K has a half-life of 1.248 billion years, which makes it eminently suitable for dating rocks.Potassium is chemically incorporated into common minerals, notably hornblende, biotite and potassium feldspar, which are component minerals of igneous rocks.For instance, the decay of carbon-14 is often used to complement the potassium-argon dating of dinosaur fossils. Radiometric dating methods Quaternary Dating Methods, by M. 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 decays over time to form argon-40.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.

Still, as a general rule, the proportional error in K-Ar dating will be greatest in the youngest rocks.

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.

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.

Still, as a general rule, the proportional error in K-Ar dating will be greatest in the youngest rocks.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.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.method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.