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Estimate the age of the wood. The carbon in humans, and plants contains a small...

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dareg17 | Student, Grade 10 | Honors

Posted February 2, 2012 at 10:53 AM via web

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Estimate the age of the wood.

The carbon in humans, and plants contains a small percentage of the radioisotope Carbon-14, which has a half life of 5730 years. for example, a piece of wood taken from a cave dwelling in New Mexico has a C-14  content that is only  25% of that of wood cut today. Estimate the age of the wood.


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najm1947 | Elementary School Teacher | Valedictorian

Posted February 2, 2012 at 3:37 PM (Answer #1)

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Half life of Carbon-14 = 5370 years

Percentage of Carbon-14 in cave wood as compared to Present day wood = 25%

Expected Age of Cave wood = (Ln(25%)/Ln(50%))*Half-Life

= (Ln(.25)/Ln(.5))*5370

= 10740 years

Estimated age of cave wood = 10740 Years


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trophyhunter1 | College Teacher | (Level 3) Senior Educator

Posted February 3, 2012 at 10:29 PM (Answer #2)

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If the orginal amount of carbon-14 in cave wood was X, then, you would have 1/2 X in 5370 years or one half-life. For the radioactive isotope to decay to 1/4 X, an additional half-life would have passed. This means that 10,740 years would have passed. Radioactive carbon dating is used for relatively recent items to date, as the half-life isn't as long as other radioactive elements. It is only used to date materials less than 62,000 years old. The C14 in organic compounds decays at a fixed rate of radioactive decay and fairly reliable dates can be attributed to archaelogical finds such as bones, clothing, etc.


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