Carbon dating measure
Sedimentary rocks- Sedimentary rocks are generally not datable using isotopic methods because the grains in sedimentary rocks may come from many different rocks of different ages.
Isotope: A version of an atom that differs from other atoms of the same element only in the number of neutrons.Atoms are arranged as a nucleus surrounded by an electron cloud, with electrons zinging around at different distances from the nucleus.Chemists conceive of these distances as shells, and define the properties of atoms by what is in each shell, according to the University of California, Davis.For example, isotopes with very long half lives are no good for dating rocks younger than about 100 million years.This is because, in just 100,000,000 years of time, not enough parent will have decayed for daughter concentrations to be reliably measured.Kelvin knew that the Earth gets hotter with increasing depth (the geothermal gradient), and took this observation as evidence that the Earth is cooling off. Chamberlain challenged Kelvins assumption that the earth started as a molten body.
He believed the Earth started off as a molten mass and subsequently transformed to a hot solid mass during cooling. Instead, Chamberlain proposed a model of cold accretion for the Earth.
The quantitative approach is admirable, but Buffon's assumptions are flawed. Silicate minerals have lower heat conductivity than steels and are better insulators leading to slower cooling rates.
Second, the calculations did not incorporate the heating effects of radioactive decay.
When this happens in a mineral, the two departing nuclei leave behind a trail of destruction in the crystal lattice. Fission track dating is ideal for samples from recent times back to 100,000,000 years.
Beyond 100,000,000 years, the density of the tracks becomes so great (saturated) that they cannot be counted reliably.
In older stars that have burned most of their hydrogen, leftover helium accumulates.