Core, Earth

Centre of Earth core Fe/air, 02 Chemical energy (and heat, temperature) Rocks, Mantle... 

The transition-metal and rare-earth core-line XPS spectra show little, if any, BE shifts at all. Nevertheless, information about atomic charge and valence states can be extracted by examining other features in the spectra. The plasmon loss satellite intensity found in the spectra of Co-containing compounds provides a particularly useful handle on the Co charge. The lineshapes of RE spectra are characteristic of their valence state, as seen in the distinction between trivalent and tetravalent cerium in CeFe4Pni2 compounds. 

Boness, D. A., J. M. Brown, and A. K. McMahan (1986). The electronic thermodynamics of iron under Earth core conditions. Phys. Earth Planet. Int. 42, 227 0. 

SNC meteorites (Harper et al., 1995 Borg et al., 1997). This isotopic anomaly requires early differentiation of mantle and crust. Because hafnium and mngsten fractionated into silicate and metal, respectively, the short-lived Hf- W system can be used to determine that martian core formation occurred within —13 milhon years of the planet s accretion (Kleine et al., 2002 Yin et al., 2002). Correlation between Nd and isotope anomalies, as well as the initial Os/ Os ratios for martian meteorites (Brandon et al., 2000), indicate synchronous differentiation of core, mantle, and cmst (Figure 14). On Earth, core formation took substantially longer, convection has stirred the mantle sufficiently to erase any evidence of early isotopic heterogeneity, and cmst formation continues throughout geologic history. 

The principal division of the Earth into core, mantle, and crust is the result of two fundamental processes, (i) The formation of a metal core very early in the history of the Earth. Core formation ended at —30 million years after the beginning of the solar system (Kleine et aL, 2002). (ii) The formation of the continental crust by partial melting of the silicate mantle. This process has... 

Sdderlind P., Moriarty J. A., and Wills J. M. (1996) First-principles theory of iron up to Earth-core pressures structural, vibrational, and elastic properties. Phys. Rev. B 53, 14063-14072. 

Lodders K. (1995) Alkali elements in the Earths core— evidence from enstatite meteorites. Meteoritics 30(1), 93-101. 

The interior of the earth consists of a molten fluid of rocks at extremely high temperatures, called magma. This magma is cooling and/or expelling heat to the earth s surface according to the second law of thermodynamics. The flow of heat is from the hot source (earth core) toward the cold sink (earth surface). The cold sink (i.e., heat sink in thermodynamics) consists of the earth s crust, surface, and atmosphere. This may be regarded as a very slow process of heat transfer. 

The table shows the growth in the core radii of homologous elements with atomic number as well as the fact that the radii of the alkaline earth cores are relatively large, while those of Cu and Ag are smaller. 

For bodies the size of Earth, core formation did not occur as one single event but took place continuously during planetary growth. To determine realistic core formation ages for bodies like the Earth the W isotope evolution during continuous core formation must be considered (8, 35-38). During protracted accretion with concomitant core formation, the ratio of Earth s mantle... 

Iron comprises approximately 4.7% of the Earth s crust. The enormous quantities of this metal in the earth core are prerequisite for the magnetic field that shields the planet from cosmic radiation and enables life. The ubiquitous availability of iron and its ability to adjust its oxidation state, redox potential and electron spin state makes it suited to participate in a large number of chemical reactions. Thus, iron has become essential for animals, plants, fungi and most bacteria, ivhere it functions in a ivide variety of iron-dependent enzymes and metal proteins. To avoid deficiency symptoms, mechanisms have evolved in these organisms to maintain iron homeostasis in situations of scarce supply, but also to avoid oxidative stress as mediated by Fenton chemistry ivhen supply is excessive. In industry, iron is used in over 2500 varieties of steel, each with different physical properties. In fact, annual steel production is almost as high as that of all other metals combined hence the environmental effects of iron must also be considered. 

Earths core is a solid iron sphere about the size of the Moon. Surrounding the inner core, there is an outer liquid core that contains a nickel-iron alloy. Scientists think the iron core formed when multiple collisions during Earths early history resulted in enough heat to melt metals. In the molten state, the densest materials, including iron and nickel, settled to the center and became Earths core. The less-dense materials remained at the surface. As Earth cooled, the outer layers solidified, creating Earths mantle and crust. 

Element Earth Core Upper mantle Continental crust... 

In some cases, only one type of soil is readily obtainable for an earth dam. If this is impervious, then the design will consist of a homogeneous embankment, which incorporates a small amount of permeable material in order to control internal seepage. On the other hand, where sand and gravel are in plentiful supply, a very thin earth core may be built into the dam if enough impervious soil is available, othenwise an impervious membrane may be constructed of concrete or interlocking steel sheet piles. However, since concrete can withstand very little settlement, such core walls should be located on sound foundations. 

Yoo CS, Holmes NC, Ross M, Webb DJ, Pike C (1993) Shock temperatures and melting of iron at earth core conditions. Phys Rev Let 70 3931-3934... 

LithophiLes are rock-loving elements found predominantly in oxide minerals or as halides. SiderophUes or iron-loving elements are found mostly in the earths core, and chalcophiles are elements found in the earths crust in combination with nonmetals, including sulfur, selenium, and arsenic. 

It is essential that portable apparatus is properly maintained, with the earth core of the flexible cable and associated earth connections being tested regularly by a competent person using a substantial current (special test sets are available) to ensure continuity and strength of the earthing. 

Wijs GA, Kresse G, Vocadlo L, Dobson D, Alfe D, Gillan MJ, Price GD. (1998) The viscosity of liquid iron under Earths core conditions. Nature 392 805—807. 

---