Uranium-Lead Dating托福聽(tīng)力原文翻譯及問(wèn)題答案

Uranium-Lead Dating托福聽(tīng)力原文翻譯及問(wèn)題答案,關(guān)于這個(gè)問(wèn)題中國(guó)教育在線(xiàn)外語(yǔ)平臺(tái)小編就簡(jiǎn)單為大家說(shuō)一下。

一、Uranium-Lead Dating托福聽(tīng)力原文：

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

MALE 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 gonna 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,uh,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'll 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,uh,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.

Uh,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 a 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 your 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,uh,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,uh,uranium-lead dating is going to become an increasingly popular dating method.There are a few pretty exciting possibilities for uranium-lead dating.

Here's 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.

二、Uranium-Lead Dating托福聽(tīng)力中文翻譯：

旁白：聽(tīng)地質(zhì)學(xué)課上的部分講座。

男教授：好的，我們開(kāi)始吧。很好，今天我想談?wù)勔环N我們能夠確定一塊土地或其他地質(zhì)特征的年代的方法。約會(huì)技巧。我要談?wù)勔环N特殊的約會(huì)技巧。為什么？良好的約會(huì)是良好分析的關(guān)鍵。換言之，如果你想知道一塊土地是如何形成的，你可能首先想知道它的年代。這是最基本的。

呃，以大峽谷為例?，F(xiàn)在，我們地質(zhì)學(xué)家認(rèn)為我們對(duì)美國(guó)西南部的大峽谷是如何形成的有了很好的了解。我們知道它是由1.5億到3億年前某處固化的砂巖形成的。在它凝固之前，它基本上只是普通的沙子，它是一片廣袤沙漠的一部分。

而且，直到最近，我們大多數(shù)人還認(rèn)為這些沙子來(lái)自一座古老的山脈，離那座山脈很近，隨著時(shí)間的推移，山脈逐漸變平。這一直是地質(zhì)學(xué)家的傳統(tǒng)智慧。但現(xiàn)在我們通過(guò)一種名為鈾鉛測(cè)年的技術(shù)，學(xué)到了一些不同的、非常令人驚訝的東西。

我應(yīng)該說(shuō)鈾鉛測(cè)年已經(jīng)存在了很長(zhǎng)一段時(shí)間，但最近有一些改進(jìn)，我馬上就要開(kāi)始討論。無(wú)論如何，鈾鉛測(cè)年法產(chǎn)生了一些令人驚訝的結(jié)果。兩位地質(zhì)學(xué)家發(fā)現(xiàn)，大峽谷中大約一半的沙子實(shí)際上曾經(jīng)是阿巴拉契亞山脈的一部分。這真是一個(gè)令人大開(kāi)眼界的消息，因?yàn)榘屠鮼喩矫}當(dāng)然在大峽谷以東數(shù)千公里處。聽(tīng)起來(lái)很不可思議，對(duì)吧？

當(dāng)然，一個(gè)明顯的問(wèn)題是，這些沙子怎么會(huì)流到這么遠(yuǎn)的西部？該理論認(rèn)為，巨大的河流和風(fēng)將沙粒帶到了西部，在那里沙粒與已經(jīng)存在的沙?；旌显谝黄稹＿@是一個(gè)革命性的發(fā)現(xiàn)，基本上是因?yàn)殁欍U測(cè)年。為什么?

這門(mén)課上的每個(gè)人都應(yīng)該知道，我們通常會(huì)觀(guān)察砂巖中的顆粒類(lèi)型，也就是砂巖中的實(shí)際顆粒，以確定其來(lái)源。你也可以做其他事情，比如看看把谷物帶到它們所在位置的風(fēng)或水，找出它們的流向。但這只在一定程度上有用，這兩位地質(zhì)學(xué)家并沒(méi)有這樣做。

鈾鉛測(cè)年使他們能夠以完全不同的方式進(jìn)行。他們所做的是觀(guān)察砂巖中的鋯石顆粒。鋯石是一種含有放射性鈾的材料，這使得它在測(cè)年方面非常有用。

