2. Content
• Introduction
• History
• Carbon Dating
• Principle of carbon dating
• Life Cycle Of Carbon 14
• Methods of carbon dating
• Application
• Summary
3. INTRODUCTION
• All carbon atoms have 6 protons in the nucleus,but the nucleus may
also contain 6, 7, or 8 neutrons.
• Their are 3 naturally occuring isotopes of carbon on earth,
1.carbon-12 : Stable nucleous (99% of all natural carbon)
2.carbon -13 : Stable nucleous (1%)
3.Carbon -14 : Unstable radioactive isotopes (Wher 1 in 1012
carbon atoms in the atomosphere is C-14)
4. History
• The carbon-14 method was developed by the American
physicist Willard Frank Libby and his team in 1946 at the
University of Chicago.
• He determined the half life to be 5568 years ± 30 years
and it is popularly known as libby half life.
• This half life has later been re-determind by Godwin as
5730 ± 40 years which is known as the Cambridge half
life.
• In 1960, Mr. Willard F. Libby was awarded the Nobel
Prize in Chemistry in recognition of his efforts to develop
radiocarbon dating.
5. Carbon dating
It is one of the form of Radiometric dating and also refered as
Radiocarbon dating or carbon-14 dating.
• This method used for determining the age of an object
containing organic material by using the properties of
radiocarbon, a radioactive isotope of carbon.
6. Principle
• Carbon 14 is continually being formed in the upper atmosphere
by the effect of cosmic ray neutrons on nitrogen 14 atoms. It is
rapidly oxidized in air to form carbon dioxide and enters the
global carbon cycle.
• Plants and animals assimilate carbon 14 from carbon dioxide
throughout their lifetimes. When they die, they stop exchanging
carbon with the biosphere and their carbon 14 content then
starts to decrease at a rate determined by the law of radioactive
decay.
• Radiocarbon dating is essentially a method designed to measure
residual radioactivity.
9. Contd....
• Animals get their C-14 dose from the food that they consume.
• When the organism (or a tissue) dies absorption of C-14
ceases and the amount of C-14 gradually decays..
• The half-life of the decay of C-14 to nitrogen is 5730 years so
the concentration halves every 5730 years.
• HALF-LIFE : The time taken for half a radioactive sample to decay
into something else.
• Radioactive carbon (C-14) β decays to nitrogen (N14) by
emitting an electron (e–) and an antineutrino ( v-) with no mass
or charge.
12. Methods of measuring C-14
There are two basic methods,
1. Radiometric :
Radiometric dating method is used to detect beta particles from
the decay of carbon 14 atoms. using a gas proportional counter (a form of
Geiger counter) or a liquid scintillation counter.
• It is cheap and It takes about a month to achieve satisfactory statistics.
2. AMS (Accelerator mass spectrometer):
Accelerator mass spectrometers count the number of carbon 14
atoms present in the sample.
• It is expensive and it takes about a week.
• It requires only about a gram.
• It is a good method for dating specific samples.
14. Application
•Carbon dating is useful to archeologists when they
need to know the approximate date of a fossil or any
other object.
•carbon dating is used to find the ages of trees,
mummies, fossils, or other organic material
•Carbon-14 is used to study the passage of carbon
dating photosynthesis in plants.
15. contd....
• Radiocarbon dating of sacred mummies from ancient Egypt.
• Radiocarbon dating can be used to date carbon containing
pigment like charcoal, it was even useful in dating cave
paintings.
• Samples that have been radiocarbon dated since the
inception of the method include,
• charcoal, wood, twigs, seeds, bones, shells, leather, peat
• lake mud, soil, hair, pottery, pollen
• wall paintings, corals, blood residues, fabrics
• paper or parchment, resins, and water.
16. Contd....
Ancientin ink : Iceman Otzi has world’s
oldest tattoos (Chinchoro mummy)
• 61 tattoos on the Iceman’s body.
Ancient Quran manuscript
(1,500 years old)
17. contd....
Prehistoric horse decorates the walls of
lascaux Cave in France.
(40.000BC to 8000 BC )
Burial site with items dug up from the
Sanauli site in Baghpa
(3800 yrs old)
18. Limitation
• This technique used only for dating organic material
• It cannot be used to date rocks (except carbonacious
rocks)
• Maximum age limit for C-14 dating is 52,000 to 62,000
years.
• Several physical, chemical, and biological processes can
cause contamination.
• Carbon exchange between the sample and the
atmosphere is a common cause of contamination in
bone, wood, and shell samples.
19. Measurement and reporting dates
• The radiocarbon measurement is termed as conventional
radiocarbon age (CRA).
• Uncalibrated radiocarbon measurements are usually reported in
years BP(Before present) where 0 (zero), BP is defined as AD 1950.
• BP notation is also used in other dating techniques but is defined
differently, as in the case of thermoluminescence dating, where BP
is defined as AD 1980.
• Half-life used in carbon dating calculations is 5568 years, the value
worked out by chemist Willard Libby, and not the more accurate
value of 5730 years, Although it is less accurate.(to avoide
inconsistencies or errors when comparing carbon-14 test )
20. Summary
• C-14 method is used for determining the age of an object containing
organic material by using the properties of radiocarbon, a radioactive
isotope of carbon.
• The half-life of the decay of C-14 to nitrogen 14 is 5730 years so
the concentration halves every 5730 years.
• When the organism (or a tissue) dies absorption of C-14 ceases,
and the amount of C-14 gradually decays in every half life.
• carbon dating is used to find the ages of trees, mummies, fossils, or
other organic materials.
