absolute dating Flashcards
what is absolute dating?
the actual date of specimen in years
what are the 2 types of absolute dating?
potassium-argon dating
carbon 14 dating
what is potassium argon dating?
method of calculating the age of a fossil or artifact using the known rate of decay of radioactive potassium
- based on the decay of radioactive potassium to form calcium and argon
what materials are dated in potassium argon dating?
volcanic deposits/minerals - igneous rock
what isotopes are involved in potassium argon dating?
potassium40 decayed into argon40 and calcium40
what is the half-life of the radioisotope in potassium argon dating?
potassium 40 - 1.25 billion years
what age range can be dated using potassium argon dating?
over 200 000 years old (1-5 million years old but is undesirable)
what are the limitations of potassium argon dating?
very large half-life so pushes the limits of detection devices currently in use so cannot be used for younger (below 200 000 years) fossils
has to be volcanic
older samples lose accuracy
younger rocks lose accuracy
what is carbon-14 dating?
based on the decay of the radioisotope of carbon to nitrogen
what materials are used for carbon-14 dating?
fossils containing carbon
what are the isotopes involved in carbon-14 dating?
carbon 14 to nitrogen 14
what is the half-life of the isotope in carbon-14 dating?
5730 years
what is the dating range for carbon-14 dating?
0 to 60 000 years
what are the limitations to carbon-14 dating?
can’t date past 60 000 years because there is not enough C14
what are the similarities between carbon-14 and potassium argon dating?
both an age of the fossil/rock - both absolute dating methods
both use radioactive decay of isotopes
both provide evidence for evolution by dating extinct organisms that are intermediate forms of species alive today
