Chemical techniques of relative dating

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.

These include the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method. Thermoluminescence (pronounced ther-moeloo-mi-NES-ence) dating is very useful for determining the age of pottery.

When a piece of pottery is heated in a laboratory at temperatures more than 930°F (500°C), electrons from quartz and other minerals in the pottery clay emit light.

By measuring the amount of carbon-14 remaining, scientists can pinpoint the exact date of the organism's death.

The range of conventional radiocarbon dating is 30,000 to 40,000 years.

Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.

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.

Relative dating methods are used to determine only if one sample is older or younger than another.

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