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Geochronometry is a branch of stratigraphy aimed at the quantitative measurement of geologic time. It is considered also a branch of geochronology. == Brief history == The measurement of geologic time is a long-standing problem of Geology.〔Hallam, Anthony, 1983 – ''Great geological controversies''. Oxford University Press, Oxford, UK.〕 When geology was at its beginnings, a major problem for stratigraphers was to find a reliable method for the measurement of time. In the eighteenth century, and during most of the nineteenth century, the ideas on the geologic time were indeed so controversial that the estimates for the age of the Earth encompassed the whole range from ca. 6000 years to 300 millions of years. The longer estimate came from Charles Darwin, who probably went closer to the truth because he had clear in mind that the evolution of life must have required a lot of time to take place. The current estimate of the age of the Earth is ca. 4500 millions of years. The solution of the dating problem arrived only with the discovery that some natural elements undergo a continuous decay. This led to the first radiometric datings by Boltwood〔Boltwood B.B., 1907, On the ultimate disintegration products of the radioactive elements. Part II. The disintegration products of uranium. American Journal of Science, v. 23, p. 77-88.〕 and Strutt.〔Strutt R.J., 1909, The accumulation of helium in geologic time III. Proceeding of the Royal Society of London A, v. 83, p. 298-301.〕 Today, the determination of the age of the Earth is not a primary scope of geochronometry anymore, and most efforts are rather aimed at obtaining increasingly precise radiometric datings. At the same time, other methods for the measurement of time were developed, so the quantification of geologic time can now be endeavored with a variety of approaches. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「geochronometry」の詳細全文を読む スポンサード リンク
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