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.
In fact, levels of Carbon-14 have varied in the atmosphere through time.
One good example would be the elevated levels of Carbon-14 in our atmosphere since WWII as a result of atomic bombs testing.
Therefore, radiocarbon dates need to be calibrated with other dating techniques to ensure accuracy.
His radiocarbon dating technique is the most important development in absolute dating in archaeology and remains the main tool for dating the past 50,000 years.Rodents, for example, can create havoc in a site by moving items from one context to another.Natural disasters like floods can sweep away top layers of sites to other locations.As long as there is organic material present, radiocarbon dating is a universal dating technique that can be applied anywhere in the world.It is good for dating for the last 50,000 years to about 400 years ago and can create chronologies for areas that previously lacked calendars.