In which layer of Earth's interior does convection occur?

Convection occurs in the mantle, which is the thick layer of semi-solid rock located between the Earth's crust and outer core. This layer is hot enough that it experiences slow, cyclical movement due to temperature differences and the resulting changes in density.

As material in the lower mantle heats up, it becomes less dense and rises toward the surface. When it reaches the cooler upper mantle, it loses heat, increases in density, and then sinks back down. This continuous cycle of rising and sinking creates convection currents, which are significant in driving plate tectonics and influencing volcanic activity.

The other layers, such as the crust, inner core, and outer core, do not experience convection in the same way. The crust is relatively rigid and does not have the required properties for convection. The inner core is solid and does not flow, while the outer core, though liquid, primarily engages in convection related to the generation of Earth’s magnetic field rather than the type of convection associated with mantle dynamics. Thus, the mantle is the only layer where the classic convection process significantly contributes to geological activity.