Radioactive dating fossils dated
This method is based on the assumption (which nearly always holds true) that deeper layers of rock were deposited earlier in Earth's history, and thus are older than more shallow layers.
The successive layers of rock represent successive intervals of time.
The two main types of dating methods are relative and absolute.With sensitive instrumentation, this range can be extended to 70,000 years.In addition to the radiocarbon dating technique, scientists have developed other dating methods based on the transformation of one element into another.The nucleus of every radioactive element (such as radium and uranium) spontaneously disintegrates over time, transforming itself into the nucleus of an atom of a different element.In the process of disintegration, the atom gives off radiation (energy emitted in the form of waves). Each element decays at its own rate, unaffected by external physical conditions.