英语听力：探索发现 科学新发现：我们的大气层-9

 We were left with this atmosphere made of molten rock and vaporous rock. It took millions of years for that atmosphere to fall out and to be replaced by an atmosphere made up of nitrogen and carbon dioxide and water vapour. These new gases came from above and below. Volcanic¹ eruptions² spewed out fresh stocks of nitrogen and carbon dioxide from within the planet’s molten core. 

 

While the vital element of water may have been delivered by icy comets, each impact brings in a new supply of frozen liquid. But the air still lacked one of its key ingredients. One of the things that was missing is free oxygen—molecular oxygen, O2, the stuff we breathe. 

 

Dr. Janet Seifert of Rice University in Texas searches for the event that produced the atmosphere’s final element. We know from the rock record that for the first half of Earth’s life there was no oxygen in the atmosphere whatsoever³. There were greenhouse gases like methane⁴ and CO2, but there was no oxygen. But the rock record shows a sudden change dated to around 2.5 billion years ago.

1 volcanic   

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。

2 eruptions   

n.喷发，爆发( eruption的名词复数 )

参考例句：

• There have been several volcanic eruptions this year. 今年火山爆发了好几次。 来自《简明英汉词典》
• Over 200 people have been killed by volcanic eruptions. 火山喷发已导致200多人丧生。 来自辞典例句

3 whatsoever   

adv.（用于否定句中以加强语气）任何；pron.无论什么

参考例句：

• There's no reason whatsoever to turn down this suggestion.没有任何理由拒绝这个建议。
• All things whatsoever ye would that men should do to you,do ye even so to them.你想别人对你怎样，你就怎样对人。

4 methane   

n.甲烷，沼气

参考例句：

• The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
• Methane may have extraterrestrial significance.甲烷具有星际意义。