首页
登录
职称英语
Volcanoes Geologists have been studying volcano
Volcanoes Geologists have been studying volcano
游客
2024-11-02
28
管理
问题
Volcanoes
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 out heat all the time as the heat inside the earth is produced by radioactive elements.
Whatever the cause of the heat may be, we do know that the earth gets hotter the farther down we dig. In deep mines and oil wells the temperature rises about 1oF. for each 50 feet. At this rate the temperature 40 miles below the earth’s surface would be over 4,000oF. This is much hotter than necessary to melt rock. However, the pressure of the rock above keeps most materials from melting at their usual melting points. Geologists believe that the rock deep in the earth may be plastic, or puttylike. In other words, the rock yields slowly to pressure but is not liquid. But if some change in the earth’s crust releases 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’s crust, a volcano may be formed. The melted rock often contains steam and other gases under great pressure. If the rock above 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 the 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 cause for the heat in the interior of the earth is _____________.
选项
A、not determined
B、the great pressure of the earth
C、radioactive elements
D、the heat remaining from the formation of the earth
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3828090.html
相关试题推荐
VolcanoesGeologistshavebeenstudyingvolcano
VolcanoesGeologistshavebeenstudyingvolcano
VolcanoesGeologistshavebeenstudyingvolcano
TheboyspentasmuchtimewatchingTVashe______studying.A、doesB、hadC、wasD
Archaeologyhaslongbeenanacceptedtoolforstudyingprehistoriccultures.
Ofthethousandsofknownvolcanoesintheworld,the______majorityareinacti
Ofthethousandsofknownvolcanoesintheworld,the______majorityareinacti
Breadandbutter______myfavouritebreakfastwhenIwasstudyingintheStates
VolcanoesGeologistshavebeenstud
VolcanoesGeologistshavebeenstud
随机试题
Whenwethinkofoil,thepartoftheworldthatcomestomindfirstmaybe
[originaltext]W:Dan,didyouwanttoseeme?M:Oh,yes,Sue,pleasesitdown.
Forthispart,youareallowed30minutestowriteashortessayaboutsomet
若旅游团无领队,入住饭店的住房卡可由()分发。A.团长 B.全陪 C.地陪
下列属于商业银行向客户提供的理财顾问服务的是( )。A.销售储蓄存款产品
道德行为是衡量学生思想品德水平高低的{}。
A.活血调经,祛瘀止痛,凉血消痈,除烦安神B.活血行气,止痛,消肿生肌C.活血行
下列工作内容中,不属于变形测量物理解释的有( )。A.对基准点的稳定性进行分析
下列关于投资基金证券与股票、证券之间区别的表述中,错误的是( )。A.发行主体不
下列选项中,能够折成如图所示立方体的是: A.如上图所示 B.如上图所示
最新回复
(
0
)