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
28
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
[audioFiles]audio_ehbm_j04001(20082)[/audioFiles]A、Pleasedtomeetyou.B、That
职位position;post;jobvacancy/opening
对于具有良好润滑、防尘的闭式硬齿轮传动,正常工作时,最有可能出现的失效形式是(
羟丙甲纤维素()。A:溶蚀性骨架材料 B:亲水凝腋型骨架材料 C:不溶性骨
在下列选项中,属于创造性思维特征的有()。A.分散思维与聚合思维有机结合
引起类白血病反应的最常见病因是A:严重感染B:创伤C:溶血性贫血D:过敏
企业及时识别、系统分析经营活动中与实现内部控制目标相关的风险,合理确定应对策略是
为及时更新房源信息,房地产经纪人需要不断与委托人联系,这表明房源具有( )的特
当采用环形网络供电时,环形网络应由2回直流电源供电,直流电源应经隔离电器接人,正
生态足迹法中将地球表面的生态生产性土地划分的六类分别是什么?
最新回复
(
0
)