NATURAL RADIONUCLIDES AND GEOCHRONOLOGY
Naturally occurring radionuclides are used in Earth Sciences for two fundamental purposes: age determination of rocks and minerals and studies of variation of the isotopic composition of radiogenic nuclides. The methodologies that are in use today allow us to determine ages spanning from the Earth's age to the late Quaternary. During this time a series of events of paramount importance for the history of the Earth took place and the use of isotopic geochronometers can set in a precise chronological scale the most relevant of those events, otherwise impossible to be dated. Biological fossils can be used for the last 700 million years of the Earth History; geochronometers based on radioactive decay act as isotopic fossils and allow the entire history of the Earth to be traced back. The age of the Earth, of the moon and meteorites, the oldest Earth rocks and the primeval forms of life, as well a other fundamental landmarks of the evolution of the planet, can be dated.