首页
登录
职称英语
Volcanoes Geologists have been studying volcano
Volcanoes Geologists have been studying volcano
游客
2023-11-23
49
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] 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
转载请注明原文地址:https://tihaiku.com/zcyy/3213524.html
相关试题推荐
Congestedcitiesarefastbecomingtesttubesforscientistsstudyingthei
Congestedcitiesarefastbecomingtesttubesforscientistsstudyingthei
Congestedcitiesarefastbecomingtesttubesforscientistsstudyingthei
Congestedcitiesarefastbecomingtesttubesforscientistsstudyingthei
Congestedcitiesarefastbecomingtesttubesforscientistsstudyingthei
Studyingabroadisincreasinglypopularamongstudents,withtensofthousand
Studyingabroadisincreasinglypopularforstudents,withtensofthousands
PassageTwo(1)It’sagoldenageforstudyinginequality.ThomasPiket
PassageTwo(1)It’sagoldenageforstudyinginequality.ThomasPiket
PassageTwo(1)It’sagoldenageforstudyinginequality.ThomasPiket
随机试题
Americansocietyisnotnap-friendly.Infact,there’sevena【B1】______again
59岁妇女,孕5产4,阴道脱出一物已4年,妇查:宫颈及宫体全部脱出至阴道口外,阴
患者,女性,28岁,因1年来胸闷不适,时有黑矇现象,1周来黑矇现象增多,伴晕厥1
由于湿性黏滞,其致病可出现的症状是( )。A.小腹胀痛 B.下肢水肿 C.
县(市)、区级地方医学会负责组织A.处理医疗事故工作B.首次医疗事故技术鉴定工作
A. B. C. D.
简述幼小衔接工作的主要内容。
某银行2008年初关注类贷款余额为4000亿元,其中在2008年末转为次级类、可
《国务院关于整合城乡居民医疗保险制度的意见》要求整合城镇居民基本医疗保险和新型农
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
最新回复
(
0
)