地质专业英语.doc

The Earth From classical times it has been known that the earth is roughly spherical in shape. Actually the planet is shaped more like a slightly flattened ball whose polar radius is about 21km shorter than its equatorial radius. The average radius is 6371km. The earths specific gravity is 5.5. It is 5.5 times as heavy as an equal volume of water. The specific gravity is greater than that of any other planet in the solar system, but not appreciably different from that of Mercury, Venus and Mars. Because the average specific gravity of surface rocks is only about 2.7, the material existing deep within the earth must have a specific gravity well in excess of the 5.5 average. Very likely, the material at the earths center has a specific gravity as high as about 15. The splendid photographs of the earth taken from space by Apollo astronauts remind us that our planet is more than a rocky globe orbiting the sun. The patterns of white clouds above the azure blue color tell us of the presence of an atmosphere and hydrosphere. Here and there one can even discern patches of tan that indicates the existence of continents. Greenish hues provide evidence of the planets most remarkable feature: there is life on earth.THE ATMOSPHERE（大气圈）We live beneath a thin but vital envelope of gases called atmosphere. We refer to these gases as air. “Pure air”is composed mainly of nitrogen (78.03%) and oxygen 920.99%). The remaining 0.98% of air is made of argon, carbon dioxide and minute quantities of other gases. One of these “other”components found mostly in the upper atmosphere is a form of oxygen called ozone. Ozone absorbs much of the suns lethal ultraviolet radiation, and is thus of critical importance organisms on the surface of the earth. Air also contains from 0.1 percent to 5.0 percent of water vapor. However, because this moisture content is so variable, it is not usually included in lists of atmospheric components.Every day, the atmosphere receives radiation from the sun. This solar radiation provides the energy that heats the atmosphere and drives the winds.Distribution of solar radiation is one of the most important factors in determining the various kinds of climate we experience on the earth.THE HYDROSPHERE（水圈）The discontinuous envelope of water that covers 71 percent of earths surface is called hydrosphere. It includes the ocean as well as water vapor. The water contained in streams and lakes, water frozen in glaciers, and water that occurs underground in the pores and cavities of rocks. If surface irregularities such as continents and deep oceanic basins and trenches were smoothed out, water would completely cover the earth to a depth of more than two kilometers.Water is an exceedingly important geologic agent. Glacier composed of water in its solid form alter the shape of the land by scouring, transporting and depositing rock debris. Because water has the property of dissolving many natural compounds, it contributes significantly to the decomposition of rocks and, therefore, to the development of soils on which we depend for food. Water moving relentlessly down hill as sheetwash, in rills, and in streams loosens and carries away the particles of rock to lower elevations where they are deposited as layers of sediment. Clearly, the process of sculpturing our landscapes is primarily dependent upon water.By far the greatest part of the hydrosphere is contained within the ocean basins. These basins are of enormous interest to geologists who have discovered that they are not permanent and immobile as once believed, but rather are dynamic and ever changing. There is ample evidence that the sea floors move, and that these movements have a direct relation to the formation of mountains, chains of volcanoes, deep sea trenches and mid-ocean ridges. In the ocean are collected the layers of sediment from which geologists decipher earth history. Here also one finds mineral resources and clues to the location of ore deposits elsewhere on the planet. The ocean provides part of our food supply and has a pervasive influence on the climate we experience. Lesson Two Common Minerals （5学时）QUARTZ(kwC:ts 石英)The mineral quartz is one of the most familiar and important of all the silicate (5silikit 硅酸盐) minerals. It is common in many different families of rocks. As mentioned earlier, quartz represents