Arthur Holmes Image goes here Arthur Holmes studied Geology at the Imperial College of Science in London. In 1913, he estimated the Earth's age to be about 4 billion years - much longer than anyone had suggested before. Holmes said that the Cambrian period was about 600 million years ago; today's scientists have confirmed the time frame to be about 590 million years ago. Arthur Holmes also did research into the theory that the continents were vast plates drifting on the Earth's crust on top of heat currents generated by the expansion of the earth's mantle.