『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 68 Lec2听力练习，Official 68 Lec2原文答案解析，Official 68 Lec2听力原文练习音频翻译。

托福TPO/Official 68 Lec2听力原答案解析-音频翻译【新东方在线】

旁白：请听一段地质学课堂的讲座。教授：就像我们上节课说的，科学家普遍认为地球有45亿年的历史。

Narrator: Listen to a part of lecture in a geology class. Professor:OK, as we said in the last class, the general consensus among scientists is that earth is 4.5 billion years old.

那么，45亿年前，地球还是一颗新行星的时候是什么样子的呢? Kitty?

So, what was earth like, when it was a new planet, 4.5 billion years ago? Kitty?

学生：它几乎被岩浆覆盖，环境非常炎热，

Student:Um, it was pretty much covered in magma, with really fiery conditions,

就像火山一样，还有巨大的岩石，陨石，它们与地球相撞，着陆后就会融化。

like volcanoes, plus there were like giant rocks, meteorites that collided with earth that would melt when they landed here.

教授：很棒，融化或蒸发。这种情况持续了上亿年。

Professor:Great, melt or vaporize. This ran on for hundreds of millions of years.

当然，那时这里还没有生命，只有火和熔岩。

There was no life here then of course, just fire and molten rock.

也没有液态水，没有海洋。你觉得什么时候会开始改变?

And no liquid water either, no oceans. And, and when do you think start to change?

学生：情况持续了5亿年，对吧? 直到地球有5亿年的历史？

Student:It lasts about five hundred million years, right? Until earth was like five hundred million years old?

教授: 好的，研究人员推断，由于我们没有在那之前任何完整的岩石作为实际证据，

Professor:OK, researchers have deduced that since we don't have proof of any intact rocks from before then,

地球在大约5亿年之后开始冷却，而在那之前的岩石，可能已经被火和热所湮灭。这也说的通，对吧?

that earth started cooling down after about five hundred million years, rocks earlier than that, would’ve been obliterated by the fire and heat. It makes sense, right?

教授：几个星期前，我们讨论了锆石。有人记得锆石吗?

Professor:OK, so a few weeks ago, we talked about Zircon. Anyone remembered anything about zircon.

学生：它是一种矿。我知道它有不寻常的特性，但是…

Student:Well, it's a mineral. Um, I know it has unusual properties, but...

教授：很好，这是个很好的开始。锆石是一种非常坚硬的矿物，它会形成晶体。

Professor:Great and know, that’s a good start. Zircon is a particularly sturdy mineral, it forms crystals.

关于锆石相关的是当它形成晶体时，这些晶体会包裹或生长在其他物质的周围。

And the thing about zircon is when it forms crystals, these crystals  encapsulate or grow around other materials.

所以，锆石晶体保留了它们当时形成时存在的条件的证据，

So, the zircon crystals retained evidence of the conditions that were present when they formed.

甚至也包含当时存在的其他物质。

And even the other materials that were present at the time.

现在，在20世纪80年代，研究人员在澳大利亚发现了一些锆石晶体。

Now, researchers in the 1980s discovered some zircon crystals in Australia.

但在那个时候，我们缺乏技术，无法对锆石中发现的材料做出任何明确的论断。

At that time though, we lacked the technology to make any definite claims about the materials found in the zircon.

似乎有一些物质证据早就存在，要早于科学家认为地球已经冷却到足以存在的时候，

There seemed to be some evidence of material from way, way back before scientists thought earth had cooled enough for to exist,

但研究人员没有那个时候的任何结论性的证据。

but researchers didn't have any conclusive evidence at the time.

学生：所以，他们仍然认为地球在5亿年前就开始冷却了。

Student:So, they still thought earth started cooling, when it was five hundred million years old.

教授：你知道，那些锆石晶体的发现令人非常兴奋。

Professor:Well, the discovery of those zircon crystals was pretty exciting, you know.

但事实上，大多数科学家不得不坚持这个理论，因为有最清楚的证据证明。

But really, most scientists had to stick with the theory, that had the clearest evidence.

