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托福TPO-06 Lecture 4

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Narrator:Listen to part of a lecture in an earth science class.

独白:请听下面一段地球科学课讲座的一部分。
Professor:We're really just now beginning to understand how quickly drastic climate change can take place.
教授:我们刚刚了解激烈的气候变化发生的有多快。
We can see past occurrences of climate change that took place over just a few hundred years.
我们看到过去几百年前发生的气候变化事件。
Take uh… the Sahara Desert in Northern Africa.
比如说,北非的撒哈拉大沙漠。
The Sahara was really different 6,000 years ago.
6000 年前的撒哈拉大沙漠可是截然不同,
I mean, you wouldn't call it a tropical paradise or anything,
我的意思是你不会称它为“热带天堂”或什么的。
uh…or maybe you would if you think about how today in some parts of the Sahara it…
嗯,如果你想想在撒哈拉的有些地方今天是什么样子你也可能会这么叫,
it only rains about once a century.
有些地方一个世纪才下一场雨。
Um… but basically, you had granary and you had water.
不过,基本上你还是有粮食和水的。
And what I find particularly interesting and amazing really, what really indicates how un desert-like the Sahara was thousands of years ago,
而且我觉得非常有趣及不可思议的是一些东西展现了撒哈拉在几千年前是多么的不像沙漠,
was something painted on the rock, pre-historic art, hippopotamuses,
它们就是岩石上的绘画,史前艺术,石头上画着的河马,
cos you know hippos need a lot of water and hence? Hence what?
因为你们知道,河马是需要大量的水才能生存,那么因此,因此什么呢?
Student:They need to live near a large source of water year round
学生:他们需要终年生活在一个巨大的水源附近。
Professor:That's right.
教授:是这样的。
Student:But how is that proved that the Sahara used to be a lot wetter?
学生:但是那怎么证明撒哈拉过去非常潮湿?
I mean the people who painted those hippos, well, couldn't they have seen them on their travels?
我是说那些画河马的人,嗯,难道就不可能是他们在旅途中见到的吗?
Professor:Okay, in principal they could, Karl.
教授:问的好,是有这种可能,卡尔。
But the rock paintings aren't the only evidence.
但是岩石绘画不是唯一的证据。
Beneath the Sahara are huge aquifers, basically a sea of fresh water,
撒哈拉下面有巨大的蓄水层,一片淡水的海洋,
that's perhaps a million years old filtered through rock layers.
那可能是经过岩石层过滤的,已经有一百万年历史。
And…er…and then there is fossilized pollen, from low shrubs and grasses that once grew in the Sahara.
并且,嗯,有一些石化的花粉,来自于曾经生长在撒哈拉的小灌木丛和草丛。
In fact these plants still grow, er…but hundreds of miles away, in more vegetated areas.
实际上,这些植物现在仍然在生长,嗯,但是是在离这里几百英里远的更多植物生长的区域。
Anyway, it's this fossilized pollen along with the aquifers and the rock paintings,
不管怎么说,就是这些石化花粉和蓄水层,还有岩石上的画作,
these three things are all evidence that the Sahara was once much greener than it is today,
这三样东西证明撒哈拉曾经比现在有更多植物的证据,
that there were hippos and probably elephants and giraffes and so on.
可能不仅有河马,还有大象和长颈鹿等等。
So what happened?
那么发生什么事儿了呢?
How did it happen?
是怎么发生的呢?
Now, we're so used to hearing about how human activities are affecting the climate, right?
现在,我们很习惯听到人类活动是如何影响气候的。
But that takes the focus away from the natural variations in the earth climate, like the Ice Age, right?
但是这却将将注意力从地球气候的自然变化转移开了,比如说冰河世纪,对吧?
The planet was practically covered in ice just a few thousand years ago.
这个星球在几千年前都是被冰雪覆盖的,
Now as far as the Sahara goes, there is some recent literature that points to the migration of the monsoon in that area.
现在就撒哈拉沙漠而言,近期有些文学作品指向了那个地区季候风的迁移。
Students:Huh?
学生:啊?
Professor:What do I mean?
教授:我说的是什么意思呢?
Okay, a monsoon is a seasonal wind that can bring in a large amount of rainfall.
是这样,季候风是指季节性的风,而这种风能够带来大量的雨水。
Now if the monsoon migrates, well, that means that the rains move to another area, right?
现在如果季候风迁移,也就意味着雨水也跟着去了另一个地区,对吧?
So what caused the monsoon to migrate?
那么是什么使得季候风迁移呢?
Well, the answer is:
嗯,答案就是:
the dynamics of earth's motions,
地球的运动动力学。
the same thing that caused the Ice Age by the way.
同样这也是造成冰河世纪原因。
The earth's not always the same distance from the sun,
地球和太阳的距离并不总是一样远,
and it's not always tilting toward the sun at the same angle.
