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 bed was flat. Sir James Clark Ross had obtained

5 a sounding of over 2,400 fathoms in 1839, but it was not until 1869, when H. M. S. Porcupine was put at the disposal of the Royal Society for several cruises, that a series 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 worthy of the most qualified physicists and geologists. A burst of activity associated with the laying of submarine cables soon confirmed the Challenger's 10 observation that many parts of the ocean were two to three 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 drawn 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

15 superimposed upon, it the continents, together with the islands and other features of the oceans. The continents form rugged tablelands which stand nearly three miles above the floor of the open ocean. From the shore line, out to a distance which may be anywhere from a few miles to a few hundred miles, runs the gentle slope of the continental shelf, geologically part of the continents. The real dividing line between continents and oceans occurs at the foot of a steeper slope.

This continental slope usually starts at a place somewhere near the 100 -fathom 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 vertical, cliffs, and gentle sediment-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 eroded from the continental masses.

T. F. GASKELL Exploring the Sea-floor from Science Survey

New words and expressions 生词和短语

navigation (1.2)/ˌnævɪ'ɡeɪʃən/n. 航海

sounding (1.5) $/$ ’saʊndɪŋ $/n$ . 水深度

fathom (1.5)/'fæðәm/n. 噚(1 噚 等于 1.8 米)

porcupine (1.5) /'pɔːkjʊpaɪn/ $n$ . 箭猪

dredge (1.7)/dredz/v. 挖掘

expedition (1.8) / ekspɪ'dɪʃən/n. 远征

physicist (1.8) /’fizisist/ $n$ . 物理学家

magnitude (1.11) $/n$ ægnɪtjuːd $/n$ . 很多

topography (1.13) /to PDGrafi/ $n$ . 地形

crust (1.14) $/\mathrm\Lambda$ st/ $n$ . 地壳

rugged (1.16) $/$ ’rʌgɪd/ adj. 崎岖不平的

tableland (1.16) /’terbal-lænd/ $n$ . 高地

sediment (1.22) /’sedɪmənt/ $n$ . 沉淀物

terrace (1.22) $/$ ter $\ni r$ la 阶地

erode (1.24) $/{I}^{\prime }r = 0\mathrm{;d}/v$ . 侵蚀 Unit 4 Lesson 30

H. M. S. Challenger at St. Paul's Rocks near the Equator

Notes on the text 课文注释

1 be confined to, 仅限于 ……。

2 shallow water, 浅水区。

3 open sea, 无边际的大海。

4 gave more than a passing thought to, 稍微想过。

5 H. M. S. 是 Her Majesty's Ship(英国船舰)的缩略形式。

6 at the disposal of, 交由 …… 支配。

7 a relief map, 地形图。

8 with, superimposed upon it, the continents, together with the islands and other features of the oceans. 这是 with 引导的一个过去分词独立主格结构。因逻辑主语太长, 所以使用了倒装语序。superimposed upon it 是逻辑谓语部分。

9 continental shelf, 大陆架。

${10}\mathrm{l}$ in ${30},1/{30}$ 。

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个海水深度, 同时通过挖掘海底, 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, 而且我们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坡脚下。 Unit 4 Lesson 30

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。

Comprehension 理解

Answer these questions:

1 What does the author mean by the phrase 'the two-dimensional shape of the sea surface'? (II.1-2)

2 Which sentence in the first paragraph suggests that before the expedition of H. M. S. Challenger the sea bed was not considered as an object for serious study?

3 What lies immediately between the continental slope and the true ocean floor?

Vocabulary 词汇

Refer to the text to see how the following words have been used, then write sentences of your own using these words: hazards of navigation (1.2); dredging (1.7); submarine (1.9); considerable magnitude (1.11); relief (1.12); crust (1.14); superimposed (1.14); vertical (1.22); tailing-off (1.23); eroded (1.24).

Summary 摘要

A Drawing your information from the first two paragraphs (lines 1-19), write a list of points in note form, outlining the author's account of the study of the sea bed.

B Using this list of points, reconstruct the author's account in not more than 120 words. Your answer should be in one paragraph.

Composition 作文

Write a composition of about 300 words on the following subject:

Man has done relatively little to exploit the wealth of the sea.

You may use some or all of the ideas given below if you wish:

1 The intensive study of the sea is comparatively recent.

2 The sea as a source of power: harnessing the tides to provide electricity.

3 The sea as a source of food: distilling water from the sea; fish; plankton as a source of protein to feed growing world population; 'cultivating' the sea bed.

