Earth's supercontinents. Vanishing oceans and supercontinents will keep the earth warm. Structural elements of the surface of the foundation and sedimentary cover of platforms
Supercontinent... Spelling dictionary-reference book
Noun, number of synonyms: 15 Amazia (2) America (31) Afro-Eurasia (1) ... Synonym dictionary
A supercontinent in plate tectonics is a continent containing almost all of the Earth's continental crust. A study of the history of continental movements showed that with a periodicity of about 600 million years, all continental blocks gather into a single block, which ... ... Wikipedia
Geological time as a diagram depicting the relative sizes of eras in the history of the Earth ... Wikipedia
This term has other meanings, see Continent (meanings). Continental Conti models ... Wikipedia
The geological time presented on the diagram is called a geological clock, showing the relative length ... Wikipedia
The scorched Earth after the Sun enters the red giant phase as imagined by the artist... Wikipedia
Simplified map of Pangea Supercontinent cycle is a theory in geology that describes the periodic connection and separation of continents. Scientists have differing opinions regarding changes in the volume of continental... Wikipedia
Geochronological scale Eon Era Period Phanerozoic ... Wikipedia
The Breakup of Pangea into Modern Continents The theory of continental drift was first proposed by German geographer Alfred Wegener and describes the movement, unification and breakup of continents based on plate tectonics. Of particular interest are those... ... Wikipedia
Books
- Monsters of the Triassic, Crumpton Nick. About the book Get ready to go on an exciting journey to the Triassic era - a time when the waters of the world's oceans washed the only supercontinent Pangea, and the Earth was inhabited by terrible...
- Monsters of the Triassic. Games with the first dinosaurs, Crumpton N.. Get ready to go on an exciting journey to the Triassic era - a time when the waters of the world's oceans washed the only supercontinent Pangea, and the Earth was inhabited by terrible...
Using paleomagnetic data, the modern theory of the formation of the earth's crust and the latest methods for determining the age of lithospheric rocks, at the end of the twentieth century, Russian scientists O.G. Sorokhtin and S.A. Ushakov restored more ancient situations in the relationship between land and sea, the distribution of continents and beds of ancient oceans on our planet. As a result, it was concluded that in the geological history of the Earth, in addition to A. Wegener’s Pangea, there were three more supercontinents.
The change in the volume of water on Earth occurred mainly during the evolution of the continents and reached a maximum 1.5 billion years ago in the Lower Riphean. During the 1.4 billion years of the Archean period (4-2.6 billion years ago), large continents did not exist. First major continent Monogea appeared on our planet about 2.6 billion years ago at the moment of formation of a dense iron oxide core near the Earth in the process of differentiation of terrestrial matter. Its remains, due to the coincidence of the age of the rocks and the direction of the ancient magnetic field recorded in them, were discovered in different areas of our planet ( Fig.1.11a) Under the influence of convective flows changing in power and direction 2.2 billion years ago the first continent broke up into small fragments - cratons (Fig.2b). Their remnants are, for example, the rocks of the Great Dyke in Zimbabwe, which are 2.4 billion years old.
1.8 billion years ago for a similar reason, the second continent in the geological history of the Earth was formed Megagay . Its existence was assumed back in 1944 due to the similarity of the geological structure of various ancient blocks on the North American, European and Siberian platforms, in Australia and South America.
Fig.1.11. Ancient supercontinents:
MONOGEA - 2.6 billion liters back(a); MEGAGAYA - 1.8 billion liters. back (b); MESOGEA (RODINIA) - 1 billion years ago (c)
(Arrows - direction of magnetic field lines; Blocks: Av - Australia; SAm and YuAm - North and South America; An - Antarctica; ZAf - West Africa; Af - Africa; Ev - Europe; In - India; K - Northern and Southern China ; Sat - Siberia
In just 100-150 million years about 1.7 billion years ago there were signs of the collapse of Megagaia, which ended completely about 1.4 billion liters n. . Geological traces of this process (fault tectonics) 1.5-1.4 billion years old (Riphean period) are today found on the North American and Russian platforms.
