LEWIS, Cherry L.E., School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, United Kingdom, cherry.lewis@bristol.ac.uk
In March 1911, when Arthur Holmes (1890-1965) was just 21 and studying for a BSc in geology at Imperial College London, he wrote the first of almost 200 papers that he published during his lifetime. Entitled ‘The Association of Lead with Uranium in Rock-Minerals, and its Application to the Measurement of Geological Time’, this paper appeared in the Proceedings of the Royal Society of London in June 1911, while Holmes was prospecting for minerals in Mozambique. The data included the U/Pb ratios of eight rocks, enabling him not only to produce the first attempt at a geological timescale from radiometric dates, but also to confirm that lead was the final decay product from uranium. From these data he concluded that the Earth must be at least 1,640 million years old, at a time when most geologists considered it to be less than 100 million years old. Like much of Holmes's work, the paper was ahead of its time, particularly since isotopes would not be discovered for another two years. Holmes spent much of the rest of his life developing his vision of a geological timescale and attempting to establish the age of the Earth.
While at the University of Durham, England, Holmes made major, and usually controversial, contributions to early ideas on mechanisms for continental drift, the formation of granites, the geology of Africa, and unravelling the Precambrian. During World War II he wrote one of the most popular geological text books of all time, Principles of Physical Geology, which thousands of people around the world still fondly remember today. By all accounts he was a remarkable educator and his students, many of whom went on to take up senior posts around the world, still speak highly of his charismatic lecturers. Today, the geological time scale has become the framework onto which we hang all geological events. Thanks to Arthur Holmes, we learnt how to tell geological time from isotopic clocks and using those clocks we discovered many of the Earth's internal processes, ultimately developing a unifying theory that explains them all – just as Holmes predicted we would. His contribution to our science cannot be over stated.