the ultimate (5Qltimit 临界的，根本的，最终的) in cross-linkage of silica tetrahedral (5tetrE5hedrEl 四面体的); it therefore will not break along smooth planes. In quartz, the tetrahedral are joined only at the corners and in a relatively open arrangement. It is thus not a dense mineral, but it is quite hard because of the strong bonding in its framework structure (架状结构). When quartz crystals (5kristl 晶体)are permitted to grow in an open cavity they may develop hexagonal (heksAEnEl 六边形的)prisms (5 prizEm 棱柱)topped by pyramids (棱锥) that are prized by crystal collectors. More frequently, the crystal faces can not be discerned because the orderly addition of atoms had been interrupted by contact with other growing crystals.Such minerals as chert (tFE:t 燧石,黑硅石), flint (flint 燧石), jasper (5dVAspE 碧玉)and agate (5AEt 玛瑙)are varieties of a form of quartz called chalcedony (kAl5sedEni 玉髓). Chalcedony is composed of extremely small fibrous (5faibrEs 含纤维的,质状的)crystals of quartz. The crystals are so tiny that their study often requires the use of an electron microscope. Spaces between the crystals are usually occupied by water molecules (5mClikju:l 分子). Among the varieties of chalcedony, chert is exceptionally abundant in many sedimentary rock units. It is a dense, hard ,usually white mineral or rock. Flint is the popular name for the dark gray or black variety of chalcedony much used by stone-age humans for making tools. Jasper is recognized by its opaque (Eu5peik 不透明的)appearance and red or yellow color derived from ironoxide (氧化铁)impurities (impurityim5pjuEriti 杂质). The term agate is used for chalcedony that exhibits bands (夹层,带)of differing color or texture (质地,纹理). There are many other varieties of quartz minerals than those briefly mentioned here.THE FELDSPARS (5feldspB: 长石)Feldspars are the most abundant constituents of rocks , composing about 60 percent of the total weight of the earths crust. There are two major families of feldspars: orthoclase (5C:WEukleis 正长石)or potassium (pE5tAsjEm 钾)feldspar group which are the potassium aluminosilicates (E7lju:mEnEu5silikeit 铝硅酸盐，硅铝酸盐), and the plagioclase (5pleidViEukleis 斜长岩)group, which are the aluminosilicates of sodium (5sEudjEm, -diEm 钠)and calcium (5kAlsiEm 钙). Members of the plagioclase group exhibit a wide range in compositionfrom a calcium-rich end member called anorthite (E5nC:Wait 钙长石)(CaAl2Si2O8) to a sodium- rich end member called albite (5Albait 钠长石) (NaAlSi3O8).Between these two extremes, plagioclase minerals containing both sodium and calcium occur. The substitution of sodium for calcium, however, is not random but rather is governed by the temperature and composition of the parent mineral. Thus, by examining the feldspar content of a once molten (5mEultEn 熔铸的)rock it is possible to infer the physical and chemical conditions under which it originated. Feldspars are nearly as hard as quartz and range in color from white or pink to bluish (5blu:iF 浅蓝色的)gray. Silica tetrahedra in the feldspars are joined in a strong three-dimensional lattice (5lAtis 格子)that is characterized by planes of weaker bonding in two directions at (or nearly at) right angles (直角) to each other. Because of this, the feldspars have good cleavage (break along smooth planes) in two directions. The resulting rectangular (rek5tANjulE 矩形的,成直角的) cleavage (5kli:vidV 解理)surfaces and a hardness of 6 are properties useful in the identification of feldspars. The plagioclase feldspars provide an example of the manner in which ions can be interchanged in a mineral group. A chemical analysis of specimens (5spesimin 标本,样品)of plagioclase taken from several different rocks would very probably reveal that the proportions of calcium, sodium, aluminum (E5lju:minEm 铝), and silicon (the principal cations (5kAtaiEn 阳离子)in plagioclase) would differ among the specimens. This variability (7vZEriE5biliti 可变性)occurs because some ions resemble each other in size and electrical properties (电性质) and are thus interchangeable (IntE5tFeIndVEb(E)l 可互换的)in a given crystal. Calcium and sodium ions are large and nearly identical (ai5dentikEl 同一的) in size. Both aluminum and silicon are small ions and not greatly different in size. Thus, calcium ions might substitute for (代替)sodium ions freely if size alone were the only requirement. However, the electrical neutrality (电中性)of the crystal must also be maintained. The