Holmes, Arthur (1890–1965)

English geologist who helped develop interest in the theory of continental drift. He also pioneered the use of radioactive decay methods for rock dating, giving the first reliable estimate of the age of the Earth.

Holmes was born in Newcastle-upon-Tyne and studied at Imperial College, London. He was appointed head of the Geology Department at Durham in 1924, moving to Edinburgh University in 1943.

Holmes was convinced that painstaking analysis of the proportions in rock samples of elements formed by radioactive decay, combined with a knowledge of the rates of decay of their parent elements, would yield an absolute age. From 1913 he used the uranium–lead technique systematically to date fossils whose relative (stratigraphical) ages were established but not the absolute age.

In 1928, Holmes proposed that convection currents within the Earth's mantle, driven by radioactive heat, might furnish the mechanism for the continental drift theory broached a few years earlier by German geophysicist Alfred Wegener. In Holmes's view, new rocks were forming throughout the ocean ridges. Little attention was given to these ideas until the 1950s.

His books include The Age of the Earth 1913, Petrographic Methods and Calculations 1921, and Principles of Physical Geology 1944.