也不总是以同样的角度对着太阳的。
There are slight variations in these two perimeters.
它们的周长有一点点变化。
They're gradual variations but their effects can be pretty abrupt.
而这种不显著的变化使得其影响却有可能很突然,
And can cause the climate to change in just a few hundred years.
可以引起气候在短短几百年间发生变化。
Student:That's abrupt?
学生:这称得上突然?
Professor:Well, yeah, considering that other climate shifts take thousands of years, this one is pretty abrupt.
教授:嗯,你们想想啊,其他的气候变化可是花了几千年啊,这个已经是很突然了。
So these changes in the planet's motions, they called it “the climate change”, but it was also compounded.
所以这些星球运动中的变化,他们称之为“气候变化”,这也是混合的。
What the Sahara experienced was um…a sort of “runaway drying effect”.
撒哈拉沙漠所经历的变化,嗯,是一种“逃离干燥效果”,
As I said the monsoon migrated itself, so there was less rain in the Sahara.
就像我说的季候风本身会迁移,所以撒哈拉沙漠的雨水变少,
The land started to get drier, which in turn caused huge decrease in the amount of vegetation,
土地开始变干燥,于是造成了植物的大量减少,
because vegetation doesn't grow as well in dry soil, right?
因为植物在干燥的土壤里无法很好的生长。
And then, less vegetation means the soil can't hold water as well, the soil loses its ability to retain water when it does rain.
后来,植物太少也导致了土壤无法保留住水分,土壤也失去了在下雨时保持住水分的能力。
So then you have less moisture to help clouds form, nothing to evaporate for cloud formation.
所以,后来湿度不够也难以形成云层,因为没有可以蒸发的能形成云层的东西。
And then the cycle continues, less rain, drier soil, less vegetation, fewer clouds, less rain etc. etc..
然后形成了这样的循环,雨水少,土地变干燥,植物变少,云层减少,下雨就更少,如此循环往复。
Student:But, what about the people who made the rock paintings?
学生:但是,那些在岩石上绘画的人呢?
Professor:Good question.
教授:这个问题提得好。
No one really knows.
没有人真正知晓。
But there might be some connections to ancient Egypt.
但是也许与古埃及有点联系,
At about the same time that the Sahara was becoming a desert…
与撒哈拉变成沙漠在同一时期。
Student:Uh-huh
学生:哦。
Professor:5,000 years ago, Egypt really began to flourish out in the Nile River valley.
教授:五千年前,埃及在尼罗河山谷真正开始兴旺繁荣。
And that's not that far away.
那离得并不远。
So it's only logical to hypothesize that a lot of these people migrated to the Nile valley when they realized that this was more than a temporary drought.
当很多人意识到这不仅仅是暂时性的干旱的时候,他们就迁移到了尼罗河山谷,这种假设也符合逻辑。
And some people take this a step further.
有些人对这点做了进一步的研究,
And that's okay, that's science and they hypothesize that this migration actually provided an important impetus in the development of ancient Egypt.
科学上假设这次的迁移实际上在古埃及的发展中提供了一个重要的动力。
Well, we'll stay tuned on that.
好的,我们会继续研究的。

重点单词   查看全部解释    
planet ['plænit]

想一想再看

n. 行星

 
retain [ri'tein]

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vt. 保持,保留; 记住

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migration [mai'greiʃən]

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n. 移民,移往,移动

 
flourish ['flʌriʃ]

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vi. 繁荣,茂盛,活跃,手舞足蹈
vt. 挥

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formation [fɔ:'meiʃən]

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n. 构造,编队,形成,队形,[地]地层

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evaporate [i'væpəreit]

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v. 蒸发,失去水分,消失

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pollen ['pɔlin]

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n. [植]花粉,[昆]粉面(双翅目昆虫的易落粉) vt

 
temporary ['tempərəri]

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adj. 暂时的,临时的
n. 临时工

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drought [draut]

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n. 干旱

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logical ['lɔdʒikəl]

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adj. 符合逻辑的,逻辑上的,有推理能力的

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