After combining coeval folded mobile belts of the Earth's surface and paleomagnetic reconstructions, the third supercontinent of the planet was restored Mesogea (Rodinia)), formed 1 billion years ago ). But after 100-150 million years it split into two parts, separated 850 million l. n wide (6-10 thousand km) oceanic basin Protothethys At the same time, all the pre-modern northern continents united into a supercontinent Laurasia, and the pro-modern southern ones amounted to Gondwana, which 800-750 million l. n shifted respectively to the North and South Poles ( Fig.1.12).
Fig.1.12. The collapse of MESOGEIA into LAURASIA and GONDWANA 800-750 million years ago (Mn - Mongolian plate; Am - Amur plate; Ir - Iranian plate. Blocks - according to Fig. 1.11)
In the equatorial zone of the Proto-Tethys ocean, a powerful trade wind current with oppositely directed branches in temperate latitudes was established, which blocked the flow of heat to the continents in high latitudes. As a result, in the second half of the Late Riphean, the African-Australian glaciation of Gondwana and the Canadian glaciation of Laurasia began. At the same time ( 800 million years ago ) in the zone of the Grenville mobile belt of Laurasia, which welded the eastern coast of North America and Greenland with the European platform, a new Proto-Atlantic ocean Iapetus 2000 km wide, and on the site of modern Western Siberia - narrow Paleouralsky ocean.
Further decay ( 650 million years ago ) Gondwana was accompanied by the formation of narrow troughs (beds) West African and Brazilian suboceans (Red Sea type), as well as African-Australian oceanic basin ( Fig.1.13).
Fig.1.13. The collapse of LAURASIA AND GONDWANA 650 million years ago.
(Ar - Arabian plate. Further - according to Fig. 1.11, 1.12)
This fact is confirmed by the similarity of the geological structure of the Mozambique belt (Africa), the Adelaide geosyncline (Australia) and the Transantarctic Mountains in Antarctica, which at that time represented passive continental margins. Thus, the “body” of the ocean - a mass of water - has existed for as long as the continents have existed - approximately 4 billion years. It was formed simultaneously with the continents.
The asymmetry of the position of Laurasia and Gondwana in the polar latitudes and their continued drift led to the fact that 550 million years ago The Earth, trying to move to a stable state, changed the orientation of the axes of the main moment of inertia, turning 90° with respect to the geographic poles. As a result, West Africa found itself at the South Pole, and North America, Europe and Australia at the equator. The Western European bloc at this time separated from West Africa and began to drift towards the European platform with which it united. Most continents thus found themselves at low latitudes, which explains the emergence of the Earth's warm climate during the Cambrian period (500-600 million years ago).
The next rotation of the Earth by 90° around an axis perpendicular to the axis of its rotation, which occurred (according to calculations) 400-200 million years ago in the early Paleozoic, led to the formation at the end of the Paleozoic 200 million years ago fourth supercontinent Pangea (see Fig. 1.5.1), which, judging by paleomagnetic data, which confirmed Wegener’s brilliant guesses, after 140 million years again broke up into its component parts, which began a centrifugal drift up to the present position.
Geological Epochs. According to these studies, there is a so-called supercontinental cycle, in which continental blocks with a periodicity of about 600 million years. go through a phase of supercontinent, followed by a phase of fragmentation. There are hypotheses linking the supercontinent cycle with the periodic transition of the Earth's mantle from a single-cell circulation system, when all downward flows are directed under the supercontinent, to a two-cell system of currents.
