首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The Earth comprises three principal layers: the dense, iron-rich core, the mantle made of silicate (硅酸盐) that are semi-molten at
The Earth comprises three principal layers: the dense, iron-rich core, the mantle made of silicate (硅酸盐) that are semi-molten at
admin
2016-10-07
55
问题
The Earth comprises three principal layers: the dense, iron-rich core, the mantle made of silicate (硅酸盐) that are semi-molten at depth, and the thin, solid-surface crust. There are two kinds of crust, a lower and denser oceanic crust and an upper, lighter continental crust found over only about 40 percent of the Earth’s surface. The rocks of the crust are of very different ages. Some continental rocks are over 3,000 million years old, while those of the ocean floor are less than 200 million years old. The crusts and the top, solid part of the mantle, totaling about 70 to 100 kilometers in thickness, at present appear to consist of about 15 rigid plates, 7 of which are very large. These plates move over the semi-molten lower mantle to produce all of the major topographical (地形学的) features of the Earth. Active zones where intense deformation occurs are confined to the narrow, interconnecting boundaries of contact of the plates.
There are three main types of zones of contact: spreading contacts where plates move apart, converging contacts where plates move towards each other, and transform contacts where plates slide past each other. New oceanic crust is formed along one or more margins of each plate by material issuing from deeper layers of the Earth’s crust, for example, by volcanic eruptions (爆发) of lava (火山 熔岩) at mid-ocean ridges. If at such a spreading contact the two plates support continents, a rift (裂缝 ) is formed that will gradually widen and become flooded by the sea The Atlantic Ocean formed like this as the American and Afro-European plates moved in opposite directions. When two plates carrying continents collide, the continental blocks, too light to be drawn down, continue to float and therefore buckle (起褶皱) to form a mountain chain along the length of the margin of the plates.
This passage is probably_____.
选项
A、a newspaper advertisement
B、a chapter of a novel
C、an excerpt from a textbook
D、a scientific report of new findings
答案
C
解析
主旨大意题。由本文的语言风格和描述内容可以判定这篇文章既不是商业性的,也不是文学性的,同时文中叙述的内容具有科普性质,不可能是太前沿性的,因此A、B、D三项都不正确,选项C为此题答案。
转载请注明原文地址:https://kaotiyun.com/show/EuY7777K
0
大学英语四级
相关试题推荐
A、Themanmustarriveontime.B、ThedoctoronlyhastimeonTuesdays.C、ThedoctorisnotavailableonTuesdaymorning.D、Them
Inmanycountries,authorityisseldomquestioned,eitherbecauseitishighlyrespected,orbecauseitis【B1】_______.Sometimes
Weoftenpassonlittlebitsofinformationtoourchildren,notknowingiftheyaretrue,andonlybecausetheywere【B1】_______
Americansbelievethatindividualsmustlearnto【B1】_______themselvesorrisklosingfreedom.Thismeansachievingbothfinanci
A、Earlyadoptionmakesforcloserparent-childrelationship.B、Mostpeopleprefertoadoptchildrenfromoverseas.C、Understandi
A、ThemancouldnotwaittoseeSusan.B、Susaniseagertopasstheinformationsheknows.C、Susantalkstopeopleonlyonthep
A、Theexamquestionsweretoodifficult.B、Thequestionshadlittleconnectionwiththecourse.C、Hecouldn’tfinishthequestio
A、ThedigitalTVsystemwillofferdifferentprograms.B、Heiseagertoseewhatthenewsystemislike.C、Hethinksitunrealis
Comparativelyfewfresh-waterspeciesoffishesarelimitedintheirdistributiontoasingleriversystem,yetnotmanyarefou
Somepeoplesaythetraditionalcalendarof180daysnolongermeetstheneedsofAmericansociety.Theypointoutthatstudents
随机试题
一女性,原发性不孕,进行性痛经6年。妇检见子宫后倾,固定,后壁能扪及两黄豆大小的痛性结节,左侧附伴区扪及1个直径约为3cm的囊性包块,右侧附件区组织略增厚。治疗宜选用()
男性,25岁,网球运动员,右肘关节外侧疼痛1个月,加重3天,持物无力,拧毛巾痛。体格检查:除右肘关节外侧局限性压痛外,无其他阳性体征。下列哪项试验最有助于诊断
A.Img静脉推注;每3~5分钟重复B.1~1.5mg/kg静脉推注;3~5分钟重复C.150mg静脉推注(10分钟),1mg/min维持D.15~20μg/min静脉谪注E.30mg/min静脉推注,最大总量17mg/kg异丙肾上腺素用法
缩写Ⅳ-DSA正确解释是
水俣病的发病原因是
不能用于平喘的肾上腺素受体激动药是
因某种疾病所致的死亡率,表示某年在多少人口中该病的死亡人数为
根据我国刑法的规定,下列说法正确的是?()
2021年4月1日,上海的甲公司与北京的乙公司签订了一份买卖合同,约定:甲公司向乙公司购买1000吨化工原料,总价款为200万元;乙公司在合同签订后1个月内交货,甲公司在验货后7日内付款。双方没有明确约定货物的交付地点。2021年4月2日,甲公司
企业财务管理体制的核心是()。
最新回复
(
0
)