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
Volcanoes—Earth-shattering News A)Volcanoes are the ultimate earth-moving machinery. A violent eruption can blow the top few kil
Volcanoes—Earth-shattering News A)Volcanoes are the ultimate earth-moving machinery. A violent eruption can blow the top few kil
admin
2020-06-08
49
问题
Volcanoes—Earth-shattering News
A)Volcanoes are the ultimate earth-moving machinery. A violent eruption can blow the top few kilometres off a mountain, scatter fine ash practically all over the globe and hurt rock fragments into the stratosphere to darken the skies a continent away.
B)But the classic eruption—cone-shaped mountain, big bang, mushroom cloud and surges of molten lava—is only a tiny part of a global story. Volcanism, the name given to volcanic processes, really has shaped the world. Eruptions have rifted continents, raised mountain chains, constructed islands and shaped the topography of the earth. The entire ocean floor has a basement of volcanic basalt.
C)Volcanoes have not only made the continents, they are also thought to have made the world’ s first stable atmosphere and provided all the water for the oceans, rivers and ice-caps.
D)There are now about 600 active volcanoes. Every year they add two or three cubic kilometres of rock to the continents. Imagine a similar number of volcanoes smoking away for the last 3,500 million years. That is enough rock to explain the continental crust.
E)What comes out of volcanic craters is mostly gas. More than 90% of this gas is water vapour from the deep earth: enough to explain, over 3,500 million years, the water in the oceans. The rest of the gas is nitrogen, carbon dioxide, sulphur dioxide, methane, ammonia and hydrogen. The quantity of these gases, again multiplied over 3,500 million years, is enough to explain the mass of the world’ s atmosphere. We are alive because volcanoes provided the soil, air and water we need.
F)Geologists consider the earth as having a molten core, surrounded by a semi-molten mantle and a brittle, outer skin. It helps to think of a soft-boiled egg with a runny yolk, a firm but squishy white and a hard shell. If the shell is even slightly cracked during boiling, the white material bubbles out and sets like a tiny mountain chain over the crack—like an archipelago of volcanic islands such as the Hawaiian Islands. But the earth is so much bigger and the mantle below is so much halter.
G)Even though the mantle rocks are kept solid by overlying pressure, they can still slowly "flow" like thick treacle. The flow, thought to be in the form of convection currents, is powerful enough to fracture the "eggshell" of the crust into plates, and keep them bumping and grinding against each other, or even overlapping, at the rate of a few centimetres a year. These fracture zones, where the collisions occur, are where earthquakes happen. And, very often, volcanoes.
H)These zones are lines of weakness, or hot spots. Every eruption is different, but put at its simplest, where there are weaknesses, rocks deep in the mantle, heated to 1,350°C, will start to expand and rise. As they do so, the pressure drops, and they expand and become liquid and rise more swiftly.
I)Sometimes it is slow: vast bubbles of magma—molten rock from the mantle— inch towards the surface, cooling slowly, to show through as granite extrusions(as on Skye, or the Great Whin Sill, the lava dyke squeezed out like toothpaste that carries part of Hadrian’ s Wall in northern England).
J)Sometimes—as in Northern Ireland, Wales and the Karoo in South Africa—the magma rose faster, and then flowed out horizontally on to the surface in vast thick sheets. In the Deccan plateau in western India, there are more than two million cubic kilometres of lava, some of it 2,400 metres thick, formed over 500,000 years of slurping eruption.
K)Sometimes the magma moves very swiftly indeed. It does not have time to cool as it surges upwards. The gases trapped inside the boiling rock expand suddenly, the lava glows with heat, it begins to froth, and it explodes with tremendous force. Then the slightly cooler lava following it begins to flow over the lip of the crater. It happens on Mars, it happened on the moon, it even happens on some of the moons of Jupiter and Uranus.
L)By studying the evidence, vulcanologists can read the force of the great blasts of the past. Is the pumice light and full of holes? The explosion was tremendous. Are the rocks heavy, with huge crystalline basalt shapes, like the Giant’ s Causeway in Northern Ireland? It was a slow, gentle eruption.
M)The biggest eruption are deep on the mid-ocean floor, where new lava is forcing the continents apart and widening the Atlantic by perhaps five centimetres a year. Look at maps of volcanoes, earthquakes and island chains like the Philippines and Japan, and you can see the rough outlines of what are called tectonic plates—the plates which make up the earth’s crust and mantle. The most dramatic of these is the Pacific "ring of fire" where there have the most violent explosions—Mount Pinatubo near Manila, Mount St Helen’ s in the Rockies and El Chicho n in Mexico about a decade ago, not to mention world-shaking blasts like Krakatoa in the Sunda Straits in 1883.
