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Rocks & Time. Your Goals. You should be able to : Define an isotope (Level 1-2 ) Describe the method used determine the age of rocks and fossils (Level 3-4) Explain how the composition of the rock and fossil allow scientists to determine their age (Level 5-6). Vocabulary.
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Your Goals • You should be able to: • Define an isotope (Level 1-2) • Describe the method used determine the age of rocks and fossils (Level 3-4) • Explain how the composition of the rock and fossil allow scientists to determine their age (Level 5-6)
Vocabulary • radiometric dating • radioactive decay • parent atom • daughter atom • half-life • stratigraphy
How tell time – geologically: stratigraphy & radiometric dating • Stratigraphy- used to determine the approximate age of rock layers • looking where the rock layer is and finding the age of rock above and below the layer • Comparing layers around the globe
Radiometric Dating • Some elements have unstable nuclei (see list) = Parent Atoms • These elements decay into stable elements = Daughter Atoms • The decay rate occurs at regular & measurable intervals (see list) = half-life • Half life = time for half of the parent atoms in a sample to decay into daughter atoms http://www.youtube.com/watch?v=phZeE7Att_s
Oldest known rock & minerals • The oldest zircon dates are 4.36 billion years – found in Australia • counted titanium concentrations showed that when these zircons formed, the temperatures on Earth were about 680 degrees Celsius (Krulwich 2013) • Uses Uranium – Lead dating • found in Northern Quebec • may be remnants of a portion of Earth's primordial crust • using Samarium-147 and neodymium-142 ratio • Age est. 4.28 billion years (McGill University, 2008)
Resources • Alden, Andrew. "Uranium-Lead Dating." About.com Geology, n.d. Web. 02 Feb. 2014. <http://geology.about.com/od/geotime_dating/a/uraniumlead.htm>. • Hadfield, Peter. "The Age of Our World Made Easy." YouTube, 28 Nov. 2007. Web. 02 Feb. 2014. <http://www.youtube.com/watch?v=w5369-OobM4>. • McGill University. "Oldest Known Rocks On Earth Discovered: 4.28 Billion Years Old." ScienceDaily, 26 Sept. 2008. Web. 02 Feb. 2014. <http://www.sciencedaily.com/releases/2008/09/080925144624.htm>. • "Zircon Chronology: Dating the Oldest Material on Earth." Ed. Edmund A. Mathez. American Museum of Natural History, 2000. Web. 02 Feb. 2014. <http://www.amnh.org/education/resources/rfl/web/essaybooks/earth/cs_zircon_chronolgy.html>.