万物简史 第307期:地下的烈火(15)
英语课
So how much do we know about what's inside the Earth? Very little. 因此说，我们对地球的内部情况究竟了解多少？很少。
Scientists are generally agreed that the world beneath us is composed of four layers, 科学家们普遍认为，我们脚底下的世界共分4层，
rocky outer crust, a mantle 1 of hot, viscous 2 rock, a liquid outer core, and a solid inner core. 一个岩石外壳，一个由炽热而又黏稠的岩石组成的地幔，一个液态的外核，以及一个坚实的内核。
We know that the surface is dominated by silicates 3, which are relatively 4 light and not heavy enough to account for the planet's overall density 5. 我们知道，地面的主要成分是硅酸盐。硅酸盐比较轻，分量还不足以说明这颗行星的整体密度。
Therefore there must be heavier stuff inside. 因此，里面肯定还有较重的东西。
We know that to generate our magnetic field somewhere in the interior there must be a concentrated belt of metallic 6 elements in a liquid state. 我们知道，为了产生磁场，里面的什么地方肯定存在着一个浓缩的液态金属元素带。
That much is universally agreed upon. 这一些是大家都承认的。
Almost everything beyond that—how the layers interact, what causes them to behave in the way they do, 除此以外，几乎一切——这几层结构是如何相互作用的，是什么原因它们才有了这种表现，
what they will do at any time in the future—is a matter of at least some uncertainty 7, and generally quite a lot of uncertainty. 未来的某个时刻它们会有什么动作，少说还都是个不大确定的问题，总的来说还都是个很不确定的问题。
Even the one part of it we can see, the crust, is a matter of some fairly strident debate. 我们可以看到，即使是其中的一个部分——地壳——也是个争论得比较激烈的问题。
Nearly all geology texts tell you that continental 8 crust is three to six miles thick under the oceans, 几乎所有的地质学文字资料都会告诉你，地壳的厚度在海洋底下为5-10公里，
about twenty-five miles thick under the continents, and forty to sixty miles thick under big mountain chains, 在大陆底下约为40公里，在大山脉底下为65-95公里，
but there are many puzzling variabilities within these generalizations 9. 但在这些一般规律之内还有许多令人费解的变异。
The crust beneath the Sierra Nevada Mountains, for instance, is only about nineteen to twenty-five miles thick, and no one knows why. 比如，内华达山脉底下的地壳厚度只有大约30-40公里，谁也不清楚是什么原因。
By all the laws of geophysics the Sierra Nevadas should be sinking, as if into quicksand. 根据地球物理学的所有原理，内华达山脉应当在下沉，犹如陷入流沙那样。
(Some people think they may be.) （有的人认为，这座山脉也许就是在下沉。）
n.斗篷，覆罩之物，罩子；v.罩住，覆盖，脸红
- The earth had donned her mantle of brightest green.大地披上了苍翠欲滴的绿色斗篷。
- The mountain was covered with a mantle of snow.山上覆盖着一层雪。
adj.粘滞的，粘性的
- Gases are much less viscous than liquids.气体的粘滞性大大小于液体。
- The mud is too viscous.You must have all the agitators run.泥浆太稠，你们得让所有的搅拌机都开着。
n.硅酸盐( silicate的名词复数 )
- Did equilibration take place before or after setting of chromite and silicates? 究竟平衡作用发生在铬铁矿和硅酸盐下沉之前，还是在其后？ 来自辞典例句
- The commercial product however, containing silica and silicates, has a positive effect. 然而含有硅石和硅酸盐的工业品都有肯定的效果。 来自辞典例句
adv.比较...地，相对地
- The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
- The operation was relatively painless.手术相对来说不痛。
n.密集，密度，浓度
- The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
- The region has a very high population density.该地区的人口密度很高。
adj.金属的；金属制的；含金属的；产金属的；像金属的
- A sharp metallic note coming from the outside frightened me.外面传来尖锐铿锵的声音吓了我一跳。
- He picked up a metallic ring last night.昨夜他捡了一个金属戒指。
n.易变，靠不住，不确知，不确定的事物
- Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
- After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。
adj.大陆的，大陆性的，欧洲大陆的
- A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
- The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。
一般化( generalization的名词复数 )； 普通化； 归纳； 概论
- But Pearlson cautions that the findings are simply generalizations. 但是波尔森提醒人们，这些发现是简单的综合资料。 来自英汉非文学 - 生命科学 - 大脑与疾病
- They were of great service in correcting my jejune generalizations. 他们纠正了我不成熟的泛泛之论，帮了我大忙。
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