Geological periods, are characterised by climatic changes and the successive types of plants and animals found.
Chemical dating. This is of two kinds i.e. Radio-Carbon dating and Potassium-Argon method. Radio-Carbon dating measures organic substances and the rate of decay of carbon14 in fossils. Potassium-Argon method measures the amount of potassium and the amount of Argon-40 to assist in dating volcanic ash and minerals.
Stratigraphy i.e. the study and interpretation of the layers of rock successively deposited at one place. It is useful in determining dates for areas affected by sedimentation.
Statistical dating. This helps in determining the length of a generation for a particular society by estimating dates for events associated with certain generations.
Lexico Statistics dating. This is the statistical study of the vocabulary of languages to determine their age and historical links with other languages.
It is based on the assumption that all languages have a basic vocabulary that will gradually change at a common rate for all languages at all times.
Glotto-Chronology, which is a subdivision of Lexico Statistics, attempts to establish that languages are historically related. It helps in expressing rates of language development by formulae precise enough to enable dates when the change occurred to be calculated. More than one method of dating can be useful in order to ascertain the dates of either fossils or artefacts.