Archaeologists and biologists are also sometimes able to use potassium-argon dating to measure the age of artifacts and fossils, when these have become trapped in or buried under volcanic rock.

The mathematical formula that is used to figure the age of the rock depends on the half-life of potassium-40 (the time it takes for half the potassium-40 in a given sample to decay).

These factors introduce error limits on the upper and lower bounds of dating, so that final determination of age is reliant on the environmental factors during formation, melting, and exposure to decreased pressure and/or open-air.

Time since recrystallization is calculated by measuring the ratio of the amount of The quickly cooled lavas that make nearly ideal samples for K–Ar dating also preserve a record of the direction and intensity of the local magnetic field as the sample cooled past the Curie temperature of iron.

But after the rock solidifies, any potassium-40 that is present continues to decay, and the argon-40 that is produced cannot escape from the rock.

If it is high relative to the amount of potassium-40 present, then the rock is old.

Relative dating methods do not tell archaeologists exactly how old things are, but only how old things are relative to each other.

Archaeologists work on the principle that objects at the bottom of an undisturbed were put there before objects that are above them, so objects found in the lower levels of a site are usually older than objects found in higher levels.

This method can give archaeologists an indication of the age of the artifacts in all Absolute dating methods can give an estimate of the real calendar age of an artifact or site.

There are several absolute dating methods that archaeologists can use, including radiocarbon dating and potassium argon dating.potassium) decays into argon over time, so the age of certain rocks or minerals can be discovered by measuring the amount of argon they contain.