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
47
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://jikaoti.com/ti/5JBFFFFM
0
大学英语六级
相关试题推荐
Researchonanimalintelligencealwaysmakesuswonderjusthowsmarthumansare.Considerthefruit-flyexperimentsdescribedb
Forthispart,youareallowed30minutestowriteashortessayentitledHowtoImproveStudents’MentalHealth.Youshouldwri
SouthAfricahas11officiallanguages.Ifyouwanttosayhello,it’s"sawubona"inZulu,and"hallo"inAfrikaans.Now,South
Nearlytwo-thirdsofbusinessesintheUKwantto【C1】______staffwithforeignlanguageskills.Frenchisstillthemosthighlyp
A、Hehelpedconstructachapel.B、Hetookoverhisfamily’sbusiness.C、HetrainedunderGuggenheim.D、Heworkedonaprojecto
A、AcitynamedMilton.B、AtownnamedMilton.C、TorontoAirport.D、MiltonAirport.B细节题。根据Ineedtogettoatowncalledum,Milt
A、Restructuringthewholecompany.B、Employingmoreforwardingagents.C、PromotingcooperationwithJayalMotors.D、Exportingth
A、Restructuringthewholecompany.B、Employingmoreforwardingagents.C、PromotingcooperationwithJayalMotors.D、Exportingth
Drought,tsunami,violentcrime,financialmeltdown—theworldisfullofrisks.Thepoorareoftenmost【C1】______totheireffect
随机试题
A.清热燥湿,泻火解毒,利胆退黄B.清热燥湿,涩肠止血,止带杀虫C.清热燥湿,祛风止痒,杀虫利尿D.清热燥湿,泻火解毒,止血安胎苦参的功效是
患者表现平静,客观面对患病现实,关注自身疾病,遵行医嘱,所体现的患者角色行为类型为
当梁突出顶棚的高度超过0.8m时,被梁隔断的每个梁间区域应至少设置一只探测器。()
久病,舌微微颤动,多属外感热病,见舌煽动者,多属
某男性患儿,5岁,2年来常在睡眠中遗尿,醒后方知,一夜2~3次,伴神疲乏力,肢凉怕冷,智力较差,舌质淡。治疗此证的首选方为
通常采用城市化率指标来测度城市化水平,城市化率的计算公式是()。[2009年考试真题]
小李年满18周岁,为某大学二年级学生,生活来源和学费全靠父母,现因家庭经济困难,向某银行申请助学贷款2.2万元,如2年后到期无力偿还,应由()来承担偿还责任。
财政财务审计是对被审计单位的会计资料及其反映的财政、财务收支活动的真实性、______、______、合法性、合规性所进行的审计。
这是一个部门全年的财力情况统计表。
Aswindler’s______isusuallyagulliblepersonwhoisunabletoresisttheswindler’straps.
最新回复
(
0
)