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
What is the main purpose of the lecture? What is the professor’s opinion about the Snowball Earth hypothesis?
What is the main purpose of the lecture? What is the professor’s opinion about the Snowball Earth hypothesis?
admin
2022-07-28
19
问题
What is the main purpose of the lecture?
What is the professor’s opinion about the Snowball Earth hypothesis?
Listen to part of a lecture in a geology class.
Professor:
So continuing with ice ages, we’ve looked at the Pleistocene Ice age up through the so-called Little Ice age in Europe, but today I’d like to talk about a controversial hypothesis that Earth went through tremendous ice ages before all these others between approximately 600 and 700 million years ago during a geologic period that’s known as the Cryogenian.
Cryo is from the Greek and means cold. The name comes from the glacial deposits going back to this period. They’re found all around the world, which indicates that glaciers spread across all the continents at that time even near the equator.
And this is the premise of a hypothesis commonly called Snowball Earth. The name pretty much described the condition, that it is just proposed existed with not only the continents, but also the oceans entirely covered with thick sheets of ice.
But how could the Snowball Earth climate have come about? In the other ice ages, we’ve looked at, up to 30% of the Earth’s surface was covered in ice. But here we’re talking way more than that.
Okay. This gives us a chance for review. When radiation from the sun reaches our planet, some of it is absorbed and some of it reflected back into space, right? And different surfaces on Earth reflect solar radiation differently. They don’t have the same surface albedo. Surface albedo is a measure that tells us how much solar radiation gets reflected back into space. Ocean water, for example, tends to absorb radiation. Its surface albedo is low. So that has a warming effect on the planet. But ice and snow reflect a lot of solar radiation. They have a higher albedo. It’s like how wearing white clothing can help you stay cooler in a hot day than wearing black clothing. Similarly, ice and snow, as well as being very cold themselves, have an additional cooling effect because they keep solar radiation from being absorbed.
Now once this process of reflection and cooling gets started, it can end up being self-perpetuating. The cooling increases the ice cover, which increases the surface albedo, so the climate gets even colder, causing more ice to form and so on. This is called the ice albedo feedback. Normally the process is kept in check by the ocean’s absorption of solar radiation, but according to the Snowball Earth hypothesis, the feedback loop didn’t stop. And so ice and snow were covering more and more land, cooling Earth’s surface more and more quickly, and got to the point where even the oceans were covered in ice.
Now for the thought of Earth as a giant snowball, I have to admit it has some dramatic appeal. And a number of geologists have come on board with it in fact, because there’s certainly evidence of extreme glaciation during the Cryogenian period. For example, in Oman, now Oman’s in the Middle East, right? So a hot climate today. Well, sedimentary rocks there provide clear evidence of glaciers in the Cryogenian period. But a new research study looked at the sedimentary rocks more closely. The technique they used, it’s useful to know this, because we will come across it again. What they look at is a measure called a chemical index of alteration. The chemical index of alteration is a gauge of chemical weathering of rock, which means the chemical changes that occurred in rock due to environmental conditions. A high rate of chemical weathering indicates a warm and humid environment. Well, a low rate of chemical weathering is consistent with cool and dry conditions. So in this rock in Oman, the chemical index of alteration suggests that the climate during the Cryogenian wasn’t consistent. There’s definitely evidence of periods with low rates of chemical weathering and therefore with cold conditions. But these alternate with intervals of high chemical weathering, which represent times of warmer weather, which means that there were periods when that deep-freeze broke. But how? If the Earth was completely frozen for a long period of time, I doubt warmer periods could have happened. The incoming solar radiation would have been reflected back, right? So the warmer periods indicate that at least some portions of the ocean weren’t frozen over.
选项
A、Its basic premise is accurate and further study will validate it.
B、It would be more plausible if the time frame were longer.
C、It has some merit but a closer examination reveals flaws.
D、It will probably never be completely discredited.
