What proposal did the british geologist arthur Holmes make in 1929?

In 1929, British geologist Arthur Holmes proposed the theory of radioactivity as a significant factor in Earth's internal heat production, which could drive convection currents in the mantle. This idea contributed to the understanding of plate tectonics by suggesting that these currents could influence continental drift. Holmes' work helped shift the geological community's perspective on Earth's dynamics and provided a scientific basis for the movement of tectonic plates.