Dating Methods

With gratitude to a various amount of modern radiometric dating methods, scientists and researchers now have the ability to decipher the age, era, or period of earth's ancient artifacts, geological strata, or fossils in which it now contains. Even the earth's formation and existence can be subject to these scientifical dating methods. These methods can be performed on samples as small as one billionth of a gram; unfortunately, most of these experiments require the utilization of special instruments such as a mass spectrometer and can often be costly to conduct. And though radiometric dating methods are rarely one hundred percent accurate, scientist and researchers are still willing to take the risk, for the sake of science or perhaps pure curiosity.

The way in which chronological dating is acquired falls within two methods of examination: Absolute Dating and Relative Dating. (Michels 1973) Generally, scientists use both methods in combination and interrelation with another. Absolute Dating is a method in which the actual age of an object or stratigraphic layer is determined. Relative Dating is a method in which it uses the absolute date to tie associated artifacts and layers into the sequence.

Among many of the radiometric dating methods, the most fundamental principle lies within the research of archeologists. The Law of Superposition is the standard in which scientists go by determining the relative ages of archeological materials within strata, the natural materials such as rocks, soil, and traces of plants and animals that settle on the earth's surface and over time that accumulate in layers.(Edwards 1985) The Law of Superposition states that young strata will be deposited on strata that are older, given the normal conditions of deposition; therefore, artifacts found within older strata will logically be older than artifacts found within younger strata. This law is the guiding principle of stratigraphy - the study of strata or layers.

With the Law of Superposition applied, the technique of Cross-Dating is used to take advantage of consistencies in stratigraphy between many different sites. For example, different layers within multiple stratigraphic columns from different sites can be aligned and arranged in chronological order based on relative vertical association.

Probably one of the most widely used absolute dating method is known as Radiocarbon or Carbon-14 Dating. This method was developed by J.R. Arnold and W.F. Libby in 1949. (Gore 1999) Its development revolutionized science by providing a means of dating deposits independent of artifacts and stratigraphic sequences, and has become a crucial element to the art of radiometric dating. Radiocarbon's method of age determination depends upon the decay to nitrogen of carbon-14. (Poole 1961) Basically, the less carbon-14 the subject has, the older the subject is. The manner in which this process works begins with the sun. As the earth's upper atmosphere is showered with cosmic radiation, atmospheric nitrogen atoms are broken down into unstable isotopes of carbon then converted to Carbon-14. The Carbon-14 atom becomes unstable because the cosmic radiation triggered the nitrogen atom to convert one of its seven protons into an extra neutron, therefore the new Carbon-14 atom caries six protons, eight neutrons, and six electrons. The Carbon-14 atom is brought to earth along with other carbon atoms by atmospheric activity and becomes fixed into the biosphere. The atoms then become attached to complex organic molecules through photo synthesis in plants and become part of their molecular makeup. Any critters that walk by and consume the plants now hold the C-14 atoms and continues to hold