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SSS 2008-09-30

时间:2010-05-15 01:44来源:互联网 提供网友:木渐浅。   字体: [ ]
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    (单词翻译:双击或拖选)

This is Scientific American's 60-Second Science. I'm Cynthia Graber. This will just take a minute.

 

The Earth’s crust is old. Billions of years old. So old that it’s nearly impossible to imagine. And now scientists have discovered what may be the oldest whole rocks ever known. Geologists1 at Carnegie Mellon University published the results of the research in the September 26th issue of the journal Science.

The rocks come from an area of the Hudson Bay in northern Quebec. In 2001 the geologists identified the site as a possible repository of very old rocks. It is made up of folds of volcanic2 and what are called metasedentary rocks. And it’s surrounded by three-and-a-half-billion-year-old tonalite.

Researchers collected rocks and measured minute isotopic3 variations in rare earth elements called neodymium and samarium. According to dating techniques, the rocks could be 4.28 billion years old. It’s rare to find rocks that date back to when the Earth’s mantle4 was forming. It was quite a tumultuous time, and most rocks were smashed up into tiny pieces again and again. Learning more about these whole rocks could help us gain a better understanding of the very beginnings of our planet.

 

Thanks for the minute for Scientific American's 60-Second Science. I'm Cynthia Graber.

 


点击收听单词发音收听单词发音  

1 geologists 1261592151f6aa40819f7687883760a2     
地质学家,地质学者( geologist的名词复数 )
参考例句:
  • Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
  • Geologists study the structure of the rocks. 地质学家研究岩石结构。
2 volcanic BLgzQ     
adj.火山的;象火山的;由火山引起的
参考例句:
  • There have been several volcanic eruptions this year.今年火山爆发了好几次。
  • Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。
3 isotopic 7ad2ece915960e8c295e01a4d04cc192     
adj.同位素的,合痕的
参考例句:
  • The isotopic signatures of most ancient limestones indicated the same process. 大多数古代石灰岩的同位素特征说明了同样的过程。 来自辞典例句
  • Isotopic discrimination is not likely. 同位素甄别是不可能的。 来自辞典例句
4 mantle Y7tzs     
n.斗篷,覆罩之物,罩子;v.罩住,覆盖,脸红
参考例句:
  • 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。
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