About Uranium-Lead Dating

Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable. Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence. Basics of Uranium-Lead Uranium comes in two common isotopes with atomic weights of 235 and 238 (well call them 235U and 238U). Both are unstable and radioactive, shedding nuclear particles in a cascade that doesnt stop until they become lead (Pb). The two cascades are different—235U becomes 207Pb and 238U becomes 206Pb. What makes this fact useful is that they occur at different rates, as expressed in their half-lives (the time it takes for half the atoms to decay). The 235U–207Pb cascade has a half-life of 704 million years and the 238U–206Pb cascade is considerably slower, with a half-life of 4.47 billion years. So when a mineral grain forms (specifically, when it first cools below its trapping temperature), it effectively sets the uranium-lead clock to zero. Lead atoms created by uranium decay are trapped in the crystal and build up in concentration with time. If nothing disturbs the grain to release any of this radiogenic lead, dating it is straightforward in concept. In a 704-million-year-old rock, 235U is at its half-life and there will be an equal number of 235U and 207Pb atoms (the Pb/U ratio is 1). In a rock twice as old there will be one 235U atom left for every three 207Pb atoms (Pb/U 3), and so forth. With 238U the Pb/U ratio grows much more slowly with age, but the idea is the same. If you took rocks of all ages and plotted their two Pb/U ratios from their two isotope pairs against each other on a graph, the points would form a beautiful line called a concordia (see the example in the right column). Zircon in Uranium-Lead Dating The favorite mineral among U-Pb daters is zircon (ZrSiO4), for several good reasons. First, its chemical structure likes uranium and hates lead. Uranium easily substitutes for zirconium while lead is strongly excluded. This means the clock is truly set at zero when zircon forms. Second, zircon has a high trapping temperature of 900Â °C. Its clock is not easily disturbed by geologic events—not erosion or consolidation into sedimentary rocks, not even moderate metamorphism. Third, zircon is widespread in igneous rocks as a primary mineral. This makes it especially valuable for dating these rocks, which have no fossils to indicate their age. Fourth, zircon is physically tough and easily separated from crushed rock samples because of its high density. Other minerals sometimes used for uranium-lead dating include monazite, titanite and two other zirconium minerals, baddeleyite and zirconolite. However, zircon is so overwhelming a favorite that geologists often just refer to zircon dating. But even the best geologic methods are imperfect. Dating a rock involves uranium-lead measurements on many zircons, then assessing the quality of the data. Some zircons are obviously disturbed and can be ignored, while other cases are harder to judge. In these cases, the concordia diagram is a valuable tool. Concordia and Discordia Consider the concordia: as zircons age, they move outward along the curve. But now imagine that some geologic event disturbs things to make the lead escape. That would take the zircons on a straight line back to zero on the concordia diagram. The straight line takes the zircons off the concordia. This is where data from many zircons is important. The disturbing event affects the zircons unequally, stripping all the lead from some, only part of it from others and leaving some untouched. The results from these zircons therefore plot along that straight line, establishing what is called a discordia. Now consider the discordia. If a 1500-million-year-old rock is disturbed to create a discordia, then is undisturbed for another billion years, the whole discordia line will migrate along the curve of the concordia, always pointing to the age of the disturbance. This means that zircon data can tell us not only when a rock formed, but also when significant events occurred during its life. The oldest zircon yet found dates from 4.4 billion years ago. With this background in the uranium-lead method, you may have a deeper appreciation of the research presented on the University of Wisconsins Earliest Piece of the Earth page, including the 2001 paper in Nature that announced the record-setting date.

