Absolute dating techniques in archaeology
A layer that is higher is of later age than a layer that is lower in order.
This means that the oldest are the strata that are lying at the bottom.
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.
These use radioactive minerals in rocks as geological clocks.
The atoms of some chemical elements have different forms, called isotopes.
These break down over time in a process scientists call radioactive decay.
There are many methods employed by these scientists, interested in the old, to get to know the age of items.
For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years.