火山爆发前会变安静
文章来源:未知 文章作者:enread 发布时间:2016-06-27 08:33 字体: [ ]  进入论坛
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When dormant1 volcanoes are about to erupt, they show some predictive characteristics--seismic2 activity beneath the volcano starts to increase, gas escapes through the vent3, or the surrounding ground starts to deform4. However, until now, there has not been a way to forecast eruptions5 of more restless volcanoes because of the constant seismic activity and gas and steam emissions7. Carnegie volcanologist Diana Roman, working with a team of scientists from Penn State, Oxford8 University, the University of Iceland, and INETER* has shown that periods of seismic quiet occur immediately before eruptions and can thus be used to forecast an impending9 eruption6 for restless volcanoes. The duration of the silence can indicate the level of energy that will be released when eruption occurs. Longer quiet periods mean a bigger bang. The research is published in Earth and Planetary Science Letters. The team monitored a sequence of eruptions at the Telica Volcano in Nicaragua in 2011. It is a so-called stratovolcano, with a classic-looking cone10 built up by many layers of lava11 and ash. They started monitoring Telica in 2009 with various instruments and by 2011 they had a comprehensive network within 2.5 miles (4 kilometers) of the volcano's summit. 
 
The 2011 eruptive event was a month-long series of small to moderate ash explosions. Prior to the eruption, there was a lack of deep seismicity or deformation12, and small changes in sulfur13 dioxide gas emissions, indicating that the eruption was not driven by fresh magma. Instead, the eruption likely resulted from the vents14 being sealed off so that gas could not escape. This resulted in an increase in the pressure that eventually caused the explosions.
 
Of the 50 explosions that occurred, 35 had preceding quiet periods lasting15 30 minutes or longer. Thirteen explosions were preceded by quiet intervals16 of at least five minutes. Only two of the 50 did not have any quiet period preceding the explosion. 
 
"It is the proverbial calm before the storm," remarked Roman. "The icing on the cake is that we could also use these quiet periods to forecast the amount of energy released."


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1 dormant d8uyk     
adj.暂停活动的;休眠的;潜伏的
参考例句:
  • Many animals are in a dormant state during winter.在冬天许多动物都处于睡眠状态。
  • This dormant volcano suddenly fired up.这座休眠火山突然爆发了。
2 seismic SskyM     
a.地震的,地震强度的
参考例句:
  • Earthquakes produce two types of seismic waves.地震产生两种地震波。
  • The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。
3 vent yiPwE     
n.通风口,排放口;开衩;vt.表达,发泄
参考例句:
  • He gave vent to his anger by swearing loudly.他高声咒骂以发泄他的愤怒。
  • When the vent became plugged,the engine would stop.当通风口被堵塞时,发动机就会停转。
4 deform L9Byo     
vt.损坏…的形状;使变形,使变丑;vi.变形
参考例句:
  • Shoes that are too tight deform the feet.(穿)太紧的鞋子会使脚变形。
  • Ice crystals begin to deform measurably.冰晶就产生某种程度的变形了。
5 eruptions ca60b8eba3620efa5cdd7044f6dd0b66     
n.喷发,爆发( eruption的名词复数 )
参考例句:
  • There have been several volcanic eruptions this year. 今年火山爆发了好几次。 来自《简明英汉词典》
  • Over 200 people have been killed by volcanic eruptions. 火山喷发已导致200多人丧生。 来自辞典例句
6 eruption UomxV     
n.火山爆发;(战争等)爆发;(疾病等)发作
参考例句:
  • The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
  • The eruption of a volcano is spontaneous.火山的爆发是自发的。
7 emissions 1a87f8769eb755734e056efecb5e2da9     
排放物( emission的名词复数 ); 散发物(尤指气体)
参考例句:
  • Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
  • Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。
8 Oxford Wmmz0a     
n.牛津(英国城市)
参考例句:
  • At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
  • This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。
9 impending 3qHzdb     
a.imminent, about to come or happen
参考例句:
  • Against a background of impending famine, heavy fighting took place. 即将发生饥荒之时,严重的战乱爆发了。
  • The king convoke parliament to cope with the impending danger. 国王召开国会以应付迫近眉睫的危险。
10 cone lYJyi     
n.圆锥体,圆锥形东西,球果
参考例句:
  • Saw-dust piled up in a great cone.锯屑堆积如山。
  • The police have sectioned off part of the road with traffic cone.警察用锥形路标把部分路面分隔开来。
11 lava v9Zz5     
n.熔岩,火山岩
参考例句:
  • The lava flowed down the sides of the volcano.熔岩沿火山坡面涌流而下。
  • His anger spilled out like lava.他的愤怒像火山爆发似的迸发出来。
12 deformation 59ryp     
n.形状损坏;变形;畸形
参考例句:
  • The deformation frequencies are not sufficiently distinctive.其变形频率不是十分明显的。
  • The calculated deformation is almost equal to the real situation by measurement.经检测,计算变形量与实际情况基本一致。
13 sulfur ps4wC     
n.硫,硫磺(=sulphur)
参考例句:
  • Sulfur emissions from steel mills become acid rain.炼钢厂排放出的硫形成了酸雨。
  • Burning may produce sulfur oxides.燃烧可能会产生硫氧化物。
14 vents 3fd48768f3da3e458d6b73926735d618     
(气体、液体等进出的)孔、口( vent的名词复数 ); (鸟、鱼、爬行动物或小哺乳动物的)肛门; 大衣等的)衩口; 开衩
参考例句:
  • He always vents his anger on the dog. 他总是拿狗出气。
  • The Dandelion Patch is the least developed of the four active vents. “蒲公英区”在这四个活裂口中是发育最差的一个。
15 lasting IpCz02     
adj.永久的,永恒的;vbl.持续,维持
参考例句:
  • The lasting war debased the value of the dollar.持久的战争使美元贬值。
  • We hope for a lasting settlement of all these troubles.我们希望这些纠纷能获得永久的解决。
16 intervals f46c9d8b430e8c86dea610ec56b7cbef     
n.[军事]间隔( interval的名词复数 );间隔时间;[数学]区间;(戏剧、电影或音乐会的)幕间休息
参考例句:
  • The forecast said there would be sunny intervals and showers. 预报间晴,有阵雨。
  • Meetings take place at fortnightly intervals. 每两周开一次会。
TAG标签: period eruption volcanoes
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