Absolute dating on rocks

Because of the alternation between dark and light sediments we can use each dark band as a marker for one year.For really old dates we need to use radioactive isotopes.

THE MORE STABLE FORM IT TURNS INTO IS CALLED THE DAUGHTER ELEMENT.

There are two main methods determining a fossils age, relative dating and absolute dating.

The atoms in some chemical elements have different forms, called isotopes.

These isotopes break down at a constant rate over time through radioactive decay.

Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.

This uses radioactive minerals that occur in rocks and fossils almost like a geological clock.For example if you have a fossil trilobite and it was found in the Wheeler Formation.The Wheeler Formation has been previously dated to approximately 507 million year old, so we know the trilobite is also about 507 million years old.Another method of determining absolute age is by looking at varves.VARVES ARE LAYERS OF LIGHT AND DARK SEDIMENT THAT SHOW YEARLY CYCLES. Each spring or summer when the glacier was melting the glacier deposits a ton of sediment it was carrying into strems of water that are melting off of it.By measuring the ratio of the amount of the original (parent) isotope to the amount of the (daughter) isotopes that it breaks down into an age can be determined.

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