DEEP DIFFERENTIATION OF SUBSTANCE.
ORIGIN OF CONTINENTS AND OCEANS
1. Depth differentiation of substance
We have cleared up in the previous chapter that all the celestial bodies of the Solar System are not invariable in the course of billions of years, as many astronomers and celestial mechanicians think. They change very appreciably. Planets and other celestial bodies expand at the expense of accretion of diffuse matter, as well as owing to the fall of other, smaller celestial bodies: both belonging to the Solar System and foreign ones.
The planets and other large celestial bodies do not remain non-differentiated in the course of their expansion. Their substance is being gradually differentiated, dividing into layers: core, mantle, crust, etc. And this differentiation of planet substance begins long before turning this celestial body to a large planet in the course of its expansion. In process of differentiation, celestial bodies go through a number of stages, the first of which begins when they are not planets yet, but still asteroids or comets. Small satellites are also referred to non-differentiated bodies.
At first, any celestial body, both circulating around a star, planet and the centre of Galaxy, is a non-differentiated body owing to its small mass and dimensions. There is too little radioactive substance in its depths near the centre of gravity; so it evolves not enough heat for warming-up deep-laid matter of the body and the differentiation of its substance cannot begin.
However, with every galactic winter, celestial bodies expand, accumulating more and more radioactive matter. This process leads to gradual heating the celestial bodies, being intensified by the heat of chemical reactions, by falling of the cosmic precipitation onto the surfaces of celestial bodies and gradual compression, densifying the substance of celestial bodies. Finally, in or near the center of a celestial body, a certain amount of heat has been collected that is enough for some substance of the celestial body to begin melting; the latter, having melted, begins to spread along the interstices of non-differentiated matter. One could suppose that the role of such a substance is played by carbon dioxide being a very widespread substance in the Universe.
At that time, water in the depths of a small celestial body is in solid state (of course, if this small body is not situated near the Sun or some other star).
Thus, according to our suggestion, the first actuating substance of geological evolution of planets was carbon dioxide; the latter played a great role in the development of celestial bodies taking active part in process of depth differentiation of substance.
Further expansion of the celestial body, accumulation of radioactive matter in it and warming-up its depths lead to wider spread of liquid carbon dioxide from the centre of heating. Having moved away from the source of heating in all directions (including upwards, to the surface of the celestial body), warm liquid carbon dioxide, contacting with colder substances, begins to cool down. In the course of cooling, carbon dioxide, like any other substance, becomes thicker and heavier. As a result, convective flows appear in the depths of the celestial body.
In the places with higher concentration of radioactive substance, the depths of the celestial body warm up more intensively; an ascending flow of liquid carbon dioxide forms here (of course, if it was carbon dioxide and not some other substance that worked as the first actuating media). Moving upwards, carbon dioxide cools down and, having spread to the sides from vertical ascending flow, begins to infiltrate down through the interstices of planet substance. Here, heavier cooled carbon dioxide fills place of ascending warmer carbon dioxide and, having been warmed up, rushes upwards as well.
Thus, in or near the center of a celestial body, there appears the circulation of carbon dioxide, slightly resembling the water circulation on Earth. This circulation gains strength in the course of expansion and warming-up the celestial bodies. Vertical ascending flows from the places of accumulation of radioactive substance become wider and higher. Ascending flows become stronger owing to a number of factors. First, because warm liquid carbon dioxide is lighter than cold liquid carbon dioxide and, consequently, it tends to raise bottom-up, while heavier cold carbon dioxide, vice versa, tends to take place at the bottom and, consequently, pours top-down. Second, in the course of further expansion of celestial bodies and warming-up their depths, carbon dioxide near the centre of the body begins to boil being warmed up to the temperature of boiling. At that, gaseous carbon dioxide mixes itself with liquid carbon dioxide in the form of gas bubbles and the resulting gas-liquid mixture, having higher temperature, lower density and higher pressure, begins to move up quicker, thereby increasing the power of ascending gas-liquid flow. And, third, the power of this ascending flow increases at the expense of involving various gases that either existed in the depths of the celestial body before, or were generated in process of warming-up: hydrogen, helium, oxygen, nitrogen, etc. Some of these gases are being entirely or partially dissolved in liquid carbon dioxide, other gases move upward with the flow of carbon dioxide in gaseous state, in the form of gas bubbles. The presence of various gases in liquid carbon dioxide reduces the density of gas-liquid mixture and promotes the increase of power and speed of carbon dioxide flow upward and then, consequently, downward.
