摘要：Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle

高效记单词：《新概念英语1词汇专练》

英汉双语阅读103：当年被嫌弃的气垫船，缘何成了当今的宠儿？

一、生词准备

1. tectonic [tekˈtɒnɪk] adj. 地壳构造的；建筑的

2. lithosphere [ˈlɪθəsfɪə(r)] n. 岩石圈

3. mantle [ˈmæntl] n. 地幔；披风；覆盖物

4. convection [kənˈvekʃn] n. 对流；传送

5. churning [ˈtʃɜːnɪŋ] adj. 翻腾的；搅拌的；n. 搅拌；搅乳

6. divergent [daɪˈvɜːdʒənt] adj. 分散的；有分歧的

7. plastic [ˈplæstɪk] adj. 可塑的；塑料的；n. 塑料；塑料制品

8. magma [ˈmæɡmə] n. 岩浆；糊剂

9. igneous [ˈɪɡniəs] adj. 火的；[岩] 火成的

10. ridge [rɪdʒ] n. 山脊；山脉；屋脊；v. 使成脊状；作垄

11. trench [trentʃ] n. 沟；沟渠；战壕；v. 挖沟；侵害

12. gentle [ˈdʒentl] adj. 温和的；文雅的；轻柔的；v. 使温和；使驯服

13. seafloor [ˈsiːflɔː(r)] n. 海底；海床

14. crust [krʌst] n. 地壳；外壳；面包皮；v. 结硬皮；结成外壳

15. Cocos [ˈkəʊkəʊz] n. 科科斯（岛或群岛，位于太平洋）

16. Nazca [ˈnæzkə] n. 纳斯卡（位于秘鲁南部）

17. Antarctic [ænˈtɑːktɪk] adj. 南极的；n. 南极洲；南极地区

18. consistent [kənˈsɪstənt] adj. 一致的；连续的；坚持的

19. upwelling [ˈʌpweliŋ] n. 上升流；上涌；v. 向上涌起

20. overlie [ˌəʊvəˈlaɪ] v. 覆盖；躺在…… 上面；压在…… 上面

21. density [ˈdensəti] n. 密度；浓稠度

22. continental [ˌkɒntɪˈnentl] adj. 大陆的；大陆性的；n. 欧洲大陆人

23. margin [ˈmɑːdʒɪn] n. 边缘；利润；页边空白；v. 加边于；成为…… 的边

24. subduction [səbˈdʌkʃn] n. 俯冲；减法

25. sediment [ˈsedɪmənt] n. 沉积；沉淀物

26. transitional [trænˈzɪʃənl] adj. 过渡的；转变的

27. Sinai [ˈsaɪnaɪ] n. 西奈半岛（位于埃及东北部）

28. peninsula [pɪˈnɪnsjələ] n. 半岛

29. Mediterranean [ˌmedɪtəˈreɪniən] adj. 地中海的；地中海沿岸的；n. 地中海

30. geologist [dʒiˈɒlədʒɪst] n. 地质学家

二、短文内容

Seafloor spreading is a geologic process in which tectonic plates - large slabs of Earth's lithosphere - split apart from each other. Seafloor spreading and other tectonic activity processes are the result of mantle convection. Mantle convection is the slow, churning motion of Earth’s mantle. Convection currents carry heat from the lower mantle and core to the lithosphere. Convection currents also “recycle” lithospheric materials back to the mantle.

Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks. Hot magma fueled by mantle convection bubbles up to fill these fractures and spills onto the crust. This bubbled-up magma is cooled by frigid seawater to form igneous rock. This rock (basalt) becomes a new part of Earth’s crust.

Mid-Ocean Ridges

Seafloor spreading occurs along mid-ocean ridges - large mountain ranges rising from the ocean floor. The Mid-Atlantic Ridge, for instance, separates the North American plate from the Eurasian plate, and the South American plate from the African plate.

The East Pacific Rise is a mid-ocean ridge that runs through the eastern Pacific Ocean and separates the Pacific plate from the North American plate, the Cocos plate, the Nazca plate, and the Antarctic plate.

The Southeast Indian Ridge marks where the southern Indo-Australian plate forms a divergent boundary with the Antarctic plate.

Seafloor spreading is not consistent at all mid-ocean ridges. Slowly spreading ridges are the sites of tall, narrow underwater cliffs and mountains. Rapidly spreading ridges have a much more gentle slopes. The Mid-Atlantic Ridge, for instance, is a slow spreading center. It spreads 2-5 centimeters (.8-2 inches) every year and forms an ocean trench about the size of the Grand Canyon. The East Pacific Rise, on the other hand, is a fast spreading center. It spreads about 6-16 centimeters (3-6 inches) every year. There is not an ocean trench at the East Pacific Rise, because the seafloor spreading is too rapid for one to develop!

The newest, thinnest crust on Earth is located near the center of mid-ocean ridges - the actual site of seafloor spreading. The age, density, and thickness of oceanic crust increases with distance from the mid-ocean ridge.

Geographic Features

Oceanic crust slowly moves away from mid-ocean ridges and sites of seafloor spreading. As it moves, it becomes cooler, more dense, and more thick. Eventually, older oceanic crust encounters a tectonic boundary with continental crust. In some cases, oceanic crust encounters an active plate margin. An active plate margin is an actual plate boundary, where oceanic crust and continental crust crash into each other. Active plate margins are often the site of earthquakes and volcanoes. Oceanic crust created by seafloor spreading in the East Pacific Rise, for instance, may become part of the ring of Fire, the horseshoe-shaped pattern of volcanoes and earthquake zones around the Pacific ocean basin.

