Crust of Earth

Hunt, J. M. (1972). Distribution of carbon in crust of Earth. Bull. Am. Assoc. Pet. Geol. 56,1272i-1277. 

The outer crust of earth has provided the solid foundation for the evolution of human beings, who are the prime focus of interest and concern to archaeology. The main components of this crust are minerals and rocks, some consolidated and others occurring as sediments, nonconsolidated deposits, created by weathering processes from the minerals and rocks. All these minerals, rocks, and sediments, as well as everything else in the universe, are made up from just over 100 chemical elements listed in Appendix I. Most of the elements in the crust of the earth occur in extremely low relative amounts, and only a few, listed in Table 1, make up almost 99% of its total bulk (Bloom 1969). 

We see that the total element abundance on the continental crust of Earth today (see Figures 1.4 and 1.5), is poorly reflected in the availability of the elements in the sea. Two major reactions affected the availability of the non-metals and the metals apart from abundances both concern solubility of salts ... 

Arsenic is ubiquitous in nature and is found in detectable concentrations in all environmental matrices. The occurrence of As in the continental crust of Earth is usually given as 1.5 to 2.0 mg/1. The distribution of arsenic in nature is extremely variable, showing little correlation with geological formation, climate, or soil. Numerous minerals, rocks, sediments and soils contain arsenic partly as constituent of sulfide minerals or complex sulfides of metal cations and partly as a constituent retained by soils and/or sediments in occluded or adsorbed forms. The latter is manifested primarily by the adsorption or occlusion of As on hydrous A1 and Fe oxides, but these are not necessarily the only source. Arsenic is also adsorbed on clay colloid, is bound to organic matter and may form slightly water soluble compounds with Al, Fe, Ca and Mg in the soil matrix. Some of the more common minerals in soils are arsenopyrite (FeAsS), Orpiment (AsgSg) etc. 

The long view from space has dramatized what we already knew—the crust of Earth is a very unusual environment, uniquely suited, at least in this solar system, for the production and support of life. Our environment is also quite heterogeneous. Mixtures abound everywhere we look, the elements and compounds are almost lost in the complicated array of mixtures produced by natural forces acting over very long periods. 

This chapter illustrates how elements and compounds are separated from the hydrosphere and crust of Earth, and put to use. The hydrosphere, which includes saltwater and freshwater above and below Earth s surface, must supply the water necessary to sustain hfe. The soluble salts in the oceans are a commercial source of magnesium, bromine, and sodium chloride, which is not only table salt but also an essential chemical raw material. 

Figure 6 Chondrite-normalized REE patterns of the primitive mantles and crusts of Earth, Mars, and the Moon. For the Earth, the continental crust is shown for the Moon, the highland crust is shown and for Mars, the bulk crust is shown...

Water contains 89 % by weight of oxygen, and the outer crust of the earth contains about 47% hence air, earth and sea together contain about 50% by weight of oxygen. 

Calcium is a metallic element, fifth in abundance in the earth s crust, of which if forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells. Never found in nature uncombined, it occurs abundantly as limestone, gypsum, and fluorite. Apatite is the fluorophosphate or chlorophosphate of calcium. 

Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Its nuclei are very stable. Iron is a principal component of a meteorite class known as siderites and is a minor constituent of the other two meteorite classes. The core of the earth — 2150 miles in radius — is thought to be largely composed of iron with about 10 percent occluded hydrogen. The metal is the fourth most abundant element, by weight that makes up the crust of the earth. 

Titanium oxide bands are prominent in the spectra of M-type stars. The element is the ninth most abundant in the crust of the earth. Titanium is almost always present in igneous rocks and in the sediments derived from them. 

Meteorites are of two kinds stony meteorites that are rock-like in character, and metallic meteorites that consist of metallic elements. The kinds of substances in the stony meteorites are very much like the substances in the crust of the earth, if we allow for the fact that the meteors could not bring gases or liquids with them. We feel that the other type, the metallic meteors, give valuable clues about the nature of the earth s central core. Experts have long believed that these meteorites are fragments from exploded planets that, perhaps, resembled the earth. 

FIGURE 14.1 These charts show the relative abundances of the principal elements in (a) the universe (the "cosmic abundances") (b) the crust of the Earth and (ci the human hody... 

Rubey, W. W. (1955). Development of the hydrosphere and atmosphere, with special reference to probable composition of the early atmosphere. In "Crust of the Earth" (A. Poldenvaart, ed.), pp. 631-650. Geological Society of America, New York. 

Precious metals have faced a significant price increase and the fear of depletion. By contrast, iron is a highly abundant metal in the crust of the earth (4.7 wt%) of low toxicity and price. Thus, it can be defined as an environmentally friendly material. Therefore, iron complexes have been studied intensively as an alternative for precious-metal catalysts within recent years (for reviews of iron-catalyzed organic reactions, see [12-20]). The chemistry of iron complexes continues to expand rapidly because these catalysts play indispensable roles in today s academic study as well as chemical industry. 

