Absolute dating of rocks and fossils

However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.

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The most widely known form of radiometric dating is carbon-14 dating.

This is what archaeologists use to determine the age of human-made artifacts. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old.

The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay.

The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.

One way that helps scientists place fossils into the correct era on the Geologic Time Scale is by using radiometric dating.

Also called absolute dating, scientists use the decay of radioactive elements within the fossils or the rocks around the fossils to determine the age of the organism that was preserved.

Knowing when a dinosaur or other animal lived is important because it helps us place them on the evolutionary family tree.

Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct. These are: Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy.

Instead, other methods are used to work out a fossil’s age.

These include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages.

But this sediment doesn't typically include the necessary isotopes in measurable amounts.

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