Improvements in dating of rocks and fossils

Sedimentary rocks are rarely useful for dating because they are made up of bits of older rocks.Uranium is present in many different rocks and minerals, usually in the form of uranium-238.This technique is, however, useful for providing relative dates for objects found at the same site.

Each volcanic eruption produces a new deposit of ash and rock.Buried bones absorb chemicals, such as uranium and fluorine, from the surrounding ground and absorb more of these chemicals the longer they remain buried.The rates of absorption depend on a number of factors which are too variable to provide absolute dates.Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.

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