Dating Methods Essay -- essays papers

General Differances Between Relative and Absolute Dating MethodsGetting dates for fogys that are found in sites beingexcavated by anthropologist is very important. Dates show theevolution from early hominid specimens to our own species, Homohomo sapiens. There are many methods that can be utilise to acquirethese dates, but all of these methods fall into one of twocatorgories. They can either give a absolute date or a relativedate. An absolute date is one in which you get an actual date in eld. Also known as chronometric methods. Relative dates donot give an actual date in terms of years, but they tell you ifone fossil is older or younger than another fossil.Ushally relative dates are given in terms of the column of populace they are found in. This is called striatigraphy. Insites like Olduvai gorge their are geological layers of vocanicash and sediment. When a anthropologist finds a fossil in aundistirbed layer of gray ash, you know that it is younger thanthe fossil in t he layer of red ash below, and that fossil isyounger than the fossil in the layer of brown ash belowit.(Johanson 65) The basic theory here is that a certian sitecantians a geolgical column key that is made up of differantstrata layers, the fossils get older as they move down the key,and are found in differant layers of strata..(Scully 2) Relative dates have a couple of major problems. One is that theearth moves in many ways and this can distrube the layers ofsediment putting younger fossils below older ones. Another isthat you can not tell exactly how untold younger or older somethingis from somethinng else and you can not date differant fossilsfrom differant sites with thes relative go out methods. Absolute dating, unlike realative dating, gives theanthropologist an exact date in terms of calander years. Thesedating methods are much more reliable and can be used in manydifferant sites with many differant fossils. Absolute datingbases its dates on the inborn radioactivity of differantelements found in the world.(Johnston 216) There are certianelements that occur in differant forms, these elements are calledisotopes. Each one of these isotopes has a differant atomic massthan others. Some of thes isotopes are radioactive, meaning thatthey give of radiation in either alpha or beta form, as theyde... ... has a half-life.C14 is the radioactive isotope of rearular carbon, c12. Thecocentration of C14 in the body is one ordinal of a gram in thebody to one gram of C12. This C14 is contantly annihilationing, butthrough animals and plants breathing it is replenashed when anorganism is alive. When the animal dies the C14 intake stops anda decay that is not replenashed.(Comas 456) During life an organism have a specific activity of 15.6disintigrations per minuate per gram of regular carbon in thierbody.(Comas 456) After life and C14 intake dispense with and theequilibrium is halted, radioactive disintigration of C14 occurs,and after 5,700 years thi s activity will have decreased to 7.8disintigratuions per minuate per gram of carbon in thebody.(Comas 457) This means that the ratio of C14 to C12 leftin the fossil when it is found can give a date in years. Carbon-14 dating has a half-life of 5,700 years, with the lowerlimit of 1,000 years. The upper limit used to be about 30,000years because after that the ratio was too small to analis. Recently reaserch by Haring and deVires has let scientist put theupper limit at 100,000 years old.(Comas 457)