The technique known as potassiumargon dating is used to date volcanicrock and ash, and thus establish dates for nearby fossils, like this 1.8-millionyear- old hominid skull. The potassium isotope 40K decays with a 1.28-billionyear half-life and is naturally present at very low levels. The most common decay mode is beta-minus decay into the stable isotope 40Ca, but 10.9% of decays result in the stable isotope 40Ar. The high temperatures in volcanoes drive argon out of solidifying rock and ash, so there is no argon in newly formed material. After formation, argon produced in the decay of 40K is trapped, so 40Ar builds up steadily over time. Accurate dating ispossible by measuring the ratio of the number of atoms of 40Ar and 40K. 1.8 million years after its formation,a. What fraction of the 40K initially present in a sample has decayed?b. What is the 40Ar/40K ratio of the sample?
The technique known as potassiumargon dating is used to date volcanic
rock and ash, and thus establish dates for nearby fossils, like this 1.8-millionyear- old hominid skull. The potassium isotope 40K decays with a 1.28-billionyear half-life and is naturally present at very low levels. The most common decay mode is beta-minus decay into the stable isotope 40Ca, but 10.9% of decays result in the stable isotope 40Ar. The high temperatures in volcanoes drive argon out of solidifying rock and ash, so there is no argon in newly formed material. After formation, argon produced in the decay of 40K is trapped, so 40Ar builds up steadily over time. Accurate dating is
possible by measuring the ratio of the number of atoms of 40Ar and 40K. 1.8 million years after its formation,
a. What fraction of the 40K initially present in a sample has decayed?
b. What is the 40Ar/40K ratio of the sample?
Trending now
This is a popular solution!
Step by step
Solved in 2 steps with 2 images
