K–Ar dating

K–Ar dating estimates the age of rocks from the radioactive decay of potassium-40 into argon-40. It is especially useful for dating volcanic rocks and minerals.

Potassium-40: A naturally occurring radioactive isotope of potassium that decays into argon-40 and calcium-40. Its decay supplies the radioactive clock measured in K–Ar dating.
Potassium–argon dating of volcanic rocks: The use of potassium–argon isotope measurements to estimate when volcanic rocks solidified. Volcanic minerals can begin retaining radiogenic argon after cooling.
Argon–argon dating: A radiometric dating method that uses argon isotopes to infer potassium-40 decay in a sample. It derives potassium information from argon measurements and often permits analysis of smaller samples.
Bertram Boltwood: An American chemist who pioneered uranium–lead dating of minerals in the early twentieth century. His work helped establish radiometric dating as a means of measuring geological time.
Argon-40: A stable isotope of argon produced in part by the radioactive decay of potassium-40. Its accumulation in a mineral records potassium-40 decay since the mineral cooled.
Geochronology: The science of determining the ages and chronological order of geological materials and events. K–Ar dating is one method for establishing geological time.
Rubidium–strontium dating: A radiometric dating method based on the decay of rubidium-87 into strontium-87. It offers a different isotope system for dating old rocks and minerals.
Arthur Holmes: A British geologist who used radiometric dating to develop quantitative geological timescales. His advocacy helped make isotope dating central to Earth history.
Radioactive decay: The spontaneous transformation of unstable atomic nuclei into different nuclei or energy. K–Ar ages rely on the predictable decay rate of potassium-40.
Paleoanthropology: The study of human evolution through fossils, archaeological evidence, and geological context. K–Ar dates on volcanic layers can constrain the ages of fossil-bearing deposits.

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