首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Geologists have been studying volcanoes for a long time. Though they have learned a great deal, they still have not discovered t
Geologists have been studying volcanoes for a long time. Though they have learned a great deal, they still have not discovered t
admin
2012-07-17
52
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 (镭), uranium (铀), thorium (钍), and other radioactive elements. These give out 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 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 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 (地壳) 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 (煤灰,余烬). 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 (熔岩,火山岩). In this way, volcanic ash, cinders, and lava build up the cone-shaped (圆锥形的) mountains that we call volcanoes.
The general idea of the last paragraph of this passage is______.
选项
A、heat at earth’s core
B、causes of volcanoes
C、roles of pressure
D、formation of volcanoes at earth’s surface
答案
D
解析
本题是一道段落大意类问题。问本文最后一段的主题是什么。仔细阅读一下最后一段内容,地球岩石内部这种气体的突然膨胀会导致爆炸,从而使熔岩以不同大小的体积喷涌到空中。在空中熔岩遇冷变成火山灰和火山渣,这些物质有些落回到地面的岩洞周围,熔岩也许会以岩浆的形式继续涌出。这样,火山灰、火山渣和岩浆形成了我们称之为火山的锥形山峰。因此,本题的正确答案应是D“地球表面火山的形成”。
转载请注明原文地址:https://kaotiyun.com/show/ZEXO777K
0
在职攻硕英语联考
相关试题推荐
DuringMcDonald’searlyyearsFrenchfriesweremadefromscratcheveryday.RussetBurbankpotatoeswere【C1】______,cutintosh
DuringMcDonald’searlyyearsFrenchfriesweremadefromscratcheveryday.RussetBurbankpotatoeswere【C1】______,cutintosh
DuringMcDonald’searlyyearsFrenchfriesweremadefromscratcheveryday.RussetBurbankpotatoeswere【C1】______,cutintosh
DuringMcDonald’searlyyearsFrenchfriesweremadefromscratcheveryday.RussetBurbankpotatoeswere【C1】______,cutintosh
I’venever______thetheorythatpeoplearemoreimportantthananimals.
TheJapanesedesireformarriagehadbeenverystrong.Inthefifth""worldyouthattitudesurvey""【C1】______bytheManagementa
Cultureisactivityofthought,andreceptivenesstobeautyandhumanefeeling.【C1】______ofinformationhavenothingtodowith
Cultureisactivityofthought,andreceptivenesstobeautyandhumanefeeling.【C1】______ofinformationhavenothingtodowith
Everynightshelistenedtoherfathergoingaroundthehouse,lockingthedoorsandwindows.Shelistened;thebackdoorclosed
Therearesomeverybeautifully______glasswindowsinthechurch.
随机试题
夜间运行的管线通常处于储气状态,某管段长为5km,管线规格为∮608×8的输气管线运行中的最低平均压力为0.8MPa,管内气体温度为25℃,忽略天然气压缩,若储气量为11071m3,求该管段运行的最高平均压力。
消费者要购买一张飞机票,但选择哪个航班,则需要到网上比较航班时间、价格等要素才能确定。这种购买行为属于
有关温抗体型自身免疫性溶血性贫血的论述,正确的是
A.CEAB.AFPC.PSAD.CA153E.CA125与卵巢癌有关的是
下列不属于细菌生理生化分类标记的是
A、酒炒品B、炒焦品C、姜制品D、制霜品E、煨制品木香应付
喷淋式蛇管换热器与沉浸式蛇管换热器相比,所具有的优点有()。
下列不属于选择项目敏感性分析中影响因素的是()。
人民防空工程的防烟楼梯间的机械加压送风量不应小于()。
查询第一作者为“张三”的所有书名及出版社,正确的SQL语句是
最新回复
(
0
)