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地壳的外部

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  Bedrock is the solid rock that is exposed at the surface or immediately underlies soil and loose surface debris. Regolith is the relatively thin covering of soil and unconsolidated rock waste that hides the bedrock in most are-as. Bedrock is continuous and may consist of any kind of rock, whereas regolith is discontinuous, although generally present②.Regolith tends to be a few tens of feet thick or less, but may be much thicker. It may develop in place by the decay and disintegration of bedrock or consist of transported materials. Soil refers to the upper portion of the regolith which has been so altered by physical, chemical, and biological processes that it can support rooted vegetation. However, soil may be absent from an area.
 
  基岩是出露于地表或直接位于土壤和松散的地表岩屑之下的坚硬岩石。浮土是由土壤和未固结岩屑组成的比较薄的覆盖层, 在许多地方掩盖着基岩。基岩是延续不断的,可由任何一种岩石 构成。而浮土虽普遍存在,但不是延续不断的。浮土一般厚几十英尺或更少,但也有厚得多的。它可能是通过基岩的腐蚀和崩解 就地生成的,或者由搬运来的物质所组成。土壤指的是浮土的上 部,它受到物理的、化学的和生物的作用而发生变化,以致能使 植物根系繁生。但是,有的地区可能缺失土壤。
 
  By direct observation, man has access to only a very thin outer part of the crust ; the deepest mines penetrate less than 2 miles (3 km) beneath the surface, and the deepest wells about 5 miles (8 km). However, certain rocks now exposed at the surface may once have been buried several miles below it.
 
  人们直接观察只能接触到地壳很薄的表层:最深的矿井深入 地下不到2英里(3公里),最深的钻井约为5英里(8公里)。 但是,某些现在出露于地表的岩石,可能一度埋在地面以下数英 里的地方。
 
  Chemical analyses have been made for rocks of various types, and the proportions of the elements in the outer 10-mile (16 km) zone of the lithosphere have been estimated. Eight elements apparently constitute more than 98% by weight of this zone: oxygen (most abundant), silicon, aluminum, iron, calcium, sodium, potassium, and magnesium (least abundant). The following mnemonic expression arranges these eight elements in the order of their relative abundances: “Only Silly Artists In College Study Past Midnight. If the materials in the atmosphere and hydrosphere are added to those of the 10-mile zone, percentages are changed only slightly.
 
  对各种类型的岩石已做过化学分析,并估算了岩石圈外部10 英里(16公里)岩带中各种元素的比例。有八种元素明显地占此 岩带重量的98%以上:氧(最多)、硅、铝、铁、钙,钠、钾和镁(最 少)。下面这句有助于记忆的话编排了这八种元素相对丰度的顺序:“Only Silly Artists In College Study Past Midnight.” (“唯艺院之痴者乃读以待旦。”)如果把大气圈和水圈中的物质加进这10英里岩带的物质中,上述百分比只有很小的变化。
 
  Of these eight elements oxygen and silicon combined as silica (SiO2) make up about three-fourths of the total. Thus the silicate minerals are the most abundant in the crust, especially the feldspars, pyroxenes, amphiboles, micas, and quartz.
 
  在这八种元素申,化合成氧化硅(SiO2)的氧和硅,约占总 量的四分之三。因此,地壳中最丰富的是硅酸盐矿物,特别是长石、辉石、角闪石、云母和石英。
 
  
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