RELATIVE AND ABSOLUTE DATING. Ashley Allen Oneonta High School Alabama Paleontological Society. Objectives. Distinguish between absolute dating and relative dating. Review law of superposition. Discuss the importance of half-life and radioactive decay. - PowerPoint PPT Presentation
RELATIVE AND ABSOLUTE DATINGAshley AllenOneonta High SchoolAlabama Paleontological Society
ObjectivesDistinguish between absolute dating and relative dating.Review law of superposition.Discuss the importance of half-life and radioactive decay.Conduct activity on relative and absolute dating.
Two Ways to Skin a CatRelative dating of fossils is a system in which a fossil is given an age designation in terms of epoch, period, or era which can be compared to other geologic units of time as older or younger, but without the burden of assigning a specific number.For example, a Pennsylvanian lycopod bark impression is older than a Cretaceous oyster and younger than a Mississippian brachiopodRelative dating is best explained when covering the law of superposition and a geologic time scaleAbsolute dating of a fossil involves assigning a specific quantity of age with a fossil such as saying that an echinoid, Hardouinia bassleri, is 83 million years old.
Two Inescapable LawsThe law of superposition states that older sedimentary rocks were deposited prior to younger sedimentary rocks, therefore, as one ascends a rock face with multiple formations, the oldest rock layer is on the bottom and the rock units get progressively younger as one ascends the exposure.The law of faunal succession states that as one views progressively older fossils, they become more and more dissimilar with modern forms of life with which we are most familiar.
Law of Superposition
Law of Faunal SuccessionNote the general appearance of more familiar species the closer one gets to the present time.
Radioactive DecayUnstable parent radioactive isotopes decay at a stable rate which cannot be altered.Each type of radioactive parent isotope has a unique half-life.A half-life is the amount of time that it takes for half of the given radioactive parent isotope to decay into a stable daughter product.By comparing the amount of radioactive parent isotope in remains to the stable daughter product, an absolute age may be determined.
Web ResourcesMany radiometric dating activities may be found by going to http://www.kn.pacbell.com/wired/fil/ or by typing filamentality into any search engine.At the core of each activity is the concept of half-life.Technology will limit the amount of detectable radioactive parent isotope or stable daughter product.
ReferencesLaw of Superposition - http://www.calstatela.edu/faculty/acolvil/geotime/grandcanyon_strat.jpgLaw of Faunal Succession - http://mpschmidt.homestead.com/files/GeoTimeScale.jpgCarbon Dating - http://ttevisual.com/physics/images/file5/dkph5.09-3_212.jpgCarbon Dating Shell - http://www.fmi.uni-sofia.bg/fmi/contmech/kmarkov/history/gifs/carbon.gif