Geography Facts About Ghana Essay - 1487 Words

Ghana is a country in Africa that is native to 25 million people. It is neighbored by the Ivory Coast to the West, Togo to the East and Burkina Faso to the North. It is also bordered by the Gulf of Guinea to the south. It is about the size of Oregon and it’s religions include Christianity, Islam, and other Indigenous beliefs (Bbc news, 2013). Ghana has different climates in different parts of the country. Near the coast, there are tropical forests, in the middle there is a transitional zone where it then transitions into the savannah in the north where it is dryer and only gets one rainy season versus two in the south (Encyclopedia of the nations). Their major exports are gold, cocoa, timber, and many other products. Their GDP is $40.71†¦show more content†¦Clearly, there is a problem here because men are dependent on for cash crops while women are dependent on for survival with food crops. With women having a lower percentage of education than men, this results in wo men having limited land rights so it is hard for them to make decisions and expand in their farming systems. But according to the 2010 MDP report, this gender inequality is decreasing which will result in a greater Ag GDP due to women being able to expand and make more decisions with more education (UNDP, Ghana, 2012, page 3). And being able to increase food production and yields through more education will result in less poverty and hunger in Ghana which will also contribute to the MDP goals. The population growth rate for Ghana is 2.19% with 38.7% of the population falling between zero and fourteen years of age. Therefore, the population pyramid definitely shows that Ghana has developing issues (Index mundi, 2013). Having a high birth rate and being a pre-industrialized country proves that Ghana is going through the demographic transition at a slow pace. 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Development of the communist t Essay Example For Students

Development of the communist t Essay If neither Marx or Engels never lived and written the books they did, former Soviet Union and China would probably be conducting their governmental systems in a different manner. Defined by Marx and Engels, the communist theory can be summed up in the single phrase: abolition of private property (Engels, Marx 80). Communists are distinguished by the lower working class which will rise to overthrow the higher supreme class (Engels, Marx 80). The second distinction can be found in the struggle of the proletariats against the Bourgeoisie, or the higher class (Engels, Marx 80). Marx and Engels state that society as a whole is more and more splitting up into the great hostile camps, or opposing classes; theProletariats and the Bourgeoisie (Engels, Marx 58). Political power, property so called is merely the organized power of one classoppressing another (Engels, Marx 95). Communism deprives no man of the power to appropriate the products of society; all that it does is to deprive him of t he power to subjugate the labor of others by means of such appropriation (Engels, Marx 86). Communists do not form a separate party opposed to other working class parties. There are ten measures needed to convert tocommunism (Engels, Marx 94). 1. Abolition of property in land and application of all rents of land to the public. 2. Heavy progressive income tax. 3. Abolition of all rights of inheritance. 4. Confiscation of the property of all emigrants and rebels. 5. Centralizing of credit in the hands of the state, by means of a national bank with a state capital. 6. Centralizing of the means of communication and transportation in the hands of the state. 7. Factories and production owned by the state and cultivation of wastelands. 8. Equal liability of all labor. Establishment of industrial armies, especially for agriculture. 9. Combining agriculture and manufacturing industries; abolition of distinction between town and country by a more equal distribution of the population. 