Conventional radiocarbon dating
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.
The rings form a distinctive pattern, which is the same for all members in a given species and geographical area.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).When the organism dies, the supply stops, and the carbon-14 contained in the organism begins to spontaneously decay into nitrogen-14.The time it takes for one-half of the carbon-14 to decay (a period called a half-life) is 5,730 years.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.
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.
When carbon-14 falls to Earth, it is absorbed by plants.