The modern continents made up the supercontinent Pangea approximately 400-200 million years ago. The current geological epoch belongs to the phase of fragmentation, the peak of which occurred in the Cretaceous period. Based on extrapolation of current geological processes, it is assumed that in 100-200 million years. the land will again gather into a single massif. Eurasia, formed in the Cenozoic, is the basis of the future supercontinent; the observed movement of Africa suggests that already after 15-20 million years. it will also form a single whole with Europe, and in place of the Mediterranean Sea, a salt desert will first arise, and then mountain ranges will rise, not inferior to the Himalayas. Australia is also likely to join Asia within 60 million years. Predictions about further tectonic processes, assessments of factors that will influence the movements of continents, differ among researchers, so there are several models for the folding of the future supercontinent: Pangea Ultima, Amasia and Neopangea, but they all assume the formation of a supercontinent in ~200 million years.
Ancient supercontinents
It is not yet possible to make confident statements about the amount of continental crust in the Archean: perhaps there were land blocks that are not clearly represented in the lithosphere today. However, it is likely that continental crust began to form in the Archean and reached near modern extents during the Proterozoic, so that the first supercontinents were not large massifs, but are so called (by definition) because they contained virtually all the continental crust of their era.
- Vaalbara (~3.6 billion years ago)
- Ur (~3 billion years ago)
- Kenorland (~2.7 billion years ago)
- Columbia, also known as Nuna, (~1.8-1.5 billion years ago)
- Rodinia (~1.1 billion years ago - ~750 million years ago)
- Pannotia (~600-540 million years ago)
- Laurussia (~300 million years ago)
- Pangea (~300-180 million years ago)
Possible future supercontinents
Scientists predict the formation of another supercontinent hundreds of millions of years later. Africa will merge with Europe, Australia will continue to move north and unite with Asia, and the Atlantic Ocean, after some expansion, will disappear altogether. Due to the approach of the African Plate, the Alps and Pyrenees mountain systems have grown, and earthquakes are shaking Greece and Turkey. Just as cold air settles into the lower layers, dense seafloor sometimes settles below the Earth's crust and pulls the edge of the platform with it.
see also
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Notes
Literature
- Xiao Xuchang & Liu Hefu (eds). Global Tectonic Zones: Supercontinent Formation and Disposal. Proceedings of the 30th International Geological Congress. Utrecht - Tokyo: VSP, 1997.
- Nield, Ted, Supercontinents: Ten Billion Years in the Life of Our Planet, Harvard University Press, 2009, ISBN 978-0674032453
- Small mountain encyclopedia. In 3 volumes = Small Encyclopedia / (In Ukrainian). Ed. V. S. Beletsky. - Donetsk: Donbass, 2004. - ISBN 966-7804-14-3.
Links
- (English) - reconstruction of supercontinents of the past on the Scotese website
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Excerpt characterizing the Supercontinent
“Mon pere ne m"a pas parle du pretendant, mais il m"a dit seulement qu"il a recu une lettre et attendait une visite du prince Basile. Pour ce qui est du projet de Marieiage qui me regarde, je vous dirai, chere et excellente amie, que le Marieiage, selon moi, est une institution divine a laquelle il faut se conformer. Quelque penible que cela soit pour moi, si le Tout Puissant m"impose jamais les devoirs d"epouse et de mere, je tacherai de les remplir aussi fidelement que je le pourrai, sans m"inquieter de l"examen de mes sentiments a l"egard de celui qu"il me donnera pour epoux J"ai recu une lettre de mon frere, qui m"annonce son arrivee a Bald Mountains avec sa femme. Ce sera une joie de courte duree, puisqu"il nous quitte pour prendre part a cette malheureuse guerre, a laquelle nous sommes entraines Dieu sait, comment et pourquoi. Non seulement chez vous au center des affaires et du monde on ne parle que de guerre, mais ici, au milieu de ces travaux champetres et de ce calme de la nature, que les citadins se representent ordinairement a la campagne, les bruits de la guerre se font entendre et sentir peniblement. Mon pere ne parle que Marieche et contreMarieche, choses auxquelles je ne comprends rien; et avant hier en faisant ma promenade habituelle dans la rue du village, je fus temoin d"une scene dechirante... C"etait un convoi des recrues enroles chez nous et expedies pour l"armee... Il fallait voir l"etat dans lequel se trouvant Les meres, les femmes, les enfants des hommes qui partaient et entendre les sanglots des uns et des autres!On dirait que l"humanite a oublie les lois de son divin Sauveur, Qui prechait l"amour et le pardon des offenses, et qu"elle fait consister son plus grand merite dans l"art de s"entretuer.
