A distinction is made between relative and absolute or nuclear geochronology. Absolute geochronology establishes the so-called absolute age of rocks—that is, an age expressed in units of time, usually in millions of years. Relative geochronology. The principle of superposition the so-called Stensen [Steno] law is commonly applied for the determination of the relative age of laminated sedimentary and pyroclastic rock, as well as volcanic rock lavas. According to this principle, each overlying stratum in an undisturbed sequence of stratification of laminated rock is younger than the underlying stratum.
Encyclopedia of Scientific Dating Methods
Uranium–thorium dating - Wikipedia
Geochronology is the science of finding the ages of rocks , fossils and sediments. It uses a number of methods. By measuring the amount of radioactive decay of a radioactive isotope with a known half-life , geologists can establish the absolute age of the parent material. A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods. More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years.
Archaeological Dating Methods
Dating techniques are procedures used by scientists to determine the age of an object or a series of events. The two main types of dating methods are relative and absolute. Relative dating methods are used to determine only if one sample is older or younger than another. Absolute dating methods are used to determine an actual date in years for the age of an object. Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative.
Carbon dating is a technique used to determine the approximate age of once-living materials. It is based on the decay rate of the radioactive carbon isotope 14 C, a form of carbon taken in by all living organisms while they are alive. Before the twentieth century, determining the age of ancient fossils or artifacts was considered the job of paleontologists or paleontologists, not nuclear physicists.