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
17
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
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)、选面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/zBfO777K
0
托福(TOEFL)
相关试题推荐
Completethetablebelow.WriteNOMORETHANTWOWORDSORANUMBERforeachanswer.CharlesWillsonPeale1741—BorninM
Completethetablebelow.WriteNOMORETHANTWOWORDSORANUMBERforeachanswer.CharlesWillsonPeale1741—BorninM
Completethenotesbelow.WriteONEWORDONLYforeachanswer.Notestobeaddedtopolicy:Addnewdriver:Name
positivethinking/thought(s)
WhatisDrSimon’sopiniononthefollowingpoints?TickcolumnAifheisinfavourTickcolumnBifhehasnostrongopinione
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.Otherrequirementsfortheprojectextractchosen
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.Otherrequirementsfortheprojectextractchosen
Completethetablebelow.WriteNOMORETHANTHREEWORDSAND/ORANUMBERforeachanswer.USARESEARCHPROJECTSINTOCLASSSIZES
Choosethecorrectanswer,A,BorC.ThestudentthoughttherewerenocrocodilesinNorthernAfricabecause
随机试题
试述大脑半球的分叶。
一般保温瓶胆为真空玻璃夹层,夹层内两侧镀银,能较长时间地保持热水的温度,是因为采取这样的措施,主要可以减少热水通过瓶胆夹层内()方式的热量损失。
施工投标报价工作包括:①工程现场调查;②组建投标报价班子;③确定基础标价;④制订项目管理规划;⑤复核清单工程量。下列工作排序正确的是()。
下列关于普通股的表述,错误的是()。
以下不属于列入黑名单情形的是()。
对待和使用心理测验,以下说法错误的是()。
(2017年聊城东昌府)在课程实施相互适应取向的视野中,教师的角色是课程变革方案主动的、积极的“消费者”。
学生在教师的指导下,利用一定的仪器设备,通过条件控制引起实验对象的某些变化,从观察这些变化中获得知识的方法就是练习法教学。()
Nowadays,oursocietyisbeingreshapedbyinformationtechnologies—computers,telecommunicationsnetworks,andotherdigitalsy
A、Theymightbeinfluencedbymothers’mood.B、Theycouldlearnassoonastheywereborn.C、Theycouldunderstandwhatpeoples
最新回复
(
0
)