Relative dating for fossils
Since certain species of animals existed on Earth at specific times in history, the fossils or remains of such animals embedded within those successive layers of rock also help scientists determine the age of the layers.Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.Narrow rings grow in cold or dry years, and wide rings grow in warm or wet years.The rings form a distinctive pattern, which is the same for all members in a given species and geographical area.Radioactive decay: The predictable manner in which a population of atoms of a radioactive element spontaneously disintegrate over time.Stratigraphy: Study of layers of rocks or the objects embedded within those layers.The older the pottery, the brighter the light that will be emitted.Using thermoluminescence, pottery pieces as old as 100,000 years can be dated with precision. Known as dendrochronology (pronounced den-dro-crow-NOL-o-gee), tree-ring dating is based on the fact that trees produce one growth ring each year.
Absolute dating methods are carried out in a laboratory.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.When carbon-14 falls to Earth, it is absorbed by plants.These plants are eaten by animals who, in turn, are eaten by even larger animals.
The age of the remains of plants, animals, and other organic material can be determined by measuring the amount of carbon-14 contained in that material.