Metals that are soft acids, such as gold and platinum, have low affinities for hard oxygen atoms, so they are not affected by O2 in the atmosphere. Consequently, these metals, including Ru, Rh, Pd, Os, Ir, Pt, and Au, are found in the crust of the Earth in their elemental form. 

Albarede F (2001) Radiogenic ingrowth in systems with multiple reservoirs applications to the differentiation of the mantle-crust system. Earth Planet Sci Lett 189 59-73... 

Explain why a line graph might not be appropriate to show the chemical composition of Earth s crust. 

Most of the liquid fuels in use today are obtained from crude oil, also called petroleum, a brownish-green to black colored viscous oil found under the crust of the Earth either on shore or off shore. This oil either flows out by itself due to underground gas or hydrostatic pressure, or it is mechanically pumped out. Petroleum almost always occurs along with gas called natural gas. When the oil well contains both oil and gas it is called a wet well, and when it contains only gas it is called a dry well. 

Many scientists thought that Earth must have formed as long as 3.3 billion years ago, but their evidence was confusing and inconsistent. They knew that some of the lead on Earth was primordial, i.e., it dated from the time the planet formed. But they also understood that some lead had formed later from the radioactive decay of uranium and thorium. Different isotopes of uranium decay at different rates into two distinctive forms or isotopes of lead lead-206 and lead-207. In addition, radioactive thorium decays into lead-208. Thus, far from being static, the isotopic composition of lead on Earth was dynamic and constantly changing, and the various proportions of lead isotopes over hundreds of millions of years in different regions of the planet were keys to dating Earth s past. A comparison of the ratio of various lead isotopes in Earth s crust today with the ratio of lead isotopes in meteorites formed at the same time as the solar system would establish Earth s age. Early twentieth century physicists had worked out the equation for the planet s age, but they could not solve it because they did not know the isotopic composition of Earth s primordial lead. Once that number was measured, it could be inserted into the equation and blip, as Patterson put it, out would come the age of the Earth. ... 

As a guide to the evolutionary history of the continents, Patterson decided to measure the lead isotope ratios of Earth s crust as a whole. As rocks erode, their minerals are collected and mixed in the oceans, where they eventually settle in layers of sediment. Patterson organized a formidable series of experiments to measure the lead isotopes on land, in various layers of ocean water, and in sediments on the sea floor. 

Colorless, reactive gas. Oxygen was not present in the initial atmosphere of the Earth, although at 50 % it is the most common element in the crust of the Earth (oxides, silicates, carbonates, etc.). The compound with hydrogen is remarkable. The hydrides of all other elements are unpleasant compounds, but H20 is the molecule of life. The 02 found in the air today, of which it makes up 20 %, was formed in the process of evolution by photosynthesis of algae, which then also allowed life on solid land. Oxidation with oxygen became and is still the dominant pathway of life forms for obtaining energy (respiration). Used in medicine in critical situations. Oxidations play a key role in chemistry (sulfuric acid, nitric acid, acetic acid, ethylene oxide, etc.). The ozone layer in space protects the Earth from cosmic UV radiation. Ozone (03) is used in the... 

The element exists as an intermediate in uranium and thorium minerals through their decay. There is no stable isotope. The longest-living isotope has a half-life of 8.3 hours. In the crust of the Earth, the total steady-state mass is estimated at a few tens of grams. Thus astatine is the rarest element (record ). A few atoms of this relative of iodine can be found in all uranium ore. It exhibits certain metallic properties. 

There are two basic types of elements metals and nonmetals. The metals, such as copper, gold, and iron (see Chapter 5), make up more than three-quarters of the total number of elements nonmetals, such as, for example, chlorine, sulfur and carbon, make up much of the rest. Other elements, however, known as the metalloids or semimetals, have properties intermediary between the metals and the nonmetals (see Appendix I). Only a few elements, such as the metals gold and copper and the nonmetal sulfur, which are known as the native elements, occur in nature uncombined. Most elements occur naturally combined with others, forming compounds. It is from these compounds, which occur in the crust of the earth as minerals, rocks, or sediments, that humans extract most of the elements that they require (Klein 2000). 

Minerals are the most abundant type of solid matter on the crust of the earth they are homogeneous materials that have a definite composition and an orderly internal structure. Minerals make up most of the bulk of rocks, the comminuted particles of sediments, and the greater part of most soils. Over 3000 minerals have been identified, and new ones are discovered each year. Only a few hundred, however, are common most of the others, such as, for example, the precious stones, are difficult to find (Ernst 1969). Table 3 lists common minerals and mineraloids. Many schemes have been devised for classifying the minerals. In the scheme presented in Table 4, minerals are arranged in classes according to their increasing compositional chemical complexity. 

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