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# KCC's Quizzes AQQ245 on Fossil Dating with Carbon14

You probably heard the method of dating fossils by measuring Carbon14 (also note C14 concentration. To refresh, the concentration of C14 in the air and on earth surface is constant (thanks to cosmic radiation) since ever (in fact it is assumed so). C14 is not stable and is changed into Nitrogen and an electron: C14 concentration versus the standard carbon (C12) decades with time. That speed is characterized by Its half-life period which is 5568 years for C14 (quantity of C14 still present in an isolated place decays by half after each 5568 years).

Today, in free air and on the earth surface, the ratio N0 = C14/C12 is 0.8 10-12

A mammoth bone has been just extracted and the concentration of C14/C12 is 0.2 10-12.

Questions:

1. How old is that bone?

2. Since humanity is constantly putting more carbon in the atmosphere. How it affects the Carbon14 dating? For example, if C12 concentration is doubled. How will be the dating of our previous bone?

Good Luck!

P.S. If you think there are colleagues who should try those quizzes, please forward them the link!

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[edited by: StephenV at 3:24 PM (GMT -4) on 18 Oct 2023]
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• 1) From 0.8 to 0.2 it is factor 4. That means C14 isotopes two times halved.
2 times 5536 years makes 11172 Years. This should last ice age, aka Last glacial period LGP

2) Due to more pollution, we will have more CO2 in future. Which produces a lot C12.
The problem by fossil oil is the C14 isotopes in oil are already diminished due to millions of years radioactive decay.
Thus the ratio C14/C12 will be in future less, and similar levels to e.g. 1000 years old material from forensic or archeology.
So we will have more uncertainty in the forensic identification.

Analogy to Electronics, our SNR (Signal to Noise Ratio) will be less.

• 1) From 0.8 to 0.2 it is factor 4. That means C14 isotopes two times halved.
2 times 5536 years makes 11172 Years. This should last ice age, aka Last glacial period LGP

2) Due to more pollution, we will have more CO2 in future. Which produces a lot C12.
The problem by fossil oil is the C14 isotopes in oil are already diminished due to millions of years radioactive decay.
Thus the ratio C14/C12 will be in future less, and similar levels to e.g. 1000 years old material from forensic or archeology.
So we will have more uncertainty in the forensic identification.

Analogy to Electronics, our SNR (Signal to Noise Ratio) will be less.

Children
• Thanks a lot Hakan for your answer and comment!

Answer to question 1 is right!

On question 2, I agree there can be many assumptions with unknowns like how fast and where (? only in the upper atmosphere level)  the C12 atoms are transformed in C14? By assuming the C12 generated by the human actvities, thus only in the very last 50 years and by assuming those additional C12 have not the time to reach the upper atmosphere layer, we can then extrapolate the C14/C12 ratio appears much less than it should be; thus giving a longer age to our bone...