“Adieu, chere et bonne amie, que notre divin Sauveur et Sa tres Sainte Mere vous aient en Leur sainte et puissante garde. "Marie."
[Dear and priceless friend. Your letter of the 13th brought me great joy. You still love me, my poetic Julia. The separation, about which you say so many bad things, apparently did not have its usual influence on you. You complain about separation, what should I say if I dared - I, deprived of all those who are dear to me? Ah, if we didn’t have religion for consolation, life would be very sad. Why do you attribute a stern look to me when you talk about your inclination towards a young man? In this regard, I am only strict with myself. I understand these feelings in others, and if I cannot approve of them, having never experienced them, then I do not condemn them. It only seems to me that Christian love, love for one’s neighbor, love for enemies, is more worthy, sweeter and better than those feelings that the beautiful eyes of a young man can inspire in a young girl, poetic and loving, like you.
The news of Count Bezukhov's death reached us before your letter, and my father was very touched by it. He says that this was the penultimate representative of the great century, and that now it is his turn, but that he will do everything in his power to ensure that this turn comes as late as possible. God save us from this misfortune.
I cannot share your opinion about Pierre, whom I knew as a child. It seemed to me that he always had a wonderful heart, and this is the quality that I value most in people. As for his inheritance and the role that Prince Vasily played in this, this is very sad for both. Ah, dear friend, the words of our Divine Savior, that it is easier for a camel to go through a needle’s ear than for a rich man to enter the kingdom of God - these words are terribly true. I feel sorry for Prince Vasily and even more for Pierre. For someone so young to be burdened with such a huge fortune - how many temptations will he have to go through! If you were to ask me what I desire more than anything in the world, I want to be poorer than the poorest of the poor. I thank you a thousand times, dear friend, for the book that you send me and which makes so much noise with you. However, since you tell me that among many good things in it there are some that the weak human mind cannot comprehend, then it seems to me unnecessary to engage in incomprehensible reading, which for this reason could not bring any benefit. I have never been able to understand the passion that some people have to confuse their thoughts by becoming addicted to mystical books, which only arouse doubts in their minds, irritate their imagination and give them a character of exaggeration, completely contrary to Christian simplicity.
Let us read better the Apostles and the Gospel. Let us not try to penetrate what is mysterious in these books, for how can we, miserable sinners, know the terrible and sacred secrets of Providence as long as we carry on ourselves that fleshly shell that erects an impenetrable curtain between us and the Eternal? Let us confine ourselves rather to studying the great rules which our Divine Savior left us for our guidance here on earth; Let us try to follow them and try to make sure that the less we give our minds wildness, the more pleasing we will be to God, who rejects all knowledge that does not come from Him, and that the less we delve into what He wanted to hide from us, the sooner He will give us this discovery with His divine mind.
Everything flows, everything changes. The whole world around us is in motion. Even the ground literally disappears from under your feet, although this is not very noticeable. Seas and oceans, continents and archipelagos - nothing knows peace. For the time being: alas, sooner or later the geological life of the planet will stop. But there is a way to delay the sentence - with the help of oceans and supercontinents.
Now every schoolchild knows that the Earth’s shell is heterogeneous and consists of relatively solid plates that are in constant motion. However, the mechanisms that control tectonic activity are very complex.
Despite all the elegance and logic of the concept “some plates move apart and others collide,” in each specific case the geophysical processes are so intricate that describing in detail, for example, the formation of mountain ranges is not an easy task.
