carbon dating!

Carbon Dating!Done By Gabriel Tan 3I109

Hubert Heng 3I113

Background info Carbon-14 dating is a way to

determine the age of certain archaeological artefacts of a biological origin up to 50,000 years old.

Used in dating things such as bone, cloth, wood and plant fibres that were created by human activities.

What about those older than 50k years?

Dates later than 50,000 years can be found using other isotopes such as• Uranium -235 (half-life = 704 million years)• Uranium -238 (half-life = 4.5 billion years)• Thorium-232 (half-life = 14 billion years)• Rubidium-87 (half-life = 49 billion years)

More info Carbon dating is a dating technique predicated

upon three things:• The rate at which the unstable radioactive

C-14 isotope decays into the stable non-radioactive N-14 isotope

• The ratio of C-12 to C-14 found in a given specimen

• And the ratio C-12 to C-14 found in the atmosphere at the time of the specimen's death.

Controversy Dates derived are wildly inconsistent

• For example, "One part of Dima (a famous baby mammoth discovered in 1977) was 40,000 RCY (Radiocarbon Years), another was 26,000 RCY, and 'wood found immediately around the carcass' was 9,000-10,000.

Assumptions made Rate of decay (5730 year half-life)

stayed constant throughout the unobservable past

Ratio of C-12 to C-14 in the atmosphere has remained constant throughout the unobservable past • So we can know what the ratio was at the

time of the specimen's death• Radiocarbon is forming 28-37% faster than

it is decaying Has not yet reached equilibrium. Ratio now is higher than in the past

Assumptions made Ratio of C-12 to C-14 in the

atmosphere has remained constant throughout the unobservable past (cont’d)• Ratio decreased during the industrial

revolution Dramatic increase of CO2 by factories

• Volcanoes spew out CO2, decreasing the ratio. Specimens which lived and died during a period

of intense volcanism would appear older than they really are if they were dated using this technique.

Deriving the formula t is the amount of years after the

death of the item. is the percent of carbon-14 in the

sample compared to the percent carbon-14 in living tissue.

-0.693 is the rate of decay of carbon-14.

is the half-life of carbon-14.

Answers for questions

∵ The chip has 45% of original carbon-14,

=6600 years (3sf) ∴ We can conclude that the volcanic

eruption took place about 6600 years ago

Answers for questions Today is 2011. 1650BC was 3661

years ago

-0.4428=lnP e-0.4428=P P=0.642(3sf) =64.2%

Carbon Dating Gadget http://www2.hci.edu.sg/y09hci0227/c

arbon_dating.php/

Biblography "HowStuffWorks "How Carbon-14 Dating Works""

Howstuffworks "Science" Web. 01 May 2011. <http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm>.

"Carbon Dating." Archaeology - AllAboutArchaeology.org. Web. 02 May 2011. <http://www.allaboutarchaeology.org/Carbon-Dating.htm>.

"Carbon 14 Dating - Math Central." Math Central. Web. 02 May 2011. <http://mathcentral.uregina.ca/beyond/articles/ExpDecay/Carbon14.html>.

The End Thank you