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2.2.1. ★地球降温** 现在的climate越来越冷了，因为2种原因。第一段列出的是因为大陆板块海洋的变化引起的，第二段就说是因为大气层二氧化碳引起的，就说二氧化碳到了海里面，然后被海洋生物还是什么吸收，然后又被排出，留在seabed上面，再影响气候……好像是这意思，就说这个周期是很长很长的。 1 iamcrystal710题目考到什么削弱第二段里的观点，有第二段可以推出什么结论，总之就是大多在第二段里找，注意下hundredsof million years，还有4000millionyears都是些细节定位的地方，在中间和靠后的都有信息要找。 2 200702061710：果然看见了传说中的整段HIGHLIGHT啊。那叫一个壮观，屏幕都变黄色了。 3 gitarrelieber730 V37下面的陈述中除了哪个都支持了第二段中那个学派的观点：A-新的石头（fresh rock）可以吸收更多的二氧化碳/B- 大陆和海洋的相对移动造成地球降温 4 gitarrelieber730 V37根据第二段的理论下面除了哪个都是正确的：A-chemical weathering 需要水/B- Uplift是吸收的二氧化碳的主要因素 V1 (综合版) 两段长篇 科学家发现最近40million years，地球不再是原来那么warm和wet了（此处有题），先给出了一个流派的若干解释：随着二氧化碳的增多，大气的降水中融解了二氧化碳，这些水降到海面，被各种过程吸收，然后沉积到海底，虽然到海底这些c最终还是要回到大气中，但是这个过程需要hundreds of millions of years（隐含40百万年对它来说是相对短的过程，此处有题），另外陆面也对二氧化碳的吸收起到一定作用，而且随着内海的面积逐渐减少，陆面的面积越来越大因而吸收c也越多。第一段的末尾说这个解释不错，但作为唯一的解释未免不让人信服。 第二段是讲好像叫M R的人提出一种观点，对第一段的解释起到支持作用，他说地质演变抬高了陆地某些位置，高了之后会有更多的fresh岩石吸收c，而且因为抬高了后这些位置比较陡，降水可以更好的冲走这些吸收了c的岩石。提出的新观点觉得有二个重要原因 a. weathering的过程 （即对第一段的解释起到支持作用）; b. 岩石陆地的上升strengthen了weathering的过程 1．一个题目在第一段，问现在环境跟原来环境有什么区别，选择较Warm, Wet（此题也许是取非题，问现在的环境怎么样，那以前的来取非） 2．第二段，这个过程（二氧化碳溶解沉入海底再回到大气这个过程）需要hundreds of millionsof years（隐含40百万年对它来说是相对短的过程，此处有题） 3．有一个Except题（注意第二段中的机理讨论部分，见版本6的总结） 4．然后有一个应该是取非条件的（注意第二段中的机理讨论部分，见版本6的总结） 5．R科学家提出，有逻辑题，以下哪项weaken了R的观点，定位于二段后半部分. 注意R的观点有两个部分 a.weathering的过程 （即对第一段的解释起到支持作用）；b.岩石陆地的上升strengthen了weathering的过程．这题要削弱的应该是第二个观点 6．第二段全划线，机理题 节选自Plateau Uplift and Climate Change (Scientific American Magazine @ March 1991) Author：William F. Ruddiman and John E. Kutzbach During the past 40 million years, and particularly during thepast 15 million years, this warm, wet climate largely disappeared. Colderclimates and much greater regional extremes of precipitation have developed.What caused this cooling and diversification of climate and vegetation into acomplex mosaic of many regionally distinctive types? One school of thought focuses on the changing positions ofthe earth’s continents and oceans. The Atlantic Ocean has expanded at theexpense of the Pacific Ocean, whereas an ancient equatorial sea that extendedacross much of Eurasia (called the Tethys Sea) has shrunk to become the modern,much smaller Mediterranean Sea. In addition, the fraction of continents floodedby shallow inland seas has slowly decreased, exposing large amounts of land andcreating climates less moderated by the temperature-stabilizing effects ofoceans. Computer model simulations show that changes in the arrangement of thecontinents and the size of inland seas can have important effects on globalclimate over very long intervals of geologic time. But they are significantlyless convincing as sole explanations for the dramatic changes of the past 40million years. Another possibility is a long-term decline in theconcentration of carbon dioxide in the atmosphere, which would lessen theamount of heat trapped by the atmosphere and lead to “greenhouse cooling.” Theamount of carbon dioxide in the earth’s atmosphere over million-year timescalesis controlled by two major processes. Chemical weathering of continental rocksremoves carbon dioxide from the atmosphere and carries it in dissolved chemicalfrom to the ocean, where it is taken in by marine biota and deposited insediments on the seafloor. Tectonic activity eventually frees this trappedcarbon dioxide, in the earth’s lithospheric plates transports the seafloor toocean trenches, where subduction carries old crust and sediments down towardthe earth’s hot interior. At great depths, the sediments melt, releasing carbondioxide, which emerges from the volcanic islands that overlie the buried curstand rejoins the atmosphere, completing the cycle. If the pace of seafloor spreading (and hence of subduction)slowed significantly, less carbon dioxide would be vented to the atmosphere,the atmosphere would become relatively depleted of carbon dioxide andtemperatures would fall. In fact, globally averaged seafloor spreading ratesslow little or no net change in the past 40 million years. Subduction and volcanism eventuallyreturn the carbon dioxide to the atmosphere, but this process requires a longtime (tens to hundreds of millions of years) to complete.
Plateauuplift may alter climate by increasing chemical weathering of rocks, therebyreducing atmospheric carbon dioxide concentrations. Carbon dioxide combineswith rainwater and ground water to form carbonic acid, which reacts withsilicate minerals in rocks during weathering. The resulting bicarbonate ionsdrain into the oceans, where they are taken up by marine animals such asplankton and corals and eventually deposited on the seafloor. The net effect isthat chemical weathering removes carbon dioxide from the atmosphere and locksit away at the bottom of the oceans.
MaureenRaymo proposed that uplift of plateaus and mountain ranges has increased therate of chemical erosion of continental rock on the globally averaged basis.Uplift could enhance chemical weathering in several ways. Heavy monsoons, whichdevelop at the margins of plateaus, unleash particularly intense rainfall. Inthese regions, uplift-related faulting and folding also expose fresh rock tothe weathering process. Moreover, the steeper slopes created by plateau upliftcause faster runoff, which removes erosion products and intensifies thechemical attack on the rock. Raymo suggests that long-term uplift in Tibet andother regions may have increased the rate at which carbon dioxide is removedfrom the atmosphere. In this way, concentrations would have fallen even thoughthe amount of carbon dioxide exhaled by volcanoes (as inferred from seafloorspreading rates) remained nearly constant. Falling carbon dioxide levels wouldreduce the ability of the atmosphere to retain heat, thereby amplifying theglobal cooling.
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发表于 2013-6-21 15:35:37
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