Some elements appear so strongly enriched in the Earth's crust, that they must be nearly entirely concentrated in the crust range. This striking enrichment has even been found in the earliest continental shields and mainly for the elements barium, lanthanium, thorium and uranium. But also the alkali and alkaline earth metals (except magnesium) as well as the rare-earth elements and aluminium are more concentrated in the Earth's crust. Strikingly, all of these elements form so-called
saline hydrides, which are solid compounds containing hydrogen as a negative ion (anion). In a hydrogen atmosphere, these saline hydrides are similarly stable as common salts like chlorides, sulfates or nitrates in our oxygen atmosphere.
The cosmic abundance describes the ratio of the chemical elements in the cosmos and has been measured rather exactly for our solar system and its further surroundings. It has been found that approximately 90% of the total mass in the cosmos is hydrogen, 9% helium, while all other elements sum up to the remaining 1%. If the total amount of the strongly enriched elements, as mentioned in section 1, is evaluated and compared to the cosmical abundance of these elements, one should be able to determine which mass was available in the formation process of the Earth. From such a calculation, a mass similar to that of Jupiter has been obtained.
If this original mass available for the formation of the Earth would be distributed within a circle around the orbit of the Earth, as high as the ecliptic and restricted to the halfs of the distances to the
orbits of Venus and Mars, then the particle density in this area would correspond to a mean free path of approximately 1cm (the mean free path being the average distance a particle is able to cover between two collisions). This makes a common hypothesis improbable, which is claiming that the volatile elements had been blown away by the solar wind and that the Earth was formed from the condensed residue. For the outer planets, this mechanism can be excluded anyway. Considering the above-mentioned high particle density, it appears more likely that the solar wind together with the magnetic field of the sun compressed the cloud of matter so much, that it could condense to a giant planet.
It is clear, that the composition of the Earth's crust deviates significantly from the original cosmic
abundance, a fact that supplies interesting information. Assuming the Earth was formed from
precondensates, then a relation between condensation temperature and deviation from the cosmic abundance should exist. However, no correlation has been found between both quantities, even if elements of similar density have been compared. Therefore, the lack of correlation cannot be caused
by a subsequent separation due to different densities. Interestingly, a very good correlation was obtained by comparison of the deviation from the cosmic abundance with certain chemical properties. For example, the more easily the compounds of an element can be reduced to the element itself, the lower is the concentration of this element in the crust, as compared to its cosmic abundance. Measures for the ability to react with hydrogen are ionization potential and electronegativity. These quantities correlate almost perfectly with the deviation from the concentration expected from the
cosmic abundance. Furthermore, the amounts of those elements, that form volatile hydrides with hydrogen, appear strongly reduced. The loss is almost proportional to the gas phase stability of these hydrides. Clearly, these elements escaped as hydrides in the gas phase (see periodic system).
Assuming the total original mass collapsed forming a giant planet, then the following structure had to be adopted due to excess of hydrogen:
the innermost shell consists of metallized hydrogen and heavy metals, further above followed by iron and magnesium in their elemental state, further above hydrogen compounds in the form of saline hydrides, the remaining alkaline earth metals, the alkali metals, aluminium and rare-earth metals. These elements are the most important constituents of the
crust, i.e. of the continents. A further layer contains relatively volatile hydrides, first of all the decomposable silan, which will become an important ingredient of the crust, after it has been converted to silica; as well as the more stable gaseous hydrides like ammonia, water, the hydrides of sulfur, phosphorus, and the halogenes. All these elements are much less frequent than expected by their cosmic abundance. The more stable the corresponding hydride, the larger the fraction of this element which lost.
Which conclusions can be drawn from the aforementioned in respect to the gravitational energy
released during the formation of the planets, and what about the further development? On the one
hand, the mechanical compressibility of solids is small, i.e. the volume changes only slightly in
response to external pressure. This is intelligible, since only other solids can be used to apply these
pressures. On the other hand, there is the opportunity to study the response of matter to high
pressures with so-called shock-wave experiments. In these experiments, the high pressures are
produced with detonation waves and can therefore exist only for fractions of a seconds. Despite of this very short time (as compared to cosmic time scales) these experiments show that matter is much more compressible and may thereby acquire large amounts of energy. A sufficient information about
the response to high pressures over a long range is however not obtained in this way. From the well-known ion contraction it can be seen how the space requirement of an atom or ion can be changed durably. For example, comparison of the radii of Ne, Na+, Mg2+, Al3+ and Si4+, all
containing 10 electrons, shows a dramatic decrease of the radii with increasing ion charge. It is mainly the excess of positive charge in the nucleus which compresses the ions. With some difficulty, these electrostatic forces can be converted and related to external pressure, with the result, that much higher densities of matter may occur. Furthermore we know, that the energy of a chemical bond increases for decreasing bond lengths. This is also confirmed by the above-mentioned shock-wave experiments. It follows, that a large fraction of the gravitational energy released during the formation of the giant planets can be stored chemically. This chemically bound energy may of course not be
confused with heat. Heat means the thermical motion of particles, but the lack of space suppresses this motion. This is a general principle in nature, named after the french chemist LE CHATELIER (Le Chatelier-Braun principle). It says, that a system adopts to an external restraint as far as possible.
In case of pressure and excess of energy, the system tends to form space-reducing and energy-consuming structures.
