Radioactive carbon dating useful
Long tree-ring sequences have been developed throughout the world and can be used to check and calibrate radiocarbon dates.
An extensive tree-ring sequence from the present to 6700 BC was developed in Arizona using California bristlecone pine (), some of which are 4900 years old, making them the oldest living things on earth.
There are two techniques for dating in archaeological sites: relative and absolute dating.
Relative dating stems from the idea that something is younger or older relative to something else.
The extra neutrons in Carbon-14’s case make it radioactive (thus the term, radiocarbon).
Radiocarbon is produced in the upper atmosphere after Nitrogen-14 isotopes have been impacted by cosmic radiation.
Absolute dating represents the absolute age of the sample before the present.
Historical documents and calendars can be used to find such absolute dates; however, when working in a site without such documents, it is hard for absolute dates to be determined.
Since plankton is the foundation of the marine food chain, Carbon-14 is spread throughout aquatic life.
The Mayan calendar used 3114 BC as their reference.
More recently is the radiocarbon date of 1950 AD or before present, BP.
Therefore, radiocarbon dates need to be calibrated with other dating techniques to ensure accuracy.
Plants are not the only organism that can process Carbon-14 from the air.
In a stratigraphical context objects closer to the surface are more recent in time relative to items deeper in the ground.