Radiometric dating resource list

A tree’s age can be found by simply counting its rings.

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The oldest reliably dated rock formation is in Greenland, where several different isotopes were used to find an age of 3.6 billion years.

To find older rocks that haven’t been eroded, we need to look beyond Earth.

Like the tree rings, this method can be verified by comparison to historical records for weather, as well as to records of volcanic eruptions around the globe that left thin dust layers on the glaciers.

Scientists have drilled ice cores deep into glaciers and found ice that is 123,000 years old in Greenland In your high school science classroom, you may have seen a large poster of the periodic table hanging on the wall.

The annual ice layers in glaciers provide a similar method that goes back much further in history.

Each year, snowfall varies throughout the seasons and an annual layer is formed.

This method can even be used on dead trees that fell in a forest long ago.

For example, the last 200 rings in the dead tree might match up with 200 rings early in the life of the living tree, so the two trees together can count back many years.

If you’ve ever seen a horizontal slice of a tree trunk, you’ve seen how a tree forms a new growth ring each year.

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