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03-13
在10号托福考试的阅读中，内容偏向于生物自然科学的多，科普类型的材料比较多，而且篇幅也比较大，生单词出现的也多，所以托福培训网建议考试之前所准备些生物自然方面的，多多练习。
第一篇： EARTH AGE
第一篇是讲的早期科学家们估计地球寿命。
首先说人们很早就在预估地球寿命了;之后一段讲的近代一位科学家采用生物一代代进化速度的方式预估了三叠纪的长度，但基于的假设是进化速率基本相同，其估计已经有一定准确度了。后来讲科学家利用这种方式预估地球寿命，其弱点是有部分化石找不到而且更基本的错误是地球在生物诞生之前那段时间无法估计。(这里有插空题)之后讲了科学家用其他方式预估，有种是采用测算地壳沉积岩石厚度的方法，但问题是没有考虑板块运动以及腐蚀。另一种是计算海水盐度发，理想地认为一开始地球海洋是淡水，不断地填充盐才有了现在这样子，但这也忽略了盐分与海底大陆架之间的复杂作用以及其他(这里会考题问科学家忽略了什么)。但作者对于科学家基于盐度推出的几千万年的寿命还是给予肯定的。因为这已经验证了地球寿命远比原先预计的几百万年要多得多。而且也有一批科学家从其他领域验证了这个结果。
The age of the Earth is 4.54 ± 0.05 billion years.This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunarsamples. Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.
Because the exact accretion time of Earth is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
【岩层研究法】Studies of strata, the layering of rocks and earth, gave naturalists an appreciation that Earth may have been through many changes during its...
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