10. Fre e education for all children in public schools. Abolition of childrens factory labor (Engels, Marx 94). According to Marx and Engels these were the ten steps to follow if you wanted your country to convert to communism. Marx and Engels had their influence in modern ideology because heads of state put their ideas into action in their own countries(Hacker 516). Words and phrases taken from Marx and Engels writings clearly constitute the ideology framework of communist power (Hacker 516). The former Soviet Union, China, and lesser communist states all claim to be guided by Marxist principles (Hacker 512). It would be wrong to say that two nineteenth century political theorists are responsible for the course of communism today. Communist leaders of the twentieth are responsible for keeping alive Marxist ideology (Hacker 516). Communist leaders have elected to utilize the books, pamphlets, letters and speeches of Marx and Engels as their official doctrine (Hacker 513). The leaders in communist states use perceptions of Marxism as merely an aid in motivating their citizens for thepursuit of political goals (Hacker 516). While Communist leaders dictate the words of Marx and Engels, they, themselves are t he ones to make and carry out plans (Hacker 516). The fact of the matter is that communist leaders are the interpreters of that Marxist ideology in their countries (Hacker 516). It has been proven that Plato had an influence on Rousseau, and Rousseau on Hugel, and Hugel on Marx and Engels (Hacker 515). The strength in an ideology is lies not only in its content of ideas but also in the spirit that moves it (Hacker 516). Obviously Marx and Engels wanted their ideas to be put to use. They condensed their theory so that their messages would move men to revolutionary activity (Hacker 515). Had a soviet power never emerged, the contribution of Marx and Engels to political theory would still be a major one (Hacker 517). In the Communist Manifesto, Karl Marx and Friedrich Engels applied the term communism to a final stage of socialism in which allclass differences would disappear (Payne 421). They declared that the course of history was discovered by the clash of opposing forces (Payne 4 21). These forces were rooted in the economic system and the ownership of property (Payne 421). The struggle between the Bourgeoisie and the Proletariat would end when the socialists started a revolution and attained a full communistic government (Payne 423). If the leaders of present day communist countries and the former communist countries were not guided by the principles of Marxand Engels they operation of the countries past and present would most definitely be different. It is true that each leader runs his country his own way, but the bottom line is that the foundation of their communist rule is rooted in the works of Marx and Engels. Without these two men the entire basis of communism and communist principles would be non-existent. .ufad2a38ffe8a0dfc398d6b9ae61299a0 , .ufad2a38ffe8a0dfc398d6b9ae61299a0 .postImageUrl , .ufad2a38ffe8a0dfc398d6b9ae61299a0 .centered-text-area { min-height: 80px; position: relative; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 , .ufad2a38ffe8a0dfc398d6b9ae61299a0:hover , .ufad2a38ffe8a0dfc398d6b9ae61299a0:visited , .ufad2a38ffe8a0dfc398d6b9ae61299a0:active { border:0!important; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .clearfix:after { content: ""; display: table; clear: both; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .ufad2a38ffe8a0dfc398d6b9ae61299a0:active , .ufad2a38ffe8a0dfc398d6b9ae61299a0:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .centered-text-area { width: 100%; position: relative ; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .ufad2a38ffe8a0dfc398d6b9ae61299a0:hover .ctaButton { background-color: #34495E!important; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .ufad2a38ffe8a0dfc398d6b9ae61299a0 .ufad2a38ffe8a0dfc398d6b9ae61299a0-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .ufad2a38ffe8a0dfc398d6b9ae61299a0:after { content: ""; display: block; clear: both; } READ: Feminism Essay ThesisBIBLIOGRAPHYEngels, Friedrich, Karl Marx. The Communist Manifesto. Washington Square Press; New York: 1964. Hacker, Andrew. Political Theory: Philosophy, Ideology, Science. The Macmillian Company; New York: 1961. Heilbroner, Robert. Marxism, For and Against. W.W. Norton Company; New York: 1980. Payne, Robert. Marx. Simon and Schuster; New York: 1968.

