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Absoulte dating

Is a process of establishing the age of an object, such as a fossil or rock layer, by determining the number of years that is exsisted. Absoulte dating. Radioactive Decay. Radioactive isotopes tend to break down into stable isotopes of other elements in a process Radioactive Decay

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Absoulte dating

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  1. Is a process of establishing the age of an object, such as a fossil or rock layer, by determining the number of years that is exsisted Absoulte dating

  2. Radioactive Decay • Radioactive isotopes tend to break down into stable isotopes of other elements in a process RadioactiveDecay • Because radioactive decay occurs at a steady pace, scientists can use the relative amounts of stable and unstable isotopes present in an object to determine object’s age.

  3. Radiometric Dating • Determining the absolute age of sample based on the ratio of parent material to daughter material • Half-Life is the time it takes for one-half of a radioactive sample to decay

  4. Types of Radiometric Dating • Uranium-Lead Method • Potassium-Argon Method • Carbon-14 Method

  5. Uranium,Potassium, and Carbon • Uranium-238 method is used for dating rocks back more than 10million years ago • Potassium -40 method is used to date rocks older than 100,000 year ago • Carbon-14 method is used mainly to date rocks that have lived within the last 50,000 years.

  6. Fossilized Organisms • Afossil is any naturally preserved evidence of life.

  7. Materials that preserve evidence of life • In Rock • Mineral Replacement • Permineralization is a process in which minerals fill in pore spaces of an organism’s tissues. • Petrification of an of organisms, occurs when the oraganisms tissues are completely replaced by minerals • Fossils in Amber(tree sap) • Mummification • When organisms die and dry out they are protected from bacteria because of the lack of water • Frozen Fossils • Fossils in Tar • One such place is the La Brea tar pits,in Los Angeles County, California. These tar pits were present 40,00o years ago

  8. Other Type of Fossils • Trace fossil are any naturally preserved evidence of an animal’s activity • Coprolites are preserved feces, or dung from , from animals • Mold is a cavity in the ground or orckehere a plant or animal was buried. • Cast is an object created when sediment fills a mold and becomes rock

  9. Using Fossils as a Door Way to the Past • Environmental Changes • Ex. By studying coral-reef fossils and applying the principle of uniformitarianism, they have determined that Iowa was once covered by a shallow sea. • Species existence on Earth • We know that fish existed before amphibians because fish were found in a lower layer of rock. In the same way, we know that amphibians existed before reptiles

  10. Using Fossils to Date Rocks • Index fossils are fossils of organisms that lived during a relatively short, well-defined time span. • Ex. Tropites, a genus of ammonites, existed for only about 2o million years, which makes it a good index fossils. • Where geologists find them in a rock layer, they know that the rock layer is between 208 million and 230 million years ago

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