There are several possibilities for a original giant planet to loose matter. Close to the sun, pressure-relief caused by the loss of hydrogen is likely. This could lead to the decomposition of
maximum-pressure compounds, a process releasing energy. This would cause eruptions leading to a further loss of matter.
Given the not improbable case, that six or eight planets were formed in a single ring of matter, say in the region of the asteroid belt, than small differences between the orbits would lead to different orbit velocities. As a result, a planet on an inner orbit would finally catch up with one on an outer orbit (both within the ring). At small distances, the gravitational attraction would cause a pressure relief on both sides facing each other, resulting in violent eruptions of matter. Having the effect of rockets, the planets shot matter at each other. The inner planet was decelerated and therefore shifted closer to the centre, the planet on the outer orbit was accelerated and consequently shifted outwards. This process would finally lead to the present stable arrangement of the planets.
Under the influence of the described processes and the solar wind, free hydrogen and helium as the
lightest elements had to leave the Earth as the first. Due to the violent eruptions, also heavier gaseous
and liquid hydrides were also able to leave the Earth. This holds for hydrocarbons (mainly methane),
ammonia, water, hydrogen halogenides, but also for all other volatile hydrides. With the reduction
of the hydrogen excess, water became able to decompose the saline hydrides of the alkali and alkaline
earth metals, since the chemical equilibrium was shifted to the side of the metal oxides. Similarly,
monosilane was decomposed gradually. In this way the Earth's crust acquired its composition, lasting
largely unchanged up to the present time. How much the saline hydrides were resonsible for the
formation of the Earth's crust becomes clear from the fact that in granite, as the primary material of
the continents, the ratio of the cationic alkali metals on one hand and the elements aluminium and boron, which form the negative ions of complex hydrides like [AlH4]-, on the other is exactly the
same as in these complex hydrides. In the present granites, it is 1.002:1, and in the whole crust still 1.02:1. This ratio is neither justified by the cosmic abundance (where it is 2.5:1) nor is it found in chondrites (where it is 2.1:1) nor in other meteorites.
If the reducible metal compounds were actually reduced to the elemental metals and if the innermost part of the Earth, the core, contained apart from metals also metallized hydrogen, then the large amounts of magnesium and iron, which should be there according to the cosmic abundance, should
to be contained in the Earth's mantle in their elemental form. However, the Earth's mantle is just as diamagnetic as if it consisted of oxides. We may therefore ask, whether magnesium and iron are able to form an intermetallic compound with closed electron shells for both magnesium and iron. Magnesium had to transfer its two valence electrons to iron, which would become an ion similar to oxygen in oxides or sulfur in sulfides.(see U2).
Several conclusion can be drawn from the aforementioned facts. For the beginning, we may select here one important process: If the matter was strongly compressed inside of the Earth, a pressure relief should allow a reversal of this process. In the equator region, a pressure relief due to the centrifugal force can be expected. Therefore the expansion of the compressed matter should start there, and the continents should break up there at first. And indeed, the northern continents (Eurasia
and North America) occupy nearly the same area as the southern continents (Africa, South America, Australia, Antarctica and India). Furthermore, several scientists from HILGENBERG to VOGEL have been able to show that the further separation of the continents is consistent with a smaller original Earth, which was completely covered by the continents. The sea bed and the present continents were formed in the process of expansion.
The following question could be answered by calculations on the basis of celestrial mechanics: Was possible that, in a compressed ring of matter in the region of the asteroid belt, by concentration of all
available matter, 6 or 8 original planets were formed, e.g. all planets from Mercur to Neptun? The subsequent shift of their orbits may be explained by the rocket-like repulsion, which should occur when the approach of two planets leads to the release of the chemically bound gravitational energy (see section 6.).
Does an equi-atomic, sufficiently homogeneous mixture of iron and magnesuim become diamagnetic at high pressure? This would happen, if magnesium transfered its two valence electrons to iron, which would lead to a closed valence shells on both iron and magnesium. An intermetallic compound of this kind should require 25% less space.
The formation of the inner planets from condensates similar to the formation of the meteorits is very questionable. The common meteorites have been sufficiently studied. No enrichment of those elements which can form saline hydrides was found, in contrast to the composition of the Earth's crust. A transportation of these elements in a oxidic/mineral Earth from any zone of the crust is similarly unlikely, especially as some of these elements (or their oxides) have a much higher density.
According to the idea of the formation of the Earth from condensates, elements should show a similar behaviour, if they (or their oxides) have similar condensation temperatures or densities. However,
those elements show large differences in the deviation from the cosmic abundance, which can be explained by a original hydridic Earth.
Some elements like silicon were not volatile in form of oxides. Since silica has a relatively low density and is therefore maily in the crust, its concentration should be much higher.
Elements, which have a high density also in form of their oxides (thorium, uranium, barium etc.) are nearly completely concentrated in the crust, even in case of the earliest continental shields. Assuming the Earth was oxidic from the beginning, it is therefore questionable, that these elements were transported into the crust by crystallizing processes (diadochy effect) or due to their densities.
Regarding the significant enrichment in the crust, these elements should have been nearly completely removed from all other parts of the planet. This would require an Earth that was completely liquid.
If the elements mentioned above crystallized as the first, then they would have sunk down. Another possibility would be, that the Earth solidified from inside. But it should rather cool from outside. If the silicates had solified first and the oxids had remained in the liquid phase, then the lighter silicates were floated and the oxides were again below. At any rate, the usual explaination is not satisfactory.