Analysis Of Maltese Falcon Essay Example For Students

Analysis Of Maltese Falcon Essay I dont recall if Gutman said it in the movie about the Falcon being coated by lacquer to obfuscate that its really made of gold and jewels. I think it was implied that nothing is what they really seem to be. This is what I believe Dashiell Hammett was trying to communicate through his novel, The Maltese Falcon. In this paper I will write about why I believe what is Hammett trying to convey through his cast of characters. These characters are unlike the image and stereotype cast upon their roles. Sam Spade isnt exactly the typical (stereotypical?) main character or rather a detective character (I think for any main character.) By his looks/appearance, He Spade looked rather pleasantly like a blond satan; (p. 3). Suggesting he is not angelic looking like lets say Humphrey Bogard (an indication that the movie isnt true to the novel). The film ruined the ironic un-charming hero concept the novel have and so do I as one of my first example of the things-are-not-what-they-seemed-theory-for-Hammetts message.; Spade is callous, avaricious, and shares a similarity with Mike from The House of Games. Why I think Mike and Spade are similar? For one thing Brigid OShaughnessy gave Spade a talk/speech about him using her pretty much the same thing Ford asked Mike in the airport. Brigids comment (p. 211-212) Youve been playing with me? Only pretending you cared-to trap me like this? You didnt-care at all? You didnt-dont-I-love-me?; Fords You used me; speech is strikingly similar to Brigids including the reaction from Mike/Spade. The two men both refused to show sympathy and they did both had sex with their respective victims er women except Mike ends up dead and Brigid ends up in jail. Ford and Mike and Spade and Brigid share many similarities from the two women being used and the men conning these women. We know what Mike did already and Spade used his devilish charm to get Brigid to solve the case. He conned her into giving him money, win his trust, and played with her feelings. The comparison between Mike and Spade is to show that Spade is more of a con men than a detective which I hope are (usually) depicted as law-abiding, straight-arrow, gentlemen. Spade is a proto-badass character. I think Hammett is trying to convey that heroes arent always good. Brigid OShaughnessy (whom I will refer as Brigid because her last name is long) is a complex character in which that she appears to be a typical damsel-in-distress but suppose to be a beautiful and treacherous woman whose loyalties shift at the drop of a dime.; (backcover) Yet Brigid is demure and gentle throughout the novel. In the movie however she seemed blunt unlike her very shy novel counterpart. She was less shy in the movie and she said why she needed Spade and Archers help right away wereas in the novel she said Could you-? I thought-I-that is-; softly. I think due to the womens movement that happened recently then they decided to make Brigid less shy. Brigids character is unlike the usual damsel-in-distress female role though she her mannerisms is. Brigids non damsel-in-distress characteristics are subtle. Brigids treacherous acts were mentioned but she was never shown acting it outright. These acts were also vague that it barely makes you think of Brigid any less. When I re ad the book I didnt see how Brigid is treacherous. Brigid lied but that doesnt seem treacherous at all maybe because I think it was written in a way as if she is telling a tiny white lie. Her so called treachery are obfuscated by her demure mannerism as if to soften them. In the end of the novel/film when she revealed that she killed Miles she said it in a way that it was an innocent accident and goes on with her You used me; speech to make it look like the victim. Brigids lines were written in a way they it makes her look victimized and sorry that we are inclined to be sympathetic of what a tortured soul she is that we cant help but not realize that she is a manipulative witch! I must say that Brigid is a well written character. Hammettt wrote her in a way that we the reader think she is what she is: a poor victimized girl when she is really subtly manipulating our judgment of her, making us think shes innocent. Thats very treacherous!Casper Gutman is very much like Santa Claus in a way that he seems jolly and calm all the time. Gutman never lost his temper once but even if he did his face always stayed jolly. In my opinion Gutman is the protagonist of the novel/film because he is the mastermind of the whole black bird caper. He has lethal underlings: Wilmer and (perhaps) Cairo. Gutman doesnt seem like a bad guy because of the way hes portrayed as Santa-like. It seems like he is the opposite of spade. Spade is the good guy who looks bad and Gutman is a bad guy who looked nice. I think Hammett never really established whos good and bad. Gutman never threatened Spade with his life to get the falcon. Gutman hired Spade and Spade just didnt agree with them that much. So Gutman is not exactly an antagonist. I dont even think there is an antagonist who try to make the protagonists life hell except maybe Dundy. Dundy however isnt the bad guy but the guy who doesnt trust a shady character which is typical nowadays in stories with a protagonist like Spade. In conclusi on, I think Hammett wants us to realize that everything isnt black and white, there are shades of gray or so the saying goes. Not all good things are good and not all bad things are bad. Meaning we cant just based everything with stereotypes and appearances for they are deceiving. Through it all its how good or bad a person is inside that determines whether they are indeed good and bad. This however cannot be seen, youll have to know this person before you can find out. Spade seemed callous as I said but he has a devoted loyalty to Miles. He didnt show he cared for Miles but he did in theend when he put his feelings for Brigid aside to bring his partners killer to justice. Of course Spade also did this because he doesnt want to be Brigids sap but like I said nothing is clear.