鋯石開(kāi)始時(shí)是熔融的巖漿，是來(lái)自火山的熱熔巖。然后巖漿結(jié)晶。當(dāng)鋯石結(jié)晶時(shí)，里面的鈾開(kāi)始變成鉛。所以，如果你測(cè)量鋯石顆粒中鉛的含量，你就能知道顆粒是什么時(shí)候形成的。之后，你可以確定不同山脈鋯石的年齡。

一旦你這樣做了，你就可以比較你樣本中砂巖中鋯石的年齡和山脈中鋯石的年齡。如果鋯石的年齡與你的一座山脈的年齡相匹配，那么這意味著砂巖實(shí)際上曾經(jīng)是那座特定山脈的一部分。大家都同意我的看法嗎？好的因此，在這種情況下，鈾鉛測(cè)年被用來(lái)確定樣品中一半的砂巖是在阿巴拉契亞山脈花崗巖形成的同時(shí)形成的。

因此，由于這種新的鈾鉛測(cè)年方法，我們能夠確定我們對(duì)大峽谷的一個(gè)主要假設(shè)是錯(cuò)誤的。正如我之前所說(shuō)，鈾鉛測(cè)年已經(jīng)存在了一段時(shí)間，但是，直到最近，為了做到這一點(diǎn)，你真的需要研究許多單個(gè)的顆粒，而且需要很長(zhǎng)時(shí)間才能得到結(jié)果。只是效率不高，也不太準(zhǔn)確。

但是技術(shù)進(jìn)步減少了你必須研究的谷物數(shù)量，所以你可以更快地得到結(jié)果。所以我預(yù)測(cè)，鈾鉛定年將成為一種越來(lái)越流行的定年方法。鈾鉛測(cè)年有一些非常令人興奮的可能性。

我想到了一個(gè)。你知道，地球各大洲曾經(jīng)連接在一起，只是最近才分開(kāi)的理論嗎？嗯，用鈾鉛測(cè)年法，我們可以更確切地證明這一點(diǎn)。如果他們有證據(jù)表明曾經(jīng)有人加入，那真的可以告訴我們很多關(guān)于這顆行星早期地質(zhì)的歷史。

三、Uranium-Lead Dating托福聽(tīng)力問(wèn)題：

Q1:1.What does the professor mainly discuss?

A.The differences in age among American mountain ranges

B.The importance of a technique used for dating geological materials

C.The recent discovery of an ancient canyon

D.A comparison of various minerals used for dating

Q2:2.Before the use of uranium-lead analysis,where did most geologists think the Grand Canyon sandstone came from?

A.An ancient lake located in the American Southwest

B.A desert that once connected two continents

C.Sands carried by a river from the Appalachian Mountains

D.A nearby mountain range that had flattened out over time

Q3:3.In the talk,the professor describes the sequence of uranium-lead dating.Summarize the sequence by putting the events in the correct order.

A.Zircon in the sandstone is matched to the zircon in a particular mountain range

B.The amount of lead in sandstone zircon is measured.

C.The age of zircon in a sandstone sample is determined.

Q4:4.According to the professor,what change has caused uranium-lead dating to gain popularity recently?

A.It can be performed outside a laboratory.

B.It can now be done more efficiently.

C.It no longer involves radioactive elements.

D.It can be used in fields other than geology.

Q5:5.Why does the professor talk about the breaking apart of Earth's continents?

A.To give another example of how uranium-lead dating might be useful

B.To explain how the Grand Canyon was formed

C.To demonstrate how difficult uranium-lead dating is

D.To disprove a theory about the age of Earth's first mountain ranges

Q6:6.What does the professor imply when he says this:

A.The class is easier than other geology classes

B.The class has already studied the information he is discussing

C.Some students should take a course in geological dating techniques

D.He will discuss the topic later in the class

四、Uranium-Lead Dating托福聽(tīng)力答案：

A1:正確答案：B

A2:正確答案：D

A3:正確答案：BCA

A4:正確答案：B

A5:正確答案：A

A6:正確答案：B

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