Geological time INDEX

As a closing remark, if we accept the carbon isotopic record of carbonates and organic carbon through geologic time as an index of the relative accumulation rates of inorganic and organic carbon on the sea floor, the carbonate carbon accumulation rate has been remarkably constant (Chapter 10). This near constancy has been maintained despite changes in Earth s surface physical and chemical environment and biotic evolution. 

U.S. Geological Survey Geologic Names Committee, 2007, Divisions of geologic time—Major chronostratigraphic and geochronologic units U.S. Geological Survey Fact Sheet 2007-3015. Available on the Internet at . 

The ingestion toxicity indices of the actinides in the wastes are shown as a function of decay time in Fig. 8.9 [P2]. Because the actinides are nonvolatile and because the wastes are expected to be geologically isolated, ingestion toxicity is probably a more important measure than inhalation toxicity. During the first 600 years the total toxicity index is controlled by the fission products, mainly Sr. It is thereafter controlled by Am and Am, followed by... 

Anke M (2000) Ultratrace element intake depending on the geological origin of the habitat, time, sex and form of diet. In Seifert M, Langer U, Schafer U and Anke M, eds. Mengen- und Spurenelemente. Author and Element Index 1981-2000, Schubert-Verlag, Leipzig, pp. 11-19. 

REEs are classified as lithophiles and are partitioned into the earth s crust and mantle. The name rare earths originated over a century ago when the elements were first identified in minerals that, at the time, were rare. The elements are actually distributed widely over the earth and relatively accessible on the earth s surface. For a comprehensive description of REE geology, geochemistry, and natural abundances, see Geology, Geochemistry, and Natural Abundances of the Rare Earth Elements. In 2010, the United States Geological Survey (USGS) estimated that there were REE reserves of 110 million metric tons (mt). The static depletion index, the ratio of reserves to present-day production, for REEs is approximately 870 years. Thus, the primary immediate consideration is whether REE production can match demand, and particularly whether it will be possible to increase the use of dysprosium and neodymium in wind turbines and the batteries of electric vehicles. 

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