4 The sea as a source of wealth: obtaining minerals; oil or gas under the sea (e.g. the North Sea).

5 The setting up of permanent villages under the sea; the pioneer work of Jacques Cousteau.

Key structures 关键句型

A Supply the correct form of the verbs in parentheses. Do not refer to the passage until you have finished the exercise:

1 Our knowledge of the oceans a hundred years ago _____ (confine) to the two-dimensional shape of the sea-surface. (ll.1-2)

Unit 4 Lesson 30

2 It was not until 1869, when H. M. S. Porcupine _____ (put) at the disposal of the Royal Society f ${}^{r}$ cruises, that a series of deep soundings _____ (obtain) in the Atlantic and the first samples _____ lect) by dredging the bottom. (ll.5-7)

3 Today enough soundings are available to enable a relief map of the Atlantic _____ (draw) and something of the great variety of the sea bed's topography. (11.12-13)

B Compare these two sentences:

Instead of saying: It was only in 1869, that a series of deep soundings was obtained in the Atlantic. We can say: It was not until 1869 ... that a series of deep soundings was obtained in the Atlantic. ( Change the following sentences in the same way:

1 I only understood what had happened when I read the report in the newspaper.

2 The plane will only take off again when the engine has been checked.

3 Tom only got home at four o'clock this morning.

4 I shall return this book to the library only after I have read it.

5 He agreed to deliver the goods only after I had paid for them.

C Compare the uses of since in these two sentences:

1 Since the sea covers the greater part of the earth's surface, form of the crust of the earth. (II.13-14)

2 I have not seen him since last week.

Write two sentences illustrating these two uses of since.

Special difficulties 难点

A Study the following pairs of words and then write sentences of your own to bring out the difference

1 flat (1.4) - level

In front of the hotel is a perfectly flat sandy beach. (= smooth without hollows and bumps)

You have to adjust it so that the front is level with the back. (= horizontal and in the same place)

2 disposal (1.6) - disposition

Waste paper is one of the biggest problems in rubbish disposal.

This old house may be charming, but the disposition of the rooms is hardly ideal. (= the way they are placed)

Verity has a sweet disposition. (= nature, temperament)

3 worthy (1.8) - valuable

Nothing particularly worthy of notice occurred during the two following days.

I won't waste any more of your valuable time.

4 confirm (I.9) - assure

Overnight reports of an explosion were officially confirmed the next day.

The police assured us that everything that could be done had been done.

5 rugged (1.16) — ragged

North Cornwall has a rugged coastline, with high cliffs.

The begger slept on a pile of ragged blankets.

B Write two sentences using the phrases 'the open sea' (1.3) and 'the open air'.

C Note that the word series (1.6) is singular. Write sentences using the following word: mathematics, news, physics, billiards.

• D Write sentences using the following words and phrases: shortly after (1.7); shortly before; shortly.

E Explain the meaning of the word feature in these sentences:

1 A burst of activity soon confirmed the existence of underwater features of considerable magnitude. (II.9-11)

2 I never enjoy feature films.

3 The present world tour of the President of the United States is featured prominently in all today's newspapers.

4 I hardly recognized him when I saw him again: his features have changed with the years.

F What do you understand by the phrase: 'the slope averages about 1 in 30.' (1.21) ?

Write sentences using the following expressions:

1 in ${10};1$ in1,000. '... the slope averages about1in ${30}\ldots$ ' (1.21)

Multiple choice questions 多项选择题

Choose the correct answers to the following questions. Comprehension 理解 1 A hundred years ago, probably no one thought the deep ocean floor was _____ (a) two dimensional (b) a hazard for navigation (c) irregular (d) flat 2 The H.M.S. Challenger expedition _____ . (a) gave the study of the ocean floor scientific respectability (b) took a sounding of over 2,400 fathoms (c) was devoted to dredging the ocean (d) was devoted to laying submarine cables 3 Continents and islands are standing on _____. (a) the topography of the sea bed (b) the earth’s crust (c) the greater part of the earth's surface (d) superimposed features of the continents 4 The continental slope _____ (a) starts immediately at the seashore (b) consists entirely of steep, probably vertical cliffs (c) ends at the 100 -fathom mark (d) gradually stretches out to the sea bed

Structure 句型

5 It was only _____ 1869 that H.M.S. Porcupine obtained soundings. (ll.5-6)

(a) on (b) at (c) until (d) in

6 The sea floor became a subject _____ studying.

(a) worthy (b) worth (c) is worth (d) worths 181 Unit 4 Lesson 30

7 Submarine cables were _____ across the Atlantic. (1.9)

(a) lying (b) lain (c) laid (d) lied

8 It is _____ to regard the sea-floor as the earth's crust. (1.14)

(a) less reasonable(b)enough reasonable(c)reasonable enough(d)so reasonable

Vocabulary 词汇

9 The Royal Society was allowed the _____ of the H.M.S. Porcupine. (II.5-6)

(b) loan (c) rental (d) exploration

10 A burst of activity _____ with the laying of submarine cables ... (1.9)

(a) coupled (b) communicated (c) connected (d) reckoned

11 ... together with the islands and other _____ of the oceans. (1.15)

(a) studies (b) observations (c) characters (d) characteristics

12 ... after being _____ from the continental masses. (ll.23-24)

(a) worn down (b) worn through (c) worn away (d) worn out