首页
登录
职称英语
Volcanoes Geologists have been stud
Volcanoes Geologists have been stud
游客
2023-11-21
45
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 1’F. for each 50 feet. At this rate the temperature 40 miles below the earth’s surface would be over 4,000’F. 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] If the temperature at the earth’s surface is twenty degrees Fahrenheit, the temperature in a coal mine 500 feet below the surface would, in degrees, be ______.
选项
A、50
B、40
C、30
D、120
答案
C
解析
参见第二段第一、二句。500英尺的垂直落差会带来10度的温差。
转载请注明原文地址:https://tihaiku.com/zcyy/3206374.html
相关试题推荐
VolcanoesGeologistshavebeenstudyingvolcano
VolcanoesGeologistshavebeenstudyingvolcano
Geologistshavebeenstudyingvolcanoesforalongtime.Thoughtheyhavel
Geologistshavebeenstudyingvolcanoesforalongtime.Thoughtheyhavel
Ofthethousandsofknownvolcanoesintheworld,the______majorityareinacti
Ofthethousandsofknownvolcanoesintheworld,the______majorityareinacti
VolcanoesGeologistshavebeenstud
VolcanoesGeologistshavebeenstud
Therearethreetypesofvolcanoes;activevolcanoes,dormantvolcanoesand____
Ofthethousandsofknownvolcanoesintheworld,the______majorityareinacti
随机试题
DreamakerTheprofessionalsthatmakeyournightscomfortableTheDreamakerPlus
[originaltext]Whereisthebusstation?(A)OnLincolnStreet.(B)Didyoustayl
Askindergartenspreparetosendoutacceptancelettersthisweek,competiti
皮亚杰的游戏理论一认知动力说认为游戏中主要是()A.同化 B.顺应 C.适
品牌形象的建立和形成是一个不懈努力的过程并且要具备一定条件,下面不属于其需具备的
朱某,男,62岁,患鼓胀病多年,现腹大胀满,或见青筋暴露,面色晦滞,唇紫,口干而
煅法可使质地坚硬的矿物、化石类药物达到质地酥脆,其主要原因是A.产生了新成分
银行承兑汇票的承兑银行,应当按照票面金额向出票人收取()的手续费。A:千分之一
在没有超额需求的情况下,生产资料价格和工资上涨过快导致的价格总水平上升,属于(
工程监理投标工作包括:①购买招标文件;②进行投标决策;③编制投标文件;④递送投标
最新回复
(
0
)