What is the primary method by which energy is transferred through the Earth's mantle?

The primary method of energy transfer within the Earth's mantle is convection. Convection is a process that occurs in fluids (liquids and gases) and involves the movement of heat through the material as warmer, less dense material rises while cooler, denser material sinks.

In the context of the mantle, the heat from the Earth's core warms the surrounding mantle material. This warmer material becomes less dense and rises toward the surface. As it nears the upper mantle, it cools down, becomes denser, and then sinks back toward the core. This continuous cycle creates convection currents that effectively transfer heat throughout the mantle.

Conduction, while it does occur, is not the primary method of heat transfer in the mantle due to the fluid nature of the rock at those depths. Radiation is typically associated with the transfer of energy through vacuum or in space, and diffusion is a process that describes the movement of particles from an area of higher concentration to an area of lower concentration, which is less applicable to the large-scale heat transfer in the mantle. Thus, convection is the dominant mechanism that facilitates energy transfer and drives geological processes such as plate tectonics.