The Origin of the Biosphere 



A. P. VINOGRADOV 



V.l. Vernadskiî Institute of Geochemistry and Analytical Chemistry of 

 the Academy of Sciences of the U.S.S.R., Moscozo 



In reviewing this Httle-studied question, I have naturally tried to assemble the 

 best-authenticated data. However, as there are not many such, I have tried to 

 fill the gaps by means of scientific reasoning. I know that I shall often repeat 

 what has been said by others before me. 



As I was not able to give a direct or unequivocal answer to the question of 

 when and under what conditions the biosphere came into being, I was obliged 

 to follow the whole course of geochemical events on the Earth before I could 

 convince myself that I had found out the place and time of its appearance. 



The fundamental propositions concerning the biosphere were, undoubtedly, 

 established by E. Süss. He introduced into science the concept of the biosphere 

 as an envelope of the Earth comprised of living things. V. I. Vernadskiî, with 

 his characteristic deep insight, showed the full significance of this envelope in 

 regard to the geochemical processes of the Earth. He said that 'from the geological 

 and geochemical point of view the problem is not that of the synthesis of an 

 individual organism, but that of the emergence of the biosphere.' Nearly a 

 hundred years earlier the happy thought occurred to Daubrée that there is a 

 similarity between the composition of meteorites and that of the layers of the 

 Earth. This idea was, scientifically, extremely fruitful. Bowen, Daly, Gold- 

 schmidt, Urey, O. Y. Shmidt and many others followed it up. I am in complete 

 agreement with this point of view. Thanks to isotopic analyses of lead and other 

 researches using radioactivity it has been possible to estabhsh that the age of the 

 substance of which the Earth is composed and that of the substance of meteorites 

 is very similar, namely about 5 x lo^ years [20]. 



THE CRUST OF THE EARTH AT PRESENT 

 The crust of the Earth as we know it consists of basaltic and granitic shells 

 overlaid by a covering of sedimentary deposits. The crust of the Earth is classi- 

 fied both according to its chemical composition and to its seismic properties. 

 The superficial part is separated from the rock of the mantle by the Mohorovicic 

 discontinuity, which Hes at a depth of about 40 km beneath the continents. Lower 

 down there he the ultrabasic rocks which are even poorer in Si02 and richer in 

 Mg and Fe. Of these ultrabasic formations, some, the dunites, sometimes 

 emerge on to the surface of the Earth, filling up cracks and deep fractures of its 

 crust. 



The basaltic shell covers the whole of the globe. The granitic shell covers about 

 half the Earth's surface and is most highly developed on the continents. It is 

 absent from the floor of the Pacific Ocean. Borings made on the Pacific atolls 



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