Gaseous carbon dioxide, appearing in process of warming-up liquid carbon dioxide by radioactive heat, raises the pressure in the depths of celestial body; as a result, the gas-liquid carbonic mixture spreads still farther from the centre of warming. Penetrating the interstices of non-differentiated substance, consisting of cosmic precipitations, carbonic gas-liquid mixture, under the influence of high pressure near the centre of celestial body, tends to spread farther from it in all directions where the pressure in the interstices is low or absent at all. But, having reached far enough from the hot centre of celestial body, the carbonic mixture cools down and the bubbles of gaseous carbonic dioxide begin to condense and liquefy themselves. The density of gas-liquid mixture increases. It increases as a result of cooling down the carbon dioxide. The latter begins to spread in all directions from the vertical ascending flow. At that, various gases leave the carbonic mixture, continue to move upward, to the surface of the celestial body and dissipate in cosmic space. Carbonic dioxide, becoming denser and heavier, begins its long way downward, to the centre of heating. The upward movement of gas-liquid carbonic mixture is stipulated by its low density and high pressure, while the downward travel – by higher density and gravitational attraction to the centre of the celestial body.
Such a circulation of carbon dioxide takes place uninterruptedly since the moment when the heat being generated in the centre of celestial body is enough for turning solid carbon dioxide to liquid, and then – to gaseous form. This great circulation of carbon dioxide in the depths of celestial bodies, resembling the circulation of water on Earth, begins and lasts for many billions of years. This circulation directly concerns the differentiation of depth substance of celestial bodies.
Moving upward from the centre of celestial body, the carbonic mixture captures small grains, crystals of water ice and, probably, some other light substances, and brings them from the centre to periphery of the celestial body. There, the carbon dioxide cools down and, leaving the crystals of water ice on top, sinks down to the centre, catching up crystals of other, heavier and more refractory substances, that partly dissolve in liquid carbon dioxide. Thus, transporting solid water (water ice) from the centre of celestial body to its periphery and other substances of cosmic precipitations – top-down, carbon dioxide performs the initial differentiation of substance of small celestial bodies into three layers: silicate core, ice shell and upper layer of sediments consisting of non-differentiated cosmic precipitations (ref. Fig. 2)
The celestial bodies, the process of depth differentiation in which has not begun yet, belong to the class of comets. And the bodies, the substance of which is divided into three spheres or shells, could be called ice planets. However, one should bear in mind that the process of differentiation of substance in different ice planets can pass through different stages. Some of them may have very thin upper layer consisting of dirty snow, while the other, smaller ice planets and satellites may have the upper layer of non-differentiated cosmic precipitations representing a considerable part of the mass of celestial body.
One might suppose that the density of silicate core of ice planets and satellites is in the range of 2 to 3 g/cm3, depending on their masses; the density of ice shell is slightly less than 1 g/cm3; while the density of the outer layer (dirty snow) is the lowest – about 0.1 g/cm3 or less. Depending upon the sizes of ice planets and satellites, their average densities may vary in a wide range – apparently, from 2 down to 0.1 g/cm3.
2. The origin of shells of celestial bodies
At first, the silicate core of ice planets and satellites was small, one can even say – tiny. However, in the course of expansion of an ice planet and warming-up its depths, its core became larger and larger. At that, the ice shell and sedimentary layer grew as well, but the growth of silicate core and ice shell was quicker than that of the outer layer. Finally, the mass of the ice planet reaches such a level that, as a result of temperature increase, the amount of heat in the centre of silicate core is enough to melt the remaining water ice. Liquid water gradually accumulates in the centre of silicate core. In the course of further expansion of the ice planet, the temperature of this water increases; having reached a certain temperature, the water begins to boil and partially turn to water steam, transferring from liquid to gaseous state.
Then the process that took place in the development of planet before, under participation of carbon dioxide, repeats itself. Water steam, having created high pressure in the centre of ice planet by means of water boiling, begins to spread (together with hot water) from the centre of silicate core to its periphery. Moving away from the hot centre of planet in the form of ascending flow, the water-steam mixture gradually cools down and, having cooled to a certain extent, turns to liquid water. The latter, flowing through colder substance and getting still colder itself, begins to spread in all directions from the ascending flow and then to drain down to the centre of silicate core. Here, water boils again, turning partially to gaseous state, and the hot steam-water mixture begins again to make its way through silicate rocks upward to a certain level.
