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
A、To prove earth’s continents were once joined together. B、To prove that the grain type within sandstone. C、To determine the act
A、To prove earth’s continents were once joined together. B、To prove that the grain type within sandstone. C、To determine the act
admin
2018-01-28
43
问题
Ok, let’s get started. Great Today I want to talk about a way in which we are able to determine how old a piece of land, or some other geologic feature is—dating techniques. I’m going to talk about a particular dating technique. Why? [22]Good dating is key to good analysis. In other words, if you want to know how a land formation was formed, the first thing you probably want to know is how old it is. It’s fundamental.
Take the Grand Canyon for instance. Now, we geologists thought we had a pretty good idea of how the Grand Canyon in the southwestern United States was formed. We knew that it was formed from sandstone that solidified somewhere between 150 and 300 million years ago. Before it solidified, it was just regular sand. Essentially it was part of a vast desert. And until just recently, [23]most of us thought the sand had come from an ancient mountain range fairly close by that flattened out over time. That’s been the conventional wisdom among geologists for quite some time.
But now we’ve learned something different, and quite surprising, using a technique called Uranium-Lead Dating. I should say that Uranium-Lead Dating has been around for quite a while. But there have been some recent refinements. I will get into this in a minute.
[24]Anyway, Uranium-Lead Dating has produced some surprises. Two geologists discovered that about half of the sand from the Grand Canyon was actually once part of the Appalachian Mountains. That’s really eye-opening news, since the Appalachian Mountain Range is, of course, thousands of kilometers to the east of the Grand Canyon. Sounds pretty unbelievable, right? Of course, the obvious question is how did that sand end up so far west? The theory is that huge rivers and wind carried the sand west where it mixed in with the sand that was already there.
Well, this was a pretty revolutionary finding. Um... and it was basically because of Uranium-Lead Dating. Why? Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone, to determine where it came from. You can do other things too, like look at the wind or water that brought the grains to their location and figure out which way it was flowing. But that’s only useful up to a point, and that’s not what these two geologists did.
[25]There are a few pretty exciting possibilities for Uranium-Lead Dating. Here is one that comes to mind. You know the theory that earth’s continents were once joined together and only split apart relatively recently? Well, with Uranium-Lead Dating, we could prove that more conclusively. If they show evidence of once having been joined, that could really tell us a lot about the early history of the planet’s geology.
22. What is the key to good analysis in geology?
23. What has been the conventional wisdom among geologists for quite some time?
24. What has produced some surprises among geologists?
25. What is one of the exciting possibilities for Uranium-Lead Dating?
选项
A、To prove earth’s continents were once joined together.
B、To prove that the grain type within sandstone.
C、To determine the actual particles in the sandstone.
D、To determine where the actual particles came from.
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/BET7777K
0
大学英语六级
相关试题推荐
TheHistoryofChineseAmericans[A]ChinesehavebeenintheUnitedStatesforalmosttwohundredyears.Infact,theChines
InthefirstyearorsoofWebbusiness,mostoftheactionhasrevolvedaroundeffortstotaptheconsumermarket.Morerecentl
SouthAfricaSafariTopFiveNationalParksandGameReserves[A]ASouthAfricasafari(游猎)istheidealwildlifetriptogoo
SouthAfricaSafariTopFiveNationalParksandGameReserves[A]ASouthAfricasafari(游猎)istheidealwildlifetriptogoo
A、Experimentalmedicines.B、Specialtreatmentcenters.C、Flexibleworkschedule.D、Innovativephysicalexercises.B细节题。男士在对话中提到听
Learningisanessentialprocessforlivingthingstoacquirenecessaryskillsandbehaviors.Scientistshavealreadyfoundthat
A、HebeganhiscareerintheUnitedStates.B、Hesuggestssimplifyinginformation.C、HisbookisfornativeEnglishspeakers.D、
A、Nothingbutthebonesoftheswanshasbeenfound.B、ThefirstremainsofaswanturnedupjustbeforeChristmas.C、Stealings
A、Doubtful.B、Supportive.C、Opposing.D、Neutral.C短文提到,政府机构坚决反对标签提供更多的信息,C的opposing(反对)与短文的disagreedstrongly一致,故正确。
Everyotherweekitseemsanewstudycomesoutthataddstoouralready-formidablestoreofparentalworries.Butevenbythose
随机试题
A.肺、脾、胃、肾B.脾、肝、肾、心C.心、肺、脾、肝D.肺、脾、肝、肾E.心、肺、脾、肾与血的生成关系最密切的是
患者30岁,右上后牙因深龋于外院行复合树脂充填治疗后1天开始发生自发性疼痛,持续2天,冷水可缓解。
ZETA信用风险分析模型中用采衡量流动性的指标是()。
下列选项中,属于内控设计缺陷的是()。
导游人员讲解的节奏体现在讲解的()等方面。
实施“进口替代”战略的基础是()
任何从【】派生的类都可以用throw语句抛出,抛出异常用来表明程序遇到的错误无法正常执行而需要异常处理。
在数据库设计中,将E—R图转换成关系数据模型的过程属于()。
在考生文件夹中新建一个FSA.TXT文件。
PresidentBushpledgedtoprovidethepoorestnationsabout_____peryear.
最新回复
(
0
)