The shell of the Earth is called the lithosphere. It includes the hard crust and the coldest, viscous part of the upper mantle. The continental and oceanic shells are different. To put it simply, they are granites and basalts. Some platforms are composed exclusively of oceanic crust, others consist of a continental block “sealed” into the oceanic one. Here's what it looks like in numbers: the thickness of the continental lithosphere ranges from 40 to 200 kilometers (and according to some estimates up to 400), including the crust - from 30 to 50 kilometers; the thickness of the oceanic lithosphere is from 50 to 100 kilometers, including the crust - from 7 to 10 kilometers. Please note that these data are approximate and may be updated in the future (illustration from the U.S. Geological Survey).
And the “mobile” point of view was established relatively recently - in the 1960s and 1970s. Before this, “stationary” ideas dominated. For example, mountains, according to a hypothesis widespread at the beginning of the 20th century, were born like wrinkles on a dried apple - as the bark cooled.
Subsequently, a number of other theories appeared, but all of them one way or another rejected the very possibility of continental movement. Even calls to compare the coastlines of Africa and South America, which seem to form an obvious puzzle, did not make any impression on official science.
The main reason for skepticism was the absence of a visible reason for continental drift: the force pushing them must be enormous. But what is its source?
There are eight largest plates: North American, Eurasian, South American, African, Indian, Australian, Antarctic and Pacific. The independence of “megaplates” as a whole is beyond doubt, but their boundaries are not always clear-cut. The largest platforms are based on ancient cores - cratons, which arose at the dawn of tectonic activity. Siberia, for example, is one of these “nuclears”. For us, the division of the lithosphere into continents and oceans is of primary importance, but it does not always coincide with the division of the lithosphere into plates (illustrations from learner.org, wikipedia.org).
The solution came from the ocean. A detailed map of its relief revealed gigantic underwater ridges (total length of more than 60 thousand kilometers), on which, in turn, traces of a young rock by geological standards were discovered.
It turned out that the interior of the Earth is penetrated by convective flows along which mantle matter moves. And the main source of energy for these currents is the temperature difference between the hot core (about 5000 °C) and the cold surface.
Further research made it possible to formulate in more detail the main causes of plate movement. There were two of them. Or rather, one, but about two persons.
When oceanic plates collide—either with each other or with continental ones—one of them “sinks” under the other. In the latter case, the “winner,” with very rare exceptions, is the mainland. This process is called subduction. The downward slab enters the hot region of the mantle and also heats up, softening at the same time. Molten rock breaks out, deforming the upper part of the lithosphere (illustration from wikipedia.org).
Firstly, this is the rise of molten rock in the areas of mid-ocean ridges, its solidification and subsequent sliding down, accompanied by expansion of the bottom - “spreading”.
Secondly, this is the compensatory subsidence of cold plates down at the border with other platforms - “subduction” or the pushing of one section of the lithosphere under another.
Modernity is a speck in the geological history of the Earth. The oldest mineral found is dated to a period of about 4.4 billion years ago, that is, essentially still a pre-geological (in the modern sense) era - Katarchaean (illustration from the site wikipedia.org/MEMBRANA).
In fact, this is a single mechanism, the result of which is a kind of mantle circulation in nature, dragging continents and oceans along with it - due to viscosity, as well as the resulting lateral pressure of adjacent platforms.
The tectonic theory was quickly confirmed with the discovery of magnetic anomalies on the ocean floor. The fact is that when volcanic rocks solidify, they retain residual magnetization, that is, the orientation of metal particles along the magnetic field lines.
Having unpacked this “archive,” geophysicists restored the position of the pole relative to each plate at different points in time. And, combining the data obtained with information on the dating of rocks, they reconstructed the historical sequence of movements of the continents.
A majestic picture of the geological past of our planet was revealed to the eyes of scientists.
