Carbon dating explanation for kids
This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.These use radioactive minerals in rocks as geological clocks.What if originally part of the material being measured was already carbon 12? Since we do not know what was there originally, the dates may be very far from correct.” anything.Scientists have some clever ways of figuring out the original composition of a sample; the calibration curves against tree rings that you mentioned are one example of this.Because of the fairly fast decay rate of carbon-14, it can only be used on material up to about 60,000 years old.Geologists use radiocarbon to date such materials as wood and pollen trapped in sediment, which indicates the date of the sediment itself.They also do a lot of cross-checks between different dating methods to figure out which ones work in which circumstances and to test the assumptions to see whether or not they are valid.
Geologists choose a dating method that suits the materials available in their rocks. Measuring isotopes is particularly useful for dating igneous and some metamorphic rock, but not sedimentary rock.Sedimentary rock is made of particles derived from other rocks, so measuring isotopes would date the original rock material, not the sediments they have ended up in.However, there are radiometric dating methods that can be used on sedimentary rock, including luminescence 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.Radiocarbon dating measures radioactive isotopes in once-living organic material instead of rock, using the decay of carbon-14 to nitrogen-14.The atoms of some chemical elements have different forms, called isotopes.