electrical charge (电荷)of the calcium ion is +2, whereas that of the sodium ion is 1. To counteract (7kauntE5rAkt 中和)the surplus (5sE:plEs 剩余的)positive charge, an aluminum ion (+3) may substitute for a silicon ion (+1) to maintain electrical neutrality. Thus, Ca2+Al3+ can interchange with Na+ and Si+. This process of interchange (7intE5tFeindV 相互交换) is called solid solution (固体溶液).THE MICA (5maIkE 云母)GROUPAs noted earlier, mica is a silicate mineral having sheet structure (层状结构), and is easily recognized by its perfect and conspicuous (kEn5spikjuEs 显著的)cleavage in one directional (di5rekFEnEl 定向的)plane. The two chief varieties are the colorless or palecolored muscovite (7mQskE5vait 白云母)mica, which is a hydrous (5haidrEs 含水的)potassium aluminum silicate (KAl2 (AlSi2O3 (OH)2) and the dark colored biotite (5baiEtait 黑云母)mica, which also contains iron and magnesium (mA5ni:zjEm 镁)(K(Mg, Fe)3AlSi3O2(OH)2). In muscovite mica, two sheets of tetrahedra are strongly held together along their surface inner surfaces by positively charged ions aluminum. These sandwich like paired sheets are in turn weakly joined to others by positively charged ions of potassium. When muscovite is cleaved (kli:v 劈开)into paper-thin layers, the separation occurs primarily along the weaker plane where the potassium ions are located. In biotite, magnesium and iron ions hold the inner surfaces of the sheets together, but once again potassium ions serve to weakly join each basic set of paired sheets to its neighbor. Identification (ai7dentifi5keiFEn 辨认,鉴定)of large specimens of mica is rarely a problem because of its planar (5pleinE 平坦的)per feet cleavage and the way cleavage flakes (fleik 薄片)snap back (迅速跳回)into place when they are bent and suddenly released. The micas are common constituents of igneous (5iniEs 火成的)and metamorphic (7metE5mC:fik 变质的)rocks, where they can be recognized by their shiny surfaces and the ease with which they can be plucked loose with a pin or pen knife. Before the manufacture of glass, one of the chief uses of muscovite mica was as window panes (pein 窗格玻璃边,面). This clear mica was quarried (quarry5kwCri 挖出,苦心找出)in Muscovy (5mQskEvi 俄国)(commonly name for Russia), and thus came to be known as “Muscovy glass” and eventually muscovite. Today, mica is used in the manufacture of electrical insulators (5insjuleitE 绝缘体)and as a filler (填充物) in plaster (5plB:stE 石膏), roofing products and rubber.HORNBLENDE (5hC:nblend 角闪石)Hornblende is a vitreous (5vitriEs 玻璃质的)black or very dark green mineral. It is the most common member of a larger family of minerals called amphiboles (5AmfibEul 闪石), which have generally similar properties. As can be seen from its chemical formula, NaCa2(Mg,Fe,Al)2(Si,Al)2O2(OH), Hornblende contains a relatively large number of elements. Because of the presence of iron and magnesium, hornblende (along with biotite, augite and olivine 7Cli5vi:n 橄榄石,黄绿) is designated a ferromagnesian (7ferEumA5ni:FEn 铁镁矿物,含有铁与镁的)mineral. Crystals of hornblende tend to be long and narrow. Two good cleavages are developed parallel to the long axis and intersect (7intE5sekt 横断,交叉)each other at angles of 56and 121. The cleavage is a reflection of the location of planes of weaker bonds that exist between the double-chain units of silica tetrahedral in the atomic (E5tCmik 原子的)lattice.AUGITE (5C:dVait 普通辉石)Just as hornblende is only one member of a family of minerals called amphiboles, augite is an important member of the pyroxene (pai5rCksi:n 辉石)family in which many other mineral species (5spi:Fiz 种类)also occur. Its chemical formula Ca(Mg,Fe,Al)(SiAl)2O3 indicates that it too is a ferromagnesian mineral and thus dark colored. An augite crystal is typically rather stumpy (5stQmpi 短柱状的)in shape with good cleavages developed along two planed that are nearly at right angles (87and 93). Thus, the cross section of a crystal appears nearly square (rather than rhombic (5rCmbik 菱形的) as in hornblende). Unlike hornblende which has a double chain silicate structure, augite is constructed of single chains, and this accounts for its having differently shaped cleavage fragments (5frAmEnt 碎片,片断).OLIVINE (7Cli5vi:n 橄榄石,黄绿)Olivine, another ferromagnesian (7ferEumA5ni:FEn 铁镁矿物)mineral, has been mentioned earlier as having isolated silicon-oxygen tetrahedral boned together by iron and /or magnesium (mA5ni:zjEm 镁)ions. Its