Continental drift from 600 million years ago to the present. The formation of the Earth as we know it today began when the ancient supercontinent Pangea began to break apart about 200 million years ago (illustration by Ron Blakey/Northern Arizona University/MEMBRANA).
The formation of the continental lithosphere began about four billion years ago (or even earlier), that is, with a delay of approximately 500–600 million years relative to the origin of the Earth itself.
Since then, there has been a consistent (but uneven) increase in the mass of the crust up to its modern size. The most intense formation of a solid surface occurred in the late Archean, about 2.6 billion years ago, when the core finally emerged in the depths of our planet.
Reconstructing past plate movements has become one of the most popular activities. The positions of the continents and the blocks from which they formed have been reconstructed in varying degrees of detail up to the Archean.
The tectonics we know today arose, according to some scientists, in the late Proterozoic. Before this, the mantle may have had a different structure, in which there were no stable convective flows (illustration by Ron Blakey/Northern Arizona University).
At the same time, researchers discovered an interesting pattern: continental shields periodically huddled together - every 400-600 million years. This approximately coincides with the number of convective cycles, that is, periods during which all the mantle matter at least once had time to completely “scroll” - through subduction and spreading.
The first supercontinent to be “discovered” was Pangea, which existed 250-200 million years ago. As a result of its collapse, modern continents were formed.
Let us note, however, that a more or less reliable paleomagnetic reconstruction can be carried out in a relatively short time by geological standards - just before the age of Pangea. With earlier periods the situation is somewhat murkier.
Pangea split into Laurasia (to the north) and Gondwana (to the south), giving rise to the Atlantic Ocean. By the way, the name “Pangea” (literally “all lands”) was coined by the founder of tectonic theory, Alfred Wegener. Nobody believed him throughout the first half of the 20th century (illustration by Ron Blakey/Northern Arizona University).
There are about a dozen supercontinents in total (including incomplete ones, but still large ones), and sometimes some scientists use different names for the same “giant”. But even with generally recognized continents, not everything is simple.
Take, for example, Rodinia, whose existence about one billion years ago does not raise questions among most experts. There are a lot of assumptions about what she looked like. Moreover, several main hypotheses are equally accepted for consideration by the scientific community.
However, despite all the numerous versions and theories, one of the main problems of geological evolution has not yet been convincingly explained to anyone. We are talking about the heat death of the Earth.
The supercontinent Rodinia supposedly began to form about 1.1 billion years ago and broke up about 750 million years ago. By the way, the name “Rodinia” comes from the Russian “Rodina” (Li et al.).
Most geophysicists are of the view that about 90% of the “convection” energy is generated due to the cooling of the core, 10% due to the decay of radioactive elements in it, and about 1% due to tidal disturbances.
Analysis of the geological history of the mantle showed that the main heat losses always occurred through the oceanic crust - through subduction and spreading. That is, de facto, the intensity of convective heat exchange can be equated to the level of tectonic activity.
So, according to all calculations, it turned out that the Earth should have cooled down a long time ago. But that did not happen. Why haven't we frozen like the tsutsiki yet?
The supercontinent Pangea appeared as a result of the contraction of the internal ocean Iapetus, and Rodinia, on the contrary, the external ancient ocean. The Pacific Ocean, which is now shrinking, is also external (illustration from wikipedia.org).
It is usually believed that the expansion of oceanic platforms and their absorption by continental ones has always existed and “operated” continuously.
At the same time, a global algorithm for plate drift was revealed: they either converge or diverge, forming a supercontinent at the end of each cycle.
Based on the cyclical version, American scientists disputed the continuity of tectonic movement, which, in their opinion, depends on the conditions of the “collapse” of the ocean (with the subsequent formation of a single “supercontinent”).
The only significant subduction zone to occur in the last 80 million years is in the Pacific Ocean (illustration by Lawver, Dalziel, Gahagan, Martin, Campbell/University of Texas).
