Chronology: Absolute Dating Methods

There are numerous scientific methods by which the age of an object can be determined depending on its material culture, the process of formation, and its surroundings. Such studies help improve understanding of the culture of a particular time, and such archaeological findings piece together the past that connects contemporary cultures today.

One such method is absolute chronology, meaning or chronometric calendar dating, which is a method that calculates the age of artefacts by measuring the physical-chemical properties and their historical association with other materials of a similar date. 

Absolute chronology medical definition in history provides a specific time range, in years. The specificity of the date depends on the method used. 

Methods of absolute dating 

The different methods of absolute dating include the following- 

Radiocarbon dating 

• The most widely used dating technique is based on radioactive (carbon 14) decay. 

• Studies are conducted on the constant decay rate of radioactive isotopes into radiogenic daughter isotopes. They are suitable for applications to the types of atoms present in the mineral or other material and their approximate age. Measuring the amount of C14 in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information on when the animal or plant died. The lesser the C14, the older the sample is.

• One limitation is the short life of carbon, making reports reliable within 60000 years. 

However, they are a suitable method when combined with other dating methods.

Dendrochronology

• Dendrochronology, meaning in history, uses tree rings/ growth rings to determine the exact year they were formed in the tree’s life.

• One ring shows a cycle of seasons or one year of the tree’s life. Along with determining the age, they also provide information regarding the climate and environment of that period. 

• They are also combined with radiocarbon dating to calibrate the radiocarbon ages.

• An advanced method called ‘isotope dendrochronology’ is focused on calculating variations in oxygen isotopes in each ring which yields results on those samples that do not work with traditional dendrochronology as a result of too few or similar rings.

Fission track dating

• A radiometric tracking technique of absolute chronology meaning in history determines the age, using damaged trails left by fragments of minerals and glasses. 

• This method makes use of a microscope rather than a mass spectrometer. The number of tracks present is used to calculate the sample’s age. 

• The most common isotope used to determine age is uranium.

• This tracking method can determine the age of samples as early as 300,000 years. 

Luminescence

• This method determines the age by measuring the dose of radiation accumulated.

• This technique is based on the principle that all objects absorb radiation from the environment, which frees electrons within minerals that remain caught within the item.

• The study of crystalline materials gives an idea of the period it was made. Usually, the age of pottery and ceramics are determined by this method. 

• This method is only 15 % effective as the radiation levels are not constant over time. One of the benefits of luminescence dating is that it can confirm how authentic an artefact is.

• Luminescence includes the following techniques- 

Optically stimulated luminescence (OSL)

Infrared stimulated luminescence (ISL)

Thermoluminescence (TL)

Potassium-argon dating 

• Other than radiocarbon dating, potassium-argon dating is a commonly used method to determine age in earlier periods. 

• Potassium 40, a radioactive isotope of potassium, decays into argon-40. The half-life of potassium is far longer than carbon-14, which allows older samples to be dated. Rocks and minerals are common examples where this is done. 

• Argon is a noble gas and determines when the rock is cooled and solidified.

Archaeomagnetic dating

• The study and interpretation of the signatures of the past times were recorded in archaeological materials such as rocks and clay.

• In a particular location, the direction and magnitude of the magnetic field change, and this method can be used to study the change in the magnetic field to constrain the age of materials. 

• When used in combination with radiometric dating, this technique calibrates the geomagnetic polarity time scale—used to determine age up to 100,000 years. 

Amino acid dating 

• The amino acid chronology, meaning history, studies the changes in the amino acid molecules from the present date to the time they were initially formed. 

• It is used in the following fields, namely, paleobiology, archaeology, forensic science, taphonomy, and sedimentary geology. The age can be determined as early as 105 – 107 years. 

Conclusion 

In order to place findings in correct relation to one another and to understand what was present in the experience of any human being at a given time and place, chronology meaning in history is essential. Preservation and studies of artefacts help not only get an idea of how the earth was millions of years ago but also this gathered information gives us ways to prepare ourselves for extreme situations that the people from the past faced.

While relative chronology medical definition provides geological events in time order, absolute dating is an actual date, or date range, in numbers of years. The discovery of absolute dating in 1947 has been a boon to humankind and will continue to provide reliable information to archaeologists.