首页
登录
职称英语
The atmosphere that originally surrounded Earth was probably much different
The atmosphere that originally surrounded Earth was probably much different
游客
2023-12-22
39
管理
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 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 10 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 time, large amounts of carbon dioxide were 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 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 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. [br] The passage suggests that oxygen remained in the atmosphere because______.
选项
A、it was caused by outgassing
B、it was heavier than hydrogen
C、hydrogen became trapped in limestone
D、rays from the sun created equal amounts of hydrogen and oxygen
答案
B
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3295744.html
相关试题推荐
Peopleofdifferentfieldscametogetherforthesamedreamofbuildingasmart
Peopleofdifferentfieldscametogetherforthesamedreamofbuildingasmart
Peopleofdifferentfieldscametogetherforthesamedreamofbuildingasmart
Peopleofdifferentfieldscametogetherforthesamedreamofbuildingasmart
Peopleofdifferentfieldscametogetherforthesamedreamofbuildingasmart
Parentingwasneverapieceofcakeinanyage,butprobablythegreatestso
Parentingwasneverapieceofcakeinanyage,butprobablythegreatestso
[originaltext]You’veprobablyheardtheslogan"savethewhales".Doyoukn
[originaltext]You’veprobablyheardtheslogan"savethewhales".Doyoukn
[originaltext]You’veprobablyheardtheslogan"savethewhales".Doyoukno
随机试题
Igot______moneywithme,soIwasn’tabletobuyevenabottleofwater!A、any
[originaltext]W:Excuseme,Dr.Tyler,yoursecretarysaidIshouldcomeright
Atonetime,scientiststhoughtthespacebetweenEarthandSunwasavacuu
地震区,框架梁与柱的连接构造,下列说法错误的是( )。A.宜采用梁贯通型 B
2018年3月,某审计组对乙公司2017年度财务收支进行了审计、有关主营业务收入
根据《测绘法》,需要拆迁永久性测量标志的应当报经( )批准。A.永久性测量标志
(2016年真题)下列各项中,属于企业采取市场渗透战略的有()。A.某酒店
乙型肝炎的保护性抗体是( )。A.抗-HBs B.抗-HBcIgM C.
施工成本分析是在成本形成过程中,将施工项目的成本核算资料与()进行比较,以了解成
当关键线路的实际进度比计划进度提前时,若不拟提前工期,应选用()的后续关键工作
最新回复
(
0
)