Geophysicists have suggested that there are two types of contraction - internal and external, and they lead to different consequences.
The fact is that, according to scientists, subduction zones do not form in the internal ocean. And these zones, let us remind you, are considered an unshakable source of geological activity, generating convective currents.
We can observe something similar right now: the Pacific Ocean, where the vast majority of seismic focal areas are located, is slowly shrinking, giving way to the Atlantic Ocean. And in the latter, over the 200 million years of its existence, the “creeping” of plates never occurred (with minor exceptions). And there are probably no prerequisites for this in the future.
In 100 million years, Australia will sail to Japan and our Sakhalin. And then, after another 100-200 million, they will be “slammed” by North America (illustration from the sites suntimes.com, utexas.edu/MEMBRANA).
Previously, it was believed that the closure of old subduction zones should be balanced by the emergence of new ones. Thus, there must be some law that would preserve the continuity of the force interaction of oceanic plates with each other, with continental shields, as well as with the mantle - influencing convective flows and, ultimately, the tectonic activity of the Earth.
However, this does not appear to be the case. The most logical assumption would be that the collision of continents as a result of the formation of a supercontinent would push the next region of the lithosphere - and so on, up to the oceanic platforms.
Nevertheless, the “impact” of Africa and Hindustan on Eurasia almost entirely “went” into the Alpine-Himalayan mountain range, and new subduction areas (to replace those lost in the ocean that lay between them) did not appear. Although 50 million years have already passed.
As thermal energy is saved, the lithosphere begins to play the role of a quasi-solid lid (stagnant lid), and convection switches to a different, “standing” mode. If heat cannot escape, moving the plates, it will seek its way not at their outskirts, but directly through the crust - which leads to much less cooling. But if the core temperature reserve is sufficient, sooner or later the supercontinent will “tear” into pieces - like Rodinia (illustration by Li et al.).
So, since we have observed that the internal ocean has not shown any signs of “pushing” for more than 200 million years, it is reasonable to assume that this situation may continue for quite some time. Hundreds of millions of years, according to American estimates.
And with the formation of a supercontinent (and the “collapse” of the Pacific Ocean completely), subduction may stop altogether. That is, the plates will slow down for some time, and the Earth’s heat transfer will sharply decrease
In support of their theory, Paul Silver and Mark Ben found traces of similar processes in more ancient volcanic rocks, dating back, for example, to the existence of Rodinia.
These rocks were discovered in the depths of the continents, far from the places of their “production”, which indicates the accumulation of heat under the continental plates - during periods of their “stagnation”.
Based on various coefficients of "tectonic efficiency" (heat loss due to the movement of oceanic plates), several scenarios were constructed by Paul Silver and Mark Behn. Even according to the most optimistic of them, the Earth should have cooled about 1 billion years ago (illustration by Silver, Behn).
It turns out that in our geological past something like a mechanism for self-regulation of thermal conditions arose - on a global scale. And this extended our life by at least one billion years.
But what consequences can all this lead to in the future?
And in the future, factors reducing tectonic activity will play an even more prominent role. At the same time, the slowdown of convective processes in the mantle will increase the periods of tectonic megacycles.
This is due to the exponential dependence of the viscosity of the mantle substance on temperature: with a decrease in the supply of thermal energy from the core to it, the viscosity of the asthenosphere will increase many times, and accordingly the friction forces that impede the movement of the plates will increase.
The most expected time for the “assembly” of Pangea Ultima is in 250 million years, but there are also estimates of 350 million. There is no consensus on what it will look like, and many geologists put forward alternative versions of the last supercontinent under different names (illustration from davidlyness.moved.in).
Moreover, since their origin, lithospheric plates have consistently reduced their speed - from 50 centimeters per year (in some places more) to its modern value of about 5 centimeters per year.
An even more radical question arises: is there enough strength to launch a new cycle? Some scientists are already calling the next supercontinent Pangea Ultima, that is, “the last Pangea.”
