Potassium argon isotope dating

25-Oct-2017 11:20

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

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

Paleoanthropologists and archaeologists must always be aware of possible radiocarbon sample contamination that could result in inaccurate dates.

PART 1: Back to Basics PART 2: Problems with the Assumptions PART 3: Making Sense of the Patterns This three-part series will help you properly understand radiometric dating, the assumptions that lead to inaccurate dates, and the clues about what really happened in the past.

In other words, the change in numbers of atoms follows a geometric scale as illustrated by the graph below.other carbon isotopes in the same ratio as exists in the atmosphere.

Following death, however, no new carbon is consumed.

Radioactive rocks offer a similar “clock.” Radioactive atoms, such as uranium (the parent isotopes), decay into stable atoms, such as lead (the daughter isotopes), at a measurable rate.

To date a radioactive rock, geologists first measure the “sand grains” in the top glass bowl (the parent radioisotope, such as uranium-238 or potassium-40).

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The mathematical formula that is used to figure the age of the rock depends on the half-life of potassium-40 (the time it takes for half the potassium-40 in a given sample to decay).

If the concentration of argon-40 is almost zero, then the rock was formed recently.

If it is high relative to the amount of potassium-40 present, then the rock is old.

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.

Thus, geologists use potassium-argon dating to measure the age of volcanic rocks.

He is presently employed in the Space & Atmospheric Sciences Group at the Los Alamos National Laboratory.