Age dating relative
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.
Dendrochronology: Also known as tree-ring dating, the science concerned with determining the age of trees by examining their growth rings.
Half-life: Measurement of the time it takes for one-half of a radioactive substance to decay.
Long before geologists tried to quantify the age of the Earth they developed techniques to determine which geologic events preceded another, what are termed "relative age” relationships.
As long as an organism is alive, the supply of carbon-14 is replenished.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.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.Carbon-14, a radioactive form of the element carbon, is created in the atmosphere by cosmic rays (invisible, high-energy particles that constantly bombard Earth from all directions in space).
Absolute dates must agree with dates from other relative methods in order to be valid.