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 gues
Grand Canyon How was the Grand Canyon formed? The truth is that no one knows for sure though there are some pretty good gues
admin
2013-04-25
28
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 100000 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 8000~10000 CFS at low water and even the 20000 CFS peak flow rates.
The word soaking in Paragraph 3 is closest in meaning to ______.
选项
A、wetting
B、draining
C、freezing
D、raining
答案
A
解析
本题是词汇题,主要考查soaking在文中的词义。原文提到了水会渗到岩石的裂缝里,soaking与并列的drying是说明裂缝的成因是由于岩石不断地浸湿或变干,由此可得知选A。选项B(排水)、选项C(结冰)和选项D(下雨)均不合题意。
转载请注明原文地址:https://kaotiyun.com/show/A0yO777K
0
托福(TOEFL)
相关试题推荐
SECTION3Questions21-30Questions21Whichthreeguestsareontheradioprogramme?Writethecorrectletteronyouranswer
SECTION4Questions31-40Questions31-32CompletethenotesusingNOMORETHANTHREEWORDSforeachanswerMainfocusoflectu
Gestures—especially______ones.Lastly,Tinapointsoutthat______canbeused.
Theprofessorsaysthatsuperhighways______.【25】
Thelecturersaysthatanessayislike______toaspecificquestion.【34】
Completethelecturenotes.UseNOMORETHANTHREEWORDSforeachanswer.PurposeoftheminilectureToexperience【T32】______
Completethenotesbelow.WriteONEWORDONLYforeachanswer.BusinessCulturesPowercultureCharacteristi
Completethenotesbelow.WriteONEWORDONLYforeachanswer.BusinessCulturesPowercultureCharacteristi
ENDANGEREDSPECIESAlthoughwecannotdoanythingabouttheplantsandanimalsthatarealready【31】________,wecandosomething
ENDANGEREDSPECIESAlthoughwecannotdoanythingabouttheplantsandanimalsthatarealready【31】________,wecandosomething
随机试题
韩某,浙江某律师事务所律师,在一起故意杀人案中,接受被告人范某的委托担任辩护人,韩某在本案的审理过程中,其下列哪些行为是被法律允许的?()
TheresponsetotheconcertswasnotwarmenoughsoIdecidedtopostponebookingtickets________laterintheyear.
Morethanfortythousandreaderstolduswhattheylookedforinclosefriendships,whattheyexpected【56】friends,whattheywer
简述心传导系统的组成。
行口对口人工呼吸时吹气毕,放开鼻孔的原因是
低蛋白饮食中,成人每天蛋白质总量应控制在多少以下()
关于城市维护建设税减免税优惠政策的说法,正确的有()。
定期库存控制中的关键在于规定()。
学校领导可以凭升学率和学生的考试成绩对班主任工作进行评价。
Fromaveryearlyage,perhapstheageoffiveorsix,IknewthatwhenIgrewIshouldbeawriter.Betweentheages【M1】______
最新回复
(
0
)