In the field of archaeology two methods of dating are used---relative and absolute. Something is dated relatively using methods of stratigraphy, linguistic dating and climate chronology to name a few. However, these methods cannot date an object precisely, because the object is dated in comparison with something else; it's not dated in its own right. However, absolute dating gives a more exact date for an object, because it uses methods like radio carbon or thermoluminescence dating techniques. How one dates an object using absolute dating depends on the object itself; the same dating method can't be used on all objects.
Using Absolute Dating Methods
Determine the material makeup of the object being dated. The elemental makeup of an object determines its dating method. Once you determine the makeup of the object, you'll then employ one of the methods of dating below to determine its age.
Use Uranium-Thorium to date objects like marine sediment, bone, wood, coral, stone and soil. This method relies on measuring the half-life of uranium-238 and thorium-230 found in an object.
Utilize thermoluminescence dating if you have rocks, minerals and pottery to date.
Draw on radio-carbon dating to date materials that are organic like wood, bone, shells and tufa (sedimentary rocks made up of organic materials).
Consider racemization for once living organisms that are older than 50,000 years old. This is the cut-off for effective radio-carbon dating. (See "Dating Lucy" in Resources.) Racemization measures certain types of amino acids in an organism after it dies and can measure the date of an item ranging from typically 5,000 to 100,000 years old. However, samples as old as 200,000 years old have been measured with this method.
Utilize potassium-argon (K-Ar) dating for rock and ash substances. This method measures the oldest of objects; Lucy, thought to be the first human ancestor before Ardi was discovered, was dated using this technique combined with relative dating techniques.
Find the absolute date of soil sample by using the oxidizable carbon ratio technique, which measures the organic carbon in the soil.
Employ the OSL (optically stimulated luminescence) method for silty and sandy sediments that have had little exposure to light; glacial deposits can be measured this way.
Use fission track dating to find the absolute date for objects like pottery, glass and fireplace hearths that have been exposed to heat. This method measures the isotopes of both Uranium U-238 and U-235 found in these objects.
Date minerals using the electron spin resonance dating method. Minerals like sedimentary quartz, fossilized teeth and egg shells are among the items that can be dated using this technique.
Rely on dendrochronology to date petrified trees and forests. It uses the rings found in trees to set to determine the age of the tree. This method can also be used as a relative dating method to date the objects in the forests found in the vicinity of the wood.
Consider astronomical dating techniques to find an absolute date for large archaeological features like Stonehenge. This is done by comparing the angle of the sunrise in prehistoric times compared with the angle of the modern sunrise.
Draw on archaeomagnitism when trying to date rocks. This principle relies on dating the shift in the earth's magnetic field, which is recorded in a rock's magnetic particles. As the earth's magnetic field shifts, so do the position of these particles in a rock.