『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 1 Lec 2听力练习：Before the use of uranium-lead analysis, where did most geologists think the Grand Canyon sandstone came from?原文题目答案解析，TPO/Official 1 Lec 2听力原文范文音频翻译。

托福TPO/Official 1 Lec 2听力原文Before the use of uranium-lead analysis, where did most geologists think the Grand Canyon sandstone came from?【新东方在线】

Narrator: Listen to part of a lecture in a geology class.

好，今天我要谈一些关于如何测定地质年份和其他关于地质特征的方法，年代测量法。

Great. Today I want to talk about a way in which we are able to determine how old a piece of land, or some other geologic feature is--dating techniques.

I'm going to talk about a particular dating technique.

为什么呢？因为一个准确的年代是一把打开分析之门的钥匙。

Why? Good dating is key to good analysis.

换句话说，如果你想知道这块地质形成的原因，你要做的第一件事就是搞清楚它的年纪了。

In other words, if you want to know how a land formation was formed, the first thing you probably want to know is how old it is.

Um... Take the Grand Canyon for instance.

现代地质学家认为我们已经形成了一个没有太多瑕疵的关于美国西南部大峡谷起源的假说。

Now, we geologists thought we had a pretty good idea of how the Grand Canyon in the southwestern United States was formed.

我们推测它的形成源于15至30亿年前砂岩的凝固。

We knew that it was formed from sandstone that solidified somewhere between 150 and 300 million years ago.

在成型之前，这些只是普通的沙子。

Before it solidified, it was just regular sand.

Essentially, it was part of a vast desert.

但最近，大多数人发现和认为这些沙子来源于逐渐风化变平的古代山脉。

And until just recently, most of us thought the sand had come from an ancient mountain range fairly close by that flattened out over time.

这是那段时间地质学家的测量方法。

That's been the conventional wisdom among geologists for quite some time.

但是现在我们得到了不同的方法和更多的惊喜，这种我们至今仍在使用的技术被称为，铀铅年份测试法。

But now we've learned something different, and quite surprising, using a technique called Uranium-Lead Dating.

虽然说铀铅年份测试法问世已经有一段时间，

I should say that Uranium-Lead Dating has been around for quite a while.

But there have been some recent refinements.

总之，铀铅年份测试法给我们带来了一些惊喜。

Anyway, Uranium-Lead Dating has produced some surprises.

两个地质学家发现大峡谷大约一半的沙子实际上源于阿巴拉契亚山脉。

Two geologists discovered that about half of the sand from the Grand Canyon was actually once part of the Appalachian Mountains.

这个发现真的令人瞠目结舌，因为大峡谷往东几千公里才到阿巴拉契亚山脉。

That's really eye-opening news, since the Appalachian Mountain Range is, of course, thousands of kilometers to the east of the Grand Canyon.

的确是这样，问题是那些沙子怎么能西移那么远？

Of course, the obvious question is how did that sand end up so far west?

理论上是这样认为的：这些沙子被大河冲，狂风刮至大峡谷处汇集、混合并沉淀。

The theory is that huge rivers and wind carried the sand west where it mixed in with the sand that was already there.

Well, this was a pretty revolutionary finding.

嗯……主要还是铀铅年份测试法的应用。

Um... and it was basically because of Uranium-Lead Dating.

这样，正如在座的每一个同学应该知道的那样，我们通常关注沙砾内部的纹理类型，也就是沙砾里的微粒，来判定它来自哪里。

Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone, to determine where it came from.

我们也有别的方法，比如关注将沙砾带至该地的风或河流，然后推出它的流向。

You can do other things too, like look at the wind or water that brought the grains to their location and figure out which way it was flowing.

然而，这种方法只在一定程度上有用，那两个地质学家没有这样做。

But that's only useful up to a point, and that's not what these two geologists did.

铀铅年份测试法给他们提供里全新的方式来推断沙砾的流向。

Uranium-Lead Dating allowed them to go about it in an entirely different way.

他们做的是：他们研究沙砾里锆石的纹理。

What they did was: they looked at the grains of Zircon in the sandstone.

锆石是一种内含放射性铀的物质，而放射性铀对年代推算很有帮助。

Zircon is a material that contains radioactive Uranium, which makes it very useful for dating purposes.

锆石源于熔岩，一种火山喷发的岩浆。

Zircon starts off as molten magma, the hot lava from volcanoes.

而当锆石凝结时，锆石里面的铀转化成铅。

And when Zircon crystallizes, the Uranium inside it begins to change into Lead.

所以，如果你测量锆石里铅的含量，你可以推算纹理是何时形成的。

So, if you measure the amount of Lead in the Zircon grain, you can figure out when the grain was formed.

之后，你就能从不同山脉来断定锆石的年份。

After that, you can determine the age of Zircon from different mountain ranges.

一旦你这样做，你就可以将样本沙石里锆石的年份和山脉里锆石的年份做比较。

Once you do that, you can compare the age of the Zircon in the sandstone in your sample to the age of the Zircon in the mountains.

如果样本沙石里锆石的年份与山脉里锆石的年份一致，那就意味着这里的沙石曾经作为这个山脉的一部分而存在。

If the age of the Zircon matches the age of one of your mountain ranges, then it means the sandstone actually used to be part of that particular mountain range.

很好。这样，铀铅年份测试法用于确认样沙里一半沙石和阿巴拉契亚山脉花岗岩的成形。

Good. So, in this case, Uranium-Lead Dating was used to establish that half of the sandstone in the samples was formed at the same time the granite in the Appalachian Mountains was formed.

