History of Earth

Evolution is accompanied by changes in biodiversity, as a result of nature imposing a limit on the existence of species. Abrupt disappearance of species and whole higher taxonomic groups also occurred during the history of Earth, as in the Alvarez s story. 

Figure 9.4 shows one interpretation of the atmospheric CO2 history of Earth over a time period of 100 million years. The geologic record of atmospheric CO2 will be addressed in detail in Chapter 10 of interest here is the possibility that humankind activities of fossil fuel burning and land use practices could lead to future atmospheric CO2 levels rivaling those of the past. Furthermore the future time scale of atmospheric CO2 change may be shorter than any period of CO2 change the Earth has experienced in 100 million years. 

The differentiation histories of Earth, Mars, and the Moon are constrained by short-lived isotope systematics and the U-Pb isotope system. The 182Hf-182W... 

The early history of Earth is greatly influenced by the probable impact of a Marssized body to form the Moon. Core-formation models suggest both Earth and the impactor were already differentiated by the time of the impact (Tonks Melosh 1992). The lack of a clear182W excess in uncontaminated lunar samples implies that the Moon-forming impact took place >50 Myr after the start of the Solar System (Touboul et al. 2007). The oldest known lunar samples are 150 Myr younger than CAIs, based on Sm-Nd dating (Touboul etal. 2007), which provides a lower limit on the Moon s age. 

B. F. WincUey (Ed.), The Early History of Earth, Wiley, New York, 1976 G. Faure, Principles of Isotope Geology, Wiley, New York, 1977... 

Bizzarro M., Baker J. A., Haack H., Ulfbeck D., and Rosing M. (2003) Early history of Earth s crust-mantle system inferred from hafnium isotopes in chondrites. Nature 421, 931-933. 

Because sedimentary carbonates are important rock types in terms of providing mineralogical, chemical, biological, and isotopic data useful in interpretation of the history of Earth s surface environment, the following sections discuss these rock types in some detail. The discussion is mainly limited to the Phanerozoic because of the more complete database for this Eon than for the Precambrian. 

What is the most difficult research job in all of science It is the task of deducing the history of Earth s evolution in its first two billion years, during the Hadean eon from 4.5 to 4.0 Ga (IGa = 10 years before present) and the Archean eon from 4.0 to 2.5 Ga. Detectives of ancient rocks are faced with a lack of clues to investigate. Most of Earth s surface is covered by water. The cores of the continents are probably underlain by rocks older than 2.5 Ga but they are hidden by a veneer of younger sediments. Even in localities where Hadean-Archean rocks are readily available, alteration by subsequent geologic events has obscured the record of conditions under which they were formed. It is revealing to compare and contrast the detailed information available in a textbook of Earth s modem ecologies with the sparse collection of facts accepted by disciplinary consensus for the Hadean-Archean eras. 

Most of us are familiar with the geologic column from high school textbooks. In short, the geologic column divides the supposed history of Earth into five eras, each of which has its appointed age. (The Cenozoic Era runs from 25 thousand to 70 million years ago, the Mesozoic Era from 70 million to 200 miUion years ago, the Fhleozoic Era from 200 to 600 rruUion years ago, the Proterozoic Era from 600 million to 1 biUion years ago, and the Archeozoic Era from 1 biUion to 1.8 biUion years ago.)... 

EARTH S LAND, WATER, AND ATMOSPHERIC SYSTEMS AND THE HISTORY OF EARTH... 

To summarize, life and evolution are realized on the expense of free energy delivered by the Sun light, this free energy is — and always has been in the history of Earth — plentiful. Of course, this only means that entropy is not sufficiently good measure to characterize biological organization. But now we have to ask how could this plentiful free energy have been used by the evolution ... 

In our century the biosphere has acquired an entirely new meaning it is being revealed as a planetary phenomenon of cosmic character... In the twentieth century, man, for the first time in the history of earth, knew and embraced the whole biosphere, completed the geographic map of the planet earth, and colonized its whole surface. Mankind became a single totality in the life on earth. .. The noosphere is the last of many stages in the evolution of the biosphere in geological history (Vernadsky 1945, p. 10). 

The theory of evolution pictures a continuous genealogical nexus, within which species or taxa can be nothing but interconnected components or chunks (Hull, 1999a). The logically subordinated hierarchy will impose sharp boundaries on that continuum, yet this cannot fully succeed. The representation of patterns of phylogenetic relationships will therefore necessarily be blurred. One can view the two pictures, one of the continuity of change, the other of the discontinuity of hierarchical relationships, as complementary (Rieppel, 1988). If looked at from this perspective, the complementarity inherent in patterns versus process analysis should warn against too much of a realistic interpretation of our theories of the history of Earth relationships. 

Aluminum is the third most abundant element on Earth (after oxygen and silicon), but it is tightly locked into insoluble minerals such as kaolinite (Al2(0H)4Si205) and bauxite (AlOOH). Acid rain from human activities is a recent change in the history of Earth, and it is introducing soluble forms of aluminum (and lead and mercury) into the environment." Below pH 5, aluminum is mobilized from minerals and its concentration in lake water rises rapidly. At a concentration of 130 fxg/L, aluminum kills fish. In humans, high concentrations... 

It is clear from table 21.1 and fig. 21.1 that the lanthanide distribution in the composite of North American shales (NASC) is different from that of the chondrites and the sun s atmosphere. Since the differences are a smooth function of atomic number (except for Eu), they are probably a result of processes of internal planetary differentiation. Differential condensation from a gas does not produce such smooth distributions (Boynton, 1975). What, then, does the NASC distribution represent, or tell us about the history of Earth ... 

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