The Origin of the Biosphere 31 



of the 30 atmospheres of CO2 required by the 'hot' theory). One may well add 

 that, inasmuch as there is not firm basis for this view, the interesting problem of 

 the kinetics of the formation of the shells of the Earth is still awaiting investigation. 



THE PRIMARY OCEAN 



The sources of the more important anions (carbonate, fluoride, chloride, 

 sulphate, borate, etc.) present in the waters of the oceans, like that of the water 

 itself, were the products of outgassing of the internal rocks of the mantle of the 

 Earth, while the sources of the more important cations (Na, K, Mg, Ca, Sr, etc.) 

 were the weathered products of the rocky formations of the surface of the Earth. 

 The main supply of gases was maintained by volcanic and intrusive activity and 

 they also emerged along with lava. Clearly, the heating of the surface of the Earth 

 and the large amount of gases in the atmosphere entailed by it must, at some 

 time, having reached a maximum. This was followed by slow cooling of the 

 surface of the Earth and condensation of the products of outgassing. These 

 events, it can only be supposed, must have occurred during the first hundreds 

 of milHons of years of the life of the planet. There is, however, no factual basis 

 for this figure. 



The processes of thickening of the crust of the Earth, increase in the amount 

 of CO2 and other gases in the atmosphere and increase in volume of the oceans, 

 occurred synchronously. They first reached a maximal rate of development, 

 later declined and are not yet complete. 



Acid vapours were neutralized by the rocks. The gases of the atmosphere were 

 in equilibrium with the waters of the oceans and, in particular, HF, HCl and 

 other acids were quickly removed from the atmosphere. As concerns CO2J 

 the more of it there was in the air the more CaCOa was dissolved in the water 

 and the formation of calcareous deposits was generally impossible under these 

 conditions [18]. The composition of the gases emanating from the interior of 

 the Earth has probably changed very little. The chemical composition of the 

 oceans has, therefore, not been submitted to any abrupt changes in regard to 

 the salts present. These changes very quickly became as insignificant as the 

 changes which we may observe in the other shells of the Earth (basaltic and 

 granitic). A more significant alteration in the composition of the salts of the 

 oceans occurred in many places when deposits of CaCOa or dolomite were laid 

 down. What were the reasons for the deposition of CaCOs ? Essentially they 

 were two: (i) The dissociation of Ca(HC03)2 by the evaporation of the water in 

 shallow seas and (2) The biological fixation of CO2 in the skeletons of organisms 

 (CaCOa) and by photosynthesis. 



The evaporation from shallow waters occurred on the greatest scale at the 

 time when the epeirogenic, or shallow continental seas were formed. These 

 seas, as we shall see later, became important at the time of the appearance of 

 the broad platforms of the continents, i.e. about 2-5 X 10^ years ago or some- 

 what earlier. In fact, we find that the percentage of carbonates in the deposits 

 of these platforms where there were shallow seas is 50 as compared with 15% 

 which is the average for all the sedimentary formations of the Earth [19]. 