答案
C
解析
题目询问教授对雪球地球假设的观点。在讲座的后半部分,教授指出,很多地质学家都同意这个假设,毕竟有证据能表明这个假设确实能解释一些情况。但她接着又提到,一项新的研究发现了证据能证明这个假设有错误的地方:化学蚀变指数表明,成冰纪时期的气候并不稳定,有冰冻期,也有气候更温暖的时期。因此,C项的表述符合题意。对阿曼地区的岩石的进一步研究表明雪球地球假设并不准确,排除A项“其基本前提是准确的,进一步研究将予以证实”。B项“如果时间范围更长,该假设会比较合理”没有相关信息。研究人员通过进一步的研究就发现了该假设的谬误,故排除D项“该假设可能永远不会被推翻”。
转载请注明原文地址:https://kaotiyun.com/show/gKfO777K
0
托福(TOEFL)
相关试题推荐
Choosethecorrectletter,A,BorC.PlanningapresentationonnanotechnologyTheybothagreethatthebestwayforRusstos
Completethenotesbelow.WriteONEWORDAND/ORANUMBERforeachanswer.SouthCityCyclingClubExampleNameofclubsecretary
Completethesentencesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.knowledge_journal.com
ChoosethecorrectletterA,BorC.Marycriticisesmultiple-choicequestions,because
Labelthemapbelow.WritethecorrectletterA-H,nexttoQuestions11-15.Stonebridge
Choosethecorrectletter,A,BorC.Thestudentthinkspeople
ChooseFOURletters,A-G.WhichFOURofthefollowingarerequiredofstudentteachers?AweeklyjournalBsamplelessonplansC
ChooseFOURletters,A-G.WhichFOURofthefollowingarerequiredofstudentteachers?AweeklyjournalBsamplelessonplansC
Accordingtothespeakers,whatfunctionhastapaplayedinthefollowingcountries?Writethecorrectletter,A,B,CorD,ne
Accordingtothespeakers,whatfunctionhastapaplayedinthefollowingcountries?Writethecorrectletter,A,B,CorD,ne
随机试题
驾驶机动车遇到这种行人应该注意什么?
男性,40岁。服用4个生鱼胆治疗目疾后无尿4天入院。脉搏96次/分,血压139/92mmHg(18.53/12.27kPa),体温37.5℃,呼吸21次/分。神志不清,烦躁。巩膜黄染。双下肢凹陷性水肿。急查血生化示Cr632μmol/L,BUN41.0mm
于先生,78岁,因上呼吸道感染诱发哮喘发作,遵医嘱用氨茶碱0.25g加入50%葡萄糖40ml静脉注射。做超声雾化吸入选用氨茶碱的目的是
抵押担保与质押担保的区别在于( )。
背景资料:某城市道路改造工程,道路施工的综合管线有0.4MPa的DN500中压燃气、DN1000给水管并排铺设在道路下,燃气管道与给水管材均为钢管,实施双管合槽施工。热力隧道工程采用暗挖工艺施工。承包方A公司将工程的其中一段热力隧道工程分包给B公司,
某公路工程施工项目在交工验收后,经整改合格,进入竣工验收阶段。施工单位向竣工验收主持单位提交了申请验收报告。竣工验收委员会由验收主持单位、建设单位、交工验收组代表、接管养护有关单位的代表组成。竣工验收委员会为全面掌握工程建设情况,应认真听取和审议如下报告:
2006年12月,中国公民王某从境内本单位取得工资收入2000元,2006年度年终奖5000元。当月从境外A国取得税后工资收入折合人民币17000元,已在境外缴纳所得税3000元。则王某在2006年12月应纳个人所得税()元。
人工工日消耗量中的其他用工包括()。
A、 B、 C、 D、 A
Whenpeoplearefreefromtheworriesoffood,theyworrythe76.______kindsoffoodtheyneed.Scientistssayitdoesn’tm
最新回复
(
0
)