What is a convection current?

Convection currents are vertical movements of fluids driven by heat. Hot fluids rise because they are less dense than cold fluids which sink. The best example would be soup boiling - stuff in the soup comes to the surface over the flame and sinks back towards the edges of the pot.

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Current caused by the expansion of a liquid, solid, or gas as its temperature rises. The expanded material, being less dense, rises, while colder, denser material sinks. Material of neutral buoyancy moves laterally. Convection currents arise in the atmosphere above warm land masses or seas, giving rise to sea breezes and land breezes, respectively. In some heating systems, convection currents are used to carry hot water upwards in pipes. Convection currents in the hot, solid rock of the Earth's mantle help to drive the movement of the rigid plates making up the Earth's surface.