新概念英语第四册Lesson 30 Exploring the sea-floor

Lesson 30
Exploring the sea-floor
海底勘探

First listen and then answer the following question.
听录音，然后回答以下问题。

How did people probably imagine the sea-floor before it was investigated?

Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land. The open sea was deep and mysterious, and anyone who gave more than a passing thought to the bottom confines of the oceans probably assumed that the sea bad was flat. Sir James Clark Ross had obtained a sounding of over 2,400 fathoms² in 1839, but it was not until of deep soundings was obtained in the Atlantic and the first samples were collected by dredging the bottom. Shortly after this the famous H. M. S. Challenger expedition established the study of the sea-floor as a subject worthy³ of the most qualified⁴ physicists⁶ and geologists⁷. A burst of activity associated with the laying of submarine cables soon confirmed the challenger's observation that many parts of the ocean were two to there miles deep, and the existence of underwater features of considerable magnitude.
Today, enough soundings are available to enable a relief map of the Atlantic to be drawn⁸ and we know something of the great variety of the sea bed's topography. Since the sea covers the greater part of the earth's surface, it is quite reasonable to regard the sea floor as the basic form of the crust of the earth, with, superimposed upon, it the continents, together with the islands and other features of the oceans. The continents form rugged⁹ tablelands which stand nearly three miles above the floor of the open ocean. From the shore line, out a distance which may be anywhere from a few miles to a few hundred miles, runs the gentle slope of the continental¹⁰ shelf, geologically part of the continents. The real dividing line between continents and oceans occurs at the foot a steeper slope.
This continental slope usually starts at a place somewhere near the 100-fatheom mark and in the course of a few hundred miles reaches the true ocean floor at 2,500-3,500 fathoms. The slope averages about 1 in 30. but contains steep, probably vertical¹¹, cliffs, and gentle sediment¹²-covered terraces, and near its lower reaches there is a long tailing-off which is almost certainly the result of material transported out to deep water after being eroded¹⁴ from the continental masses.
T.F.GASKELL Exploring the Sea-floor from Science Survey

New words and expressions 生词和短语
navigation
n. 航海
sounding
n. 水深度
fathom¹
n. 寻（1寻等于1.8米）
porcupine¹⁵
n. 箭猪
dredge
v. 挖掘
expedition
n. 远征
physicist⁵
n. 物理学家
magnitude
n. 很多
topography
n. 地形
crust
n. 地壳
rugged
adj.崎岖不平
tableland
n. 高地
sediment
n. 沉淀物
terrace
n. 阶地
erode¹³
v. 侵蚀

参考译文
100年前，我们只知道海洋是二维平面形的，以及靠近陆地浅水区的深浅不一能给航行带来危险。无边无际的海洋深邃而又神秘，凡是稍稍想过大海海底的人大概都会认为海底是平坦的。1839年，詹姆斯.克拉克.罗斯爵士曾测得海水深度超过2，400英寻；但直到1869年，皇家学会用英国“豪猪”号舰艇进行了几次巡航后，才在大西洋测得一个海水深度，同时能过挖掘海底，取得了研究海底的首批样品。此后不久，英国著名的“挑战者”号舰艇对海底的那次考察，把对海床的研究确立为一个值得一流物理学家和地质学家从事的研究课题，铺设海底电缆的热潮很快证实了“挑战者”号的观察结果：海洋中很多地方可深达两三英里，水下特征差异极大。
现在已有足够的水深测量数据来绘制一张大西洋洋底地形图，而且我对海底地形的千变万化也有了一定的了解。既然海洋覆盖着地球的大部分表面，因此完全有理由把海床看作地壳的基本模壳，上面附加着大陆以及岛屿和海洋的其他形态。大陆是崎岖不平的高地，高出辽阔的海洋海底近三英里。从海岸线向大海延伸几英里到几百英里的区域是大陆架慢坡，从地质学上来说，它是大陆的一部分。大陆和海洋的真正分界线是在陡破脚下。
大陆架慢坡一般是从差不多100英寻水深的地方开始的，一直延伸到几百英里远深达2，500至3，500的地方，那里才是真正的海底。坡度平均约为1/30，但其中包括陡峭的、乃至垂直的峭壁和沉积物覆盖的缓和的阶梯地带，在这个地带的低处是很长的一段尾沙地段，基本上可以断定这个地段是大陆块体上侵蚀下来的物质被水冲到深水处形成的。

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1 fathom   

v.领悟，彻底了解

参考例句：

• I really couldn't fathom what he was talking about.我真搞不懂他在说些什么。
• What these people hoped to achieve is hard to fathom.这些人希望实现些什么目标难以揣测。

2 fathoms   

英寻( fathom的名词复数 )

参考例句：

• The harbour is four fathoms deep. 港深为四英寻。
• One bait was down forty fathoms. 有个鱼饵下沉到四十英寻的深处。

3 worthy   

adj.(of)值得的，配得上的；有价值的

参考例句：

• I did not esteem him to be worthy of trust.我认为他不值得信赖。
• There occurred nothing that was worthy to be mentioned.没有值得一提的事发生。

4 qualified   

adj.合格的，有资格的，胜任的，有限制的

参考例句：

• He is qualified as a complete man of letters.他有资格当真正的文学家。
• We must note that we still lack qualified specialists.我们必须看到我们还缺乏有资质的专家。

5 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

6 physicists   

物理学家( physicist的名词复数 )

参考例句：

• For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技
• Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

7 geologists   

地质学家，地质学者( geologist的名词复数 )

参考例句：

• Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
• Geologists study the structure of the rocks. 地质学家研究岩石结构。

8 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。

9 rugged   

adj.高低不平的，粗糙的，粗壮的，强健的

参考例句：

• Football players must be rugged.足球运动员必须健壮。
• The Rocky Mountains have rugged mountains and roads.落基山脉有崇山峻岭和崎岖不平的道路。

10 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

11 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

12 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

13 erode   

v.侵蚀，腐蚀，使...减少、减弱或消失

参考例句：

• Once exposed,soil is quickly eroded by wind and rain.一旦暴露在外，土壤很快就会被风雨侵蚀。
• Competition in the financial marketplace has eroded profits.金融市场的竞争降低了利润。

14 eroded   

adj. 被侵蚀的，有蚀痕的 动词erode的过去式和过去分词形式

参考例句：

• The cliff face has been steadily eroded by the sea. 峭壁表面逐渐被海水侵蚀。
• The stream eroded a channel in the solid rock. 小溪在硬石中侵蚀成一条水道。

15 porcupine   

n.豪猪， 箭猪

参考例句：

• A porcupine is covered with prickles.箭猪身上长满了刺。
• There is a philosophy parable,call philosophy of porcupine.有一个哲学寓言，叫豪猪的哲学。