a deep-water trough - a volcanic island arc - a back-arc basin. A deep-water trench is formed in the zone of bending and underthrust of the subducting plate. As this plate sinks, it begins to lose water (which is 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 island arc volcanoes. In the rear of the volcanic arc, some extension usually occurs, which determines the formation of a back-arc basin. In the zone of the back-arc basin, the extension can be so significant that it leads to the rupture of the plate crust and the opening of the 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 formed in spreading zones. This provision emphasizes the opinion about the constancy of the volume of the Earth. But such an opinion is not the only and definitively proven. It is possible that the volume of the plan changes pulsatingly, or there is a decrease in its decrease due to cooling.

The subduction of the subducting plate into the mantle is traced by earthquake foci that occur at the contact of the plates and inside the subducting plate (which is colder and therefore more fragile than the surrounding mantle rocks). This seismic focal zone is called the Benioff-Zavaritsky zone. In subduction zones, the process of formation of a new continental crust begins. A much rarer process of interaction between the continental and oceanic plates is the process of obduction - thrusting of a part of the oceanic lithosphere onto the edge of the continental plate. It should be emphasized that in the course of this process, the oceanic plate is stratified, and only its upper part is advancing - the crust and several kilometers of the upper mantle.

Collision of continental lithospheric plates

When continental plates collide, the crust of which is lighter than the substance of the mantle and, as a result, is not able to sink into it, a collision process occurs. In the course of 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 one, 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. At the same time, at the beginning of the collision process, when the edges of the continents have already approached, the collision is combined with the subduction process (the remains of the oceanic crust continue to sink under the edge of the continent). Collision processes are characterized by large-scale regional metamorphism and intrusive granitoid magmatism. These processes lead to the creation of a new continental crust (with its typical granite-gneiss layer).

The main cause of plate movement is mantle convection, caused by mantle heat and gravity currents.

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

The rocks heated in the central zones of the Earth expand, their density decreases, and they float, giving way to descending colder and therefore heavier masses, which have already given up part of the heat in near-surface zones. This process of heat transfer goes on continuously, resulting in the formation of ordered closed convective cells. At the same time, in the upper part of the cell, the flow of matter occurs in an almost 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 "drag" by convective currents. In addition, a number of other factors act on the plates. In particular, the surface of the asthenosphere turns out to be somewhat elevated above the zones of ascending branches and more lowered in the zones of subsidence, which determines the gravitational "slip" of the lithospheric plate located on an inclined plastic surface. Additionally, there are processes of pulling the heavy cold oceanic lithosphere in the subduction zones into the hot, and as a result 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 bottom 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 velocity of the asthenospheric current, 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 higher than under the oceans, the magnitude of the FDC force is almost an order of magnitude inferior to that of the FDO. Under the continents, especially their ancient parts (continental shields), the asthenosphere almost wedges out, so the continents seem to be “sitting aground”. Since most of the lithospheric plates of the modern Earth include both oceanic and continental parts, it should be expected that the presence of a continent in the composition of the plate in the general case should “slow down” the movement of the entire plate. This is how it actually happens (the fastest moving are the almost purely oceanic plates Pacific, Cocos and Nasca; the slowest are the Eurasian, North American, South American, Antarctic and African, 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 (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 episodically and only in certain geodynamic settings, for example, in the cases of the collapse of slabs through the 670 km section described above.

Thus, the mechanisms that set the lithospheric plates in motion can be conventionally assigned to the following two groups: 1) associated with the forces of the mantle “dragging” (mantle drag mechanism) applied to any points of the bottom of the plates, in the figure - the forces of FDO and FDC; 2) associated with the forces applied to the edges of the plates (edge-force mechanism), in the figure - the forces FRP and FNB. The role of this or that driving mechanism, as well as these or those forces, is evaluated individually for each lithospheric plate.

The totality of these processes reflects the general geodynamic process, covering areas from the surface to deep zones of the Earth. At present, a two-cell closed-cell mantle convection is developing in the Earth's mantle (according to the through-mantle convection model) 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 the mantle matter are located in northeast Africa (approximately under the junction zone of the African, Somali and Arabian plates) and in the area of Easter Island (under the middle ridge of the Pacific Ocean - the East Pacific Rise). The mantle subsidence equator runs along an approximately continuous chain of convergent plate boundaries along the periphery of the Pacific and eastern Indian Oceans. 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 the collision of the 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 on the basis of 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 angle of rotation. Based on this position, the position of the continents in past geological epochs 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 is further disintegrated. As a result of the split of such a supercontinent Pangea, which occurred 200-150 million years ago, modern continents were formed.

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

The age of the oceanic crust according to magnetic anomalies (Kenneth, 1987): 1 - areas of lack of data and dry land; 2–8 - age: 2 - Holocene, Pleistocene, Pliocene (0–5 Ma); 3 - Miocene (5–23 Ma); 4 - Oligocene (23–38 Ma); 5 - Eocene (38–53 Ma); 6 - Paleocene (53–65 Ma) 7 - Cretaceous (65–135 Ma) 8 - Jurassic (135–190 Ma)

At the end of the 80s. completed another experiment to test the movement of lithospheric plates. It was based on baseline measurements relative to distant quasars. Points were selected on two plates, at which, using modern radio telescopes, the distance to quasars and their declination angle were determined, and, accordingly, the distances between points on two plates were calculated, i.e., the baseline was determined. The accuracy of the determination was a few centimeters. Several years later, the measurements were repeated. Very good convergence of results calculated from magnetic anomalies with data determined from baselines was obtained.

