How has Earth's cooling affected geological activity over geologic time?

As Earth has cooled over geologic time, its behavior and the intensity of its geological activity have changed. While the fundamental physical laws governing these processes have remained constant, the planet’s internal thermal state has evolved due to the irreversible loss of heat.1

This cooling process is significant because Earth’s internal heat—driven in part by the decay of radioactive isotopes such as uranium-235, uranium-238, and thorium—is the primary engine for plate tectonics. Elevated internal temperatures allow rock to deform plastically, facilitating mantle convection, seafloor spreading, and continental drift.123

As temperatures have fallen, the extent of igneous activity and the movement of the crust have shifted. Consequently, the plate tectonics observed today may have been preceded by different processes of deformation during Precambrian time. While Lord Kelvin initially underestimated Earth's age based on this cooling, his core observation that the planet suffers an irreversible loss of energy remains a valid aspect of its thermal evolution.1