所以，正因为这种，这种进行铀铅年份测试的新方法，我们有能力判定我们对大峡谷的重大假设之一是错误的。

So because of this, this new way of doing Uranium-Lead Dating, we've been able to determine that one of our major assumptions about the Grand Canyon was wrong.

像我之前说过的那样，我们已经使用铀铅年份测试法有一段时间了。

Like I said before, Uranium-Lead Dating has been with us for a while.

但，嗯……直到最近，要完成这样的测试，你还真得研究很多（沙砾的）纹理。

But, um... until recently, in order to do it, you really had to study many individual grains.

当然，要得出结果是需要很长一段时间的。

And it took a long time before you got results.

但是，技术的进步能缩减你需要研究的纹理的数量，这样你会更快地得到结果。

But technical advances have cut down on the number of grains you have to study, so you get your results faster.

我估计铀铅年份测试法将成为越发受人欢迎的年份测试法。

So I'll predict that Uranium-Lead Dating is going to become an increasingly popular dating method.

在铀铅年份测试法里有几个令人兴奋的可能性。

There are a few pretty exciting possibilities for Uranium-Lead Dating.

大家都知道地球大陆板块始合近分的理论吧？

You know the theory that earth continents were once joined together and only split apart relatively recently?

用铀铅年份测试法，我们能将这一理论论证得更具总结性。

Well, with Uranium-Lead Dating, we could prove that more conclusively.

如果能有证据表明始合，那些证据就能给我们提供很多地球地质学的早期史料。

If they show evidence of once having been joined, that could really tell us a lot about the early history of the planet's geology.

Before the use of uranium-lead analysis, where did most geologists think the Grand Canyon sandstone came from?

In the talk, the professor describes the sequence of uranium-lead dating. Summarize the sequence by putting the events in the correct order. Drag your answer choices to spaces where they belong.

According to the professor, what change has caused uranium-lead dating to gain popularity recently?

Why does the professor talk about the breaking apart of Earth's continents?

What does the professor imply when he says this

Listen to part of a lecture in a geology class. Professor Ok, let’s get started. Great. Today I want to talk about a way in which we are able to determine how old a piece of land, or some other geologic feature is - dating techniques. I’m going to talk about a particular dating technique. Why? Good dating is key to good analysis. In other words, if you want to know how a land formation was formed, the first thing you probably want to know is how old it is. It’s fundamental. Uh… Take the Grand Canyon for instance. Now, we geologists thought we had a pretty good idea of how the Grand Canyon in the southwestern United States was formed. We knew that it was formed from sandstone that solidified somewhere between 150 and 300 million years ago. Before it solidified, it was just regular sand. Essentially it was part of a vast desert. And until just recently, most of us thought the sand had come from an ancient mountain range fairly close by that flattened out over time. That’s been the conventional wisdom among geologists for quite some time. But now we’ve learned something different, and quite surprising, using a technique called Uranium-Lead Dating. I should say that Uranium-Lead Dating has been around for quite a while. But there have been some recent refinements. I will get into this in a minute. Anyway, Uranium-Lead Dating has produced some surprises. Two geologists discovered that about half of the sand from the Grand Canyon was actually once part of the Appalachian Mountains. That’s really eye-opening news, since the Appalachian Mountain Range is, of course, thousands of kilometers to the east of the Grand Canyon. Sounds pretty unbelievable, right? Of course, the obvious question is how did that sand end up so far west? The theory is that huge rivers and wind carried the sand west where it mixed in with the sand that was already there. Well, this was a pretty revolutionary finding. Um… and it was basically because of Uranium-Lead Dating. Why? Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone, to determine where it came from. You can do other things too, like look at the wind or water that brought the grains to their location and figure out which way it was flowing. But that’s only useful up to a point, and that’s not what these two geologists did. Uranium-Lead Dating allowed them to go about it in an entirely different way. What they did was: they looked at the grains of Zircon in the sandstone. Zircon is a material that contains radioactive Uranium, which makes it very useful for dating purposes. Zircon starts off as molten magma, the hot lava from volcanoes. This magma then crystallizes. And when Zircon crystallizes, the Uranium inside it begins to change into Lead. So if you measure the amount of Lead in the Zircon grain, you can figure out when the grain was formed. After that, you can determine the age of Zircon from different mountain ranges. Once you do that, you can compare the age of the Zircon in the sandstone in your sample to the age of the Zircon in the mountains. If the age of the Zircon matches the age of one of the mountain ranges, then it means the sandstone actually used to be part of that particular mountain range. Is everybody with me on that? Good. So, in this case, Uranium-Lead Dating was used to establish that half of the sandstone in the samples was formed at the same time the granite in the Appalachian Mountains was formed. So because of this, this new way of doing Uranium-Lead Dating, we’ve been able to determine that one of our major assumptions about the Grand Canyon was wrong. Like I said before, Uranium-Lead Dating has been with us for a while. But, um… until recently, in order to do it, you really had to study many individual grains. And it took a long time before you got results. It just wasn’t very efficient. And it wasn’t very accurate. But technical advances have cut down on the number of grains you have to study, so you get your results faster. So I’ll predict that Uranium-Lead Dating is going to become an increasingly popular dating method. There are a few pretty exciting possibilities for Uranium-Lead Dating. Here is one that comes to mind. You know the theory that earth’s continents were once joined together and only split apart relatively recently? Well, with Uranium-Lead Dating, we could prove that more conclusively. If they show evidence of once having been joined, that could really tell us a lot about the early history of the planet’s geology. Well, this was a pretty revolutionary finding. Um… and it was basically because of Uranium-Lead Dating. Why? Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone, to determine where it came from.

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