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
The atmosphere that originally surrounded Earth was probably much different from the air we breathe today. Earth’s first at
The atmosphere that originally surrounded Earth was probably much different from the air we breathe today. Earth’s first at
admin
2005-01-30
101
问题
The atmosphere that originally surrounded Earth was probably much different from
the air we breathe today. Earth’s first atmosphere (some 4.6 billion years ago) was most
likely hydrogen and helium--the two most abundant gasses found in the universe--as
well as hydrogen compounds, such as methane and ammonia, Most scientists feel that
5 this early atmosphere escaped into space from the Earth’s hot surface.
A second, more dense atmosphere, however, gradually enveloped Earth as gasses
from molten rocks within its hot interior escaped through volcanoes and steam vents.
We assume that volcanoes spewed out the same gasses then as they do today: mostly
water vapor (about 80 percent), carbon dioxide (about ten percent), and up to a few
10 percent nitrogen. These same gasses probably created Earth’s second atmosphere.
As millions of years passed, the constant outpouring of gasses from the hot
interior--known as outgassing--provided a rich supply of water vapor, which formed
into clouds. Rain fell upon Earth for many thousands or years, forming the rivers,
lakes, and oceans of the world. During this Lime, large amounts of carbon dioxide were
15 dissolved in the oceans. Through chemical and biological processes, much of the carbon
dioxide became locked up in carbon sedimentary rocks, such as limestone. With much
of the water vapor already condensed into water and the concentration of carbon dioxide
dwindling, the atmosphere gradually became rich nitrogen.
It appears that oxygen, the second most abundant gas in today’s atmosphere, probably
20 began an extremely slow increase in concentration as energetic rays from the sun split
water vapor into hydrogen and oxygen during a process called photodissociation. The
hydrogen, being lighter, probably rose and escaped into space, while the oxygen remained
in the atmosphere.
This slow increase in oxygen may have provided enough of this gas for primitive
25 plants to evolve, perhaps two to three billion years ago. Or the plants may have evolved
in an almost oxygen-free (anaerobic) environment. At any rate, plant growth greatly
enriched our atmosphere with oxygen. The reason for this enrichment is that plants, in
the presence of sunlight, process carbon dioxide and water to produce oxygen.
选项
A、The original atmosphere on Earth was unstable.
B、The atmosphere on Earth has changed over time.
C、Hot underground gasses created clouds, which formed the Earth’s atmosphere.
D、Plant growth depended on oxygen in the Earth’s atmosphere.
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/jByO777K
0
托福(TOEFL)
相关试题推荐
Youshouldspendabout20minutesonQuestions14-27,whicharebasedonReadingPassage2below.Wo
Youshouldspendabout20minutesonQuestions1-13,whicharebasedonReadingPassage1below.Asong
Completethesummaryusingthelistofwords/phrases,A-l,below.ProblemsforpreschoolusersofvideogamesPr
TacklingHungerinMsekeniATherearenotenoughclassroomsattheMsekeniprimaryschool,sohalfthelessonstakeplaceinth
Choosethecorrectletter,A,B,CorD.Writeyouranswersinboxes37-40onyouranswersheet.Duringtheearlymodernera,a
Choosethecorrectletter,A,B,CorD.Writethecorrectletterinboxesonyouranswersheet.Whatistheauthor’sopiniono
Completethetablebelow.WriteNOMORETHANTWOWORDSORANUMBERforeachanswer.CharlesWillsonPeale1741—BorninM
Manyorganisationswillpayforthecostofavolunteer’s______toAfrica.Peoplewithout______orextensiveeducationcane
Gavin’sapartmentislocatedonthe______.
HistoricalBackground→TheepicpoemBeowulf,writteninOldEnglish,istheearliestexistingGermanicepicandoneoffou
随机试题
华润公司于2002年3月25日为该公司包括李某在内的每位高级管理人员在甲保险公司投了人身意外伤害保险,签订保险合同时公司在受益人一栏直接记载了公司的名称,保险期限为1年,华润公司按照约定交纳了保险费。2002年11月23日李某乘坐本公司的司机刘某驾驶的汽车
Thatistheday______I’llneverforget.
溃疡病急性穿孔具有诊断价值的是
关于主动脉狭窄的说法错误的是
不属于脑颅骨的是
情景模拟测试的常用方法有()。
计算机中的Cache是指()。
“淡”是人生最深的滋昧蒋醺(中国台湾)苏东坡在落难的时候,才在岸边写下了“大江东去,浪淘尽”这样完美的诗句。受到皇帝赏识时,他的书法漂亮、工整、华丽,而且得意。因为他是一个才子,才子总是很得意的。但是他从来没有想过,他让很多人受过伤。他得意的时候,很多
虽然他们身份不同,但他们心中迫切需要的肯定都同样是力量和勇气,______为了欺骗,______为了真实,没有任何时刻比现在这样更强烈的需要彼此依靠。填入划横线部分最恰当的一项是()。
债务人岳某向债权人段某表示同意履行债务,这将在法律上引起()。
最新回复
(
0
)