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Holmes, Arthur

time decay rocks absolute

(1890–1965) British geologist and geophysicist: devised modern geological time-scales.

While a student in London, Holmes spent a vacation on field work in Mozambique. He contracted malaria which prevented him joining the army in 1914 with his friends, who largely died in the first year of the First World War. From 1924 he headed geology at Durham and from 1943 at Edinburgh.

Holmes pioneered the use of radioactive decay methods for dating rocks, whereby careful analysis of the proportions of elements formed by radioactive decay, combined with a knowledge of the rates of decay of their parent elements, yields an absolute age. He was the first to use the technique, in 1913, to systematically date fossils whose strati-graphic (ie relative) ages were established, and was thus able to put absolute dates to the geological time scale for the first time.

In 1928 he suggested that convection currents within the Earth’s mantle, driven by radiogenic heat, might provide the driving mechanism for the theory of continental drift, which had been advanced by some years earlier. He also proposed that new oceanic rocks were forming throughout the ocean basins, although predominantly at ocean ridges. Little attention was given to his ideas until the 1950s, when palaeomagnetic studies established continental drift as a fact.

In successive and revised editions, his Principles of Geology (1944) has been an influential and much-used text book.

Holmes, Dwight Oliver Wendell(1877–1963) - College president, Chronology [next]

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