Notes 10-13-06

Notes 10-13-06 - amount of uranium in surrounding area and...

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ABSOLUTE DATING TECHNIQUES A) Radiometric 1. Radiocarbon Dating (near present-75,000) 2. Discovered by Libby- 1949 3. Recalibration using dendrochronology 1. we realized c-14 was variable 4. Accelerator Mass Spectrometry (AMS) Half Life of C-14 5,730 +- 40 years -c-14 comes from sun neutrons -sun does not always produce same amount of neutrons -carbon 14 is a direct dating technique B) Potassium Argon Dating (1000,000 y.a. – 5 m.y.a. (way long ago) 1. when potassium decays it turns into argon 2. volcanic actions contain potassium which releases the Argon and resets the half life INDIRECT dating technique C) Fission Track (U238) 100,000 y.a.- 1 m.y.a. 1. on average one in a million uranium deposits will explode. 2. what we do is study the explosion (fission track) and the
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Unformatted text preview: amount of uranium in surrounding area and explosion to determine date 3. indirect dating method D) Seasonal markers 1. Dendrochronology (8,200 y.a. to current; here in SW 6,000 y.a.) location, species sensitive 2. Obsidian Hydration- when obsidian is broke open it starts absorbing “hydration” band (only accurate if local temp. does not vary more or less than 10 degrees (only good at equator) 3. Magnetic Changes- composition of Earth has created a magnet (archaemangnetism 4,000 y.a.)- Magnetic north varies and this change is registered in various different iron rich features ie. Hearths, kilms, clay tiles EXAM WILL BE ON TUESDAY (questions taken from student tests online) GLOBE QUESTION FROM CHP. 5 about dates...
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