首页
登录
职称英语
Geologists have been studying volcanoes for a long time. Though they have l
Geologists have been studying volcanoes for a long time. Though they have l
游客
2023-11-23
15
管理
问题
Geologists have been studying volcanoes for a long time. Though they have learned a great deal, they still have not discovered the causes of volcanic action. They know that the inside of the earth is very hot, but they are not sure exactly what causes the great heat. Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers. Or the heat may be left from the time when the earth was formed. During the last sixty years scientists have learned about radium, uranium, thorium and other radioactive elements. These give ont heat all the time as they change into other elements. Many scientists now believe that much of the heat inside the earth is produced by radioactive element.
Whatever the cause of the heat may be, we do know that the earth get hotter the farther down we dig. In deep mines and oil wells the temperature rises about 1 for each 50 feet. At this rate the temperature 40 miles below the earth’s surface would be over 4,0007 This is much hotter than necessary to melt rock. However, the pressure of the reek above keeps most materials from melting at their usual melting points. Geologists believe that the rock deep in the earth may be plastic, or putty-like. In other words, the rock yields slowly to pressure but is not liquid. But if some change in the earth’s crust re leases the pressure, the rock melts. Then the hot, liquid rock can move up toward the surface.
When the melted rock works its way close to the earth crust, a volcano may be formed. The melted rock often contains steam and other gases under great pressure. If the rock above often gives way, the pressure is released. Then the sudden expansion of the gases causes explosions. These blow the melted rock into pieces of different sizes and shoot them high in the air. Here they cool and harden into volcanic ash and cinders. Some of this material falls around the hole made in the earth’s surface. The melted rock may keep on rising and pour out as lava. In this way, volcanic ash, cinders and lava build up the cone-shaped mountains that we call volcanoes. [br] The subject of this passage is the ______.
选项
A、formulation of volcanoes
B、results of volcanic actions
C、work of geologists
D、interior of the earth
答案
A
解析
根据标题和文章内容,C、D明显不是文章所谈的主题,予以排除。B项为细节所介绍的内容,过窄,也应排除。剩下的A项为本题答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3211059.html
相关试题推荐
Hepolitelyrefrainedhimself______sayingwhathethoughtofherhat.A、against
______,hedoesgetannoyedwithhersometimes.A、AlthoughmuchhelikesherB、Mu
VolcanoesGeologistshavebeenstudyingvolcano
VolcanoesGeologistshavebeenstudyingvolcano
Althoughhethoughthewashelpingustopreparethedinner,hewasactually____
Thoughjanewasoffendedbyhersister’sruderemarks,sheonly______herlips
HealwaysthoughtofhimselfasaVIP,butheactuallyhelda_______positionin
______I’dliketo,Ican’tcome.A、MuchthoughB、ThoughmuchC、MuchasD、Asmuch
TheboyspentasmuchtimewatchingTVashe______studying.A、doesB、hadC、wasD
Thoughheviewshimselfasarealist,Michaelsaysthathisfindingsmakehimve
随机试题
IntheSenateoftheU.S.,thetermsof______ofthesenatorsexpireeverytwoy
Yearsago,doctorsoftensaidthatpainwasanormalpartoflife.Inpartic
绝大多数的突出,在突出发生前都有预兆,没有预兆的突出是极少数。突出预兆可分为有声
工程投运前1个月,运维单位应配备足够数量的()等。运维班应做好检验、入库工作,建
终身学习是教师专业发展不竭的()A.灵魂 B.动力 C.内在要求
(2016年真题)对干粉灭火系统进行周期性检查维护管理,下列检查项目中,不属于
产于云南的道地药材有A.三七 B.木香 C.重楼 D.茯苓 E.草果
流感病毒发展变化很快,小孩每年都要接种流感疫苗,但是小孩还是流感易感人群。抗病毒
工程施工合同履行过程中,建设单位迟延支付工程款,则施工单位要求建设单位承担违约责
男性68岁,发热伴咳嗽1周,表情淡漠,气急,近2天全身散在出血点及瘀斑,血压8/
最新回复
(
0
)