UC Berkeley. Geologists use radiometric dating to estimate how long ago rocks formed, and to tell the ages of fossils contained within those rocks.
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The universe is full of naturally occurring radioactive elements. When molten rock cools, forming what are called igneous here, radioactive atoms are trapped inside. Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
Fossils are generally found in sedimentary rock — not igneous rock.
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Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years. So in order to date most older fossils, scientists radiometric for layers of igneous rock or volcanic ash above and below the fossil. Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.
Read more about how radiometric dating factored into the history of evolutionary thought.
Radiometric dating
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Radioactive elements decay The universe is full of naturally occurring radioactive elements. Bracketing the you Fossils are generally found in sedimentary rock — not igneous rock.
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