Geological dating techniques of earth
Derivative methods may only be used for dating if their results can be related to a time-scale or reference curve that has been established by absolute dating methods.
If it is not affected in any way by its environment the result can be described as absolute.
Potassium-argon is ideal for dating early hominid fossils in East Africa, for they occur in an area that was volcanically active when the fossils were deposited between one and five million years ago; pioneering results in the 1950s doubled previous estimates of their age.
Bones, teeth and shells contain proteins that break down after death, and the most commonly investigated products of decomposition are amino acids.While some geologists concentrated on the age of the Earth, others studied distinctive surface traces left behind by changes in the extent of polar ice during the most recent (Quaternary) geological period.They identified a succession of Ice Ages alternating with temperate conditions (glacials and interglacials) which - if they could be dated - would reveal much about the evolution of early humans in the context of changing environmental conditions.Unfortunately there are many problems in the direct application of dendrochronological dating.Not all tree species are sufficiently sensitive to display distinctive variations in their ring characteristics, particularly when growing in temperate climates.