The main relative dating method is stratigraphy (pronounced stra-TI-gra-fee), which is the study of layers of rocks or the objects embedded within those layers.
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.
These plants are eaten by animals who, in turn, are eaten by even larger animals.
Eventually, the entire ecosystem (community of plants and animals) of the planet, including humans, is filled with a concentration of carbon-14.
Radioactive decay: The predictable manner in which a population of atoms of a radioactive element spontaneously disintegrate over time.
xx is xxxxxxxxx xx xxxxxxxxx the xxx xx x fossil or xxxxxxxxx xxxx xx xx unearthed, so xxxx further analysis xxx xx xxxxxxx xxx xxxxx on facts.