Methods of dating the earth

Herein lies the true advantage of the radiocarbon method, it is able to be uniformly applied throughout the world.

Included below is an impressive list of some of the types of carbonaceous samples that have been commonly radiocarbon dated in the years since the inception of the method: The historical perspective on the development of radiocarbon dating is well outlined in Taylor's (1987) book "Radiocarbon Dating: An archaeological perspective".

14C also enters the Earth's oceans in an atmospheric exchange and as dissolved carbonate (the entire 14C inventory is termed the carbon exchange reservoir (Aitken, 1990)).

Plants and animals which utilise carbon in biological foodchains take up 14C during their lifetimes.

The C14 technique has been and continues to be applied and used in many, many different fields including hydrology, atmospheric science, oceanography, geology, palaeoclimatology, archaeology and biomedicine.

There are three principal isotopes of carbon which occur naturally - C12, C13 (both stable) and C14 (unstable or radioactive).

The 14C formed is rapidly oxidised to 14CO2 and enters the earth's plant and animal lifeways through photosynthesis and the food chain.

The rapidity of the dispersal of C14 into the atmosphere has been demonstrated by measurements of radioactive carbon produced from thermonuclear bomb testing.

Thus, one carbon 14 atom exists in nature for every 1,000,000,000,000 C12 atoms in living material.The half-life () is the name given to this value which Libby measured at 556830 years. After 10 half-lives, there is a very small amount of radioactive carbon present in a sample.At about 50 - 60 000 years, then, the limit of the technique is reached (beyond this time, other radiometric techniques must be used for dating).Renfrew (1973) called it 'the radiocarbon revolution' in describing its impact upon the human sciences.Oakley (1979) suggested its development meant an almost complete re-writing of the evolution and cultural emergence of the human species.