Evolution of the Hydrosphere

The ocean, as pointed out earlier, was probably formed along with the Earth. It could have been close to the present volume even 4.5 billion years ago. However, its area and chemical composition were quite different from those existing now. 

According to Isaac Asimov, the following conditions must be met to create the ocean  

In the previous subchapters we have noted that there are 4 most abundant elements in the Earth (without inert He and Ne) such as H, 0, C, and N. Let s consider the STP values of hydrogen and its chemical combinations. The hydrogen itself melts at -259.2 °C and boils at -252.8 °C (1 atm) and these conditions are not met in the Earth surface even 4.5 billion years ago. However, there are different combinations of hydrogen and other most abundant elements H2O, NH3 and CH4. The physical properties of these compounds under STP are shown in Table 3. 

Most authors assume that the proto-ocean resembled modem Ocean in that sodium (Na+) and chloride (Cl ) were the major ions followed by potassium (K+), magnesium (Mg +), calcium(Ca +) and bicarbonate (HC03 ). Sulfate (S04 ) was absent since the waters were neutral or slightly acidic. These pH values would have been related to the high CO2 atmospheric partial pressure at that time (see above 2.32). Close to this viewpoint the soda ocean concept was suggested for the explanation of ancient abiotic water chemistry (Box 3.). This concept supposes that sodium carbonate would have been the main chemical species during primordial Ocean. 

Soda Ocean Concept, after Degens, 1989 This concept is based on two assumptions  

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Synopsis of the origin and evolution of the hydrosphere-atmosphere-sedimentary lithosphere... 

SYNOPSIS OF THE ORIGIN AND EVOLUTION OF THE HYDROSPHERE-ATMOSPHERE-SEDIMENTARY LITHOSPHERE... 

The equilibrium model allows certain inferences to be drawn concerning the geochemical environment which might have existed when sediments were formed, from knowledge of the thermodynamic properties of these sediments today. Thus, one can speculate about the evolution of the lithosphere, hydrosphere, and atmosphere, by assuming that equilibrium states were approached at various stages in geological history. 

In summary, it can be stated that there is nothing markedly unusual about the Isua supracrustal facies and their organic contents. They can be compared closely with younger Precambrian, and in some cases Phanerozoic lithologies and successions. Depositional mechanisms and hydrosphere — atmosphere chemical equilibria appear to have been within the range of more recent times (Nutman et al., 1984)119). It seems from all indication that the advent of photoautrophy preceeded Isua times. It was probably the most crucial single event to make an impact on the evolution of the terrestrial atmosphere. 

Schaefer MW (1990) Geochemical evolution of the Northern Plains of Mars Early hydrosphere, carbonate development, and present morphology. J Geophys Res 95 14,291-14,300... 

Vinogradov has pointed out that with the appearance of the biosphere somewhere on the verge of 3-10 yr ago, there was a major upheaval in the evolution of the Earth. Oxidizing processes were abruptly accelerated, a nitrogen atmosphere arose in which carbon dioxide predominated over methane, and free carbon was oxidized to CO2. After the carbon was oxidized or at the same time as that process, there began oxidation of divalent iron (at — 10 ), which led to subsequent wholesale deposition of the sediments of the Precambrian BIF. Free carbon in equilibrium with the atmosphere appeared only after complete oxidation of ferrous iron compounds in the hydrosphere and on the land surface. 

Thus in highly reducing conditions iron can migrate in a wide pH range (from 0 to 6) and precipitates as sediment in the form of oxides and hydroxides only in neutral environments. The acidity of the environment, as a natural geochemical barrier governing the precipitation of iron, is appreciably reduced. Variation in the redox potential as a result of the overall evolution of the atmosphere, hydrosphere, and biosphere plays a large role. 

Typical BIF are metamorphosed chemogenic cherty iron sediments, deposition of which was typical only of the Precambrian and ceased in subsequent geologic epochs. The formation of these rocks reflects a certain stage in the irreversible process of evolution of the Earth s crust, atmosphere, hydrosphere and biosphere. The period of intensive deposition apparently was preceded by a long period of accumulation of dissolved iron and silica in the waters of the original sedimentary basins. 

On the basis of thermodynamic analysis of the evolution of the ancient atmosphere and hydrosphere, the sequence of oxidation reactions occurring when oxygen was introduced and increased is ascertained ... 

Bau M. and Mdller P. (1993) Rare earth element systematics of the chemically precipitated component in Early Precambrian iron formations and the evolution of the terrestrial atmosphere-hydrosphere-lithosphere system. Geochim. Cosmochim. Acta 57, 2239-2249. 

In this chapter we consider the development and evolution of modem biosphere during its geological history. The reader will find a brief description of the formation of the lithosphere, atmosphere, and hydrosphere and their chemical composition. Creation and evolution of the biogeochemical structure of the biosphere and hydrosphere is also a subject of discussion. Finally, we show the role of biogeochemical cycles in formation of biogenic depositions (oil and gas). 

The evolution of the Earth is a long and interesting story — one that is much too complex to be discussed in one chapter. The discussion will follow the essential points in evolution of the main components of prebiotic Earth lithosphere, atmosphere and hydrosphere. Much more detail can be found in E. Degens (1989), S. Butcher et al. (1992), M.H. Engel and S.A. Macko (1993) and T. Fenchel et al. (1998). 

Huston, D. and Logan, G.A., 2004. Barite, BIFs and bugs evidence for the evolution of the Earth s early hydrosphere. Earth Planet. Sci. Lett., 220, 41-55. 

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