Potassium 40 dating formula speed dating west palm beach florida

The method is based on the fact that the potassium-40 isotope of potassium decays over time to form argon-40.

The useful fact about these two substances is that at normal temperatures, potassium is a solid, but argon is a gas.

Potassium-40 decays to calcium-40 89% of the time and to argon-40 11% of the time.

Almost all atmospheric argon (99.6%) is argon-40, whereas the argon in the Sun and stars, produced by stellar nucleosynthesis, is mostly argon-36.

This suggests that primordial argon is in the form of argon-36 and essentially all of the argon in the atmosphere was produced by the decay of potassium-40 to argon-40.

The total mass of the argon in the Earth's atmosphere is (total mass of atmosphere) x 1.3% = (5.1 x 10 kg argon in the atmosphere Thus, the amount of argon in the atmosphere is about 1.4% of the amount of argon-40 produced in the Earth's crust over the past 4.5 billion years.

Most of the argon produced in the crust remains locked in the rock.

Therefore, the amount of argon-40 produced by the decay of potassium-40 is 11% of the total mass of potassium that has decayed: 4.2 x 10 kg of argon-40 produced in the Earth's crust Argon is a common gas, making up 0.9% by volume or 1.3% by mass of the atmosphere.

Only nitrogen and oxygen (and sometimes water vapor, depending on the humidity) are more plentiful in the atmosphere.

Therefore, during volcanic eruptions, any argon that is present escapes from the rock.

But after the rock solidifies, any potassium-40 that is present continues to decay, and the argon-40 that is produced cannot escape from the rock.

Only about 1.4% has escaped and entered the atmosphere.

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