Such a process repeats again and again for many billions of years. Simultaneously, in the upper layers of the planet, the circulation of carbon dioxide goes on resulting in the expansion of silicate core by means of its buildup at its border with the ice shell.
Water, moving now upward – in steam-water state, now downward – in liquid state, does not move “empty”: like carbon dioxide, it transports in both directions the substances of various rocks, performing the differentiation of depth substance of silicate core into layers of different chemistry and density. Some, as a rule, heavier rocks, especially those soluble in liquid water, are being transported by water downward. Other, mainly lighter rocks, especially those soluble in steam state, are being transported upward by water and steam.
As a result of this underground water circulation, the silicate core is being separated into three spheres. In the centre of the planet, there appears a small core consisting of the densest rocks, predominantly of basalt type with considerable addition of metals and their compounds. Around the basalt core, there appears small (at first) shell of lighter (less dense) silicate rocks of granite type. Above the granite layer, the dehydrated (though not entirely) silicate rocks are situated (ref. Fig. 3).
In the course of further expansion of planet (satellite), taking place predominantly during galactic winters, basalt core and granite shell grow more and more owing to differentiation of silicate shell by water and water steam. However, the silicate shell does not disappear since it, being decreased from the bottom, from centre at the expense of water circulation in the central part of the planet, at the same time is being built up from the top, from outside thanks to the circulation of carbon dioxide at the periphery of the planet.
If previously, at the initial stage of existence of celestial body, its substance consisted of non-differentiated cosmic precipitations, and if, at the next stage, the substance of the ice planet consisted of three shells: silicate core, ice shell and the layer of sediments, then now the planet consists of five spheres: basalt core in the centre of planet, granite, silicate and ice shells, and, from the outside, the layer of cosmic sediments.
With the expansion of planet, the increase of masses of all its layers takes place, but the growth of basalt core is the quickest. The point is that other spheres are being diffused from one side (inside), while being built up from the other side (outside). These layers lose from the inside, but gain from the outside. They as if gradually move from the centre to the periphery. But the basalt core is being only built-up from the top, at the border with granite rocks.
At a certain stage of expansion and geological development of ice planet, in the course of increase of temperature, density and pressure in its centre, the excessively grown basalt core begins to be subject to one more circulation of a new actuating substance, more refractory and dense than carbon dioxide and water. Soviet researchers S.I.Griroryev and M.T.Nemtsov think that the role of such a substance could be played by sulfur. If that’s the case, then sulfur begins a new stage of differentiation of depth substance. Sulfur, having melted in the course of heating and then boiling, begins, like carbon dioxide and water, to circulate up and down, now boiling and turning to gaseous-liquid mixture in the centre of basalt core, now cooling down at its periphery and flowing down. At that, sulfur, like carbon dioxide and water, begins to transport basalt rocks, dividing them into heavier (denser) ones that deposit in the centre, and lighter ones situated between the new dense core and basalt shell.
Thus, at the new stage of geological development of the planet, the latter consists already of seven spheres or shells. However, as we know, the substance of modern terrestrial planets consists of still greater number of layers: solid central core, large liquid core, lower, medium and upper mantle, basalt and granite shells, and the layer of sediments
One can draw two conclusions from this. First, in big planets after the differentiation of basalt core with the participation of sulfur (or some other actuating substance) and the appearance of two new spheres in it, one (or several) more differentiation takes place: either by means of some new actuating substance (maybe, it was lead, zinc or mercury), or as a result of melting the rocks in the centre of the planet under the influence of high temperature. Second, in some terrestrial planets and satellites, the melting of ice shell and, consequently, sinking the layer of cosmic sediments onto the bottom of the appeared hydrosphere take place; as a result, the sediment layer amalgamates with silicate shell into a single layer.
Although, it is more probable that, at some planets and satellites distant from the Sun, first, the layer of sediments had disappeared completely owing to its differentiation, a then the melting of ice shell with full or partial evaporation of it into interplanetary space took place (Io, Europa, Triton, Uranus and Neptune).
