Convection currents in the mantle are caused by heat produced by which process?

• A. Solar radiation
• B. Radioactive decay in the core
• C. Mantle cooling
• D. Gravitational effects

Answer: (B)

The movement of mantle material is driven by internal heat that creates temperature and density differences. When parts of the mantle are heated by radioactive decay inside the Earth, they become less dense and rise; cooler, denser material sinks, setting up convection cells. Solar radiation doesn’t reach the mantle to power these motions, so it isn’t the cause. Mantle cooling over time helps sustain convection, but the energy source behind the convection is internal heat from processes like radioactive decay in the core. Gravitational effects simply act on the resulting density differences. So the heat produced by radioactive decay in the core best explains mantle convection.