Arthur Holmes

Arthur Holmes (18901965) was an English geologist. He made two important contributions: the use of radioactive isotopes for dating minerals, and the suggestion that convection currents in the mantle play an important role in continental drift. 
Holmes showed us that thermal convection currents were strong enough to move large land masses, which contributed to Alfred Wegener's theory of continental drift or theory of Plate tectonics. Harry H. Hess (19061969) also supported this view.
Holmes was a pioneer of geochronology, and performed the first accurate uranium-lead radiometric dating while an undergraduate in London. This gave a date of of 370 mya to a Devonian rock from Norway. This result was published in 1911, after his graduation in 1910.
Holmes worked on the problem of the age of the Earth all his life. He reached an approximately correct estimate by the 1940s of 4,500±100 mya.