Argon isotope dating
A precise amount of argon-38 is added to the gas as a "spike" to help calibrate the measurement, and the gas sample is collected onto activated charcoal cooled by liquid nitrogen.Then the gas sample is cleaned of all unwanted gasses such as H A variant of the K-Ar method gives better data by making the overall measurement process simpler.As the K-40 in the rock decays into Ar-40, the gas is trapped in the rock.In this simulation, a unit of molten rock cools and crystallizes. Note that time is expressed in millions of years on this graph, as opposed to thousands of years in the C-14 graph.This is actually a mini-simulator, in that it processes a different sample each time and generates different dates.K-Ar Processing The Potassium-Argon dating method is an invaluable tool for those archaeologists and paleoanthropologists studying the earliest evidence for human evolution.
By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined.These each have 19 protons and 21 neutrons in their nucleus.If one of these protons is hit by a beta particle, it can be converted into a neutron.As with any dating technique, there are some significant limitations.The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.
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Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.