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
Grand Canyon How was the Grand Canyon formed? The truth is that no one knows for sure though there are some pretty good guesses,
Grand Canyon How was the Grand Canyon formed? The truth is that no one knows for sure though there are some pretty good guesses,
admin
2013-08-12
51
问题
Grand Canyon
How was the Grand Canyon formed? The truth is that no one knows for sure though there are some pretty good guesses, and it is usually thought that a number of processes combined to create the views that you see in today’s Grand Canyon. The most powerful force to have an impact on the Grand Canyon is
erosion
, primarily by water(and ice)and secondly by wind. Other forces that contributed to the Canyon’s formation are the course of the Colorado River itself, vulcanism, continental drift and slight variations in the earth’s orbit which in turn causes variations in seasons and climate.
Water seems to have had the most impact basically because our planet has lots of it and it is always on the move. Many people cannot understand how water can have such a profound impact considering that the Canyon is basically located in a desert. This is one of the biggest reasons that water has such a big impact here. Because the soil in the Grand Canyon is baked by the sun it tends to become very hard and cannot absorb water when the rains come. When it does rain the water tends to come down in torrents which only add to the problem. The plants that grow in the Grand Canyon tend to have very shallow root systems so that they can grab as much water as possible on those rare occasions when it does rain. Unfortunately these root systems do nothing to deter erosion by holding the soil in place. Now you’ve got lots of water, no place for it to go, but down to the Colorado River, and nothing holding the soil and rock in place. The result is frequently a flash flood roaring down a side canyon that can move
boulders
the size of automobiles, buses and even small houses. If automobiles, buses and small houses are in the way then
it
will take them too.(A)
Luckily no one builds houses in the Grand Canyon so that’s not a problem but there are a few autos, vans and buses sitting at the bottom of the Colorado River. This mass that moves down a side canyon during a flash flood is more like fast flowing concrete than water and it can be very dangerous. You should always be well informed of weather conditions when you are hiking through side canyons in the Grand Canyon.
(B)
In the colder months, especially on the north rim, water seeps into cracks between the rocks. These cracks can be caused by seismic activity, or by the constant
soaking
and drying of the rocks.(C)
When the water freezes it expands and pushes the rocks apart and widens the cracks. Eventually rocks near the rim are pushed off the edge and fall into the side canyons. These rocks sometimes hit other rocks and are stopped but on occasion one fall by a large rock will cause a cascading effect and create a rock fall that will alter the landscape drastically in the side canyon. Debris from rock falls piles up at the bottom of the side canyons and is then carried down to the Colorado River the next time there is a flash flood. Rock falls frequently take out sections of trail in the Grand Canyon requiring the Park Service to close these trails until they can be repaired.(D)
Once the ice has pushed the rocks off the edge and the water in the flash floods has carried them down to the river, then the Colorado itself takes over. The erosive action of the Colorado has been severely constrained by the building of the Glen Canyon Dam, which ended the annual spring floods, but there is still a lot of water flowing relatively quickly through a very narrow gorge. Before building the dam the Colorado River had spring floods that would exceed a flow rate of 100 000 CFS(cubic feet per second). All of that snow melting in the Colorado Rockies came pouring down through the Grand Canyon in May and June every year, like clock-work. These spring floods were considerably larger than today’s "
trickle
" of 8 000~10 000 CFS at low water and even the 20 000 CFS peak flow rates.
The word
it
in Paragraph 2 refers to______.
选项
A、the rain
B、the flood
C、the canyon
D、the river
答案
B
解析
本题是指代关系题,要求考生认定代词与篇章中其他词语的指代关系。南第27题得知,雨量大时爆发的洪水会带走土石,文章还说如果有车辆或房屋的话,也会被卷走的。从原文“The result is frequently a flash flood roaring down a side canyon that can move boulders the sizeof automobiles...If automobiles…are in the way then it will take them too”可知是被flood卷走,因此选B。选项A、D有一定的干扰性,不过仔细联系上文不难确定it在这里指的是flood。
转载请注明原文地址:https://kaotiyun.com/show/KIfO777K
0
托福(TOEFL)
相关试题推荐
Completethenotesbelow.WriteONEWORDAND/ORANUMBERforeachanswer.Requirements:GoodliftaccessLargel
Completethetablebelow.WriteNOMORETHANTWOWORDSORANUMBERforeachanswer.CharlesWillsonPeale1741—BorninM
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.DepartmentofEducationQuestionnaireReasons
Completetheformbelow.WriteONEWORDAND/ORANUMBERforeachanswer.TAUBERINSURANCECo.Policy#:
Completethenotesbelow.WriteONEWORDONLYforeachanswer.BusinessCulturesPowercultureCharacteristi
Completethenotesbelow.WriteONEWORDONLYforeachanswer.BusinessCulturesPowercultureCharacteristi
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.Otherrequirementsfortheprojectextractchosen
Completethenotesbelow.WriteONEWORDAND/ORANUMBERforeachanswer.ThingstodobeforewegoExam
Choosethecorrectletter,A,BorC.Thestudentthoughttheresearchpaperwas
Thougharespectededucator,AlexanderGrahamBell______theinventorofthetelephone.
随机试题
王某1998年于医科大学本科毕业分配到市级医院工作,《中华人民共和国执业医师法》颁布3个月后,其依照有关开办医疗机构的规定申请个体开业。依据《执业医师法》卫生行政部门应
关于环境污染对人体健康危害的特点,哪项是错误的
位于A县的某热水瓶厂生产了一批热水瓶,其在B县与代理商签订合同协议约定由代理商负责在C县销售。住在D县的杨某在旅游到C县时购买了该热水瓶,后在拿回家使用的过程中因为该热水瓶爆炸而造成杨某面部严重受伤,杨某欲以侵权损害赔偿为由提起诉讼。则对该案具有管辖权的法
主要适用于以最大限度地满足招标文件实质要求为主要评标因素的复杂的和有特殊要求的项目的方法是()。
根据我国对标准级别的划分,对没有国家标准和行业标准而又需要在该地区范围内统一的技术要求所制定的标准是( )。
以学生发展为本的课程,要求把课程改革建立在脑科学研究、心理学研究和()研究的基础之上,把学生的发展作为课程开发的着眼点和目标。
利得与所有者投入资本无关。()
班里有6个男生4个女生,现以随机抽签的方式选取3人去开会,则抽中1名男生、2名女生的概率在以下哪个范围之内?
AvalancheandItsSafetyAnavalancheisasuddenandrapidflowofsnow,oftenmixedwithairandwater,downamountainside.A
ConradHiltonreallywantedtobeabanker.Instead,hesuccessfullychangedthe【C1】______purchaseofaTexaslow-endhotelinto
最新回复
(
0
)