Scheme illustrating the results of measurements of the mutual displacement of lithospheric plates, obtained by the method of interferometry with an extra long baseline - 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 the baselines from which the ISDB measured enough data 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, lithospheric 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 the current movement of lithospheric plates, the speed of expansion 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.

Such a 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 due to this, the Mediterranean Sea will gradually be liquidated. The Strait of Gibraltar will disappear, and the “turned” Spain will close the Bay of Biscay. Africa will be split by the great African faults and the eastern part of it 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 that 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 refinement. Much here is still debatable and unclear.

sources

http://www.pegmatite.ru/My_Collection/mineralogy/6tr.htm

http://www.grandars.ru/shkola/geografiya/dvizhenie-litosfernyh-plit.html

http://kafgeo.igpu.ru/web-text-books/geology/platehistory.htm

http://stepnoy-sledopyt.narod.ru/geologia/dvizh/dvizh.htm

And let me remind you, but here are some interesting ones and this one. Look at and The original article is on the website InfoGlaz.rf Link to the article from which this copy is made -

Lithospheric plates- large rigid blocks of the Earth's lithosphere, limited by seismically and tectonically active fault zones.

The plates, as a rule, are separated by deep faults and move along the viscous layer of the mantle relative to each other at a rate of 2-3 cm per year. Where continental plates collide, they form mountain belts . When the continental and oceanic plates interact, the plate with the oceanic crust moves 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 separate parts of the mantle, there are powerful flows of heat and matter rising from its depths to the surface of the planet.

Over 90% of the Earth's surface is covered 13 the 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 the rifts there is an outpouring of magma, new faults, horsts, grabens appear. Mid-ocean ridges are forming.

First continental drift hypothesis (i.e. the horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. On its basis, created theory of lithospheric plates m. According to this theory, the lithosphere is not a monolith, but consists of large and small plates, "floating" on the asthenosphere. The boundary regions 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 sections (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 basalt 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 along the mantle in a horizontal direction. Near mid-ocean ridges, lithospheric plates move apart and build up due to matter rising from the bowels of the Earth; in deep-sea trenches, one plate moves under another and is absorbed by the mantle. In places where plates collide, folded structures are formed.

A feature of lithospheric plates is their rigidity and ability, in the absence of external influences, to maintain their shape and structure unchanged for a long time.

Lithospheric plates are mobile. Their movement along the surface of the asthenosphere occurs under the influence of convective currents in the mantle. Separate lithospheric plates can diverge, approach or slide relative to each other. In the first case, tension zones with cracks along the plate boundaries appear between the plates, in the second case, compression zones accompanied by thrusting of one plate onto another (thrust - obduction; underthrust - subduction), in the third case - shear zones - faults along which sliding of neighboring plates occurs. .

At the convergence of continental plates, they collide, forming mountain belts. This is how the Himalaya mountain system arose, for example, 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 formation of an oceanic type of earth's crust as a result of this is shown in Fig. 3.

The axial zones of mid-ocean ridges are characterized by rifts(from English. rift- crevice, crack, fault) - a large linear tectonic structure of 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 of seismic activity and volcanism. These sources are concentrated within relatively narrow zones, along which mutual displacements and frictions of adjacent plates occur. These zones are called seismic belts. Reefs, mid-ocean ridges and deep-sea trenches are mobile areas 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 very intensive.

Rice. 3. Divergence of lithospheric plates in the zone among the nano-oceanic ridge

Rice. 4. Scheme of rift formation

Most of the faults of the lithospheric plates are at the bottom of the oceans, where the earth's crust is thinner, but they are also found on land. The largest fault on land is located in eastern Africa. It stretched for 4000 km. The width of this fault is 80-120 km.

At present, seven 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 is also referred to as large, which is several times smaller in size than each of the seven largest ones. At the same time, scientists suggest that in fact the Nazca plate is much larger than we see it on the map (see Fig. 5), since a significant part of it went under the 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 the continental lithosphere.

The theory of lithospheric plates is important. First of all, it can explain why mountains are located in some places on the Earth, and plains in others. With the help of the theory of lithospheric plates, it is possible to explain and predict catastrophic phenomena occurring at the boundaries of plates.

Rice. 6. The outlines 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 noted that when looking at the map, one can notice that the coasts of Africa and South America seem compatible when approaching (Fig. 6).

The emergence of the hypothesis of the movement of the continents 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 the continents first came to my mind ... 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.

Between Gondwana and Laurasia 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 mainland Pangea (white - land, dots - shallow sea)

Rice. 9. Location and directions of continental drift in the Cretaceous period 180 million years ago

A. Wegener found a lot of evidence for the existence of a single continent of the Earth. Particularly convincing seemed to him the existence in Africa and South America of the remains of ancient animals - leafosaurs. These were reptiles, similar to small hippos, that lived only in freshwater reservoirs. This means that they could not swim huge distances in salty sea water. He found similar evidence in the plant world.

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plate movement

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Continental drift theory

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