Crust of the earth

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. 

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. 

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. 

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. 

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). 

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. 

Marble occurs in many locations on the crust of the earth, so that many types of marble were known to the ancients. White Pentelic marble, from... 

Limestone varieties differ greatly from one another in their texture and the impurities they contain, and consequently they also differ in color. The color of limestone may vary from white (when it contains practically no impurities) to off-white and even to intensely colored. Minor inclusions within the limestone structure are often of silica, usually in a concentration below 5%, as well as feldspar and clay in still lesser amounts. Many types of limestone also include embedded fossils. Much limestone deposits in the outer crust of the earth are altered during geologic metamorphic processes that involve mainly pressure and heat but also liquids and gases. Marble, for example, a metamorphic rock derived from calcium carbonate, is white when composed only of this substance colored metal ions and other impurities impart to marble a wide range of colors such as red, yellow, and green and also give... 

The first alloys made by humans were probably those of copper, namely, bronze and brass, which were already being made during the Chalcolithic period (see Table 33). The most important, however, later became the alloys of iron, known as the ferrous alloys (from the Latin word ferrum, for iron). Since iron ores are one of the most abundant metalliferous ores on the crust of the earth, and its alloys are relatively easy to produce, ferrous alloys have been the most widely used alloys for the last three millennia (see Table 34). 

Iron is one of the most abundant metals in the upper crust of the earth. It is the fourth mineral-forming element (after silicon, oxygen, and aluminum), constituting about 5% of the earth s crust (see Table 1). Large deposits of its ores are numerous, widely distributed, and easily accessible. 

Iron does not occur in nature as a native metal. Lumps of meteoritic iron, which fell to the surface of the earth from outer space, are often found, however. It has been argued whether the earliest iron used by humans was of meteoritic origin or smelted from ores (Piaskowsky 1988). Combined with other elements, iron occurs in a varied range of ferruginous (iron-containing) ores that are widely dispersed on the upper crust of the earth some common iron ores often used for smelting are listed in Table 37. 

Tin (chemical symbol Sn, from the Latin name of the metal, stannum) occurs as a native metal only as small, rare nuggets it is very doubtful, therefore, whether native tin would have been noticed, never mind used, by ancient people. Nevertheless, tin was one of the earliest metals to have been produced. Tin ores occur in few places on the upper crust of the earth, mostly as the mineral cassiterite or tin stone (composed of tin oxide) from which most tin has been and still is extracted. Tin stone is a usually brown or black,... 

The environment has negative effects on most metals thus, when metallic archaeological objects are eventually found, they are generally in an advanced state of decay. The decay of metals and alloys caused by the chemical action of gases and/or liquids in the environment is known as corrosion. Corrosion processes are natural destructive processes that result in the waste of most metals and alloys. The ultimate result of all corrosion processes is the reversion of most metals from the metallic condition in which they are used, to the chemically combined form in which they naturally occur in the crust of the earth. Rust, the reddish-brown corrosion product that forms on... 

Most of the rocks that make up the upper crust of the earth lie hidden beneath layers of sediments, unconsolidated accumulations of particles derived from the weathering of minerals and rocks (see Fig. 44 and Textbox 45) (Keller 1957). Once formed, the particles are either carried away or moved by the wind, rain, and gravitational forces into the seas and oceans or, before they get there, into depressions in the land. There they accumulate in a wide range of shapes and sizes (see Table 49) (Rocchi 1985 Shackley 1975). 

Carbon, a common element in the outer crust of the earth, and the main component of all biological and organic substances, occurs in three isotopic forms carbon-12 or C-12 for short (whose chemical symbol is 12C), carbon-13 or C-13 (13C), and carbon-14 or C-14 (14C) (see Fig. 8 and Table 66). 

The hydrosphere (the Greek prefix hydro means water) is the great mass of water that surrounds the crust of the earth. Water is one of a few substances that, at the temperatures normal on the surface of the earth (which range between about -50 and 50°C), exists in three different states liquid, gas, and solid. Liquid water makes up the oceans, seas, and lakes, flows in rivers, and underground streams. Solid water (ice) occurs in the polar masses, in glaciers, and at high altitudes, and gaseous water (moisture) is part of the atmosphere (O Toole 1995). Liquid and solid water cover over 70% of the surface of the earth. 

The elements occur in widely varying quantities on earth. The 10 most abundant elements make up 98% of the mass of the crust of the earth. Many elements occur only in traces, and a few are synthetic. Fortunately for humanity, the elements are not distributed uniformly throughout the earth. The distinct properties of the different elements cause them to be concentrated more or less, making them more available as raw materials. For example, sodium and chlorine form salt, which is concentrated in beds by being dissolved in bodies of water which later dry up. Other natural processes are responsible for the distribution of the elements which now exist on earth. It is interesting to note that the different conditions on the moon—for example, the lack of water and air on the surface—might well cause a different sort of distribution of the elements on the earth s satellite. 

The two rare earth elements niobium (Nb) and tantalum (Ta) were the main subject of study in the investigation referred to. Both elements have very similar properties and almost always occur together in our solar system. However, the silicate crust of the Earth contains around 30% less niobium (compared to its sister tantalum). Where are the missing 30% of niobium They must be in the Earth s FeNi core. It is known that the metallic core can only take up niobium under huge pressures, and the conditions necessary for this may have been present on Earth. Analyses of meteorites from the asteroid belt and from Mars show that these do not have a niobium deficit. 

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