formula (Fe,Mg)2SiO4 indicates that it is a solid solution mineral, containing variable proportions of iron and magnesium. The substitution (7sQbsti5tju:FEn 替代)of these ions for each other is facilitated (facilitate fE5siliteit 助长,促进)by their having similar ionic radii (5reidiai 半径)and two electrons (电子)in their outer electron shell (电子壳层). The ions in olivine are so strongly held by ionic bonding (结合,粘合)that the mineral has a hardness of 6.5. As you might guess from its name, this glassy-looking mineral often has a green color. Frequently, it occurs as masses of small sugary grains or as tiny vitreous crystals in black lavas (5lB:vE 熔岩,火山岩). It is also an important constituent of stony meteorites. If large unblemished crystals of magnesium-rich olivine are found, they may be cut and polished into attractive gemstones (5dVem7stEun 经雕琢的宝石)called peridot (5peridCt 贵橄榄石). Lesson Three Sedimentary Rocks （5学时）Once weathering products (风化产物) have been formed from pre-existing rocks (原岩，先成岩). The next stage in the sequence of events leading to (导致，产生) sedimentary rocks is the removal and transport of those products. Many denudational (7di:nju: 5deiFEnl 剥蚀作用的)agencies (angency5eidVnsi 媒介), including running water, and moving ice, and wind assist (5sist 帮助)in this removal. The wind is an effective agent in picking up and blowing away the smaller and lighter particles. Glacial (5gleisjl,5glAsjl 冰川的) ice can move very large pieces of rock and carry an immense (i5mens 巨大的，极大的)load (载重，负荷) of coarse sediment (粗粒沉积物). Streams are also exceptionally (ik5sepFli 格外地，异常地)effective in carrying not only solid particles of sediment but invisible dissolved salts as well. Ultimately (5Qltimtli 最后，终于), sediment-laden (携带大量泥沙的，含沙量大的)streams flow into lakes or the sea and their load of sediment is deposited. It may form sandy beaches (沙滩), silty (5silti 粉砂质的) flood-plains (泛滥平原，漫滩，洪积平原), and sometimes muddy boggy (5bCgi 沼泽的)areas of estuaries (estuary5estjui 河口湾)and deltas (5delt 三角洲).The solid particles carried by wind or water will be deposited whenever (wen5ev 无论何时)there is insufficient (7ins5fiFnt 不足的) energy to carry them further. For example, if the velocity (5vilCsiti 速度，速率)of dust-laden wind abates (E5beit 减少), there will be insufficient energy to carry particles of a given size ,and those particles will be dropped. Similarly (5similli 同样地，相似地), if a streams velocity is checked (受到阻止，减弱), as when entering a standing (静态的) body of water (水体，储水池), the stream also loses energy and is unable to continue to carry the material formerly carried at the higher velocity.A reduction in a streams velocity does not, of course, affect the dissolved materials as it does suspended (ss5pend 悬挂，悬浮) solid particles. Material carried in solution (s5lju:Fn 溶液)is deposited by a process called precipitation (pri7sipi5teiFn 沉淀作用), in which dissolved material is changed to a solid and separated from the liquid in which it was formerly dissolved. For example, calcium (5kAlsim 钙) carbonate (5ka:bneit 碳酸盐), the principal (5prinspl 主要的) substance in the widespread (5waidspred 分布广泛的，普遍的) sedimentary rock known as limestone (5laimstun 石灰岩), may be precipitated from water that contains calcium in solution as indicated below： Ca2+ + 2HCO3 CaCO3 + H2O + CO2(dissolved (dissolved (calcium (water) (carbon calcium bicarbonate(bai5ka:bnit) carbonate) dioxide)ions) ions) 碳酸氢盐The bicarbonate ions that participate in the above reaction can be derived (di5raiv 得到)from the ionization (9ainai5zeiFn 离子化，电离)of carbonic (ka:5bCnik 碳的，含碳的)acid (5Asid 酸). As indicated by the arrows（箭头）, the reaction will proceed toward the right and calcium carbonate will be precipitated. If, however, carbon dioxide（二氧化碳） is added to sea water, then the amount of carbonic acid in the water would build, and the reaction would proceed to the left. This would result in (导致) a chemical environment not conducive (kn5dQktiv 对.有益的，对.有帮助的) to (有益于) calcium carbonate precipitation (pri7sipi5teiFn 沉淀(作用), and one in which existing calcium carbonate might begin to dissolve. As is evident here, the precipitation of calcium carbonate is a complex (5kCmpleks 复杂的)and delicate (5delikit 精密的，精细的) process in nature. It is influenced by organisms that utilize or liberate (5libreit 解放，释放)carbon dioxide, by processes that alter the acidity (5siditi 酸度) or alkalinity (7Alk5linit