就像我说的，技术还没有达到可以真正挑战公认观点的地步。

And like I said, technology just wasn’t of the point yet where could really challenge accepted view.

学生：但是，他们如何确定锆石之中物质的年代呢?

Student:But, how do they date the zircon in the material in it.

教授: 在20世纪80年代，他们使用了一种特殊的方法‘iron micro-probe’。

Professor:Well, in the 1980s, they used a special kind of iron micro-probe.

因此，他们使用特殊的iron micro-probe方法，从锆石表面取下少量原子，然后比较这些物质的质量。

So, with the special iron micro-probe, they removed a few atoms from the zircon’s surface, then they compare the mass of those items.

这就是他们测量原子组成的方法。这使得研究人员能够确定锆石的年代。

That’s how they measured the composition of the atoms. And this is what enabled the researchers to date the zircons.

事实上，利用这项技术，他们可以确定锆石单个晶体的特定部位的年代。

In fact, using this technique, they could date, specific parts of a single crystal of zircon.

教授：几年后，在1999年，他们开始重新研究。

And then years later, in 1999, they began to reinvestigate.

拥有改善的‘iron micro-probe’技术, 他们分析了另一组晶体, 发现有一些晶体超过四十亿岁,

With an improved iron micro-probe, they analyzed another group of crystals and found that a few of them were more than four billion years old,

也就是说, 那些晶体在地球最初的五亿年就存在了，

which means, they were around, during those first five hundred million years，

当我们认为地球还是一个极度火热的地方，能够摧毁任何接触到地球的岩石晶体。

when we thought earth was a very fiery place that destroyed any rocks of crystals they came to contact with it.

学生：但出于某种原因，这些锆石晶体怎么没有被破坏?

Student:But for some reason, these zircon crystals weren’t destroyed?

教授：是的。我们知道锆石承受力很强，但它肯定不可能经受得住持续的火球去燃烧它。

Professor:That’s right. I mean we know zircon can withstand a lot, but it definitely couldn't have survived constant fireball.

所以问题是，这些锆石晶体是否表明地球开始冷却的时间比我们想象的要更早。

So, the question was, were these zircon crystals and indication that earth started cooling earlier than we thought.

在我们研究的这些晶体中，最古老的，似乎在地球只有一亿岁的时候就存在了。

Out of those crystals that we’re looking at, the oldest one, seemed to have been around when earth with only one hundred million years old.

如果我们对早期地球的看法是正确的，那这种情况应该是不可能的。好了，有趣的地方来了。

If our view of earlier earth was correct, that shouldn't be possible. OK, now here’s where gets interesting.

他们对锆石晶体做了进一步的测试。还记得我说过锆石不仅包含物质证据还包含它们形成时的条件，

They did some further testing on the zircon crystals. Remember how I say zircons contained evidence not just materials but also what the conditions were like when they formed,

他们发现在最古老的锆石中结晶的岩石氧同位素比率很高。

they found the rock that was crystallized inside the oldest zircons had high oxygen isotope ratios.

学生：岩石中的锆石是如何获得高含量氧同位素的?

Student:How do zircons in rocks get high oxygen isotope ratios.

教授：嗯，必要的条件是，还有这个，液态水和比较低的温度。

Professor:Hum, the required conditions are, and get this, liquid water and low temperatures.

这是在岩石中的锆石当中，存在高含量氧同位素比率的唯一已知方式。是的，水和低温，所以...

This is only known way that high oxygen isotope ratios can occur in zircon in rocks. Yup, water and low temperatures, so.

学生：所以，当地球只有一亿年的时候，真的不同于...

Student:So, and that's when earth was only one hundred million years old, that's really different from a...

教授：非常不同，所以我们真的需要重新思考当时地球上的情况。

Professor:A very different, so we really had to rethink our ideas of the conditions on earth back then.

Prior to the 1980s researchers believed that Earth's climate was extremely hot during its first 500 million years. What led researchers to this belief?

According to the professor, what is true about the mineral zircon? Click in the correct boxes.

The professor mentions research done in Australia in the 1980s. What is the professor's opinion of the result of that research?

What can be concluded from the information obtained from the improved ion microprobe?

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