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Studying the layers of rock or strata can also be useful. If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks.
Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.
No other scientific method has managed to revolutionize man’s understanding not only of his present but also of events that already happened thousands of years ago.
Archaeology and other human sciences use radiocarbon dating to prove or disprove theories.
Scientists can use certain types of fossils referred to as index fossils to assist in relative dating via correlation.
Index fossils are fossils that are known to only occur within a very specific age range.
So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range for the fossil containing rocks.
The atoms in some chemical elements have different forms, called isotopes.
If a radioactive isotope is said to have a half-life of 5,000 years that means after 5,000 years exactly half of it will have decayed from the parent isotope into the daughter isotopes.
An age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against an internationally used reference standard.
The impact of the radiocarbon dating technique on modern man has made it one of the most significant discoveries of the 20th century.
It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.
Then after another 5,000 years half of the remaining parent isotope will have decayed.