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'''Potassium-argon dating''' is a method for estimating the age of volcanic rocks by measuring the ratio of potassium-40 to argon-40 present.
'''Potassium-argon dating''' is a method for estimating the age of volcanic rocks by measuring the ratio of potassium-40 to argon-40 present.
The method is based on the fact that the potassium-40 [[isotope]] of potassium [[radioactive decay | decay]]s 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. 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.
The method is based on the fact that the potassium-40 [[isotope]] of potassium [[radioactive decay|decay]]s 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. 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.
Thus, geologists use potassium-argon dating to measure the age of volcanic rocks. 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. Archaeologists and biologists are also sometimes able to use potassium-argon dating to measure the age of artifacts and fossils, when these have become trapped in or buried under volcanic rock.
Thus, geologists use potassium-argon dating to measure the age of volcanic rocks. 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. Archaeologists and biologists are also sometimes able to use potassium-argon dating to measure the age of artifacts and fossils, when these have become trapped in or buried under volcanic rock.