Potassium-argon or K-Ar dating is a method used by archaeologists and geologists to ascertain the date of ancient mineral deposits. Archaeology or sometimes in American English archeology (from the Greek words αρχαίος = ancient and λόγος = word/speech) is the study of human cultures through the recovery, documentation and analysis of material remains, including architecture, artefacts, biofacts, human remains, and landscapes. ... A geologist is a contributor to the science of geology. ...

The potassium isotope ⁴⁰K decays to ⁴⁰Ar with a half-life of 1.3x10⁹ years. As argon is a gas any traces of that element will escape from rocks when they are molten. Therefore, any argon found in solid rocks must have been produced since that molten state ended and the rock solidified. The ratio of ⁴⁰K to ⁴⁰Ar can be analysed and a numerical date since the last molten state can be assigned. General Name, Symbol, Number potassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4, s Density, Hardness 856 kg/m3, 0. ... Isotopes are forms of a chemical element whose nuclei have the same atomic number, Z, but different atomic masses, A. The word isotope, meaning at the same place, comes from the fact that all isotopes of an element are located at the same place on the periodic table. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ...

Due to the long half-life, the technique is most applicable in archaeology to Lower Palaeolithic sites older than 100,000 years and has been used at Olduvai Gorge in dating the strata created from ancient lava flows found above and below the archaeological deposits there. It has also been indispensable in other early east African sites with a history of volcanic activity such as Hadar, Ethiopia. Importance and applicability Most of human history is not described by any written records. ... The Paleolithic or Palaeolithic – lit. ... Olduvai Gorge from space Topography of Olduvai Gorge The Olduvai Gorge is a 30 mile long, steep-sided ravine, part of the Great Rift Valley which stretches along eastern Africa. ... Lava is molten rock that a volcano expels during an eruption. ... Africa is the worlds second-largest continent in both area and population, after Asia. ... This article is about volcanoes in geology. ... Hadar is a site on the River Awash in Ethiopia, in the Afar Triangle. ...

References

• K-Ar N. Mex. Geochron. Lab
• Potassium-Argon Dating Univ. Cal.