The technique known as potassium-argon dating is used to date volcanic rock and ash, and thus establish dates for nearby

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The Technique Known As Potassium Argon Dating Is Used To Date Volcanic Rock And Ash And Thus Establish Dates For Nearby 1 (79.93 KiB) Viewed 13 times

The technique known as potassium-argon dating is used to date volcanic rock and ash, and thus establish dates for nearby fossils, like this 1.8-million-year-old hominid skull. The potassium isotope 40K has a 1.28-billion-year half-life and is naturally present at very low levels. The most common decay mode is beta-minus decay into the stable isotope 40 Ca, but 10.9% of decays result in the stable isotope 40 Ar. 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 40 Ar builds up steadily over time. Accurate dating is possible by measuring the ratio of the number of atoms of 40 Ar and 40K. (Figure 1) Part A What fraction of the 40K initially present in a sample has decayed 1.65 million years after its formation? Express your answer as a percentage. ΠΑΠ ΑΣΦ 1 NK No Submit Part B X Incorrect; Try Again; 4 attempts remaining .89 NAT NK Previous Answers Request Answer Submit What is the 40 Ar/40K ratio of the sample 1.65 million years after its formation? IVE ΑΣΦ Request Answer ? ? %