In other cases, oceanic crust encounters a passive plate margin. Passive margins are not plate boundaries, but areas where a single tectonic plate transitions from oceanic lithosphere to continental lithosphere. Passive margins are not sites of faults or subduction zones. Thick layers of sediment overlay the transitional crust of a passive margin. The oceanic crust of the Mid-Atlantic Ridge, for instance, will either become part of the passive margin on the North American plate (on the east coast of North America) or the Eurasian plate (on the west coast of Europe).

New geographic features can be created through seafloor spreading. The Red Sea, for example, was created as the African plate and the Arabian plate tore away from each other. Today, only the Sinai Peninsula connects the Middle East (Asia) with North Africa. Eventually, geologists predict, seafloor spreading will completely separate the two continents - and join the Red and Mediterranean Seas.

三、短文注释

1. seafloor spreading：海底扩张，是一种地质过程，板块（地球岩石圈的巨大板块）相互分离，地幔对流导致海底地壳的形成和扩张。

2. tectonic plates：构造板块，地球岩石圈的巨大板块，它们在软流圈上移动，相互作用引发各种地质活动。

3. mantle convection：地幔对流，地球地幔的缓慢搅动运动，对流将热量从下地幔和地核带到岩石圈，并循环岩石圈物质。

4. divergent plate boundaries：离散型板块边界，板块相互远离的边界，是海底扩张发生的地方，岩浆上涌形成新地壳。

5. mid - ocean ridges：大洋中脊，从海底升起的大型山脉，是海底扩张的主要场所，如大西洋中脊、东太平洋海隆等。

6. the mid - atlantic ridge：大西洋中脊，将北美板块与欧亚板块、南美板块与非洲板块分开，是慢速扩张中心，每年扩张 2 - 5 厘米。

7. the east pacific rise：东太平洋海隆，贯穿东太平洋，将太平洋板块与北美板块、科科斯板块、纳斯卡板块和南极板块分开，是快速扩张中心，每年扩张 6 - 16 厘米。

8. the southeast Indian ridge：东南印度洋海岭，是南印度洋 - 澳大利亚板块与南极板块形成离散边界的地方。

9. slow spreading ridges：慢速扩张海岭，其特征是有高大狭窄的水下悬崖和山脉，如大西洋中脊。

10. rapidly spreading ridges：快速扩张海岭，坡度更为平缓，如东太平洋海隆，因扩张速度快没有形成海沟。

11. oceanic crust age：洋壳年龄，离大洋中脊越远，洋壳年龄越大，因为新的洋壳在大洋中脊处形成。

12. oceanic crust density：洋壳密度，随着洋壳远离大洋中脊，其温度降低，密度增大。

13. oceanic crust thickness：洋壳厚度，从大洋中脊向两侧，洋壳厚度逐渐增加。

14. active plate margins：活动板块边缘，是真正的板块边界，洋壳和陆壳在此碰撞，常是地震和火山活动的发生地。

15. ring of fire：环太平洋火山带，围绕太平洋盆地的火山和地震带，由东太平洋海隆扩张形成的洋壳可能成为其一部分。

16. passive plate margins：被动板块边缘，不是板块边界，是单一构造板块从海洋岩石圈过渡到大陆岩石圈的区域。

17. sediment overlay：沉积物覆盖，被动板块边缘有厚厚的沉积物覆盖在过渡地壳上。

18. geographic features creation：地理特征形成，海底扩张可创造新的地理特征，如红海就是板块分离形成的。

19. African plate：非洲板块，地球的一个主要板块，与阿拉伯板块分离形成了红海。

20. Arabian plate：阿拉伯板块，与非洲板块分离，其运动影响了红海和周边地区的地质构造。

21. Sinai peninsula：西奈半岛，连接中东（亚洲）和北非，随着海底扩张，未来可能会被完全分开。

22. (the) Red Sea：红海，因非洲板块和阿拉伯板块分离而形成，未来可能会进一步扩张并连接地中海。

23. (the) Mediterranean sea：地中海，与红海未来可能因海底扩张而相连，其周边地区地质活动也受板块运动影响。

24. plate separation：板块分离，海底扩张的本质是板块相互分离，导致新地壳形成和海洋面积扩大。

25. magma upwelling：岩浆上涌，在地幔对流作用下，岩浆上升填充板块分离产生的裂缝，冷却后形成新的洋壳。

26. igneous rock formation：火成岩形成，上涌的岩浆被海水冷却后形成火成岩（如玄武岩），成为新地壳的一部分。

27. ocean trench formation：海沟形成，在慢速扩张海岭，如大西洋中脊，会形成类似大峡谷大小的海沟，而快速扩张海岭不易形成。

28. tectonic activity and heat transfer：构造活动与热传递，地幔对流传递热量促使板块运动和海底扩张，是地质活动的重要动力。

29. continental crust and oceanic crust interaction：大陆地壳与海洋地壳相互作用，在活动板块边缘，两者碰撞引发地震、火山等地质现象。

30. future geological prediction：未来地质预测，地质学家预测随着海底扩张，非洲和亚洲可能完全分离，红海和地中海将相连。

【Source】www.education.nationalgeographic.org

【Translated by】Spark Liao (廖怀宝)

【Illustration】From Bing

来源：沪上英语教与学