Volcanic fire and glacial ice are natural enemies. Eruptions at glaciated volcanoes typically destroy ice fields, as they did in 1980 when 70% of Mount Saint Helens ice cover was demolished. During long dormant intervals, glaciers gain the upper hand cutting deeply into volcanic cones and eventually reducing them to rubble. Only rarely do these competing forces of heat and cold operate in perfect balance to create a phenomenon such as the steam caves at Mount Rainier National Park.
Located inside Rainier’s two ice-filled summit craters, these caves form a labyrinth of tunnels and vaulted chambers about one and one-half miles in total length. Their creation depends on an unusual combination of factors that nature almost never brings together in one place. The cave-making recipe calls for a steady emission of volcanic gas and heat, a heavy annual snowfall at an elevation high enough to keep it from melting during the summer, and a bowl-shaped crater to hold the snow.
Snow accumulating yearly in Rainier’s summit craters is compacted and compressed into a dense form of ice called firm, a substance midway between ordinary ice and the denser crystalline ice that makes up glaciers. Heat rising from numerous opening (called fumaroles) along the inner crater walls melts out chambers between the rocky walls and the overlying ice pack. Circulating currents of warm air then melt additional openings in the firm ice, eventually connecting the individual chambers and, in the larger of Rainier’s two craters, forming a continuous passageway that extends two-thirds of the way around the crater s interior.
To maintain the cave system, the elements of fire under ice must remain in equilibrium. Enough snow must fill the crater each year to replace that melted from below. If too much volcanic heat is discharged, the crater’s ice pack will melt away entirely and the caves will vanish along with the snows of yesteryear. If too little heat is produced, the ice, replenished annually by winter snowstorms, will expand, pushing against the enclosing crater walls and smothering the present caverns in solid firn ice.
31. With what topic is the passage mainly concerned?
32. According to the passage, long periods of volcanic inactivity can lead to a volcanic cone’s ______.
33. The second paragraph mentions all of the following as necessary elements in the creation of steam caves EXCEPT ______.
34. According to the passage, heat from Mount Rainier’s summit craters rises from ______.
35. “smothering” (Paragraph 4) means ______.
问题1选项
A.The importance of snowfall for Mount Rainier.
B.The steam caves of Mount Rainier’s.
C.How ice covers are destroyed.
D.The eruption of Mount Saint Helens in 1980.
问题2选项
A.strong eruption
B.sudden growth
C.destruction
D.unpredictability
问题3选项
A.a glacier
B.a crater
C.heat
D.snow
问题4选项
A.crystalline ice
B.firns
C.chambers
D.fumaroles
问题5选项
A.eliminate
B.enlarged
C.prevented
D.hollowed
第1题:B
第2题:C
第3题:A
第4题:D
第5题:A
31.【试题答案】B
【试题解析】主旨大意题。题干意思是“这篇文章主要讨论什么主题?”。文章第一段通过火山火和冰川冰的竞争引出雷尼尔山国家公园的蒸汽洞穴的话题,随即第二段介绍了蒸汽洞穴形成的特征,第三段讲述冰川与火山口相互作用形成蒸汽洞的具体过程,最后一段讲述了蒸汽洞的维持需要热与雪在火山口的独特平衡。综上所述,这篇文章主要讨论的是雷尼尔山的蒸汽洞穴,B项“雷尼尔山的蒸汽洞穴”正确。A项“降雪对雷尼尔山的重要性”属于以偏概全。C项“冰雪是如何被破坏的”和D项“1980年圣海伦斯火山爆发”只是少部分提及或者举例,也属于以偏概全。因此,该题选择B项正确。
32.【试题答案】C
【试题解析】事实细节题。题干意思是“根据这篇文章,长时间的火山不活动会导致火山锥的……”。定位第一段第三句During long dormant intervals, glaciers gain the upper hand cutting deeply into volcanic cones and eventually reducing them to rubble.(在长时间的休眠期间,冰川占据上风,深深地切割火山锥,最终将它们夷为平地)可知,如果火山长时间不活动,那么冰川会把火山锥夷为平地,C项“破坏”正确。A项“强烈的火山喷发”和B项“突然的增长”与原文相反,属于反向干扰。D项“不可预测性”属于无中生有。因此,该题选择C项正确。
33.【试题答案】A
【试题解析】事实细节题。题干意思是“第二段提到了除了……以外的所有蒸汽洞穴的必要元素”。定位第二段第二句The cave-making recipe calls for a steady emission of volcanic gas and heat, a heavy annual snowfall at an elevation high enough to keep it from melting during the summer, and a bowl-shaped crater to hold the snow.(建造洞穴的方法需要稳定的火山气体和热量的释放,在海拔足够高的地方每年有大量的降雪,以防止在夏季融化,还有一个碗状的火山口来容纳雪)可知,蒸汽洞穴的必要元素是火山口、降雪和热量,B项“火山口”、C项“热”和D项“雪”都正确。只有A项“冰川”没提到。因此,该题选择A项正确。
34.【试题答案】D
【试题解析】事实细节题。题干意思是“根据这篇文章,雷尼尔山山顶火山口的热量从……上升”。定位第三段第二句Heat rising from numerous opening (called fumaroles) along the inner crater walls melts out chambers between the rocky walls and the overlying ice pack.(沿着火山口内壁的大量喷气孔上升的热量融化了岩壁和上面的冰袋之间的洞穴)可知,D项“喷气孔”正确。定位第一句Snow accumulating yearly in Rainier’s summit craters is compacted and compressed into a dense form of ice called firn, a substance midway between ordinary ice and the denser crystalline ice that makes up glaciers.(在雷尼尔山顶的陨石坑里,每年积累的雪被压实并压缩成一种称为硬冰的密集形式,这种物质介于普通冰和构成冰川的更致密的结晶冰之间)可知,A项“结晶冰”和B项“积雪”与题干无关,属于出处错位。C项“洞穴”也属于出处错位。因此,该题选择D项正确。
35.【试题答案】A
【试题解析】语义推测题。题干意思是“第四段的smothering的意思是……”。定位第四段最后一句If too little heat is produced, the ice, replenished annually by winter snowstorms, will expand, pushing against the enclosing crater walls and smothering the present caverns in solid firn ice.(如果产生的热量太少,每年由冬季暴风雪补充的冰就会膨胀,挤压周围的陨石坑壁,并用坚实的冰smothering现在的洞穴),结合前一句If too much volcanic heat is discharged, the crater’s ice pack will melt away entirely and the caves will vanish along with the snows of yesteryear.(如果火山释放出过多的热量,火山口的冰块将完全融化,洞穴将和去年的雪一起消失),这两句分别是阐述热量过少和热量过多时,蒸汽洞穴的变化,前一句提到了vanish,所以smothering的意思也和vanish相近,表示“消失”,A项“消除”符合题意。B项“放大”、C项“预防”和D项“挖空”都是曲解原文。因此,该题选择A项正确。