The earth's crust
2002; Elsevier BV; Linguagem: Inglês
10.1016/b978-012073461-0/50059-4
AutoresRonald A. Bailey, Herbert M. Clark, James P. Ferris, Sonja Krause, Robert L. Strong,
Tópico(s)Marine and environmental studies
ResumoThe present structure of the earth consists of a largely molten core composed chiefly of iron and nickel, surrounded by lighter rocks. The outer few miles, the crust, is the only portion of the earth that is accessible, and is the source of most of the substances used in a technological society. This chapter describes the structure, composition, and evolution of earth crust, and the processes that take place in it. The volume of material to be mined and processed, the energy requirements, and the waste disposal problems clearly set economic and environmental restrictions on the minimum concentration that can be employed for large-scale use of any substance but the society generally uses atypical, high concentration sources for most of its mineral needs. Bacteria can also be used for recovery of metals from low-grade sources in an economical way through microbial mining. Surface rocks are subject to breakup and chemical change by several weathering processes including physical disintegration, chemical reactions, and biological effects that lead to soil formation. Soil is a vital substance but its degradation is of serious concern in terms of its impact on future food needs. Human activity frequently causes degradation of soil in ways that range from loss of nutrients to changes in physical character of the soil to contamination with toxic materials to loss of the soil itself. Different types of soils, their composition and process of formation, soil contamination, and methods of decontamination such as bioremediation, are also presented in the chapter.
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