As a result (if we don’t consider the giant planets, inner structure of which is unknown for us), there had been formed two groups of planets of sharply different structure and density. In silicate planets and satellites, there is the layer of sediments (on Earth – also hydrosphere) above the granite layer. In the ice planets and satellites (Pluto, Ganymede, Callisto, Titan, etc.), above the granite layer there is the shell of non-differentiated dehydrated silicates, then – ice shell, and, finally, the sediment layer (dirty porous snow).
As everybody knows, the external shells of planets, i.e. sediments, granites, basalts, form the lithosphere. The upper mantle is usually referred to the latter as well. On silicate planets and satellites, the lithosphere is of small thickness – about 100 to 300 km. The things are different on ice planets and satellites. Here, the lithosphere is very thick, since it contains ice, silicate, and sediment shells. If the lithosphere of silicate planets forms a minor part of their depths, then that of ice planets, on the contrary, represents the major part of the celestial body. Perhaps, on some planets and satellites, the lithosphere takes an intermediate position; for example on Ganymede and Callisto.
3. Origin of continents and oceans
Considering the depth differentiation of matter, we proceeded from the simplified assumption that the cosmic precipitations having fallen onto the surface of a celestial body are being distributed more or less uniformly over it (with respect to their amount and chemistry). And, consequently, the differentiation of substance passes equally at all the surface of the planet. However, in reality, the things are somewhat different.
The cosmic precipitations, especially solid bodies and, along with them, radioactive matter; distribute themselves not absolutely uniformly over the surface of the planet during falling on it. It causes gravitational and temperature anomalies in the substance of the planet. Gravitational anomalies produce the flexures on the planet surface, while temperature anomalies cause the non-uniform differentiation of substance in different places of the planet.
Most often, gravitational and temperature anomalies act jointly in the same places of the planet. And it strengthens their influence upon geological evolution of the planet, deflecting it from the above picture.
In case of deep flexure of planet surface in only one place (though, there may be several such places), cosmic precipitations fill it during a regular galactic winter, just as the snow, during earthly winters, fills all the ravines leveling them with the Earth surface. However, under the weight of cosmic precipitations that fill the flexure (and the amount of them per unit of area in this place is multiply more than that on the planet in average), the flexure of surface in this place becomes still sharper because of violation of gravitational balance formed owing to formation of the flexure.
During the next galactic winter, the increasing flexure absorb even greater amount of cosmic precipitations per unit of area; further sharpening of this flexure takes place during and after the galactic winter. And what is more, after the completion of the galactic winter, the cosmic precipitations being spread over the whole surface of the planet begin to move under the influence of atmosphere and hydrosphere (if the latter is available) and, in the course of sinking the substance over the flexure, fill it again and again.
As a result, the flexure of planet surface turns to a kind of “gravitational well”, through which, the cosmic sediments penetrate inside the planet. Of course, not all the sediments that get inside the planet do this through the gravitational wells; however, starting with a certain stage of geological development of the planet, a considerable, maybe the major part of sediments penetrates inside in this very way.
At the same time, the above mechanism of differentiation of the planet substance goes on working, but now the major part of cosmic precipitations gets inside the planet through one or several limited regions of surface (sea trenches). Some of these trenches may be of great size. Perhaps, the biggest ancient oceanic trench on Earth was the ancient Pacific Ocean, the borders of which being, approximately, modern Pacific ridges passing along the outskirts of the modern Pacific Ocean. As to the other part of planet surface, it changes slowly; this fact leads, in the end, to grandiose consequences in geological development of the planet.
Cosmic precipitations, being drawn inside the planet through the sea trenches, go through all the above stages of substance differentiation: first, by means of carbon dioxide, then – water, sulfur, etc. The appearance of gravitational wells changes not the very mechanism of differentiation of matter, but only the speed of this differentiation in various parts of the planet. As a result, with the retention of the pace of growth of the planet, there appears the deceleration of expansion of external shells of the planet. If previously, when the differentiation of substance proceeded approximately uniformly along all the directions from the centre of the planet, the latter grew only from the outside; then now that the gravitational wells appeared, the planet begins to grow not only (and not so much) from the outside, but also on the inside. And this leads to the origin of powerful, more and more growing stresses in external shells of the planet that as if turns to a steam boiler, the pressure of steam in which grows more and more.
