# Question: How is the age of a sample determined by absolute dating?

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Absolute dating methods determine how much time has passed since rocks formed by measuring the radioactive decay of isotopes or the effects of radiation on the crystal structure of minerals. Paleomagnetism measures the ancient orientation of the Earths magnetic field to help determine the age of rocks.

## How can we find the absolute age of a sample?

To determine the absolute age of this mineral sample, we simply multiply y (=0.518) times the half life of the parent atom (=2.7 million years). Thus, the absolute age of sample = y * half-life = 0.518 * 2.7 million years = 1.40 million years.

## What is an example of absolute age dating?

For example, the decay of potassium-40 to argon-40 is used to date rocks older than 20,000 years, and the decay of uranium-238 to lead-206 is used for rocks older than 1 million years. Geologists choose a dating method that suits the materials available in their rocks. There are over 30 radiometric methods available.