Let us recall that we are now observing a contraction of the external ocean, which means that we are in for a happy reduction in tectonic activity and the “conservation” of heat in the mantle. Plus, fewer faults mean fewer volcanoes and earthquakes.
True, living in “supercontinental” conditions will still not be very sweet, not to mention the fact that the concentration of all plates “on one side” of the Earth will have unpredictable consequences for the climate as a whole. Most likely sad.
Well, let's hope that the mechanism of tectonic self-regulation described by American scientists really exists, and that it will once again prolong the life of our beautiful planet.
To the question what was the name of the first continent on earth asked by the author Bakir Gurbanov the best answer is Gondwana is the name of a large continent that existed for a long time in the southern hemisphere.
Gondwana consisted of the modern continents of Africa, South America, Antarctica, Australia, as well as the island of Hindustan, which after a collision with Laurasia became the Hindustan Peninsula.
Gondwana arose approximately 530-750 million years ago and was located around the South Pole for a long time. After a sharp movement to the north, it united during the Carboniferous period (360 million years ago) with the North American-Scandinavian continent into the giant protocontinent Pangea. However, during the Jurassic period about 180 million years ago, Pangea split again into Gondwana and the northern continent of Laurasia. 30 million years later, Gondwana itself began to break up into the above continents.
The result of African pressure on Europe was the Alps, and the collision of India and Asia created the Himalayas.
Answer from Strabismus[guru]
Pangea (Greek Πανγαία, all-earth) is the name given by Alfred Wegener to the protocontinent that arose during the Paleozoic era.
Pangea split approximately 150-220 million years ago into two continents. The northern continent of Laurasia later split into Eurasia and North America, while the southern continent of Gondwanaland later gave rise to Africa, South America, India, Australia and Antarctica.
But this is not the very first continent. Older than Pangea is Rodinia (from Russian. Rodina is a hypothetical supercontinent that supposedly existed in the Proterozoic - the eon before the Cambrian period. It arose about 1.1 billion years ago and broke up about 750 million years ago. At that time, the Earth consisted of one giant piece of land and one giant ocean called Mirovia. Rodinia is often considered the oldest known supercontinent, but its position and outline are still the subject of debate. Geophysicists suggest that other supercontinents existed before Rodinia. After Rodinia, the broken continents managed to unite once again into the supercontinent Pangea. disintegrate.
It is assumed that in the future the continents will once again gather into a supercontinent called Pangea Ultima.
Answer from Varuzhan Amirjanyan[guru]
Just. See Wikipedia
Answer from I-beam[active]
Pangea
Answer from Space[active]
At first there was one single continent - Pangea, which was divided into Laurasia and Gondwana, if that's what you're talking about
Answer from Liliya Bukhtoyarova[newbie]
Rodinia
Answer from Rostik Morkvych[newbie]
Vaalbara is the first hypothetical supercontinent on Earth, which existed 3.6-2.8 billion years ago (Archaean). Its formation began 3600 million years ago, after the frozen surface of our planet, and ended 3100 million years ago. There is no general agreement on exactly when it began to diverge, however geochronological and paleomagnetic studies indicate that the two cratons (protocontinents) experienced a circular lateral separation at an angle of 30° approximately 2.78 - 2.77 billion years ago, implying that ~2.9 billion years ago they no longer touched.
Supercontinents have diverged and converged again throughout the history of our planet:
~ 2.8 billion years ago the supercontinent Kenorland.
~ 2 billion years ago supercontinent Columbia.
~ 1 billion years ago the supercontinent Rodinia.
~ 550 million years ago supercontinent Pannotia.
~ 300 million years ago the supercontinent Pangea.
~ 208 million years ago, 2 large continents were formed: Laurasia and Gondwana.
Thus, the last supercontinent at the moment was Pangea
According to some forecasts, in the future the continents will once again gather into a supercontinent in 200-300 million years called Pangea Ultima
