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Write the name of each layer What is an important property of that layer?. Absolute Time. Radiometric or Isotopic dating Tells an “exact” age Radioactive decay Parent nucleus becomes more stable daughter nuclei Give off energy Constant rate Half-life 100g → 50g + 50g → 75g + 25g. - PowerPoint PPT Presentation
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Write the name of each layer What is an important property of that
layer?
Absolute Time Radiometric or
Isotopic dating Tells an “exact” age Radioactive decay
◦ Parent nucleus becomes more stable daughter nuclei
◦ Give off energy◦ Constant rate
Half-life◦ 100g → 50g + 50g◦ → 75g + 25g
% parent left = # of half-lives → age What do we use?
◦ Carbon-14◦ Uranium-235◦ Potassium-40
Carbon Dating Various forms of carbon
◦ Most common = carbon-12
◦ Radioactive = carbon-14 Carbon-14
◦ Used for things that were alive
◦ During life - constantly replaced
◦ After death - amount starts to decrease
◦ Half-life of 5,730 years
Half-Life Fraction carbon -14 left
Percentage carbon-
14 left
Age
1
2
3
4
You are a CSI Detective…• You found a skeleton contains 12.5% of
it’s original carbon.1. How many half lives have passed?2. How old is it? (how long ago did this
person die?)
You are an anthropologist and found this animal!
• This skeleton contains 3.125% of it’s original carbon.1. How many half lives have passed?2. How old is it?