• Question: How can you know how old some rocks are?

    Asked by Vita to Jess on 15 Nov 2019.
    • Photo: Jessica Franklin

      Jessica Franklin answered on 15 Nov 2019:

      Rocks are made up of crystals called minerals, these minerals are made up of lots of different elements. In some of these minerals there are radioactive elements that break down over time, at different rates. We can analyse the chemistry of these minerals and count how many radioactive elements there are, from this we can work out the age of the rock.

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