Official 04 Set 5

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Moving Rocks

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What does the professor mainly discuss?
  • A. His plans for research involving moving rocks.

  • B. A difference between two geological forces that cause rocks to move.

  • C. Theories about why desert rocks move.

  • D. Reasons why geologists should study moving rocks.

显示答案 正确答案: C

我的笔记 编辑笔记

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

    Now we've got a few minutes before we leave for today. So I'll just touch on an interesting subject that I think makes an important point.

    We've been covering rocks and different types of rocks for the last several weeks. But next week we are going to do something a bit different.And to get started I thought I'd mention something that shows how uh... as a geologist, you need to know about more than just rocks and the structure of solid matter.

    Moving rocks, you may have heard about them.It's quite a mystery.Death valley is this desert plain, a dry lake bed in California surrounded by mountains and on the desert floor these huge rocks, some of them hundreds of pounds.And they move. They leave long trails behind them, tracks you might say as they move from one point to another.But nobody has been able to figure out how they are moving because no one has ever seen it happen.

    Now there are a lot of theories, but all we know for sure is that people aren't moving the rocks.There are no footprints, no tyre tracks and no heavy machinery like a bulldozer... uh, nothing was ever brought in to move these heavy rocks.

    So what's going on?Theory NO.1 - Wind?Some researchers think powerful uh... windstorms might move the rocks.Most of the rocks move in the same direction as the dominant wind pattern from southwest to northeast.But some, and this is interesting, move straight west while some zigzag or even move in large circles.Um... How can that be?

    How about wind combined with rain?The ground of this desert is made of clay.It's a desert, so it's dry.But when there is the occasional rain, the clay ground becomes extremely slippery.It's hard for anyone to stand on, walk on.Some scientists theorized that perhaps when the ground is slippery the high winds can then move the rocks.There's a problem with this theory.One team of scientists flooded an area of the desert with water, then try to establish how much wind force would be necessary to move the rocks.And get this, you need winds of at least five hundred miles an hour to move just the smallest rocks.And winds that strong have never been recorded.Ever! Not on this planet.So I think it's safe to say that that issue has been settled.

    Here is another possibility - ice.It's possible that rain on the desert floor could turn to thin sheets of ice when temperatures drop at night.So if rocks... uh becoming embedded in ice, uh... OK, could a piece of ice with rocks in it be pushed around by the wind?But there's a problem with this theory, too.Rocks trapped in ice together would have moved together when the ice moved.But that doesn't always happen.The rocks seem to take separate routes.

    There are a few other theories.Maybe the ground vibrates, or maybe the ground itself is shifting, tilting.Maybe the rocks are moved by a magnetic force.But sadly all these ideas have been eliminated as possibilities.There's just no evidence.I bet you are saying to yourself well, why don't scientists just set up video cameras to record what actually happens?Thing is this is a protective wilderness area.So by law that type of research isn't allowed.Besides, in powerful windstorms, sensitive camera equipment would be destroyed.So why can't researchers just live there for a while until they observe the rocks' moving?Same reason.

    So where are we now?Well, right now we still don't have any answers.So all this leads back to my main point - you need to know about more than just rocks as geologists.The researchers studying moving rocks, well, they combine their knowledge of rocks with knowledge of wind, ice and such... not successfully, not yet.But you know, they wouldn't even have been able to get started without uh, earth science understanding - knowledge about wind, storms, you know, meteorology.You need to understand physics.So for several weeks like I said we'll be addressing geology from a wider perspective.I guess that's all for today. See you next time.

  • 旁白:请听一段地质学上的演讲。

    离下课还有几分钟我想谈一下某个有趣的话题,我想这是有重要意义的一点。

    过去几周我们一直在讨论各种不同的岩石。但是下周我们将说到一些不同的内容。而首先我想我要提到某些显示…呃, 作为一个地理学家,你需要知道的不仅仅是岩石极其固体结构

    移动岩石,你们可能听过。挺神奇的。死亡山谷就是这种沙漠平面,这是加利福尼亚的一个干涸的湖泊沉积矿,四面环山,而在沙漠地面上,这些巨大的岩石有的重达几千镑。而这些岩石会移动留下长长的尾痕,随着他们从一地移到另一地,他们留下各种痕迹。然而没人知道他们是怎么移动的,因为没人目睹过。

    如今人们提出很多理论,但我们所能知道的就是这不是人为的。没有人的足迹,没有轮胎痕迹,也没有重机械像推土机的痕迹。呃,没有人带来任何机器移动这些岩石

    那么到底是怎么回事呢?理论一:风力移动?某些研究人员认为强劲的风暴可能移动了岩石。盛行风移动模式是自西南向东北,岩石移动方向一致。但是有趣的是,某些岩石直线移动,其他一些曲折或甚至绕着大圈子移动。嗯,这怎么可能呢?

    是不是风雨交加造成的?该片沙漠地面是黏土这是一个沙漠,所以干燥。但有时也会下雨,黏土地面便会变得特别滑。人很难在上面站立行走。某些科学家提出理论,说可能当地面大话,强风便可以移动岩石。但是该理论存在一个问题。一组科学家在这片沙漠注水,然后试着测量多大的风力可以将岩石移动。你们猜猜多少,要至少5 千米每小时的风速才可以移动最小的石头。而他们也记录了强风时的情况。别想了,地球上是不可能的。所以我想,保守的说,这个理论已经站不住脚了。

    另一种说法即是冰。当夜晚温度降低时,沙漠地面上的雨水转变成一层薄薄的冰是有可能的。所以,当岩石,呃,被冰包裹,呃,ok,可能变成一块被冰包裹的岩石,风一吹就滑动。但这个理论也有一个问题。岩石被包裹在冰里的话,冰一移动,岩石也跟着移动。但不是什么时候都有冰的。岩石的移动路线似乎是分开的。

    还有其他几个理论。也许地面震动,抑或也许地面移动,倾斜。也许岩石是由于地磁力才移动的。但是遗憾的是,这些看法都已经被推翻。就是没有证据证明是对的。我想你们也会这样说,为什么科学家不架起一台摄像机记录整个过程?问题是,这是一块受保护的原始地带。所以法律上讲,这种研究方式是不允许的。此外,强劲的风暴可以摧毁摇摇欲坠的录像设备。那么为什么研究人员不能再那儿住一段时间,直到他们观察到岩石的移动情况呢?理由也是一样的。

    好的,我们刚刚讲到哪了?嗯,现在我们还没有找到答案。那么这些都回到主要观点了。要成为地理学家,你们要知道不仅仅是岩石而已。研究人员研究移动的岩石,嗯,他们把岩石的知识和风,冰等的知识结合起来,但还没有取得成功。但你们知道,他们如果连地球科学的知识都不知道的话,那他们都不知道从哪开始好。这些知识是关于风,风暴等气象的知识。你们要懂得物理。所以接下来几周,就像我说的,我们将会从一个更为广泛的角度解决地理问题。那么今天就到这吧下次课见。

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  • 本题对应音频:
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    题型分析:主旨题

    原文定位

    Moving rocks. You may have heard about them.

    选项分析

    教授提出了一个奇怪的现象,然后给出了一些可能的答案,后文有提到Theory number one,Here’s another possibility,There are a few other theories。所以正确答案C。

    A选项,plans未提及。B选项,difference未提及。D选项,reasons未提及。

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