征服六級講座聽力：講座篇之Lecture 1 冰川運動

我們將主要體會各個學科的講座特點，我們要達到的目標是：

 1. 瞭解講座中常用的專業術語。

 2. 熟悉講座的基本結構和語言特點。

3. 體會講座聽力中的高頻考點。

 4. 熟悉講座聽力考試中常見提問方式。

Word tips

glacier  n. 冰川

crystallize  v. 結晶

basal  n. 基地，基部

bedrock  n. 岩牀

lubricant  n. 潤滑劑

friction  n. 摩擦

deformation   n. 變形        

distorted  n. 扭曲的，變形的

ooze  v. 緩慢滲出        

realign  v. 重新排列

downhill    adv. 向下

surge  n. 激增，涌動

Listen to the following recording and answer Questions 1-4.

1) A. explanations of how glaciers move

B. landscape changes caused by glacial movement

C. climate changes that influence glacial movement

D. causes of glacial formation

2) A. the thickness of glacial ice

B. the slipping or sliding of a glacier across bedrock

C. the amount of water beneath the glacial ice

D. the temperature of the glacial ice

3) A. to explain the process of deformation

B. to provide the background information

C. to give a brief description of glacier formation

D. to draw the students’ attention

4) A. It affects the amount of glacial ice that forms.

B. Sometimes it is fast enough to be noticed

C. It is reduced by cracks in the ice.

D. It is unusually high in colder regions.

聽力原文

 Last time, we started to talk about glaciers and how these masses of ice form from crystallized snow, and some of you were amazed at how huge some of these glaciers are. Now, even though it may be difficult to understand how a huge mass of ice can move or flow, it's another word for it, it's really no secret that the glaciers flow because of gravity. But how they flow, the way they flow, needs some explaining.

        Now, the first type of glacier flow is called: basal slip. Basal slip or sliding as it's often called, basically refers to the slipping or sliding of a glacier across bedrock, actually across a thin layer of water on top of the bedrock. So, this process shouldn't be too hard to imagine. What happens is that the ice at the base of the glacier is under a great deal of pressure -- the pressure coming from the weight of the overlying ice. And you probably know that under pressure, the melting temperature of water, of the ice I mean, is reduced. So, ice at the base of the glacier melts, even though it's below zero degree Celsius. And this results in a thin layer of water between the glacier and the ground. This layer of water reduces friction is...is like a lubricant. And it allows the glacier to slide or slip over the bedrock. OK?

         Now the next type of movement we will talk about is called: deformation. You've already known that ice is brittle, if you hit it with a hammer, it will shatter like glass. But ice is also plastic, it can change shape without breaking. If you leave, for example, a bar of ice supported only at one end, the end, the unsupported end will deform under its own weight, it'll kind of flatten out at one end, get distorted, deformed. Think of deformation as a very slow oozing. Depending on the stresses on the glacier, the ice crystal within it reorganize. And during this re-organization the ice crystals realign in a way that allows them to slide pass each other. And so the glacier oozes downhill without any ice actually melting.

        Now, as you probably know, glaciers generally move really slowly. But sometimes, they experience surges, and during these surges, in some places, they can move at speeds as high as 7000 meters per year. Now, speeds like that are pretty unusual, hundreds of times faster than the regular movement of glaciers, but you can actually see glacier move during these surges, though it is rare.

Questions:

1. What is the lecture mainly about?

2. According to the professor, what is basal slip? 

3. Why did the professor give the example of “a bar of ice supported only at one end”?

4. What does the professor say about the speed of glaciers?

參考譯文：

   上次我們談論了冰川，以及大型的冰川如何從結晶雪形成而來，很多學生都爲一些冰川之大感到驚訝。現在，即便了解大型冰川如何移動或漂浮這個現象有些困難，但這已經不再是一個祕密，冰川其實是靠地心力來漂浮的。但是冰川怎樣浮動，爲什麼會浮動卻仍然需要解釋一下。

  那麼，第一種冰川漂移叫做基面滑移。基面滑移，或者也被稱作底部滑動，其實就是指冰川在基岩上的滑動，細緻來講應該是在基岩頂上的一層水上滑動的現象。因此這個過程應該就不難理解了。實際上就是冰川底部的冰塊承受來自上方冰塊重量的巨大壓力。那麼你們可能知道，冰塊在壓力下融化溫度就會降低。所以說，冰川底部的冰塊就會融化，即便它的溫度還是在零度以下。這就是地面和冰川之間那層薄薄的水存在的原因。這層水能減少摩擦，就像…就像潤滑劑一樣。這就給冰川在基岩上滑動創造了條件。

   好了，下面一種滑動我們稱之爲變形。大家都知道冰塊易碎，倘若你拿錘子敲擊，它會立即如玻璃一樣碎裂。但是冰同樣也有可塑性，你無需打碎它也能重新塑形。比如，如果你放置一塊只有一面有支撐的冰，那麼未被支撐的這邊冰在重力下將會重新塑形，通過扭曲變形，使冰塊變得平穩。變形是一種緩慢的過程，取決於冰川的壓力，冰晶需要重新組織構架。在此期間，冰晶會在允許它們相互移動的情況下重新聯合在一起。因此冰川往下坡移動時是沒有冰塊融化的。

   現在，你們也許已經知道了，冰川一般移動起來很慢。但是有時候，它們也會移動很快，有些地方的冰川移動速度甚至可以達到每年7000米。那麼這種速度往往是不尋常的，是一般冰川移動速度的數百倍快，在這樣的速度下，你還可以看見冰川的移動，儘管並不常見。

參考答案：

1. A    2. B    3. A    4. B