Radiocarbon dating bp relative dating webquest
The half-life is the time taken for an amount of a radioactive isotope to decay to half its original value.
Because this decay is constant it can be used as a “clock” to measure elapsed time assuming the starting amount is known.
The absolute radiocarbon standard is 1890 wood, the OX-I standard has an activity of 0.95 of this wood.
The definition of year “0”, “modern” or “present” is 1950, there is no real reason for this other than to commemorate the publication of the first radiocarbon dates.
The radiocarbon age is determined by the equation where -8033 represents the mean lifetime of 14C (Stuiver and Polach, 1977), Asn is the activity in counts per minute of the sample and Aon is the counts per minute of the modern standard.
A variant of this equation is also used when the samples are analysed by AMS.
The age of known artefacts from Egypt were too young when measured by radiocarbon dating.
A scientist from the Netherlands (Hessel de Vries) tested this by radiocarbon dating tree rings of know ages (de Vries, 1958).
From there it is incorporated into shell, corals and other marine organisms.This means that it can be difficult to effectively clean the samples and remove enough contaminating carbon to obtain an accurate date.In the late 1970s and early 1980s the dating of small samples became possible using Accelerator Mass Spectrometry (AMS; Muller, 1977; Nelson et al., 1977).This method needs less than 1 mg of carbon and directly measures the abundance of the individual ions of carbon (14C, 12C and 13C).To obtain a radiocarbon age the sample activity or the 14C/12C ratio must be compared to a standard material of known age.
He noted some discrepancies indicating that radiocarbon results would need to be “calibrated” to convert them to calendar ages.