N)But volcanoes are not very predictable. That is because geological time is not like human time. During quiet periods, volcanoes cap themselves with their own lava by forming a powerful cone from the molten rocks slopping over the rim of the crater; later the lava cools slowly into a huge, hard, stable plug which blocks any further eruption until the pressure below becomes irresistible. In the case of Mount Pinatubo, this took 600 years.
O)Then, sometimes, with only a small warning, the mountain blows its top. It did this at Mont Pelee in Martinique at 7.49 a.m. on 8 May, 1902. Of a town of 28,000, only two people survived. In 1815, a sudden blast removed the top 1,280 metres of Mount Tambora in Indonesia. The eruption was so fierce that dust thrown into the stratosphere darkened the skies, canceling the following summer in Europe and North America. Thousands starved as the harvest failed, after snow in June and frosts in August. Volcanoes are potentially world news, especially the quiet ones.
Volcanic eruptions have split continents, lifted mountain chains, formed islands, and finally determined the topographic shape of the earth.
选项
答案
B
解析
本题意为火山爆发分裂大陆,抬高山脉,形成岛屿,最终决定地表的形状。题干中的“continents”,“mountain chains”,“islands”为关键词,锁定B段Eruptions have rifted continents,raised mountain chains,constructed islands and shapedthe topography of the earth.“火山喷发撕裂大陆,抬高山脉,构筑岛屿,最终造就了整个地球的形状。”题干中“split”,“lifted”,“formed”分别对应原文中“rifted”,“raised”,“constructed”。
转载请注明原文地址:https://kaotiyun.com/show/6LP7777K
0
大学英语六级
相关试题推荐
A、Toshowtherelationshipbetweenfearfulnessandenvironment.B、Togiveexamplesofanimalsthattheyaren’tfearful.C、Toco
A、Improvementsofchildren’sachievementsinschoolcanbemade.B、Children’sheathcanbeimproved.C、Theschoolneedstocare
A、Therightsofprivatebusinessownersshouldbeprotected.B、Thegovernmentshouldn’tinterfereinprivatebusiness.C、Politic
NewDiscoveriesofPublicTransportA)AnewstudyconductedfortheWorldBankbyMurdochUniversity’sInstituteforSciencean
A、WhyAmericanindustriesgrewrapidlyinthenineteenthcentury.B、HowadvancesintransportationhelpedAmericancitiesdevelo
Imaginingbeingaskedtospendtwelveorsoyearsofyourlifeinasocietywhichconsistedonlyofmembersofownsex,howwoul
A、Ignoringthesignsandsymptomsofaging.B、Adoptinganoptimisticattitudetowardslife.C、Endeavoringtogiveupunhealthyl
Drought,tsunami,violentcrime,financialmeltdown—theworldisfullofrisks.Thepoorareoftenmost【C1】______totheireffect
WhyIndiaIsPoorandCorruptWhileJapanIsRichandCleanA)IntheFarEast,Malaysia,Singapore,Korea,Taiwan,HongKong,an
随机试题
下列因素哪项与原发性肝癌无密切关系
决定CT机连续工作时间长短的最关键指标是
细菌性肝脓肿最主要的原因是
案情:2007年2月,甲乙丙丁戊五人共同出资设立北陵贸易有限责任公司(简称北陵公司)。公司章程规定:公司注册资本500万元:持股比例各20%;甲、乙各以100万元现金出资,丙以私有房屋出资,丁以专利权出资,戊以设备出资,各折价100万元;甲任董事长兼总经理
钢筋与钢板作丁字形焊接,宜采用()。
演播室灯光施工中调光系统的调试的最后一步是打开所有负载的()%并保持1.5~2h,检测电源电压的波动情况,电力电缆的电流和温度,空气开关的表面温度,调光柜的运行情况及散热系统,直至调光系统所有设备全部正常工作。
已取得或受聘高级会计专业技术资格(职称)及具备相当水平的会计人员无须接受会计人员继续教育。()
按照投资的风险分散理论,以等量资金投资于A、B两项目( )。
一个研究报道说,一种特殊的教育计划增加了研究对象为3岁到5岁的孩子以后上学成功的机会。因此,把相同的计划引进到所有3岁到5岁的孩子身上,将促进他们以后上学成功的机会。下面哪一个如果正确,最能削弱上面的论述?()
20世纪90年代以来,改编、翻拍“红色经典”成为影视剧艺术生产领域的一股潮流。有些翻拍作品,对原著的故事情节、人物性格胡改乱编,想当然地杜撰所谓人性内容,随意增添爱情“佐料”,淡化甚至消解原作的精神立场,以达到纯粹消遣、娱乐,迎合市场的目的。这启示我们(
最新回复
(
0
)