The isotopic make-up of original material is important, as is mixing of magma with surrounding material.The conditions of formation are also important, because both the cooling rate and the opportunities for mixing affect isotope ratios.Furthermore, the same method can produce different ages on different parts of the same rock.
Some rocks dated older than the 4.5 billion year evolutionary age for Earth. Isochron dating can also produce negative ages, by producing a negative slope.K-Ar and Ar-Ar can result in negative ages when atmospheric argon is considered.However, it is typically unknown and simply assumed whether these ratios of elements are the result of radioactive decay over time or other processes that have taken place in the rock.Ages of Rocks in Millions of Years Sometimes different methods used on the same rock produce different ages.This is particularly important in light of the Biblical flood.
How a rock is formed is important to understanding its isotopic make-up and any dates derived.
Accepted Dating Methods Here we outline some dating methods, both absolute and relative, that are widely accepted and used by the scientific community.
Absolute dating supplies a numerical date whilst relative dating places events in time-sequence; both are scientifically useful.
To date rocks or other objects, scientists typically use radiometric dating.
In short, the ratio of radioactive and stable isotopes in the sample are determined and the measured rate at which the isotopes decay is used as an indicator of the age of the sample.
One key factor is the fact that Ar-Ar dating needs a standard of "known" age.