Early Evolution of the Earth

When the Earth was in its early stages of accretion, it was presumably a cool object. In the final stages, accretional energy was appreciable and must have heated the upper regions of the Earth s interior. When the Earth approached its present mass, projectiles would impact at a minimum velocity of 

Planet Relative pressure Principal gases (%) Other gases (ppm) 

Briefly describe the general features of the distribution of different elements in the solar system and the processes that produce this distribution. 

How do the compositions of the terrestrial planets differ from the average composition of the solar system  

What sources of energy can contribute to the high temperatures of the Earth s core  

It is likely that a major portion of the upper parts of the Earth also melted at some time druing the final stages of accretion. 

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Halliday, A. N., Rehkamper, M., Lee, D.-C. and Yi, W. (1996) Early evolution of the Earth and Moon new constraints from Hf-W isotope geochemistry. Earth and Planetary Science Letters, 142, 75-89. 

Abe Y, Matsui T (1986) Early evolution of the Earth Accretion, atmosphere formation, and thermal history. J Geophys Res 91(B13) E291-E302... 

Schmitt W., Pahne H., and Wanke H. (1989) Experimental determination of metal/sihcate partition coefficients for P, Co, Ni, Cu, Ga, Ge, Mo, and W and some implications for the early evolution of the Earth. Geochim. Cosmochim. Acta 53, 173-185. 

Although global transport balance modelling thus provides some perspective on the rate at which CO2 could have been removed from the atmosphere in early Earth history, the resolution of the method is inherently poor and it can provide only broad outlines. The large uncertainties and the problems encountered highlight the need to find independent constraints on weathering and erosion rates in Archaean time to understand the early evolution of the Earth s atmosphere, climate and life. 

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