And, sooner or later, the pressure of depth substance towards the external shells reaches such a critical value that the cracks in external shells appear. And the latter split into several parts; there appeared deep breaks between them being gradually filled with depth substance from below and (more rapidly) with cosmic precipitations - from above.
After splitting the external shells into parts (plates), the latter begin as if to go away from one another. Differentiation of matter on the surfaces of these plates almost stops. All the cosmic precipitations are being drawn into the appeared breaks under the influence of atmospheric masses; the differentiation of cosmic sediments takes place now mainly in the breaks.
The planet continues to grow gradually, but the area of continental plates does not change. The growth of planet surface takes place at the expense of widening the breaks and the increase of their surface. And though the continental plates are not (or almost not) subject to horizontal shifts, they gradually move away from one another, since they move up in vertical direction, while the volume, surface area and radius of the planet increase as the latter expands.
In the regions of breaks of external shells of the planet, new shells begin to form; this process proceeds mainly at the expense of cosmic precipitations, filling the breaks during and after galactic winters and being subject to accelerated differentiation in these breaks. However, the differences of the levels of plates and breaks remain for a long time, though getting less apparent in the course of time. The planet surface, being previously unified (not taking the sea flexures of small area into account), divides itself into continental eminences and oceanic trenches. Only mid-oceanic ridges point to the places of breaks of previously unified continental crust.
But in some, comparatively long period of time, the heights of continents and oceans become even at the expense of buildup of external shells in oceanic trenches. And the planet, having “healed” the deep scars on its surface, takes its former appearance. But time will pass and everything will be repeated again. Once again the gravitational wells will appear; once again the planet will swell from within; once again the external ice (or ice and silicate, etc.) shell will burst with thunder; once again continents and oceans will occur – to disappear again in the course of time.
During the latest break of continental crust of the Earth, three new oceans appeared: Atlantic, Indian and Northern. The Pacific Ocean had only increased its dimensions, since one of the breaks of lithosphere went along its bottom near the coasts. One might suppose that the ancient Pacific Ocean, being several times smaller than the modern one, was formed either as a result of a flexure owing to gravitational-temperature anomalies, that took place at its territory in still older times, or as a consequence of the last but one break of continental crust (along with lithosphere) into continental plates that later had grown together as a result of filling all the oceanic trenches with cosmic sediments. Merging did not occur only in one place: in the biggest flexure, where the ancient Pacific Ocean was situated. Now, it is the central part of the modern Pacific Ocean. The fact that the unified continental crust of Earth was, probably, subject to several breaks is confirmed by the difference of age of continental platforms. If we mentally join all the ancient platforms of the same age, we would have the initial lithosphere of the small Earth. It is interesting that, in such a case, West Siberian lowland, Ural ridge and its continuation – Severnaya Zemlya would vanish from the face of Earth. The fact that the eastern border of the ancient East European platform and the western border of the ancient East Siberian platform are of the same shape proves that previously they were united in a single platform. Then this platform had split itself up in the course of a break of the Earth lithosphere and the ancient Ural-Mongol Ocean appeared between the plates having moved apart. And the modern Ural ridge and Novaya Zemlya are the remnants of the ancient mid-ocean ridge, the south-eastern part of which had been broken by powerful northern winds (atmospheric and hydrospheric erosion).
It is interesting that the shapes of ancient platforms of Africa and Southern America from the direction of the Atlantic Ocean do not match, as their modern coastlines do. Apparently, there were several breaks between these two continents.
At a certain stage of the planet development, the ice shell begins to thaw under the influence of internal or solar heat, as a result, permanent or temporary hydrosphere appears on the planet surface. The hydrosphere promotes the accelerated transfer of cosmic sediments over the planet from the surface of continents to oceanic trenches and breaks or sea flexures, thereby speeding up the cycle of origin and disappearance of continents and oceans (ref. Fig. 5).
[Table of contents] [Foreword]
[COSMOGONICAL HYPOTHESES] [EXPANSION OF CELESTIAL BODIES]
[DEEP DIFFERENTIATION OF SUBSTANCE. ORIGIN OF CONTINENTS AND OCEANS] [DECELERATION OF CELESTIAL BODIES IN GAS-DUST ENVIRONMENT]
[EVOLUTION OF THE SOLAR SYSTEM] [ORIGIN OF THE SOLAR SYSTEM]