Which term describes the movement of fluids driven by temperature differences, such as in the atmosphere and Earth's mantle?

• A. Convection currents
• B. Conduction
• C. Radiation
• D. Advection

Answer: (A)

Convection is the movement of fluids driven by temperature differences that create density differences. When part of a fluid is heated, it becomes lighter and rises, while cooler, denser parts sink, establishing a circulating flow. In the atmosphere, this buoyancy-driven motion powers vertical air currents, clouds, and storms. In Earth’s mantle, hot mantle material rises while cooler material sinks, slowly driving the convection that moves tectonic plates. Conduction is heat transfer by direct contact without bulk motion, radiation is heat transfer by electromagnetic waves, and advection is the transport of properties by the bulk flow of the fluid—convection specifically emphasizes the buoyancy-driven circulation caused by temperature-induced density changes.