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托福tpo听力音频及文本下载(1-34完整版)

2015-06-09 15:29 三立在线 lihongyan

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摘要:托福tpo听力音频及文本下载(1-34完整版)!很多同学在复习托福听力时首先会找一些托福TPO内容来了解下听力的基本内容,由于很多地方只有TPO听力文本资料没有音频资料很不利于大家学习,因此小编特为大家整理出了托福tpo听力音频及文本下载(1-34完整版)内容。

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  以下是托福tpo听力音频及文本下载(1-34完整版)的具体内容:

  TPO 1 Lecture2 Geology

  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.

托福tpo听力音频及文本下载(1-34完整版)

  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 .

  TPO 1 Conversation 2

  Narrator

  Listen to part of a conversation between a student and his professor.

  Professor

  Hi Mathew, I’m glad you could come in today. You’ve been observing Mr. Grable’s third-grade class for your approaches to education paper, right?

  Student

  Um, yes. I go over to Johnson Elementary School, you know, to watch Mr. Grable teach the children in class. It’s been amazing, I mean, I’m just learning so much from just watching him. I’m so glad the classroom observations are a requirement for the education program. I mean it’s like the best thing ever to prepare you to be a good teacher.

  Professor

  Well, I’m glad to see you feel that way, Mathew. You know, that’s the goal. So, I’ve been reading over your observation notes and I’m quite interested in what’s going on, in particular with the astronomy unit he’s been teaching.

  Student

  The astronomy unit?

  Professor

  It seems that Mr. Grable has mastered the interdisciplinary approach to teaching that we’ve been talking about in class.

  Student

  Oh! OK, yeah, so like when he was teaching them astronomy, he didn't just teach them the names of the planets, he used it as a way to teach mythology.

  Professor

  Really! So, how did he do that?

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