新东方背诵文选 L36.Plate Tectonics and Sea-floor Spreading
时间：2018-12-01 作者：英语课 分类：新东方背诵文选
英语课
The theory of plate tectonics describes the motions of the lithosphere 1, the comparatively rigid 2 outer layer of the Earth that includes all the crust and part of the underlying 3 mantle 4. The lithosphere(n.[地]岩石圈)is divided into a few dozen plates of various sizes and shapes, in general the plates are in motion with respect to one another. A mid-ocean ridge 5 is a boundary between plates where new lithospheric 6 material is injected from below. As the plates diverge 7 from a mid-ocean ridge they slide on a more yielding layer at the base of the lithosphere.
Since the size of the Earth is essentially 8 constant, new lithosphere can be created at the mid-ocean ridges 9 only if an equal amount of lithospheric material is consumed elsewhere. The site of this destruction is another kind of plate boundary: a subduction zone. There one plate dives under the edge of another and is reincorporated into the mantle. Both kinds of plate boundary are associated with fault systems, earthquakes and volcanism, but the kinds of geologic 10 activity observed at the two boundaries are quite different.
The idea of sea-floor spreading actually preceded the theory of plate tectonics. In its original version, in the early 1960's, it described the creation and destruction of the ocean floor, but it did not specify 11 rigid lithospheric plates. The hypothesis was substantiated 12 soon afterward 13 by the discovery that periodic reversals of the Earth's magnetic field are recorded in the oceanic crust. As magma rises under the mid-ocean ridge, ferromagnetic 14 minerals in the magma become magnetized in the direction of the magma become magnetized in the direction of the geomagnetic field. When the magma cools and solidifies 15, the direction and the polarity of the field are preserved in the magnetized volcanic 16 rock. Reversals of the field give rise to a series of magnetic stripes running parallel to the axis 17 of the rift 18. The oceanic crust thus serves as a magnetic tape recording 19 of the history of the geomagnetic field that can be dated independently; the width of the stripes indicates the rate of the sea-floor spreading.
1 lithosphere
n.陆界，岩石圈
- The hydrosphere and the lithosphere together form the Earth's surface.水圈与岩石圈一起形成地球的表面。
- They slide on a more yielding layer at the base of lithosphere.它们在岩石圈底部更柔软的一层滑动。
2 rigid
adj.严格的，死板的；刚硬的，僵硬的
- She became as rigid as adamant.她变得如顽石般的固执。
- The examination was so rigid that nearly all aspirants were ruled out.考试很严，几乎所有的考生都被淘汰了。
3 underlying
adj.在下面的，含蓄的，潜在的
- The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
- This word has its underlying meaning.这个单词有它潜在的含义。
4 mantle
n.斗篷，覆罩之物，罩子；v.罩住，覆盖，脸红
- The earth had donned her mantle of brightest green.大地披上了苍翠欲滴的绿色斗篷。
- The mountain was covered with a mantle of snow.山上覆盖着一层雪。
5 ridge
n.山脊；鼻梁；分水岭
- We clambered up the hillside to the ridge above.我们沿着山坡费力地爬上了山脊。
- The infantry were advancing to attack the ridge.步兵部队正在向前挺进攻打山脊。
6 lithospheric
adj.岩石圈的
- The existence and movement of large lithospheric plates seems well established. 巨大岩石圈板块的存在与位移似乎已完全确定了。 来自辞典例句
- In the case of sufficiently young chasmic basins high heat flows are due to lithospheric cooling. 这种相当年轻的裂陷盆地的高热流是由岩石圈冷却所引起的。 来自辞典例句
7 diverge
v.分叉，分歧，离题，使...岔开，使转向
- This is where our opinions diverge from each other.这就是我们意见产生分歧之处。
- Don't diverge in your speech.发言不要离题。
8 essentially
adv.本质上，实质上，基本上
- Really great men are essentially modest.真正的伟人大都很谦虚。
- She is an essentially selfish person.她本质上是个自私自利的人。
9 ridges
n.脊( ridge的名词复数 )；山脊；脊状突起；大气层的)高压脊
- The path winds along mountain ridges. 峰回路转。
- Perhaps that was the deepest truth in Ridges's nature. 在里奇斯的思想上，这大概可以算是天经地义第一条了。
10 geologic
adj.地质的
- The Red Sea is a geologic continuation of the valley.红海就是一个峡谷在地质上的继续发展。
- Delineation of channels is the first step of geologic evaluation.勾划河道的轮廓是地质解译的第一步。
11 specify
vt.指定，详细说明
- We should specify a time and a place for the meeting.我们应指定会议的时间和地点。
- Please specify what you will do.请你详述一下你将做什么。
12 substantiated
v.用事实支持（某主张、说法等），证明，证实( substantiate的过去式和过去分词 )
- The results of the tests substantiated his claims. 这些检验的结果证实了他的说法。
- The statement has never been substantiated. 这一陈述从未得到证实。 来自《现代汉英综合大词典》
13 afterward
adv.后来；以后
- Let's go to the theatre first and eat afterward. 让我们先去看戏，然后吃饭。
- Afterward,the boy became a very famous artist.后来，这男孩成为一个很有名的艺术家。
14 ferromagnetic
adj.铁磁的, 铁磁体
- Materials which have magnetic properties similar to iron are ferromagnetic.具有类似于铁那样的磁性的材料就是铁磁物质。
- It is sometimes difficult to draw the line separating ferromagnetic from paramagnetic substances.严格区别铁磁性与顺磁性物质有时是很困难的。
15 solidifies
（使）成为固体，（使）变硬，（使）变得坚固( solidify的第三人称单数 )； 使团结一致； 充实，巩固； 具体化
- Jelly solidifies as it gets cold. 肉冻冷却就凝固。
- It is stirred with 10%sodium carbonate solution(50ml)and then with water (50ml), after which It'solidifies. 与10％碳酸钠溶液（50毫升）混合搅拌，然后再用50毫升水混合搅拌，从而析出固体。
16 volcanic
adj.火山的；象火山的；由火山引起的
- There have been several volcanic eruptions this year.今年火山爆发了好几次。
- Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。
17 axis
n.轴，轴线，中心线；坐标轴，基准线
- The earth's axis is the line between the North and South Poles.地轴是南北极之间的线。
- The axis of a circle is its diameter.圆的轴线是其直径。