Archaeological dating radioisotopes
Radiocarbon is then taken in by plants through photosynthesis, and these plants in turn are consumed by all the organisms on the planet.So every living thing has a certain amount of radiocarbon within them.
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. 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.Plankton absorbs, Carbon-14 from the ocean much like terrestrial plants absorb Carbon-14 from the air.Since plankton is the foundation of the marine food chain, Carbon-14 is spread throughout aquatic life.Shellfish remains are common in coastal and estuarine archaeological sites, but dating these samples require a correction for the “reservoir effect” a process whereby "old carbon" is recycled and incorporated into marine life especially shellfish inflating their actual age in some cases several centuries.
In recognition of this problem archaeologists have developed regional reservoir correction rates based on ocean bottom topography, water temperature, coastline shape and paired samples of terrestrial and marine objects found together in an archaeological feature such as a hearth.
The Greeks consider the first Olympic Games as the beginning or 776 BC.
The Muslims count the Prophet’s departure from Mecca, or the Hegira, as their beginning at AD 662.
When it comes to dating archaeological samples, several timescale problems arise.
For example, Christian time counts the birth of Christ as the beginning, AD 1 (Anno Domini); everything that occurred before Christ is counted backwards from AD as BC (Before Christ).
The extra neutrons in Carbon-14’s case make it radioactive (thus the term, radiocarbon).