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
42
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/3213522.html
相关试题推荐
Studyingabroadisincreasinglypopularamongstudents,withtensofthousands
PassageTwo(1)It’sagoldenageforstudyinginequality.ThomasPiket
PassageTwo(1)It’sagoldenageforstudyinginequality.ThomasPiket
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
OnFeb.2,2007,theUnitedNationsscientificpanelstudyingclimatechang
VolcanoesGeologistshavebeenstudyingvolcano
随机试题
[audioFiles]audio_etoefz_025(20051)[/audioFiles]A、She’sworriedthatthemanwi
Whichofthefollowingsentenceshasadirectobject?A、Isendyoumywarmestcon
危险温度、电火花和电弧是导致电气火灾爆炸的三大要因,电气设备或线路短路是形成危险
经测定某检测系统的测量装置的A类不确定度分别是0.1、0.1、0.2个单位,B类
下列关于建设工程索赔成立条件的说法,正确的是( )。A.导致索赔的事件必须
红颜∶娥眉∶女性A.襁褓∶垂髫∶幼儿 B.花甲∶耄耋∶老人 C.四海∶八荒∶
有些学生能根据题目的不同要求应用各种规则、原理和规律,有些学生则显得比较困难,这
证券公司操纵市场行为的根本目的是为了获取利益或减少损失。( )
(2007年)根据学生在课堂上表现出来的注意、情感、意志、定势与思维等状态水平,
关于契税的计税依据,下列说法正确的是( )。 A.土地使用权出售、房屋买卖
最新回复
(
0
)